Bio1.J. Linn. Sot., 2, pp, 125-171. W i t h 6figures
June 1970
The classification of the Proterosuchia
A. J. CHARIG, F.L.S.
British Museum (Natural History), London, S. W.7
AND
0. A. REIG, F.L.S.
Universidad Central de Venezuela, Caracas, Venezuela
Accepted f o r publication 4 November 1969
The earliest archosaurs (Upper Permian and Lower Trias) have been classified in many
different ways. All classifications introduced during the period 1945-67 are compared and then
themselves classified and evaluated.
The typical characters of these archosaurs are listed. Most of them may be placed in a
single suborder, the Proterosuchia, which is divided into two families, the Proterosuchidae
and the Erythrosuchidae. The composition of each family is considered. Lists of genera in
each family are given and of those generic names which should be regarded as tzomina dubia.
The placing of several genera in the synonymy of Erythrosuchus is rejected. The possible
conspecificity of Channtosaurus vanhoepetri and C . alexanderi is considered.
A simplified scheme for the evolution of the Proterosuchia is drawn up.
CONTENTS
General introduction
The ‘primitive taxon’
Introduction .
Characters .
Rank and nomenclature .
Composition .
Lower Triassic genera to be excluded:
Mesorhinosuchus
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Euparkeria
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Browniella
Wangisuchus .
Fenhosuchus .
Chigutisaurus and Zcanosaurus .
Genera of uncertain affinities and/or age:
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Ocoyuntaia and Seemannia
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Arizonasaurus and Anisodontosaurus
Later genera which have been wrongly included:
Rauisuchus
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Hoplitosuchus .
Saurosuchus .
Dasygnathoides
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1 Typothorax .
Conclusions .
Subordinate Taxa
Introduction
Characters
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A. J. CHARIG AND 0. A. REIG
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The Shansisuchidae .
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‘Proterosuchidae’ or ‘Chasmatosauridae’?
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Composition .
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Deviations from the standard pattern .
Problems in the Proterosuchidae: .
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Proterosuchusand Chasmatosaurus
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Ankistrodon and Charmatosaurus
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Archosaurus, Chasmatosuchus and Chasmatosaurus
Elaphrosuchw and Chasmatosaurus
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Chasmatosaurusvanhoepem and C. alexandm‘
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Problems in the Erythrosuchidae :
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Three-headedribs .
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Vjushkovia = Erythrosuchus?
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Garjaima-Erythrosuch?
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Dongusia = Erythrosuchus?
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Cuyosuchus = Erythrosuchus? .
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Dasygnathoides = Erythrosuchw ?
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Shansisuchus heiyuekouensis
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Conclusions .
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Summary
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Acknowledgements .
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Addendum
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References
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Abbreviationsused in figures
Rank and nomenclature
Rank of subordinatetam
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GENERAL INTRODUCTION
The earliest archosaurs known comprise one genus from the Upper Permian
(Archosaurus)and about 18 or 20 genera from the Lower Trias. They should include
the ancestors or near-ancestors of all the later archosaurs. They therefore occupy a
position of peculiar importance in evolutionary history; for the later archosaurs not
only constituted the dominant element of the terrestrial and aerial vertebrate faunas
from the beginning of the Upper Trias until the end of the Cretaceous, invading the
seas as well during the middle part of the Mesozoic, but they have also persisted up to
the present day as the crocodiles and the birds. (The latter, of course, are not formally
classified as archosaurs, but it is generally agreed that they originated from members
of that order.)
These basal forms have been classified in a great many different ways. The present
article is intended to be an objective assessment of the various classifications and
nomenclatures.
Systems of classification introduced before 1945, however, are not considered in
the following discussion. In the light of present knowledge they often appear so
confused as to be meaningless. For example, Kuhn (1933) listed three Lower Triassic
genera-which form the basis of the group under discussion-in the same two families
as three Upper Triassic genera with which they are no longer believed to have any close
relationship (Proterosuchuswith Dyoplax 0.Fraas 1867 and ErpetosuchusNewton 1894;
Erythrosuchus and Chasmatosaurus with Acompsosaurus Mehll915). Some older works
even included forms which, it is now known, are not archosaurs at all; for instance,
von Huene (1926) regarded five genera from the Trias of Brazil (Scaphonyx A. S.
Woodward 1907, Cephalonia and three other new genera) as primitive archosaurs,
but it was soon recognized that these were in fact rhynchosaurid rhynchocephalians
and that the beds were younger than von Huene had thought.
CLASSIFICATION OF THE PROTEROSUCHIA
127
The 25 systems considered are given below. They are arranged chronologically
according to the year of publication (alphabetically within a given year):
1961 Reig
1945 Camp
1961 Tatarinov
1945 Romer
1962 von Huene
1946 Kuhn
1963 Hughes
von
Huene
1948
1964 Maleev in Rozhdestvenskii &
1954 Haughton & Brink
Tatarinov
1955 Hoffstetter in Piveteau
1964 Young
1956 von Huene
1965 Ewer
1956 Romer
1965 Krebs
1957 Watson
1965 Kuhn
1958 Ochev
1966 Kuhn
1960 von Huene
1966 Romer
1960 Kuhn
1967 Charig in Harland et al.
1961 Kuhn
Some of these classifications are complete and are detailed explicitly, others are only
partial and are merely implied. The last (1967 Charig in Harland et a2.) is based upon
the conclusions reached in the present paper and will not be considered further.
I n several of these works, however, the authorship and dates of certain names have
been cited wrongly. As far as we can ascertain, the authorship and dates of the various
names used should be :
Ordinal names
Thecodontia Owen 1859
Subordinal names
Proterosuchia Broom 1906b (used by Williston (1925) for a separate order based on
Proterosuchus, which he considered to be a diapsid but not an archosaur)
Pelycosimia von Huene 191 1 (originally an ordinal name, for a separate order based
on Erythrosuchus)
Erythrosuchia Goodrich 1930
Also:
Parasuchia Huxley 1875
Aetosauria Lydekker in Nicholson & Lydekker 1889
Pseudosuchia Zittel 1890
Phytosauria Baur 1894
Ornithosuchia von Huene 1908 (nom. transl. Reig 1961 ex familia Ornithosuchia
von Huene 1908 nom. imperf.)
Eosuchia Broom 1914
Desmatosuchia Case 1920
Superfamily names
Proterosuchia Broom 1906b
Pelycosimioidea von Huene 1936
Proterosuchoidea Camp 1945
128
A. J. CHARIG AND 0. A. REIG
Table 1. Genera and species of U. Permian and L. Triassic archosaurs, together with all
other forms attributed (rightly or wrongly) to the Proterosuchia
Period
L. Trias
U. Trias
L. Trias
L. Trias
L. Trias
L. Trias
L. Trias
L. Trim
L. Trias
L. Trias
L. Trias
M. Trias
M. Trias
L. Trias
L. Trias
L. Trim
L. Trias
M. Trias
M. Trias
L. Trias
L., possibly
M. Trias
L., possibly
M. Trias
L. Trias
L. Trias
L.Trias
L. Trias
L. Trias
L. Trias
M.-U. Trias
Generic and specific names
Provenance
Ankistrodon indicus Huxley 1865
Dasygnathus Huxley 1877 non Macleay 1819 (see
Dasygnathoides Kuhn 1961):
D. longidens Huxley 1877
Epicampodon Lydekker 1885 nom. wan., nom. subst.
pro Ankistrodon Huxley 1865 non Ancistrodon
Roemer 1849 etc.
Proterosuchusfergusi Broom 1903
Erythrosuchus africanus Broom 1905
Mesorhinus Jaekel 1910 non Ameghino 1885 (see
Mesorhinosuchus Kuhn 1961):
M . fraasi Jaekel 1910
Euparkeria capencis Broom 1913a
Browniella africana Broom 1913b
Chasmatosaurus vanhoepeni Haughton 1924
C . yuam' Young 1936
C . ultimus Young 1964
C. alexandm' Hoffman 1965
Stagonosuchus nyassicus von Huene 1938
S . tanganyikaensis Boonstra 1953
Chasmatosuchus rossicus von Huene 1940
C . parvus von Huene 1940
C. ( ?)wjushkowz' Ochev 1961
Dongusia colorata von Huene 1940
Hoplitosuchus raui von Huene 1942a
Hoplitosaurus von Huene 1942a (non Lucas 1902)
norn. null. = Hoplitosuchus von Huene 1942a
(lapsus calam')
Rauisuchus tiradentes von Huene 1942a
Elaphrostichus rubidgei Broom 1946
Panchet Series, Bengal
Arizonasaurus babbitti Welles 1947
Upper Moenkopi Formation, Arizona
Anisodontosaurus grem. Welles 1947
Ocoyuntaia arquata Rusconi 1947a
? Typothorax punctulatus Rusconi 19476
Chigutisaurus tunuyanensis Rusconi 1948
Icanosaurus rectifrons Rusconi 1950
Garjainia prima Ochev 1958
Seemannia aalaeotriadica von Huene 1958
Saurosuchuiaalilk Rein 1959
Shansisuchuskoung 1959 norn. nud.
Vjushkovia von Huene 1959 nom. nud.
Vjushkowia triplicostata von Huene 1960
L. Trias
U. Permian Archosaurus rossicus Tatarinov 1960
Cuyosuchus huenei Reig 1961
L. Trias
Dasygnathoides Kuhn 1961 nom. subst. pro
Dasygnathus Huxley 1877 non Macleay 1819:
D . longidens (Huxley 1877)
U. Trias
Mesorhinosuchus Kuhn 1961 nom. subst. pro
Mesorhinus Jaekel 1910 non Ameghino 1885:
M . fraasi (Jaekell910)
L. Trias
Shansisuchus shansisuchus Young 1964
L. Trias
S . heiyuekouensis Young 1964
L. Trias
L. Trias
Fenhosuchus cristatus Young 1964
Wangisuchus tze-yii Young 1964
L. Trias
U. ( ?)Trias Anisodonsaurw Romer 1966 nom. null. =
Anisodontosaurus Welles 1947 (lapsus calami)
Lossiemouth Beds, Scotland
Procolophon Zone, South Africa
Cynognathus Zone, South Africa
Bunter, Germany
Cynognathus Zone, South Africa
Cynognathus Zone, South Africa
Lystrosaurus Zone, South Africa
Lystrosaurus Beds, Sinkiang
Ehrmaying Series, China
Lystrosaurus Zone, South Africa
Manda Formation, Tanganyika
Manda Formation, Tanganyika
Zone V, Russia
Zone V, Russia
Zone V, Russia
Zone VI, Russia
Santa Maria Formation, Brazil
Santa Maria Formation, Brazil
Lystrosaurus Zone, South Africa
Upper Moenkopi Formation, Arizona
Cacheuta Beds, Argentina
Cacheuta Beds, Argentina
Cacheuta Beds, Argentina
Cacheuta Beds, Argentina
Zone V, Russia
Bunter, Germany
Ischigualasto Formation, Argentina
Zone VI or VII, Russia
Zone IV, Russia
Cacheuta Beds, Argentina
Lossiemouth Beds, Scotland
Runter, Germany
Ehrmaying Series, China
Ehrmaying Series, China
Ehrmaying Series, China
Ehrmaying Series, China
CLASSIFICATION OF THE PROTEROSUCHIA
129
Family names
Proterosuchidae Broom 1906b or von Huene 1908 ? (nom.transl. von Huene 1914
ex subordine Proterosuchia Broom 1906b, or nom. correct. von Huene 1914 ex
familia Proterosuchia von Huene 1908 nom. imperf. ?)
Erythrosuchidae Watson 1917
Chasmatosauridae Haughton 1924
Garjainiidae Ochev 1958
Vjushkoviidae von Huene 1960
Shansisuchidae Young 1964
Also:
Pelycosimiidae Abel 1919
Euparkeriidae von Huene 1920
Subfamily names
Proterosuchinae Broom 1906b or von Huene 1908 ? (nom. transl. Tatarinov 1961 ex
Proterosuchidae Broom 19066 or von Huene 1908 ? q.v. above)
Erythrosuchinae Watson 1917 (nom. transl. Tatarinov 1961 ex Erythrosuchidae
Watson 1917)
Chasmatosaurinae Haughton 1924 (norn. trawl. Kuhn 1966 ex Chasmatosauridae
Haughton 1924)
Shansisuchinae Young 1964 (nom. trawZ. Kuhn 1966 ex Shansisuchidae Young 1964)
Generic and specific names
These are given in Table 1. This list includes all named genera and species of Upper
Permian and Lower Triassic archosaurs and supposed archosaurs, including some of
uncertain age, together with Middle and Upper Triassic forms which have been
classified with them in any classification of 1945 or later. Where there is more than one
species of a genus the first-named is the type-species. The genera are arranged in
chronological order.
All questions relating to the genus Cuyosuchus are left aside for consideration in the
full account of that genus by Reig & Charig (in press). Incidentally, it may be noted
here too that the holotype of the type-species (Cuyosuchus huenk) was originally
described by Rusconi (195 1) as belonging to the brachyopid amphibian Chigutisaurus
tunuyanensis Rusconi 1948.
THE ‘PRIMITIVE TAXON’
Introduction
With few exceptions (see below), all the archosaur genera from the Upper Permian
and Lower Trias are usually placed together in a special subdivision of the order
Thecodontia. Indeed, the only recent classifications which do not recognize the
existence of this ‘primitive taxon’ are those of Kuhn (1946), von Huene (1962), Kuhn
(1965) and perhaps Krebs (1965). But the rank and name given to this group vary from
author to author.
One type of classification regards the ‘primitive taxon’ as a single family within the
130
A. J. CHARIG AND 0. A. REIG
order or suborder Pseudosuchia. This type includes the classifications of Romer (1945)
and Haughton & Brink (1954),both of which call the family Erythrosuchidae, and that
of Maleev in Rozhdestvenskii & Tatarinov (1964), which calls the family Proterosuchidae.
The second type ranks the ‘primitive taxon’ as a superfamily, still within the order
or suborder Pseudosuchia, and then divides it into two or more families. This type
includes the classifications of Camp (1945) and Hoffstetter in Piveteau (1955) (superfamily Proterosuchoidea, with families Proterosuchidae and Erythrosuchidae) ; von
Huene (1948, 1956) (‘family circle’ or ‘Familienkreis’ Pelycosimioidea, with families
as in Camp (1945); Kuhn (1961) (superfamily Proterosuchia ‘Broom 1911’ =
Pelycosimia=Proterosuchoidea, with families as in Camp (1945);Young (1964) (superfamily Proterosuchia, families as in Camp (1945) with addition of Shansisuchidae);
and Kuhn (1966) (superfamily Proterosuchoidea, with families Proterosuchidae-including the Erythrosuchidae of other authors-and Shansisuchidae). Kuhn (1961),
however, did suggest that the Proterosuchia might be a separate suborder. A slight
variation on this approach is that of Tatarinov (1961) who, though ranking the
‘primitive taxon’ as a superfamily (Proterosuchoidea), considers that it contains only
one family (Proterosuchidae) and then divides that into two subfamilies
(Proterosuchinae, Erythrosuchinae).
The third type of classification accords subordinal rank to the ‘primitive taxon’;
it is thus distinct from the other thecodont suborders Pseudosuchia” and Parasuchiat.
This type includes the classifications of Romer (1956) (suborder Proterosuchia =
Pelycosimia, containing only the one family Erythrosuchidae = Proterosuchidae) ;
presumably Watson (1957) (‘group’ Erythrosuchia, rank of taxon not stated explicitly
and subordinate taxa not mentioned); Kuhn (1960 as Romer, 1956); Reig (1961)
(suborder Proterosuchia, with families Proterosuchidae, Erythrosuchidae, Garjainiidae,
Vjushkoviidae); and Hughes (1963) and Romer (1966) (both having suborder
Proterosuchia, with families Chasmatosauridae ( =Proterosuchidae) and Erythrosuchidae).
As mentioned above, von Huene (1962) does not recognize the existence of the
‘primitivetaxon’. He simply includes the families Proterosuchidae and Erythrosuchidae
within the Pseudosuchia, with no especial connexion between them (see also below,
p. 147). Krebs (1965) does not commit himself but seems to incline towards a
similar view, suggesting that the Proterosuchia (Chasmatosauridae = Proterosuchidae ;
Erythrosuchidae) and Pseudosuchia have many characters in common which they do not
share with the Parasuchia-the bones of the limb girdles, both pectoral and pelvic,
being especially noteworthy in this connexion-and therefore casting doubts upon the
desirability of segregating them into different superfamilies. A more extreme example
of the non-recognition of a ‘primitivetaxon’ is in an earlier classificationof Kuhn (1946),
who placed the two families concerned in dzjGrent suborders of the Thecodontia-the
+The Pseudosuchia of most authors were regarded as two separate suborders by Reig (1961)
-Omithosuchia, Desmatosuchia-and by Romer (1966)-Pseudosuchia,
Aetosauria ; but further
discoveries which have afforded a better understanding of thecodont organization and evolution have
led Reig to change his mind on this point, and he is now more inclined to the generally accepted view
that the Pseudosuchia form a natural unit.
t The Parasuchia are called the Phytosauria by many authors, e.g. Hoffstetter in Piveteau (1955),
Romer (1966).
CLASSIFICATION OF T H E PROTEROSUCHIA
131
Proterosuchidae in the Pseudosuchia and the Erythrosuchidae in the Parasuchia ; the
Eosuchia were cited as another (and presumably the most primitive) suborder, and it
was suggested that the Proterosuchidae should perhaps be united with the Ornithosuchidae. No reasons were given for this arrangement, which was abandoned by its author
in subsequent classifications. Finally, in yet another classification expressed only in a
diagram, Kuhn (1965, fig. 8) listsfour families of the Thecodontia which, though not
united into any larger taxon, are shown by dotted lines as having a presumed common
origin ;these are the Proterosuchidae, Erythrosuchidae, Garjainiidae and Viushkoviidae
(Sic).
Ochev (1958) described the new Lower Triassic genus Garjainia and made it the
type of a new family, Garjainiidae. Von Huene (1960) likewise described the new Lower
Triassic genus Vjushkowiaand made it the type of another new family, Vjushkoviidae.
In neither case was there any suggestion of a particular connexion with other Lower
Triassic thecodont families.
Hughes’ survey (1963) gives the wrong impression on certain points in the classifications adopted by earlier workers (e.g. Williston, Tatarinov).
The two Lower Triassic genera usually excluded from the ‘primitive taxon’ are
Mesorhinosuchus and Euparkeria (the latter including Bromiella); and it now seems
likely that two other newly described Lower Triassic genera, Fenhosuchus and
Wangisuchus, might also be excluded. Conversely, all writers save one have restricted
the ‘primitive taxon’ to Lower Triassic genera (and the even older Archosaurus); the
exception is Hughes (1963), who has assigned certain Middle and Upper Triassic
forms to the Proterosuchia (see below). In addition, Tatarinov (1961) has referred one
un-named fragment from the Middle Trias to this basal group.
Characters
Most of the genera in question clearly fall into two distinct-indeed, very differentcategories, typified respectively by Chasmatosaurusand Erythrosuchus (see below). But
there is an essential connexion between those two categories, reflected in every explicit
modern classification (except that of von Huene, 1962); for, as far as can be determined
from material which is often sadly incomplete, the members of both groups do have
certain primitive characters in common:
(1) They were undoubtedly quadrupedal, despite the typical archosaurian limb disparity, with hindlimbs longer than the fore-limbs (see Charig, 1965,1966). The propodials are longer than the epipodials,
and were more or less horizontal in position; thus the normal stance was of the sprawling type.
(2) A postfrontal bone, a very small parietal (pineal) foramen and a median postparietal bone (interparietal or dermal supraoccipital), all of which are absent in nearly all other archosaurs, are present
in most of these forms. (A postfrontal, however, is present also in many later thecodonts and
in rhamphorhynchoid pterosaurs.)
(3) The prefrontal is relatively large, and projects laterally like a cornice over the side of the skull.
(4) The parietal is short and broad.
(5) The external naris is of moderate size, lateral and almost terminal in position, separated from the
antorbital fenestra by a considerable width of bone. Part of this wide expanse is formed by the premaxilla,
which extends backwards and upwards to exclude the maxilla from the border of the external naris; it
does this also in certain later groups among the archosaurs, e.g. Ornithischia.
( 6 ) The antorbital fenestra is of moderate size; and there may be a second fenestra in the side of the
snout, even further forward, between the premaxilla, the maxilla, and the nasal.
(7) The upper temporal fenestra is directed dorsally; it is hardly seen in a lateral view of the skull,
or not seen at all.
( 8 ) The squamosal and quadratojugal do not project forwards into the lower temporal fenestra
A. J. CHARIG AND 0. A. REIG
132
en
A
FIGURE
1. Reconstruction of skull of Chasmutosaurus uunhoepmi Haughton (after Broili &
Schroder 1934).
A,From left side; B,from above; C,from below (without lower jaw).
All drawings approximately 4 natural size.
The observations of Walker (see pp. 152 et seq.) suggest that Broili&Schrijder’s reconstructions
are inaccurate in various respects. This is mainly because, when they were made, it was not
realized that the skull had been distorted and damaged by crushing. For the reasons stated in
the text (p. 154), however, we have made no attempt to modify Broili & Schroder’s drawings in
the light of Walker’s comments.
CLASSIFICATION OF T H E PROTEROSUCHIA
133
(contrast pseudosuchians and saurischians, where these bones produce at least a slight sinuous convexity
of the posterior border of that fenestra and, at most, a pronounced V-shaped contour).
(9) The squamosal does not project back beyond the head of the quadrate.
(10) The otic notch is not much developed.
(11) The jaw articulation may lie well behind the level of the occipital condyle.
(12) There is a long, narrow median vacuity between the pterygoids, extending forwards between the
vorners and between the hinder ends of the premaxillae.
(13) The maxillae do not meet in the mid-line; there is not the least indication of the formation of an
incipient secondary palate.
(14) The epipterygoid is well developed.
(1 5) The marginal teeth are generally more or less isodont.
(16) The insertion of the marginal teeth, thecodont in later archosaurs, is only subthecodont (perhaps
even acrodont in some cases).
(1 7) Small palatal teeth may be present on the pterygoid, and less commonly on the vomer.
(18) The atlantal centrum and axial intercentrum are not suturally united with the axis to form an
‘odontoid’.
(19) Intercentra, absent in the region between the axis and the tail of nearly all other archosaurs, are
generally present in the neck and occasionally in the dorsal region too.
(20) The clavicle and interclavicle are well developed.
(21) The humerus is short and stout; the two ends are greatly expanded, the planes of expansion being
strongly inclined one to the other to give a ‘tetrahedral’ form to the bone as a whole.
(22) The ulna bears no olecranon.
(23) The two halves of the pelvis are relatively far apart one from the other.
(24) The triradiate development of the pelvis is expressed only weakly. The anterior process of the
iliac blade is either absent altogether or very little developed; the posterior process, however, is fairly
long and powerful. The pubis and ischium are comparatively short, and the ischium does not taper
distally into a narrow rod.
(25) The proximal end of the femur bears an internal trochanter and an intertrochanteric fossa; the
typical archosaurian development of a fourth trochanter, lower down the shaft, is either absent altogether
or developed very weakly. The form of the femur agrees well with the suggestion that it was held in an
almost horizontal, sprawling position.
(26) The proximal tarsal elements, astragalus and calcaneum, are quite simple, being without the
various specializations found in all other Triassic archosaurs ; in particular, the calcaneum does not bear
a posteriorly directed tuber, although it has a more or less well developed lateral process. The functional
ankle-joint was tarsal/metatarsal and, in at least some cases, mesotarsal as well.
(27) There is no dermal armour of any sort.*
Few of these characters are present in every genus. But this does not mean that those
several other characters which are absent in some genera should not be included in the
diagnosis of the ‘primitive taxon’ as a whole. T h e ‘primitive taxon’, like most taxonomic
aggregates, is a concept of the type known as polythetic (see discussion in Sokal &
Sneath, 1963: 14); the polytypic arrangement as defined by Beckner (1959: 22) was
re-named ‘polythetic’ by Sneath (1962). A class is monothetic if all the characters used in
defining that class (and forming a unique set) are shared by all its members; it is polythetic if some (but not necessarily all) the characters so used are not shared by all its
members; it is fully polythetic only if there is no character used in its definition which
is common to all the members.
I t is also true that some of the characters used above in defining the ‘primitive taxon’
are found also in later forms. But this indicates only that certain characters evolved in
mosaic fashion during the early evolution of the archosaurs.
* One small bone found with the type-material of Erythrosuchus ufricanus was believed by Broom to be
a dermal ossification of that animal. H e wrote (1905) ‘One small dermal ossification has been found, but
it shows no evidence of pitting or other ornamentation.’ He referred to it in similar terms in his more
complete account of Erythrosuchus (1906~).
Watson (1917) included ‘Feeble dorsal armour’ as a diagnostic
character of his new family Erythrosuchidae, presumably basing this upon Broom’s report. But, with one
exception, all other works dealing with Erythrosuchus and the Erythrosuchidae have ignored this supposed
dermal ossification, either stating specifically that there was no armour (Romer 1956; Ewer 1965) or
making no mention of the subject. The sole exception is by Kuhn (1961), who lists ‘starke Panzerung
( I)’as a character of the Erythrosuchidae; the basis for this assertion is unknown to the present authors.
134
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J. CHARIG AND 0.A. REIG
Further consideration of the philosophical foundation of our taxonomic treatment
of the early archosaurs is beyond the scope of the present work and has been developed
separately in another publication by Reig (1970). Meanwhile, all things considered,
it seems both logical and practical to regard the genera in question as constituting a
single taxonomic unit; in particular, this point of view seems not inconsistent with the
little that is known at present of the evolutionary background.
Another character which has sometimes been regarded as typical of the ‘primitive
taxon’ (e.g., by von Huene, 1948 and 1956: 441) is the lack of a lateral fenestra in the
lower jaw. This fenestra, virtually peculiar to the archosaurs (and to the pelycosaurs
Ophiacodon and Varanops; see Romer & Price 1940: 229, 273), is found in more
advanced thecodonts. But, while it is certainly absent in Chasmatosaurus,it is now known
to be present in some or all of the other genera. Broom (1946) described it in
Elaphrosuchus,Ochev (1958) in Garjainia, von Huene (1960) in Vjushkooiaand Young
(1964) in Shansisuchus.As for Erythrosuchusitself, von Huene (1911, pl. 11) reconstructed its mandible without a lateral fenestra, and his reconstruction has been generally
accepted; but Tatarinov (1961) points out that in only one specimen of E. africanus
(Brit. Mus. (Nat. Hist.) Palaeont. Dept., R. 3592) are the lower jaws known, that in that
specimen the region which would include the lateral fenestra-if any-is missing on
both sides, and that the form of the angular and surangular bones suggests the presence
rather than the absence of a lateral fenestra. A first-hand examination of the specimen
by one of us (A.J.C.) confirms Tatarinov’s observation; indeed, we believe that the
fragment which vonHuene described as the left angular was in fact wrongly orientated
by him (1911, pl. l), with the front end at the back and oice oersa, and that part of the
margin of the lateral fenestra is still preserved. The absence or presence of a lateral
fenestra, therefore, cannot be used to distinguish members of the ‘primitivetaxon’ from
later thecodonts. On the other hand, it might be useful in distinguishing
Chasmatosaurus-likeforms from Erythrosuchus-like forms (see below, p. 142).
Rank and nomenclature
Roiner (1956: 593) segregated these forms as members of a distinct suborder on the
grounds that ‘They are notably more primitive than other thecodonts’, and preferred
the name Proterosuchia to Pelycosimia because ‘this [latter] term (seldom used) has
unfortunate connotations as to relationship’. We support his assignment of subordinal
rank to the ‘primitive taxon’, consisting of those genera which possess the characters
listed above ;and we too prefer the name Proterosuchia for that suborder, our objections
to Pelycosimia being the same as Romer’s and our objections to Erythrosuchia being
on the grounds that the name is based upon a late and rather specialized genus. Thus,
in the classification proposed here, the order Thecodontia would consist of the three
suborders Proterosuchia, Pseudosuchia and Parasuchia.
Composition
Lower Triassic genera to be excluded
Mesorhinosuchus.The only Lower Triassic thecodont which has never been classified
as a proterosuchian is Mesorhinosuchus (originally described as Mesorhinus). This has
always been regarded as the only Lower Triassic phytosaur, the several other genera
CLASSIFICATION OF THE PROTEROSUCHIA
135
in the suborder Parasuchia apparently being restricted to the upper part of the Upper
Trias. Gregory (1962) has recently cast doubts upon the so-called evidence afforded by
the unique specimen of the genus. He believes that the specimen cannot be regarded as a
phytosaur with certainty and that the documentation concerning its geographical and
stratigraphical position is quite unreliable. He therefore writes that ‘So many doubts
exist concerning both its morphological character, and (I believe) its age and provenance,
that no useful conclusions may be drawn from the specimen.’ If Mesorhinosuchus be
ignored the known stratigraphical range of the Parasuchia is reduced considerably,
and the hitherto puzzling fact that the suborder has not been found elsewhere in beds of
Lower or Middle Triassic age is at once explained.
Eupurkeriu. This is rather different from the other early archosaurs and has generally
been classified as a pseudosuchiansensu stricto rather than a proterosuchian; it has often
a ‘typical’ primitive
been regarded as a good example-indeed, the only example-f
pseudosuchian, not specialised in any direction, which could well be ancestral
to all later archosaurs. Hughes, however (1963) is impressed by its resemblances to
Erythrosuchus in some respects and accordingly classifies it as an erythrosuchid,
although in other respects (e.g., the presence of palatal teeth) it resembles Chmmutosuurus rather than Erythrosuchus. Ewer (1965) has just completed a detailed revision of
Eupurkeriu, using hitherto undescribed material as well as that already described, and,
in the text, her attitude towards its classification is completely equivocal ; she writes
that ‘To argue at length as to whether Euparkeriu should be classified amongst the
primitive forms with which it shares many characteristics, or amongst the forms that
have proceeded further along the same type of evolutionary pathway, does not seem a
very profitable occupation at the present time’. In the abstract, however, she writes:
‘It is concluded that Eupurkeriu, although a progressive form, is closely related to the
latter family [Erythrosuchidae] with which it may be convenient, for the time being, to
classify it.’ Our own feeling is that the characters of Eupurkeriu justify the conventional
view that it is a pseudosuchian rather than a proterosuchian. Particularly noteworthy
in this connexion are the large antorbital fenestra lying in a basin-like depression;
the concavity in the back of the quadrate (which may be regarded as a fully developed
otic notch and which also produces a convexity in the posterior border of the lower
temporal fenestra so that the squamosal and quadratojugal project forwards a little
into that fenestra); the position of the jaw articulation, only a very short distance behind
the occiput; the slender elongated limb-bones and the probability that the animal was
occasionally bipedal ;the ‘semi-crocodiloid’ tarsus; and, perhaps most important of all,
the presence of scutes. There may also have been very slight heterodonty of the
marginal dentition. Eupurkeriu is nevertheless a primitive pseudosuchian, with such
atypical characters as a separate postparietal, an interpterygoid vacuity, palatal teeth,
and intercentra between all the presacral vertebrae ;it might also be mentioned that the
external naris is subterminal and lies far forward of the antorbital fenestra, that the
coracoid is large and that the pubis and ischium are rather short. Even if this genus were
regarded as a proterosuchian, its characters would nevertheless preclude it from
membership of the Erythrosuchidae as at present defined (see below, pp. 141-142). Of
particular significance in this connexion are the small size, the presence of palatal teeth,
136
A. J. CHARIG AND 0.A. REIG
and the certain presence of intercentra throughout the vertebral column, all of which
suggest that-in these characters at least-Eupurkeriu is more primitive, not more
progressive, than the Erythrosuchidae.
BrownielZu. This is represented by a single individual (originally thought by Broom to
be parts of two) found together with Eupurkeriu.Haughton( 1922) believed that the specimen was simply a rather large Eupurkeriu cupensis, perhaps showing sexual dimorphism ;
he then (quite incorrectly, according to accepted modern practice) designated an
isolated femur from the same locality as ‘the type’ of BrownieZlu ufricunu, and it is this
femur which is cited as the type by Haughton& Brink (1954: 30). Hoffstetter (1955 :670)
on the other hand, suggested that Browniellu might be a small erythrosuchid. Ewer
(1965) has re-examined the original material, developing it further, and is entirely in
agreement with Haughton’s conclusion that Broom’s type of Browniellu ufricunu is a
large Eupurkeriu cupensis. Browniellu may therefore be regarded as a subjective junior
synonym of Eupurkeriu.
Wungisuchus.Young (1964) regards his newly described genus Wungisuchusas another
euparkeriid, although much larger and differing in several important respects from
Eupurkeriu itself. In many characters it seems too advanced to be a proterosuchian;
for example, it has three sacral vertebrae (more than most pseudosuchians), slender
limb-bones, tibia longer than femur (though radius much shorter than humerus),
calcaneum with a tuber, and various dermal scutes. However, it must be borne in mind
that the material referred to this genus by Young represents a number of individuals,
of which he writes: ‘The above enumerated specimens fit in size and structure for a
single species according to the study of the present author. But the possibility can not
be entirely excluded that some ones may belong to some other form or forms not yet
recognized.’ If it be assumed that this Wungisuchus material is not merely a random
collectionof heterogeneousspecimens,but actuallyrepresents a valid genus, Young must
surely be correct in regarding the genus as a pseudosuchian rather than as a proterosuchian; there seem to be no grounds whatever for placing it in the Proterosuchia.
Fmhosuchus. In the same publication Young (1964) describes another new genus of
thecodont as Fenhosuchus, referring it provisionally to the Rauisuchidae (characteristically a Middle Triassic family). This reference appears to be based upon certain
similarities between Fenhosuchus and the supposed rauisuchid Stagonosuchus in the
form of the vertebrae, proximal end of the humerus, pubis and ischium; there are also
resemblances between the various types of scute found in Fenhosuchus and those of
Ruuisuchus itself, which are rounded laterally and quite different from the transversely
elongate, rectangular scutes found in such forms as Aetosuurus and Stagonolepis. The
astragalus is described as ‘prosauropod-like’, and Young also suggests a close relationship with the parasuchians (phytosaurs). The Fenhosuchus material, just like the
Wungisuchus material, represents a number of very incomplete individuals; many of
these, according to Young, are abnormally developed or pathologically deformed, and
even Young himself casts doubts upon their conspecificity. It is therefore reasonable to
consider the genus as incertae sedis and yet to reject the possibility of its being a
proterosuchian.
CLASSIFICATION OF THE PROTEROSUCHIA
137
Chigutisaurus and Icanosaurus. Romer (1966: 368) lists these two South American
brachyopid amphibian genera as members of the suborder Proterosuchia, ?Chigutisaurus
in the family Chasmatosauridae and ?Icunosaurus in the Erythrosuchidae. This is
evidently an error; the same work not only lists both genera also in their correct
systematic positions among the Amphibia (p. 363) but Cuyosuchus, the thecodont of
which the post-cranial skeleton was originally believed to belong to Chigutisuurus, is
itself listed as an erythrosuchid. Indeed, ?Icanosaurus is placed in the synonymy of
Cuyosuchus.
Genera of uncertain afinities and/or age
Ocoyuntaia and Seemannia. These two generic names were each erected upon a single
isolated tooth, of which little can be said beyond the fact that they are typically
archosaurian (and hence, since they are from Lower Triassic beds, probably proterosuchian). Ocoyuntaia Rusconi 1947u from the Cacheuta Beds of Argentina is one,
Seemannia von Huene 1958 from the Bunter of Germany is the other. Von Huene
originally stated that the Lower Triassic age of Seemannia indicated that it must be a
pseudosuchian of the family Proterosuchidae, but later (1962) he placed it in a list of
incompletely known genera not yet assigned to families. Rusconi, however, did in fact
classify Ocoyuntaia as a parasuchian; his opinion appears to be unsupported by any
evidence and is unlikely to be correct if, as seems probable, the Parasuchia are indeed
restricted to the upper part of the Upper Trias (see p. 135). Romer (1966: 368) lists
?Ocoyuntaia as a thecodont incertae sedis and ?Seemannia in the Erythrosuchidae.
I t seems to us that both generic names, together with their respective specific names,
are based upon such inadequate and indeterminate material that they can only be
regarded as nomina dubia. They should therefore be excluded from any definite list of
proterosuchian genera.
Arizonasaurus and Anisodontosaurus. Two further genera which might be Lower
Triassic thecodonts are Arizonasaurus and Anisodontosaurusfrom the Upper Moenkopi
Formation of northern Arizona. While the Upper Moenkopi is generally regarded as
being of probable Lower Triassic age, the possibility of a Middle Triassic age must also
be borne in mind (see Welles, 1947; Colbert & Gregory, 1957). T h e remains of both
genera are so few and fragmentary that their systematic position cannot be determined;
it is not even certain that Anisodontosaurusis a thecodont. Thus, in 1956 Romer (p. 597)
regarded both Arizonasaurus and ?Anisodontosaurus as pseudosuchians incertae sedis
of Middle Triassic age; but in 1966 the same author lists ?Arizonasaurus in the
Erythrosuchidae (p. 368), Anisodonsaurus (sic-presumably a lapsus calumi) as an
Upper Triassic thecodont incertae sedis (p. 368), and ?Anisodontosuurus as a Lower
Triassic trilophosaurid proterosaur (p. 371). These genera have been mentioned only
for the sake of completeness and will not be considered further in the present work.
Later genera which hare been wrongly included
Hughes (1963) is the first and almost only author to have referred to the Proterosuchia
certain archosaur genera from the Middle and Upper Trias; more specifically, he has
assigned them all to the family Erythrosuchidae. Four genera are concerned: Rauisuchus,
Hoplitosaurus von Huene 1942a non Lucas 1902 (correctly Hoplitosuchus von Huene
138
A. J. CHARIG AND 0. A. REIG
1942a), Saurosuchus, and Dusygnathus Huxley 1877 non Macleay 1819 (correctly
Dasygnathoides Kuhn 1961). Romer (1966: 368) follows him in this with regard to
?Rauisuchus, ?Hoplitosuchus and PSaurosuchus. We cannot agree that any of the forms
mentioned are proterosuchians and shall consider them individually below. We shall
also consider the case of the genus Typothorax, otherwise known only from the Upper
Trias, to which Rusconi (19474 provisionally referred a new Lower Triassic species.
Meanwhile two other cases, apparently similar, may be discounted immediately.
Haughton & Brink (1954) listed the Middle Triassic Stagonosuchus as a genus of the
family Erythrosuchidae; but since the diagnosis of the genus begins with the words
‘A large Stagonolepid’,it seems likely that its inclusion as an erythrosuchid was a Zapsus
calami. Most authors now believe that Stagonosuchus may be placed with other Middle
Triassic pseudosuchians in the family Prestosuchidae (Charig, 1956 ;Romer, 1966 : 368)
or Rauisuchidae (Reig, 1961; Krebs, 1965). Von Huene (1962), like Hughes a year
later, places the Upper Triassic ‘Dasygnuthus’ in the Erythrosuchidae; but in that work
von Huene does not recognize a ‘primitive taxon’ and considers the Erythrosuchidae
to be just another family of pseudosuchians distinct from the Proterosuchidae.
Rauisuchus. This genus, from the Santa Maria Formation (Middle Trias of Brazil), is
tentatively assigned to the Erythrosuchidae because, according to Hughes (1963), its
vertebrae and pelvis resemble those of Erythrosuchus. But the incomplete material
shows none of the diagnostic characters of the Proterosuchia; and, more particularly,
Rauisuchus possesses scutes of several different sorts.
Hoplitosuchus. An analysis of Hughes’ arguments (1963) for regarding Hoplitosuchus
(also from the Santa Maria Formation) as a proterosuchian not far removed from
Erythrosuchus shows that they are actually based upon one solitary fact-the presence of
a large trochanter on the femur ‘which can only be an internal trochanter, suggesting
comparison with Erythrosuchus.’ But the figures show quite clearly that the trochanter
is actually a fourth trochanter, exactly as described by von Huene; this structure is
characteristic of such typical Middle Triassic pseudosuchians as Mandasuchus. As for
its size, the relative size of a trochanter is manifestly a function of the absolute size of the
animal. In any case, it is evident from the illustrations that the Hoplitosuchus material
is either inadequately prepared or grossly malformed (i.e., the animal must have been
suffering from some pathological condition such as pachyostosis).
Saurosuchus. Hughes’ list (1963) includes ‘?Saurosuchus’ from the Ischigualasto
Formation (upper Middle Trias of Argentina) as a member of the Erythrosuchidae.
In his text, however, he seems to change his mind twice. After attempting to justify
this inclusion (not stated here explicitly, but clearly implied), he ‘automatically’
excludes the genus from the Proterosuchia on different grounds, and is then sufficiently
impressed by yet another supposed character to decide to place it ‘on the border-line
between the Proterosuchia and Pseudosuchia.’
As might be expected, his arguments for these various conflicting points of view
are confused and a little difficult to follow. Careful study of his text, however, reveals
that the essence of his arguments for regarding Saurosuchus as an erythrosuchid are
the similarity of its skull to that of Rauisuchus and the similarity of its ilium to the ilia
of Rauisuchus and Stagonosuchus; somewhat paradoxically, it is the similarity of its
CLASSIFICATION OF T H E PROTEROSUCHIA
139
femur (illustrated by Reig, 1961, fig. 10) to that of Erythrosuchus itself which eventually
leads him to decide on a border-line position for Saurosuchus between the Proterosuchia
and Pseudosuchia. On the other hand, he believes that ‘the possession o f . . . elongate
ischia automatically excludes Saurosuchus from the Proterosuchia’, and he then notes
that ‘The ischia of Rauisuchus are not known but should they prove to be similar to
those of Saurosuchus then it too must be excluded from the Proterosuchia.’
Hughes’ arguments for the inclusion of Saurosuchus in the Erythrosuchidae are
easily demolished. The alleged similarities of Saurosuchus to Rauisuchus and Stagonosuchus carry little weight in this connexion if it be borne in mind that, although Hughes
considers that Rauisuchus may be an erythrosuchid, we do not (see above, p. 138); that
not even Hughes himself considers Stagonosuchus to be an erythrosuchid ; and that,
in any case, the structure of the ilium is remarkably uniform throughout most of the
early archosaurs. T h e supposed characters of the femur of Saurosuchus which finally
led Hughes to retain a diminished affinity between that genus and Erythrosuchus
are the dorsad turning of the articular head, the presence of an intertrochanteric fossa
(which, so he presumes, indicates the presence of an internal trochanter), the presence
of a ‘greater trochanter’ about one-third of the way down the shaft on the lateral border,
and the inferred laterally projecting position of the femur as a whole. But it is clear from
Reig’s figure that the articular head of the femur in question has been reconstructed;
further, the specimen is in any case referred only provisionally to the genus Saurosuchus.
We are obliged to consider Saurosuchus as a pseudosuchian rather than as a proterosuchian. Further evidence of this is afforded by undescribed material of the genus:
a crocodiloid tarsus, similar to the tarsi of the undoubted pseudosuchians Prestosuchus,
Mandasuchus and Ticinosuchus.
Dasygnathoides. As far as Dasygnathoides is concerned, Walker has made a careful
study of the fragmentary maxilla from the Lossiemouth Beds (Upper Trias of Elgin,
Scotland) originally described as Dasygnathus and of a pterygoid referred to the same
individual. In 1961 he suggested that this genus was allied to Erythrosuchus; but he
later changed his mind, and now believes (1964: 64-66) that the bones in question (and
certain others associated with them) are, apart from their larger size, indistinguishable
from the corresponding elements of Ornithosuchus, which he now places in the
Saurischia as a primitive carnosaur. Dasygnathoides Kuhn 1961 may therefore be
regarded as a subjective junior synonym of Ornithosuchus Newton 1894.
?Typothorax. The new species ?Typothorax (sic) punctulatus Rusconi 19473, from the
Lower Trias (Cacheuta Beds of Argentina), has in this case been referred by its author
to a genus of armoured thecodont which is otherwise confined to the Upper Trias. T h e
material is very scanty, consisting only of two osteoderms found in association with coprolites. The scutes probably do belong to an armoured thecodont ; Reig (1961) considers
that a close relationship with Typothorax or any other member of the StagonolepididaeW
* This is the correct family name (Lydekker 1887), although the form ‘Stagonolepidae’ (linguistically
incorrect and attributed to von Huene 1908 as an original family name) has been in fairly frequent use for
the last 60 years. It is now generally accepted (see Walker, 1961) that Aetosaurus and Stagonolepis belong
to the same family; Walker, however, not knowing of Lydekker’s authorship of the name Stagonolepididae
in July 1887 took as the senior synonym Aetosauridae Baur September 1887 (nom. correct. Cope 1889pro
Aethosauridae Raur 1887 nom. imperf.; not, as Walker believed, nom. correct. Emerson & Loomis 1904).
140
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J. CHARIG AND 0.A. REIG
is very unlikely, but suggests a comparison with Stegomosuchus from the Upper Trias
of North America. As mentioned above (p. 133), dermal armour is unknown in the
Proterosuchia.
Conclusions
T h e following conclusions seem reasonable. Most Lower Triassic archosaurs of
certain age and affinities, together with the Upper Permian Archosaurus but with no
later forms, may be referred to the one ‘primitive’ suborder Proterosuchia; the only
exceptions are Mesorhinosuchus, Euparkeria (which includes Browniella), Wangisuchus
and Fenhosuchus. The diagnostic characters of the Proterosuchia have been listed above
(pp. 131-133). In certain cases the remains are so scanty as to make the reference uncertain, but at least there are no contrary indications.
A complete list of genera in the Proterosuchia, assigned to their respective families
and with nomina dubia listed separately, is given on p. 165. T h e only well known
genera are Chasmatosaurus, Erythrosuchus and Shansisuchus, and even of those our
knowledge is far from complete.
SUBORDINATE TAXA
Introduction
Romer (1945: 597; 1956: 593), Haughton & Brink (1954), Kuhn (1960) and Maleev
(1964) placed all the proterosuchians together in one family; Watson (1957) simply
placed them all in one ‘group’, Erythrosuchia, without mention of subordinate taxa.
The works cited, however, are of a general nature, giving no indication of subfamily
groupings (except, occasionally, in Romer, 1956); therefore this lack of subdivision
does not necessarily suggest that the authors responsible believe the proterosuchians
to be a homogeneous group. In any case, none of those authors (except Brink and
Haughton) has ever published any detailed studies of the reptiles in question.
A rather peculiar classification is that of Kuhn (1966: 71-72) who places all the
proterosuchians except Shansisuchus in the one family Proterosuchidae, considering
Shansisuchus to be the sole genus of the Shansisuchidae (see following paragraph).
T h e Proterosuchidae, however, he divides into at least three subfamiliesChasmatosaurinae, Proterosuchinae and Erythrosuchinae.
All other modern classifications, including those of authors who have made intensive
studies of Proterosuchia (von Huene, Tatarinov, Hughes, Young), recognize a
distinction between Chasmatosaurus-like forms and Erythrosuchus-like forms ; and all,
save one, group them into two families accordingly. The solitary exception is Tatarinov
(1961)) who considers that all the Proterosuchia are sufficiently alike to be placed in
one family, which should then be divided into two subfamilies. Young (1964) erected a
third family to include only his new genus Shansisuchus.
Characters
T h e two groups may be distinguished by a suite of contrasting characters. Although
not every one of these characters is universally applicable, together they provide
CLASSIFICATION OF THE PROTEROSUCHIA
141
convenient diagnoses. They are summarized in Table 2, in which all comparisons are
relative to absolute size.
Table 2. Comparison between Chasmatosaurus-like forms and Erythrosuchus-like forms
Chasmatosaurus-like forms
Erythrosuchus-like forms
GENERAL
size
general build
medium to large
slender, crocodile-like
large to very large
massive, with short thick limbbones; have been likened to
hippopotamus
SKULL
absolute size
relative size
shape
frontal
prefrontal
postparietal
premaxilla
medium to large (length 18-46 cm)
average
low
anterior and posterior widths more
or less equal
narrow
projecting a little upwards
large to enormous (length 43-96 cm)
disproportionately large
high, with long narrow face
much wider behind, narrower in
front
broader
projecting backwards as a conical
Peg
projecting forwards beyond lower not projecting forwards, more or
jaw and curving downwards at tip
less straight
absent
present
notch in lower border of
skull in lateral view,
between premaxilla and
maxilla
lateral and almost terminal
external naris
similar, but more dorsal than
ventral
antorbital fenestra(e)
sometimes two
one
more or less circular
orbit
more or less elongated vertically,
inclined slightly backwards
paroccipital process
comparatively slender, not
distally expanded in the vertical
expanded distally, slanting
plane, backward slant a little less
diagonally backwards
pronounced
plane of occiput
facing obliquely upwards and back- almost vertical
wards
quadrate
generally long, slanting obliquely shorter, almost vertical
downwards and backwards
far behind occipital condyle
position of jaw
variable, from far behind occipital
articulation
condyle to almost level with it
lateral fenestra in lower absent or small
always present, usually large
jaw
smaller and more numerous
marginal dentition
larger and fewer
p m 7-8.
~ XYS 13-27
pmx 5. mx 9-15
d18-25
d13-16
more irregular in size
regularly isodont
insertion of marginal
subthecodont, possibly acrodont ?
always subthecodont
teeth
palatal dentition
present
absent
(
(
)’
VERTEBRAL COLUMN
neck
dorsal region
tail
I0
long, with elongated cervical
vertebrae
intercentra occasionally present
long
short, with length of each cervical
centrum far less than its diameter
intercentra never present
short
142
A. J. CHARIG AND 0. A. REIG
Table 2 (continued)
Chasmutosaurus-like forms
GIRDLES AND LIMBS
short and broad
scapula
fairly large
coracoid
strongly developed
deltopectoral crest of
humerus
distance apart of two relatively far
halves of pelvis
anterior process of iliac absent altogether
blade
posterior process of iliac fairly long
blade
well developed
lateral process on
calcaneum
present as a free element
central tarsal
distal tarsals
OCCURRENCE
first known occurrence
greatest abundance
last known occurrence
4 (I-Iv)
Erythtosuchus-like forms
longer and narrower
smaller
even more strongly developed,
extending even further down the
shaft
not quite so far
incipient
a little longer
less well developed
not present as a free element
(probably incorporated into
astragalus)
2 (111-IV)
uppermost Permian (Archosaurus base of the Trias (Gajainia prima
rossicus in the Russian Zone IV)
in the Russian Zone V)
base of the Trias (Russian Zone V, upper part of Lower Trias (Russian
Lystrosmrus zone)
Zone VI, Cynognathus zone)
near top of Lower Trias (Chasmuto- near top of Lower Trias (e.g.
sauws ultimus in the Ehrmaying
Shansisuchus shansisuchus in the
Series of China)
Ehrmaying Series of China)
In this connexion it is interesting to note Haughton’s original definition of the family
Chasmatosauridae (1924) : ‘Thecodonts with elongated snout, small antorbital vacuity,
large lateral temporal vacuity, no pineal foramen, and a few pterygoidal teeth.’
At least some of the Erythrosuchw-like forms are remarkable in that they possessed
tricephalous ribs in the anterior dorsal region, each of which was attached to three
articular facets on the corresponding vertebra. Tatarinov (1961) however, claims that
this character was also present in Chusmatosaurus and in Chasmatosuchus. The matter
is considered more fully below (pp. 155-157).
One of these differences between the groups, seemingly unnoticed until now, might
well prove to be a useful diagnostic character. There is no lateral fenestra in the lower
jaw of Chasmatosuurus; but a large fenestra is certainly present in the Erythrosuchus-like
forms Vjwhkovia and Shanrisuchus, and its presence may be inferred in Erythrosuchus
itself with a high degree of probability (see above, p. 134). An intermediate condition,
with a small lateral fenestra, is found in Elaphrosuchus (in most other respects like
Chasmutosaurus) and in Garjuinia (the earliest of the Erythrosuchus-like forms).
Rank and nomenclature
Although the distinction between Chasmatosaurus-like forms and Erythrosuchus-like
forms is generally recognized, there are differences of opinion on other matters. One
of these concerns the rank of the taxa in which these two groups are placed (and now, in
CLASSIFICATION O F T H E PROTEROSUCHIA
143
addition, the status of Young’s new family Shansisuchidae). Another concerns the
correct name of the taxon created for Chasmatosaurus and its allies.
Rank of subordinate taxa
Of the systems of classification which recognize the distinction between the
Chasmatosaurus-like group and the Erythrosuchus-like group, all save two regard those
two groups as families. As mentioned above, however, Tatarinov (1961 :129)thinks that
both groups should be placed together in one family (name unspecified) but segregated
into separate subfamilies (Proterosuchinae and Erythrosuchinae). He attempts to
justify his placing of both groups in one family by citing a number of similarities
between them :
(1) The nature of the insertion of the teeth. (This, Tatarinov claims, is not acrodont in the
Proterosuchinae, but thecodont in both groups; the teeth are set in well formed alveoli, and only their
intimate connexion with the walls of the alveoli has led to the prevalance of the opinion that proterosuchids
have acrodont teeth.) But thecodonty is common to all other archosaurs, and therefore its presence in
both these groups as well would be without special significance.
(2) The degree of downward bending of the premaxilla. But the premaxilla is not bent downwards
in many proterosuchians, and is bent down in some later archosaurs, e.g. the Upper Triassic Heterodontosau~usCrompton & Charig 1962.
(3) The metakinetic skull, and the movable articulation of the quadrate with the squamosal.
(4) The retention of a parietal foramen (in most proterosuchians).
(5) T h e base of the skull (mentioned as being rather similar in Chn~matosuchusand ‘ E i y t h ~ o s u c h ’ ,
i.e. Vjushkooia).
(6) The retention of small intercentra between the vertebrae.
(7) The tricephalous anterior dorsal ribs. But these are not known in all, or even most,
proterosuchians.
Thus numbers 1, 2 and 7 may be discounted. Numbers 4 and 6 are included in our
own list (pp. 131-133) of the characters found in all, or nearly all, proterosuchians.
On the other hand, Tatarinov justifies his segregation of the two groups into separate
subfamilies by listing several differences between them, all (except the first) based
entirely on skull characters. These may be represented most clearly in tabular
form:
Table 3
Proterosuchinae
(1) size
(2) skull shape
(3) premaxilla
(4) downward bend of
premaxilla
(5) premaxillary teeth
(6) palatal teeth
(7) orbit
(8) metakinetism
comparatively small (skull up
to 40 cm long)
very low
long
distinct
up to eight
retained
round
strongly pronounced
Erythrosuchinae
very large (skull up to 100 cm long)
comparatively high, with elongated and
very narrow facial portion
shortened alveolar edge
slight
five
lost
elongated dorso-ventrally
less pronounced (because of the growth of
the upper edge of the prootic along the
ventral surface of the skull roof)
All except number 8 are included in our own more comprehensive list (pp. 141-142) of
the characters distinguishing Chasmatosauw-like forms from Erythrosuchus-likeforms.
144
A. J. CHARIG AND 0.A. REIG
Further peculiarities of the Erythrosuchinae listed by Tatarinov include a deep notch
between premaxilla and maxilla (on our list), an elongated prefrontal with convex
outer border which almost excludes the frontal from the margin of the orbit, and a
massive skull base which bears a pair of horizontal ridges.
The other classification which ranks Chasmatosaurus-like forms and Erythrosuchuslike forms as two subfamilies of one family (making also a third subfamily of Protmosuchus-like forms) is that of Kuhn (1966: 71). Unlike Tatarinov, however, Kuhn does
not try to justify this.
What rank in the hierarchy should actually be accorded to these two main groupsChmatosaurus-like and Erythrosuchus-like-is a purely subjective question and,
indeed, not very important ; it is a matter of logic, common sense and economy. Our
own view is that what might be termed ‘intercalary’ grades, distinguished by the
prefixes super-, sub- and infra-, should be introduced into the hierarchical system only
when really required. More specifically,when the general similarity of all Proterosuchia
has already been recognized by their being placed together in that suborder, to assign
them all to only one family and then to classify them into two subfamilies is surely an
unnecessarilycomplex procedure; there is no fundamental distinction between ‘familial’
and ‘subfamilial’ differences. We therefore propose to accept the majority opinion
and regard the two subdivisions of the Proterosuchia as two separate families.
The Shansisuchidae
Young (1964) described the new genus Shansisuchus, type-species S. shansisuchus,
and erected the family Shansisuchidae upon it. Thus, in his classification there are
three families in the superfamily Proterosuchia :Proterosuchidae, Erythrosuchidae and
Shansisuchidae.As mentioned above, Kuhn (1966 :71-72) followsYoung in recognizing
the family Shansisuchidae, including only the one genus Shansisuchus, but unlike
Young he places all the other ‘Proterosuchoidea’ in the Proterosuchidae and then
divides the latter into subfamilies.
The diagnosis of Young’s new genus and family indicates that the Shansisuchidae
are ‘very similar in general features to the family Erythrosuchidae’, with subthecodont
teeth, but differ from the latter in certain particulars which, if correct, cannot all be
discounted as minor. In fact, five characters of the Shansisuchidae are mentioned-the
presence of two antorbital fenestrae (instead of one), the absence of a parietal foramen,
the presence of a lateral fenestra in the lower jaw, the absence of any trace of intercentra
in the vertebral column between axis and tail, and the comparativelyslender build of the
limbs-in which, presumably, the sole member of the family differs from members of
the Erythrosuchidae. (The lack of intercentra is cited despite Young’s own observation
that ‘There is no sure proof of the presence of the intercentrum of the neck vertebrae
but may probably be so as in the case of Erythrosuchus.’) But the supposedly contrasting
condition in Erythrosuchus and its allies is, in some instances, probably much as in
Shansisuchus, earlier indications to the contrary being based on inadequate evidence
(seepp. 134,159-160); and, in theothers, it is variable within the Erythrosuchidae (e.g.,
actual intercentra are unknown in Erythrosuchus itself but, according to Tatarinov, are
present in Garjainia and T.’jushkooia,while the relative slenderness or stoutness of the
CLASSIFICATION OF THE PROTEROSUCHIA
145
skeleton is dependent upon absolute size). In this last connexion it may be noted that
Shansisuchus, though large, is appreciably smaller than Erythrosuchus. The length of
the largest of the several Shamisuchus skulls known is estimated at 62 cm, that of
Erythrosuchus at 96 cm.
Hughes (1963), incidentally tentatively refers Shansisuchus to the Erythrosuchidae ;
Young had established the name in 1959 as a nomen nudum and, in a letter to Hughes in
1960, had likened the genus to Erythrosuchus. Romer (1966: 368) follows Hughes on
this point of classification.
It seems to us that Erythrosuchus and Shansisuchus are extraordinarily alike in many
respects ; indeed, Shalzsisuchus resembles Erythrosuchus more closely than do other
genera referred to the Erythrosuchidae. Young himself writes that ‘the family Erythrosuchidae may be a synonymous with Shansisuchidae, if the former proved to have
two preorbital openings.’ Since it cannot be shown for certain that Erythrosuchus had
only one antorbital fenestra, and since the other family differences cited by Young
do not or may not really exist, the segregation of Shansisuchus into a separate family
cannot be justified. Kuhn’s 1966 classification, with Erythrosuchus in the same family
as Chasmatosaurus yet with Shansisuchus in a family of its own, is certainly quite
unacceptable.
According to Young’s comparative table, however, there are a number of less
significant characters (nos. 2, 4, 7, 8, 11, 28, 29 and 31 of Young’s list) in which
Shansisuchus and Erythrosuchus are quite different ;the most important of these are the
comparative narrowness of the skull in the Chinese form, the peculiar shape of the upper
temporal fenestra, and the 3hape of the frontal and its exclusion from the border of the
orbit. I t therefore seems reasonable to continue to regard Erythrosuchus and
Shansisuchus as generically distinct.
‘Proterosuchidae’ or ‘Chasmatosauridae’?
As to the naming of the Chasmatosaurus-like group, Hughes (1963) calls it Chasmatosauridae rather than Proterosuchidae; Romer (1966 : 368) does likewise, while Krebs
(1965) seems to prefer the former name. Hughes’ reason for this change in nomenclature
is presumably that he regards Proterosuchus as ‘probably a specimen of Chasmatosaurus
vanhoepeni as Broom (1946) believed. The specimen is a fragmentary, weathered skull,
probably now lost (Broom 1946) and certainly best forgotten !’ It is true that in an earlier
paper (1932) Broom had stated that ‘it is very difficult to say whether the two [Proterosuchus fergusi and Chasmatosaurus vanhoepenal belong to the same species. Certainly
they are very closely allied . . . . I t seems to me probable that Chasmatosaurus will prove
to have been founded on a better specimen of Proterosuchus.’ Indeed, in the Explanation
of plate 2 of the same paper he had gone further and written ‘Chasmatosaurus vanhoepeni
Haughton (=probably Proterosuchusfergusi Broom).’ But Broom had obviously changed
his opinions on this matter in the 1946 article referred to by Hughes; in that work he
placed the unique skull of P . fergusi in generic, not specific synonymy with
C . vanhoepeni, and only tentatively at that.
Let it be supposed, however, that there is sufficient reason to consider the two forms
congeneric (though not necessarily conspecific). If that were so, the senior synonym
146
A. J. CHARIG AND 0.A. REIG
would be Proterosuchus Broom 1903, not ChasmatosaurusHaughton 1924. But, in any
case, the priority of family names is unaffected by the synonymy, objective or subjective,
of the generic names upon which they are based; it depends entirely upon the
chronological order of the dates of their own publication, so that it is even possible for
the correct family name to be based upon a junior synonym. The dates of publication in
this case are 1906or 1908 for Proterosuchidae and 1924 for Chasmatosauridae. Thus the
only way in which it would be possible to reject the family name Proterosuchidae in
favour of Chasmatosauridaewould be to declare Proterosuchus a mmen dubium, a name
based upon material which is generically indeterminable; and we consider (see below,
pp. 147-148) that the specimen cannot be regarded as sufficiently indeterminable to
warrant such a declaration. Under these circumstances it is clear that Proterosuchidae,
not Chasmatosauridae, is the correct family name.
Composition
There is but little disagreement concerning which genera should be placed in each of
the two families Proterosuchidae and Erythrosuchidae (excluding the matter of the four
post-Lower Triassic genera referred to the Erythrosuchidae by Hughes, and ignoring
also such dubious genera as Arizonmaurusand Seemannia,all of which have already been
dealt with above). Most workers list five genera in the Proterosuchidae :Protuosuchus,
Chasmatosaurus, Channatosuchus, Elaphrosuchus, and, since its publication in 1960,
Archosaurus. But only one genus, Erythrosuchw itself, appears as an invariable component of the Erythrosuchidae. Most of the more recent classifications (Tatarinov, 1961;
Hughes, 1963 ;Ewer, 1965 and Romer, 1966 but not Young, 1964) place certain Russian,
South American and Scottish forms (always Garjainia and Vjushkosia, sometimes
Dongusia, Cuyosuchus or Dusygnathoides) in the Erythrosuchidae, regarding them as
junior synonyms of Erythrosuchus.Young, on the other hand, believing that Garjainia,
Vjushkosia and DonguSia are certainly generically distinct from Erythrosuchus, is even
doubtful as to their family affinities; and Krebs (1965) obviously considers at least
Vjushkuwia to be distinct. The matter is discussed in detail below.
Dewiationsfrom the standard pattern
Deviations from this pattern are generally of a minor nature (except in the case of
von Huene’s 1962 classification). Romer (1945,1956 but not 1966) listed all the ‘basic’
proterosuchids together with Erythrosuchus in the one family Erythrosuchidae ;
Haughton & Brink (1954) did likewise, but, since they were cataloguing only African
genera, they omitted Chasmatosuchus; Maleev (1964) places all the proterosuchians
in the family Proterosuchidae; and Kuhn (1966) lumps all proterosuchian genera
(except S h a h h u s ) together, but, as indicated above, recognizes at least three
subfamiliesbased on Chusmatosaurus,Proterosuchusand Erythrosuchus.Romer referred
‘?Dongusia’ to the Ornithosuchidae in 1945 and to the Euparkeriidae in 1956 rather
than to the Erythrosuchidae, but in 1966 he places DonguSia in the synonymy of
Erythrosuchus.Hoffstetter (1955) tentatively assigned Dungm‘u to the Proterosuchidae
and Browniella to the Erythrosuchidae; and von Huene (1956) followed Hoffstetter’s
classification of the former genus. The new families Garjainiidae Ochev 1958 and
Vjushkoviidae von Huene 1960 retain their separate identity in Reig’s classification
CLASSIFICATION OF THE PROTEROSUCHIA
147
of 1961 (within the Proterosuchia); Kuhn’s 1960 classification omits mention of the
Garjainiidae and places the Vjushkoviidae outside the Proterosuchia, in the Pseudosuchia; Kuhn’s 1961 classification (which includes the Proterosuchia as a superfamily
of the Pseudosuchia) places the Vjushkoviidae in another superfamily, the Ornithosuchoidea, and the Garjainiidae in ‘Superfam. indet.’ ; and Kuhn’s phylogenetic tree
(1965) simply shows all four families (Proterosuchidae, Erythrosuchidae, Garjainiidae
and Vjushkoviidae) as constituents of the Thecodontia. Neither Kuhn nor Reig lists
genera, and Kuhn (1960,1966, but not 1961, 1965), like Romer (1956), considers that
Erythrosuchidae = Proterosuchidae. Von Huene (1962) places both Dongusia and
‘Dasygnathus’ in the Erythrosuchidae, Vjushkoeia in the Sphenosuchidae ( !) and
Garjainia in a list of incompletely known genera not yet assigned to families; this
classification, however, departs widely from standard practice in many ways without
offering much justification for doing so. Euparkeria, which we do not even regard as a
proterosuchian (see above, pp. 135-136), is placed by Hughes (1963) in the Erythrosuchidae; Ewer (1965) agrees with this classification in her abstract.
Problems in the Proterosuchidae
Proterosuchus and Chasmatosaurus.The first two problems in the Proterosuchidae are
whether the name Proterosuchus should be declared a mmen dubium and, if not, whether
Proterosuchus and Chasmatosaurusshould be regarded as subjectively synonymous. As
mentionedabove(p. 145),Broomfirsttooktheview(1932)thatP. fergusiandC. vanhoepeni
were probably conspecific. Later, however (1946), he decided that the two forms
were probably specifically distinct, although they could well be congeneric; indeed,
he believed that the very fine specimen of Chasmatosaurus which Broili & Schroder
(1934) had described as C. vanhoepeni was also specifically distinct, representing a
third-as yet unnamed-species of the genus. Hughes, on the other hand (1963), has
misunderstood Broom’s 1946 paper and, like Broom in 1932, considers that P. fergmand C . vanhoepeni are probably conspecific; he rejects the names Proterosuchus and
fergusi and thereby places Proterosuchus in the synonymy of Chasmatosaurus (as does
Romer, 1966: 368, though in an uncertain manner).
Hughes’ rejection of the names Proterosuchus and fergusi is worded in such a way as
to imply that he regards them as nomina dubia. Yet the very fact that first Broom, then
he, and now we ourselves believe that we can draw valid conclusions, albeit tentative
conclusions, about the relationships of P . fergusi show that it is neither specifically nor
generically indeterminable; Broom’s illustrations (1903, pl. 19) show that the unique
specimen, now lost, was altogether too well preserved to permit those names to be
declared nomina dubia.
Differences between P . fergusi and C . vanhoepeni certainly exist, although, as
Haughton pointed out (1924), ‘Comparison. . . is only possible at one or two points’. The
most obvious difference concerns the far greater number and distribution of the palatal
teeth in P. fergusi, where they occur on the vomer (‘prevomer’ of Broom) as well as on
the pterygoid. This character, noted by Hoffstetter (1955 : 668), suggests that P .fergusi
is the more primitive form. Other characters, however, suggest the opposite: the
maxillary tooth count (18 or 20, according to Broom’s estimate) is far fewer than the
corresponding figure for C. vanhoepeni (26-27), replacement of those maxillary teeth
148
A. J. CHARIG AND 0.A. REIG
is alternate, and P . fergusi also occurs at a slightly higher horizon (Procolophon zone
instead of Lystrosaurus zone). There appears to be another striking difference in the fact
that, judged from the figures, the vomer of Proterosuchus is far more extensive than that
of Chasmatosaum. Anteriorly it sutures with the maxilla and prevents the premaxilla
from reaching the margin of the internal naris (the opposite condition obtains in Chasmatosaurus);posteriorly it extends further back and has a more substantial suture with
the palatine. But Walker (pers. comm.) has pointed out that the figures are not really
comparable; Broom’s reconstruction of the palate of Proterosuchw (1903:pl. 19,fig. 3)
is based on his fig. 2,a factual view of the upper side of the bones of the palate, whereas
Broili & Schroder’s reconstruction of the palate of Chasmatosaurus(1934:235,fig. 4see our Fig. 1C)is evidently based on far better material seen from below. Indeed, it is
clear from Broili & Schroder’s description (1934)and from their fig. 5 that the vomer
passes forwards above the ventral process of the premaxilla, so that the dorsal surface of
the vomer must appear longer than the ventral. Similar considerations might have
applied to the junction of the vomer with the palatine.
In conclusion, we agree with Broom’s suggestion that Proterosuchus fergusi and
Chasmatosaurus vanhoepeni, though specifically distinct, might be congeneric, but we
consider that both generic names should remain in use until there is more evidence to
support such a claim (see Addendum p. 167-168).
Ankistrodon and Chasmatosaum. Another problem in the Proterosuchidae concerns
the name to be used for the proterosuchian material from the Panchet Series of Bengal,
generally known as Chasmatosaurus indicus. Huxley (1865) described as Ankistrodon
indicus a fragment of a small jaw bearing two teeth. In the same work he tentatively
referred a number of vertebrae, from all the major regions of the column but not all of
commensurate sues, to his new species Dicynodon Orientalis; D. orientalis was based
upon cranial material, pectoral girdle and humeri with which no other vertebral material
was associated. Lydekker (1885)proposed the new name Epicampodon for Ankistrodon
Huxley on the grounds that the latter name was preoccupied. Von Huene (1942b)
transferred the jaw fragment to the genus Chasmatosaum as C. indicus because the teeth
were so like those of Young’s C. yuuni; this synonymy has been generally accepted (e.g.,
by Romer, 1966: 368). Von Huene also pointed out that the ‘Dicynodon orientalis’
vertebrae did not belong to an anomodont but were certainly those of an archosaur; he
referred them to C. indicus, apparently because the cervical vertebrae were elongated,
because they could not belong to a saurischian (there being no saurischians at the time),
and because he believed Chasmatosaurus to be the only genus of thecodont with elongated cervical vertebrae-a belief, incidentally, which is far from correct.
From a purely nomenclatural standpoint, Lydekker’s proposed substitution of the
nameEpicampodonfor Atskistrodonis quite incorrect because, in fact, Ankistrodon was not
preoccupied. First, the supposedly senior homonyms to which he referred (Agkishodon
De Beauvois 1799 = Agkistrodon De Beauvois 1799 = Ancistrodon Wagler 1830,
Ancistrodon Roemer 1849) all differ from Ankistrodon sufficiently to prevent
homonymy; Ankistrodon is a valid generic name, and Epicampodon is a nomen vanum,
an unjustified replacement name which becomes a junior objective synonym of
Ankistrodon. Secondly, if Ankistrodon 1865 and Chasmatosaum 1924 are indeed to be
CLASSIFICATION OF THE PROTEROSUCHIA
149
regarded as congeneric, Ankistrodon is the senior synonym; A. indicus cannot be
transferred to the genus Chasmatosaurus, but the various species of Chasmatosaurus
must be transferred to Ankistrodon. Thirdly, irrespective of the genus in which the
species indicus is to be placed, von Huene was quite wrong in attributing that species
to Lydekker (1885) instead of to Huxley (1865) ;Tatarinov (1961) and Hughes (1963) are
equally wrong in attributing it to Lydekker(1867) and to von Huene (19426)respectively.
But, in any case, it seems to us that the type-material of Ankistrodon indicus is so
scanty and poor as to be indeterminate. Consequently the names Ankistrodon and
indicus should be regarded as nomina dubia and cannot be applied to the vertebrae
described by Huxley. Further, von Huene’s grounds for associating the vertebrae with
the jaw are patently inadequate. On the other hand, the vertebrae do resemble those of
Chasmatosaurus and it seems reasonable to cite them as ‘cf. Chasmatosaurus sp.’
Additional fragmentary material from the Panchet Series has now been described as
Chasmatosaurus sp. by Satsangi (1964).
It may be recorded here that vertebrae very like those of Chasmatosaurus were
collected in 1963 in the Ntawere Formation of north-eastern Zambia. Cox (1969)
considers this formation to be of Lower Anisian age [i.e., more or less on the boundary
between Lower and Middle Triassic]. The vertebrae are now in the British Museum
(Natural History); unfortunately they are coated with an extremely hard layer of
haematite which defies preparation, and, in consequence, they have not yet been
described.
Archosaurus, Chasmatosuchus and Chasmatosaurus. The generic distinction of the
Russian forms Archosaurus and Chasmatosuchus from Chasmatosaurus and from each
other has never been doubted. Maleev( 1964:497-498) gives a summary of the characters
of all three genera which affords a concise indication of their differences. In any case,
Archosaurus is geologically older than the other two.
Elaphrosuchus and Chasmatosaurus. The distinction between Elaphrosuchus and
Chasmatosaurus, however, is not accepted by everyone. In his original description of
Elaphrosuchus Broom (1946) pointed out a number of differences between these two
South African forms, including the presence in Elaphrosuchus of a lateral fenestra in
the lower jaw; his fig. 2 showed how different was the unique skull of E. ru6idge-i (A)
from that of Chasmatosaurus sp. (B, after Broili & Schroder’s drawing of the specimen
which they referred to C. vanhoepeni but which Broom considered to be a distinct
species). Broom therefore rejected the possibility that Elaphrosuchus was merely a
young Chasmatosaurus. Brink (1955) did not question the independent status of
Elaphrosuchus; indeed, when describing his new skull of Chasmatosaurus in the same
paper, he wrote of its maxillary teeth that ‘They are proportionally much smaller than
in Elaphrosuchus so that the latter, although a young individual, cannot belong to the
same genus.’ But Hughes (1963) accepts that E. rubidgeimight be a young C. vanhoepmi,
although he mentions that the former has fewer teeth and a fenestra in the lower jaw.
It is true that Elaphrosuchus is by far the smallest proterosuchian known, with a
skull about 18 cm long; the possibility that the animal was ajuvenile cannot bediscounted
altogether. But it seems to us, as it did to Broom and later to Brink, that it is quite
distinct from Chasmatosaurus. Indeed, in several characters it is more like a member of
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A. J. CHARIG AND 0. A. REIG
the Erythrosuchidae than of the Proterosuchidae; we instance (a) the more dorsal
position of the external naris, (b) the notch in the lower margin of the skull between premaxilla and maxilla, (c) the lateral fenestra in the mandible (mentioned above), and
(d) the less isodont dentition, with far fewer and relatively larger teeth alternating
perfectly between the loose and the fixed condition. The maxillary tooth count (13)has
already been reduced to a lower figure than that of the erythrosuchid Gavjainia (15).
If the Elaphrosuchw type-skull really does represent an immature individual of a
genus of proterosuchid, then it provokes the very tentative suggestion that the Erythrosuchidae may have had a neotenous origin from the Proterosuchidae.
In any event, the small skull from Brandkraal must continue to be called
Elaphrosuchw rubidgei.
FIGURE
2. Skull of Elaphrosuchus rubidgei Broom (after Broom 1946).
From above, approximately 2 natural size.
Chusmatosaurusoanhoepeni and C.alexanderi. The Proterosuchia are a little known
group, and for few genera has more than one species been described ; indeed, most of
the genera are based upon a unique specimen. It is not our intention in the present
paper to examine the claims to separate status of non-type species in those few polyspecific genera; but in the case of Chusmatosaurus alexandmi we are obliged to do so
because certain important characters of Chusmatosaurus,the most ‘central’ genus of the
Proterosuchia and the one for which we have chosen to give the most complete illustrations of the skull, are greatly affected thereby. In particular, Hoffman implied that the
turning down of the premaxilla was a specific character peculiar to C. alexanderi and
was not a character of the genus Chusmatosaurw as a whole.
Five specimens of Chusmatosaurushave been described from South Africa, two being
the respective holotypes of C. oanhoepeni Haughton 1924 (redescribed by von Huene
in 1926) and of C. alexandmi Hoffman 1965. Of the three other specimens, Hoffman
leaves one (described by Broom in 1932) in the species C. wanhoepeni and refers the
CLASSIFICATION OF THE PROTEROSUCHIA
151
other two (Broili & Schroder, 1934; Brink, 1955) to his own new species. He states
(1965) that his grounds for erecting the latter are ‘the marked differences [from C.
vanhoepent] in the preorbital region’ and ‘the remarkable curvature of the snout’.
It should be noted here that Hoffman’s description of C. alexanderi is but a very
brief account of the skull, which (judged by the photographs) was only partly developed
at the time; indeed, Hoffman himself writes ‘No details of the base of the skull and of
the occipital region are available. Further development of the specimen is needed.’
No information is given on the lower jaw, which was ‘not yet fully developed’, and ‘A
more detailed description of the skull and post-cranial skeleton will follow later.’
Hoffman’s grounds for erecting his new species should therefore be examined. I n
his paper he reproduces the original authors’ reconstructions of all five specimens,
together with a second reconstruction of the type of C. vanhoepeni (taken from von
Huene, 1926: fig. 9, though with certain inaccuracies and omissions). These appear
to illustrate his two points satisfactorily. He writes ‘The prefrontals and the lachrymals
in Chasrnatosaurus alexanderi and in the specimens described by Brink and Broili &
Schroder differ remarkably from Chmiatosaurzls vanhoepeni as described and figured
by Haughton, Broom and von Huene (see comparative illustrations). In the latter forms
the lachrymal is shown to lie immediately and completely below the prefrontal.
In C. alexanderi the lachrymal lies in front of the prefrontal.’ Unfortunately, however,
Hoffman failed to notice that the prefrontal-lachrymal region is not well preserved,
either in the type of C. vanhoepeni or in the specimen described by Broom which he,
Hoffman, considered to belong to the same species. Haughton’s description of the type
makes no mention of either element; it would seem from his photographs and the
diagrams based thereon that both are missing; and in his reconstruction the outlines of
both are drawn entirely in broken lines. In von Huene’s re-description of the same skull
(1926) the prefrontal (though not the lachrymal) is mentioned briefly and is depicted in
his drawings (figs 8b, c, h) of the roof and side of the skull; but its form does not seem to
differ greatly from that of the same bone in Broili & Schroder’s specimen, and his
reconstruction of the bones in this region (fig. 9) is again entirely speculative, with the
outlines of both prefrontal and lachrymal drawn in broken lines and the shape of the
former bearing no apparent relationship to its shape as shown on the drawings of the
actual skull, Broom (1932) mentioned that Haughton’s type had a fragment of one
prefrontal. As for Broom’s own specimen, there is nothing whatever in his description
of this ‘very fragmentary’ skull or his solitary drawing thereof (pl. 2, fig. 1 ;a very simple
reconstruction) to suggest that anything at all is known of either prefrontal or lachrymal.
Thus, since Hoffman’s understanding of the anatomy of the prefrontal-lachrymal
region of ‘C. vanhoepeni’ (i.e., Haughton’s and Broom’s specimens) is based entirely on
hypothetical reconstructions, his comparison of it with the anatomy of the same region
of ‘C. alexanderi’ (his own, Broili & Schroder’s and Brink‘s specimens) is quite
meaningless.
Whereas Hoffman tries to draw a distinction on the structure of this region of the
skull between Haughton’s and Broom’s specimens on the one hand and Broili &
Schroder’s, Brink‘s and Hoffman’s on the other, Brink had already (1955) noted the
‘remarkable difference between the arrangement of the prefrontals and lachrymals’
in his specimen and in those previously described; i.e., he placed the Broili& Schroder
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A. J. CHARIG AND 0.A. REIG
specimen with Haughton’s and Broom’s, not with his own. However, he considered
that the difference (which he described in great detail) was ‘probably . . . due to imperfect preservation in the other [other than his own] specimens.’ His comment that
‘Judging from Broili & Schroder’s figure it appears as if their lachrymal corresponds
to this [downward] process of the prefrontal in the present specimen, with the only
difference that in the present specimen it does not reach the maxillary’ is difficult to
accept on a mere examination of the figure in question (fig. 1); but Walker, who has
examined the specimen in Munich, agrees (pers. comm.) that the left lachrymal has
indeed been lost from Broili & Schroder’s specimen.
If Hoffman’s other diagnostic character of C. alexanderi be considered, ‘the remarkable curvature of the snout’, the only other mention of this in his paper is the fact that
‘the anterior portion of the snout is curved down as in the specimen described by
Broili & Schroder.’ But this is true also of Haughton’s type of C. oanhoepeni,where the
flexure is quite distinct; the lower margin of the premaxilla, which is more or less
straight, is bent down through an angle of some 60” on the left side and 50” on the right
from an imaginary forward extension of the lower margin of the maxilla. (A comparable
figure for Broili & Schroder’s specimen, where the lower margin of the premaxilla is
curved in an arc, might be taken as 60”.) Haughton, oddly enough, did not comment on
this, but subsequent workers at first attributed this peculiarity of the snout to crushing
after death. Von Huene (1926) wrote that ‘die Praemaxilla [ist] heruntergebogen’ ;
Broom (1932) stated that ‘In the specimen [which specimen ? Haughton’s or his own ?
It is not at all clear] the premaxillae are bent down, but it appears to me that this is
due to post-mortem crushing, and the fact that the lower jaw is practically straight
makes it probable that the upper jaw was also moderately straight.’ Both von Huene
and Broom straightened the lower margin of the upper jaw in their reconstructions.
Later, however (1946), Broom recanted on this point: ‘In the specimen described by
Haughton the premaxilla is similarly bent down. Both von Huene and I considered it
likely that this bent-down premaxilla was displaced and straightened it out in our
restoration. Grossarth‘s specimen [i.e., the specimen described by Broili & Schroder]
shows that it is probably the natural condition.’ This must surely be correct; if the
lower margin of the front end of the upper jaw had been bent downwards after death,
as had been suggested by von Huene and by Broom in his earlier paper, why did the
upper margin still show a smooth curve with no sign of deformation ? (See Haughton
1924, pl. 7; von Huene 1926, fig. 8c.) The presence of such curvature of the premaxilla
is not in dispute in the other specimens of Chasmatosaurus from South Africa, all of
which are placed by Hoffman in the species C. alexanderi; it is unequivocally present
in Broili & Schroder’s and Hoffman’s specimens, and of Brink‘s specimen Brink himself wrote (1955) ‘Although the anterior portion of the snout is missing, there are
indications that the snout was curved down as in the type and in Broili & Schroder’s
specimen.’ A downturned premaxilla is also present in C. yuani from Sinkiang (Young,
1936: figs 2, 3), the bending being through an angle of about 70”, while in C. ultimus
Young 1964 from China (first described and figured as C. yuuni-see Young, 1958:
fig. 1, pls 1-3) the premaxillae are not preserved.
In any case, there is nothing inherently improbable about a downturned premaxilla;
such a structure may be found in other early archosaurs.
CLASSIFICATION OF THE PROTEROSUCHIA
153
It would therefore seem that there is no justification for Hoffman’s separation of
Chasmatosaurus alexanderi from the type-species, C. vanhoepeni, on the grounds cited.
There are, however, other very notable differences between Broili & Schroder’s
specimen on the one hand and those of Brink and Hoffman on the other; Brink
mentioned some of them (1955), but Hoffman failed to comment. Most of them
relate to the rear end of the skull.
The Brink and Hoffman specimens appear to differ from Broili & Schroder’s skull
(as evidenced by the reconstruction of the latter) in that, in both of them, the upper end
of the quadrate clearly articulates with the squamosal and not with the paroccipital
process. The quadrate is much more nearly upright in position and is obviously
streptostylic; the squamosal occupies a much greater area on the lateral surface of the
skull and appears to have a shallow otic notch in its posterior margin; and the lateral
rami of the parietals and of the paroccipital processes are comparatively straight and
diverge backwards from the mid-line at an angle of about 45”. I n Brink’s specimen the
quadrate is also much more massive, much broader in lateral view. Further, in
Hoffman’s specimen there seems to be a lateral fenestra in the lower jaw; Hoffman
does not mention this in the text, but it is shown in his reconstruction (1965, fig. 2A).
T h e Broili & Schroder skull, now conserved in Munich, was examined by Walker in
1968; his detailed observations (pers. comm.), also mostly concerned with the rear end
of the skull, confirm his much briefer published statements (1968). They are very
relevant to the problem of the specific identity of these several specimens and to our
evaluation of the generic characters of Chasmatosaurus. Walker attributes many of the
differences between this skull and those described by Brink and Hoffman to postmortem deformation of the Munich skull and to the loss of certain superficial elements.
Most of the deformation, according to Walker, is due to lateral compression of the
back end of the skull. This had the following results:
(1) The upper temporal fenestra (on the left side) is reduced in width.
(2) The upper ends of the quadrates, capped on both sides by a thin layer of squamosal,
are displaced medially and each touches the paroccipital process of its side instead
of the squamosal. (This misled Broili & Schroder into believing that the upper end of
the quadrate articulated with the paroccipital process instead of with the squamosal.
I n fact there is no reason to doubt that the upper end of the quadrate lay slightly
lateral to the paroccipital process, not quite touching it, and that it articulated with the
squamosal, just as in Brink’s and Hoffman’s specimens and as in archosaurs in general.)
(3) The squamosal (on the right side) also is displaced medially and is parted from
its junction with the postorbital.
(4)The lateral wings of the parietals, inclined outwards and backwards, have been
pushed back towards each other so that the angle between them appears to be reduced;
the paroccipital processes are likewise pushed towards each other so that (a) the angle
between them is reduced and (b) they curve towards each other distally. This point is
readily confirmed by an inspection of Brink’s reconstruction of the skull roof of his
specimen (1955, fig. lB), by Hoffman’s photograph (1965, fig. 5 ) , and, if considered
relevant, by Broom’s illustration of Elaphrosuchus (1946, fig. 1).
The rear of the skull has also been compressed dorsoventrally. Thus the quadrate,
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A. J. CHARIG AND 0.A. REIG
which would normally be in a more vertical position, lies much more horizontally than
it should; its lower end is too far back, and, since that lower end forms the hinge for
the mandible, the whole of the mandible itself has been pulled back from its natural
position and is no longer in its correct relationship to the downturned premaxilla.
One other peculiarity of Hoffman’s specimen, the apparent presence of a lateral
mandibular fenestra, was also noted by Walker (pers. comm.) in Broili & Schroder’s
specimen,but-even more remarkable-on the left side only. Walker suggests, however,
that the apparent fenestra may be nothing more than a recessed area on the surangular.
As for the unusually low tooth count noted by Hoffman in the upper jaw of his
specimen (6 premaxillary and 19 maxillary teeth), Walker considers it evident that these
figures do not include empty alveoli ;he estimates that there were 26 teeth in the maxilla,
which is about the same number as in Broili & Schroder’s specimen.
Walker also comments on the loss of certain parts of the Broili & Schroder skull.
These include the posterior process of the squamosal (on both sides) ;the left lachrymal
(see above, p. 152); and, on the right side, of various elements from the region of the
antorbital fenestra. Further, he believes that there was an otic notch in the squamosal;
in this he opposes the views of Sill (1967), who states that ‘In the earliest thecodonts,
there is no indication of an otic notch (later thecodonts do possess one . . .)’. Walker’s
other observations pertain to details-e.g., the position of the fenestra ovalis-which
are neither mentioned in our work nor shown in the reconstructions by Broili &
Schroder reproduced here (Fig. lA, ByC).
While we have rejected Hoffman’s claim to separate specific status for C. alexanderi
on the grounds cited, we are by no means certain that all the specimens of ChasmatoSaum from South Africa are conspecific. Walker (in Zitt.) ‘was sceptical from the
beginning about the validity of Hoffman’s species’, and he suspects that the apparent
differences between the specimens concerned may be due partly to [individual]
variation and partly to distortion or damage. As we ourselves have not handled or seen
the material, and as a complete revision of the osteology of Chasmatosaurus involving
new material is at present being undertaken by Cruickshank in Johannesburg, we do
not wish to express a more definite opinion. Again, it is obvious that Broili & Schroder’s
reconstruction of the skull requires extensive modification in the light of Walker’s
comments; but, for the same reasons, we have refrained from altering the drawings and
have contented ourselves with a warning in the legend that Walker’s observations
should be borne in mind.
Problems in the Erythrosuchidae
The main problem in the Erythrosuchidae is whether or not certain other genera
should be placed in the synonymy of Erythrosuchus.
The prime and original exponent of the ‘lumping’ approach is Tatarinov (1961),
who believes that the forms described as Dongusia, Garjainia and Vjwhkovia should all
be regarded as separate species of Erythrosuchus. Indeed, he would include in the latter
genus, though with a certain amount of doubt, the post-cranial skeleton described as
Cuyosuchus Reig 1961(Tatarinov’s ‘Erythrosuchus?sp. l’-see Reig & Charig, in press)
and the unnamed mandibular fragment of a large pseudosuchian from the Middle Trias
of Cis-Uralia (‘Erythrosuchus? sp. 2’). Finally, he also believes that the premaxilla
CLASSIFICATION OF THE PROTEROSUCHIA
155
from Zone V described as Chasmatosuchus ( ?) vjushkovi Ochev 1961 cannot be congeneric with Chasmatosuchusrossicus but may in fact belong to a very young individual
of Erythrosuchusprimus [Garjainia].
This ‘lumping’ is largely accepted by Hughes (1963), Maleev (1964), Ewer (1965)
and Romer (1966) but rejected by Young (1964). A more detailed analysis of the
situation is therefore required in order that the validity of these synonymies may be
assessed objectively.
I n deciding synonymy or otherwise the onus of proof lies with him who wishes to
establish it. But when the elements known in the various forms include but few in
common, and when those few are damaged and incomplete, comparisons are generally
impossible. Even when direct comparisons between the forms are possible and show
striking similarities, this may mean very little if only one or two elements are involved;
for there are many instances where two forms, taxonomically widely separated and
with most of their bones differing greatly, have other bones which are virtually indistinguishable (e.g., the ilium of the pseudosuchian Mandasuchus is, in every particular,
exactly like that of a parasuchian referred to the species Phytosaurus [Belodon] kapfi
(von Meyer 1861)). Finally, even when two forms are very similar in the morphology
of all the available elements, the degree to which they should be linked together in the
classification remains a largely subjective matter ; an objective evaluation is virtually
impossible from the evidence to hand.
It must be remembered that, in the vast majority of cases, the remains of fossil
animals consist only of skeletal material; there can be no certain or precise knowledge of
their soft parts, their physiology, their ecology or their behaviour. Thus two skeletons
which are identical or separated by only minute morphological differences may in fact
be derived from two different species. At best such ‘homomorphs’ may represent two
very closely related species which do not interbreed (e.g. among living forms, ‘cryptic’
species isolated from each other by small physiological differences, sibling species which
are sympatric but isolated from each other by small differences in preferred habitat
or by mating behaviour) ; at worst two apparently identical skeletons may be the
distantly related products of convergent evolution. Conversely, the skeletons of two
animals belonging to the same species may differ greatly because of differences in age
or sex, because of pathological deformation, or simply because of intraspecific variation.
Three-headed ribs. One of the most important pieces of evidence by which Tatarinov
(1961) justifies his placing of Vjushkovia, Garjainia and (tentatively) Dongmu in the
synonymy of Erythrosuchus is that all these forms are supposed to have possessed ribs
with three heads (instead of with two) in the anterior part of the trunk. Vjushkovia
certainly did possess such ribs, hence von Huene’s specific name triplicostata. T h e
anterior dorsal ribs are unknown in the other genera mentioned, but Tatarinov believes
that the presence of three pairs of rib facets on the corresponding vertebrae may be
demonstrated in Erythrosuchus s m u strict0 and inferred in Garjainia and Dongusia
(as well as in other proterosuchians).
This is very hard to substantiate. Most of the vertebrae in question are broken,
weathered and/or deformed to such an extent that it is often extremely difficult to tell,
even from the specimen itself, just how many rib facets it did possess. After all, the
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A. J. CHARIG AND 0.A. REIG
parapophysis and diapophysis were connected by a continuous buttress of variable
thickness, and both processes and the buttress have usually been broken off and/or
weathered in an irregular manner ;the broken end-surfaces may therefore be of almost
any shape, and any intermediate swelling on the connecting buttress may be regarded as
an accessory process. Indeed, the two sides of any one vertebra often differ greatly in
appearance. Worse, attempts to answer the same question from other workers’ drawings
are doomed to almost certain failure; the illustrations are generally inadequate and, in
particular, do not distinguish between true and broken surfaces.
Most misleading of all, the vertebra of Erythrosuchus ufricunus upon which Tatarinov
(1961) bases his claim that the anterior trunk vertebrae of that genus had three pairs of
rib facets is in fact a composite specimen. It was originally figured by von Huene as a
cervical (1911, presumably fig. 10; part of the skeleton registered in the B.M.(N.H.)
Palaeont. Dept. as no. R.3592), but Tatarinov calls it the first dorsal. The centrum and
the neural arch have been plastered together; and one of us (A.J.C.), who has examined
the specimen, is quite convinced that the centrum and the arch do not belong to the
same vertebra, the arch being too long for the centrum in an axial direction. I n any case,
the processes which bear the rib facets are damaged and incomplete. (In fairness to
Tatarinov, it must be mentioned that none of this is evident from von Huene’s drawings
or description.) The fact that this ‘vertebra’ seems to have three pairs of rib processes
is therefore without significance;we believe that there is no evidence whatever to suggest
the presence of three-headed ribs in Erythrosuchus, although this does not necessarily
mean that they were absent in that genus.
Tatarinov (1961) also argues that this triple condition of the rib articulation is arrived
at by division of the diapophysis into two; and, moreover, that further back along the
vertebral column, where only two rib facets are again found on each side, those two
are borne on the divided diapophysis (the parapophysis having been lost). Thus the two
processes in those more posterior vertebrae would be the ventral and dorsal parts of
the diapophysis, not (as generally supposed) the parapophysis and diapophysis respectively. Hughes, however, points out (1963) that what actually occurred in this region of
the vertebral column of VjusMowia (‘E. triplicostutus’) may be interpreted in three
differentways: the parapophysis may have displaced the ventral part of the diapophysis,
fused with it, or disappeared entirely (Tatarinov’s explanation), so that the resultant
process may respectively be regarded as parapophysis, parapophysisplus ventral moiety
of diapophysis, or ventral moiety of diapophysis only.
Tatarinov (1961) then goes on to suggest that, in the dorsal region of more advanced
archosaurs-in which none of the vertebrae bears more than two pairs of rib facets-it
may always be a divided diapophysis which bears both facets (the parapophysis being
absent throughout the entire dorsal series and not, as in proterosuchians, in the posterior
dorsals only). But it can be seen from any good series of pseudosuchian vertebrae,
extending from the middle of the neckto the middle of the back(as is known, for example,
in Mundasuchus), that this is very unlikely. Each successive vertebra shows a further
stage in the gradual upward and backward migration of both major rib processes, the
parapophysis following the diapophysis and eventually becoming confluent therewith
in the hinder part of the trunk. A similar migration seems to occur in the proterosuchians
(Hughes, 1963: fig. 1) and in Eupurkeria (Ewer, 1965).
CLASSIFICATION OF T H E PROTEROSUCHIA
157
Tatarinov (1961), in any case, pushes his argument too far. He claims that threeheaded ribs were also present in Chasmatosaurus (‘C. indieus’”) and in Chasmatosuchus,
which, so he admits, are certainly distinct genera and to be placed in a different subfamily from the several forms included by him in Erythrosuchus. Further, he suggests
that three-headed ribs in the anterior dorsal region may well have been characteristic
of all early archosaurs; and since his paper was published Ewer (1965, fig. 8d) has
reported the occurrence of ‘virtually three-headed’ ribs in Euparkeyia. If this were all
true, then the presence of three-headed ribs in certain selected species could hardly be
used to justify his inclusion of those species, but of no others, in the one genus
Erythrosuchus.
Certain incidental points deserve comment. We would dispute Hughes’ contention
that ‘The position of the cervical rib facets close together and very low down on the
anterior rim of the centrum is met with amongst archosaurs only in the small group to
which Chasmatosaurus and Erythrosuchus belong. The usual condition, as seen in a
crocodilian for example, is with the parapophysis low down on the central rim and the
diapophysis higher up, and well back along the neural arch.’ T h e position of parapophysis and diapophysis in, say, Mandasuchus or Hesperosuchus does not seem to differ
significantly from thatinChasmatosaurus. Likewise we cannot agree withHughes that ‘In
the pectoral region of pseudosuchians . . . none [of the vertebrae] has a lamella of bone
[between parapophysis and diapophysis] comparable to that of Chasmatosaurus.’
Finally, von Huene’s drawings of the vertebrae of Vjushkovia triplicostata suggest to
us, familiar as we are with archosaur vertebrae, that he has not always assigned them to
their correct positions in the vertebral column. For example, the vertebrae shown in his
Plate 13, figs 11, 12 and 13, which he describes as 17th, 19th and 22nd pre-sacrals
respectively (= loth, 12th and 15th dorsals), resemble the more anterior dorsal
vertebrae of other archosaurs.
We shall now discuss in turn the various genera of the Erythrosuchidae which, so
it is claimed, are synonyms of Erythrosuchus.
Vjushkovia = Erythrosuchus? Tatarinov (1961) makes a detailed comparison of
Vjushkovia triplicostata with Erythrosuchus africanus. First he considers the structure of
the skullroof. Whencomparedwiththespecimenof E. africanusdescribed byBrink( 1955,
fig. 2), V . triplicostata shows an exact correspondence in every particular save one : the
external margin of its prefrontal is more convex. But these two forms-V. triplicostata
and Brink’s E. africanus -differ in two further respects from the big specimen of E.
africanus described by von Huene (R.3592). First, the parietal foramen of the big
E. ufricanus is quite large (diameter about 1 cm), while in Brink‘s specimen and in
V.triplicostata it is very small or absent. Secondly, in the big E. africanus the postfrontal
(which, so says Tatarinov (1961) von Huene did not record, referring all of it to the
postorbital) reaches the upper temporal fenestra, while in Brink‘s specimen and in
V. triplicostata it does not. (In Broom’s holotype of E. africanus, the skull, apart from
a few indeterminate fragments, is not preserved.)
* Tatarinov (1961) cites von Huene’s figures of the Panchet vertebrae which we call cf. Chasmatosaurus
sp., taken by von Huene from Huxley. Hughes (1963) ‘can make out no such condition’ with three facets
in Huxley’s figures. But we believe that the anterior dorsal vertebrae illustrated by Huxley in his pl. 2,
fig. 5 could well have had three pairs of facets.
I1
158
A. J. CHARIG AND 0. A. REIG
Another supposed difference between E. africanus and V . triplicostata concerns the
lateral fenestra in the lower jaw, which, according to von Huene, is absent in the former
but present in the latter. As mentioned above (p. 134), Tatarinov (1961) rightly
points out that such slight evidence as there is suggests its presence in E. africanus
rather than its absence, and this supposed difference may therefore be discounted.
Further comparison of the skull of E. africanus (again using R.3592) with that of
V. triplicostata shows more similarities ; Tatarinov (1961) mentions the premaxilla,
squamosal, quadratojugal, jugal, postparietal and prootic, not all of which were
correctly described by von Huene. Most important in this connexion is Tatarinov’s
conclusion that the posterior border of the lower temporal fenestra in V. triplicostata
was not very different from that found in E. africanus; there is no evidence for the Vshaped contour shown in von Huene’s reconstruction of this border in the Russian
reptile, which, it may be presumed, was made only in the mistaken beliefs that Vjushkovia was a pseudosuchian rather than a proterosuchian and that this ‘V’ was a typical
pseudosuchian character (see Walker, 1964). Von Huene’s reconstruction of the antorbital fenestra of V . triplicostata, as a large opening lying in a basin-like depression,
is likewise entirely conjectural and was presumably based on the same unwarranted
assumption of the animal’s pseudosuchian nature.
Tatarinov also considers the post-cranial skeletons of the two genera concerned.
He believes that the appendicular skeletons show a profound similarity and differ only
in second-degree details; the differences, incidentally, are listed by von Huene (1960).
As for the vertebral column, there are differences in proportion between the vertebrae
(which are relatively much shorter in E. africanus), but these occur also between individuals of the same species and may be related to absolute size and differential growth.
Tatarinov therefore concludes that Erythrosuchus africanus and Vjushkovia triplicostata are congeneric but specifically distinct. The latter is distinguished mainly by
its smaller size and by the more convex external margin of the prefrontal.
Hughes (1963)notes that the skull of Vjushkovia is smaller than that of Erythrosuchus,
that the maxilla is relatively longer (with 13 teeth instead of 1 l),that the pectoral centra
are less shortened and the tibio-femoral index much higher. He believes that the
differences in proportion may be correlated with the difference in size, and that the two
forms are certainly congeneric; he consequently lists Vjushhovia in the synonymy of
Erythrosuchus. On the other hand, he considers that the presence of three-headed
pectoral ribs in the Russian form justifies its specific distinction as E. triplicostatus.
Young (1964) thinks otherwise. Because Vjushkovia is much smaller then Erythrosuchus, because it has three-headed ribs which are unknown in Erythrosuchus, because
the parietal foramen is absent whilst in von Huene’s specimen it is present, and because
of many minor differences, the view that these two forms (together with Garjainia and
Dongusia) are congeneric is ‘too good to be true’. Some of Young’s dozen or so minor
differences are imaginary, being based on characters which are unknown in one or both
genera (such as the number of teeth in the dentary and the presence or absence of cervical
intercentra), but others are real enough. He writes that Vjushkoaiu is ‘very similar to
Erythrosuchus as observed by Tatarinov, although it is by no means a synonymous
[sic] of it.’
Our own opinion is as follows. Tatarinov asserts the generic identity of Erythrosuchus
CLASSIFICATION OF THE PROTEROSUCHIA
159
africanus and Vjushkovia triplicostata on the grounds that one skull roof of the former
species (Brink‘s specimen) is very like the skull roof of the latter species. At the same
time he ignores the implication of the fact that another skull roof of E. ufricanus (von
Huene’s specimen) seems to be different from both of these. If one isolated skull roof
referred to E. africanus, and that alone, resembles V. triplicostata more closely than it
does the most complete and best-known specimen of E. africanus, is it not more logical
to refer that skull roof alone to the genus Vjushkovia rather than to place the two entire
genera in synonymy ? Indeed, the latter course would be justified only if the type of
E. africanus were also to resemble TT. triplicostata in its skull roof; and, as mentioned
above, the type has no skull.
BY
Itf
91
FIGURE
3. Reconstruction of skull of Erythrosuchus ufricantrs Broom, based on B.M.(N.H.)
specimen no. R.3592 (modified from von Huene 1911).
From above, approximately 4 natural size.
By not going into this more thoroughly Tatarinov weakens his own case, for both the
apparent differences in the skull roofs mentioned above can be safely discounted. First,
let us consider the question of the absence or presence of a large parietal foramen.
Von Huene’s specimen of E. africanus certainly has a large hole in about the right place;
but the skull roof (as in all these specimens) has a median depression, with consequent
thinning of the bone, in the region of the fronto-parietal suture, and the hole, which is
irregular in outline and has no clearly defined natural edge, could well have been
greatly enlarged during the rather crude mechanical preparation to which the specimen
appears to have been subjected. The preparator, indeed, may well have been responsible
for the very existence of the ‘foramen’. I n any case, the taxonomic significance of this
character may have been greatly over-rated, for the condition seems to vary between
individuals which are clearly of the same species; thus Haughton (1924, pl. 8, fig. 1)
described and figured Chasmatosaurus vanhoepeni without a parietal foramen, as did
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A. J. CHARIG AND 0.A. REIG
Broili & Schroder with a second specimen (1934, fig. 2), but Brink (1955, fig. 1B)
noted the presence of ‘a very tiny parietal foramen’ in a third individual.
Secondly, it is simply not true that von Huene did not record the postfrontal in the
B.M.(N.H.) specimen of E. africanus when describing it in 1911. On p. 7 he wrote:
‘Postfrontale: Das linke Postfrontale (Taf. 111, Fig. 2) ist recht unvollstandig, vom
rechten fehlt derjenige Teil, der an die Schlafengrube grenzt. Eine kurze Strecke
bildet das Postfrontale den Hinterrand der Orbita.’ In other words, the hinder part of
the postfrontal is not preserved on either side; this is confirmed by an examination of
the actual specimen. Yet von Huene, in his reconstruction of the skull roof as seen
from above (1911: 13, fig. 9a), extended the postfrontal backwards to form part of the
border of the upper temporal fenestra (so that it ‘an die Schlafengrube grenzt’) and to
separate-at least on the dorsal surface of the skull-the parietal from the postorbital ;
as far as we know, there was no evidence to support this part of his reconstruction.
Thus it is clear that Tatarinov’s other supposed difference between the skulls of the
B.M. (N.H.) E. africanus on the one hand and of Brink’s E. africanus and of Vjushkovia
on the other is based not on fact but on a probably erroneous conjecture.
In conclusion, it would seem that the various specimens referred to Erythrosuchus
africanus and Vjushkovia trzplicostata show no very great differences from each other,
either in the skull or in the post-cranial skeleton, although V . triplicostata is not known
to grow as large as E. africanus and exhibits many minor differences in the form and
proportions of the constituent elements. Tatarinov places the two genera in subjective
synonymy while Young refuses to do so ; Tatarinov’s view might be preferred because
he has had access to the Vjushkowia material and Young has not. But the presence of
three-headed anterior dorsal ribs, so characteristic of V . triplicostuta, has not been
satisfactorily demonstrated in E. africanus. Until such time as this may be done we
prefer to regard Erythrosuchusand Vjushkoviuas two separate genera, albeit closely allied.
Garjainia = Erythrosuchus? Ochev (1958) placed Garjainia relatively near to the
Proterosuchidae; it may be presumed that one of his reasons was the slight downward
bend of the snout. At the same time he considered that certain progressive characters
of the genus-the thecodont insertion of the marginal teeth, the absence of palatal
teeth, of postparietal and of cervical intercentra-precluded its actual reference to
the Proterosuchidae and justified his erection of a new family Garjainiidae. (Another
progressive character, not used in the family diagnosis was the absence of a parietal
foramen.) According to Ochev Gurjuinia differed from Erythrosuchus in all these
characters (except the nature of the tooth insertion) and also in the lighter build of
the skull and lower jaw, the different form of the skull vacuities, and the presence of a
lateral mandibular fenestra.
Tatarinov (1961) points out that Garjainia has a higher skull than the proterosuchids,
with orbit and temporal fenestrae of different shape. On the other hand, he claims that
Ochev was mistaken in three of his five ‘progressive’ characters-that Garjainia
probably possessed a postparietal (subsequently lost), that supplementary preparation
has revealed a very small parietal foramen, and that the remains include one
intercentrum; Garjainia could therefore be an erythrosuchid. (As for Ochev’s other two
‘progressive’ characters, neither thecodont tooth insertion nor the absence of palatal
CLASSIFICATION OF THE PROTEROSUCHIA
161
teeth would controvert such a proposition.) Tatarinov also mentions that, while Gurjuinia
prima is smaller than Erythrosuchus ufricunus,with a relatively lower skull, it corresponds
with ‘E. triplicostatus’ [ Vjushkoviu] in the detailed structure of the skull, in the number
of premaxillary teeth (five), in the presence and position of the lateral mandibular
fenestra, in the structure and moderate elongation of the vertebrae, and in the form of
the pectoral girdle. (This last is a little difficult to understand. Ochev (1958) declared
that the unique specimen of Gurjainia included only skull, right ramus of lower jaw
and four cervical vertebrae. Tatarinov, although he does not specifically state that there
is any new material or material undescribed by Ochev, refers to four posterior dorsal
vertebrae and to the pectoral girdle as well as to the intercentrum mentioned above.)
Unfortunately it is not known whether the anterior dorsal ribs of G.prima were three-
FIGURE
4. Skull of Guijuiniu prima Ochev (after Ochev 1958).
From left side, approximately 4 natural size.
headed. Finally Tatarinov attempts to show, not very convincingly, that the slight
downward bend of the snout, present in Garjuinia, was present also in E. ufricunus
and ‘E. triplicostatus’. On these grounds he places Garjainia in the synonymy of
Erythrosuchus, although he maintains its specific independence.
Hughes (1963) accepts Tatarinov’s thesis that the premaxillae turn downwards in
E. africanus and the Russian skulls. He says of Gurjuinia: ‘Clearly Tatarinov (1961)
is right in referring this specimen to Erythrosuchus and the specific characters he
enumerates may well be rendered worthless when more material is forthcoming.’
He lists Garjainia in the synonymy of Erythrosuchus.
Young (1964), on the other hand, again rejects Tatarinov’s synonymy. This is
because Garjuinia is much smaller than E. ufricunus, with the various skull openings
of different shapes ‘especially the highly and obliquely orientated single anteorbital
opening’ and a more backwardly slanting quadrate. He also denies that any [other]
erythrosuchid-or his new Shansisuchus-has a downward bend of the muzzle.
We again agree with Young. A mere comparison of the illustrations of the skulls of
Gurjainia, Vjushkoviu and Erythrosuchus africanus is sufficient to dispose of any
162
A. J. CHARIG AND 0. A. REIG
suggestion that Gurjuiniu might be congeneric with either (or both) of the other two.
Gurjuiniu is clearly allied to the other two, and may be classified with the Erythrosuchidae. I n some characters, however, it is more primitive than other erythrosuchids-as,
indeed, might be expected in an animal occurring rather lower in the succession; such
characters as are known accord quite well with a phylogenetic and stratigraphical
position intermediate between the Proterosuchidae and the Erythrosuchidae. T h e
downwardly bent snout, typically a proterosuchid character, and the high skull,
typically an erythrosuchid character, are both present but are developed only weakly ;
there is still only one antorbital fenestra on each side; the number of teeth in the upper
jaw has been reduced, though not to the same degree as in other erythrosuchids (see
Fig. 5); the lateral fenestra in the lower jaw, typical of erythrosuchids and later archosaurs, is still rudimentary; and the cervical centra, which are as long as high, have not
undergone the extreme shortening characteristic of Erythrosuchus and Shansisuchus.
As for ‘Chusmutosuchus ( ?)vjushkovi’, Tatarinov’s suggestion (1961) that it might
be a young Gurjainiu seems not unreasonable. But, like Hughes (1963) and Young
(1964), we believe that it is too imperfectly known to be referred to any particular genus.
Dongusia = Erythrosuchus? This genus is known from only one vertebra, described by
von Huene (1940) as an anterior dorsal and named Dongusiu coloruta. Romer (1945 :
597) referred the genus to the Ornithosuchidae.
Tatarinov (1961) claims (a) that this vertebra is remarkably similar, in nearly every
detail, to the posterior dorsals of ‘Erythrosuchus triplicostatus’ [ Vjushkovia] and ‘E.
primus’ [Gurjainia]; (b) that the only apparent difference of any significance is the
presence in D. coloruta of a hyposphene, while in the posterior dorsals of the other two
species named there is in its place a paired structure, each half of which consists of a
lamella bending downwards from the inner edge of the postzygapophysis and separated
from its fellow by a median cleft; and (c) that his examination of the structure in
Dongusiu which von Huene described and figured as a hyposphene shows it to be not a
hyposphene but a paired structure exactly like that of ‘E. triplicostatus’ and ‘E.primus’.
For these reasons he concludes (a) that the Dongusiu vertebra is a posterior dorsal, not
an anterior dorsal; (b) that Dongusiu is congeneric with Erythrosuchus; and (c) that
the specific independence of ‘E. coloratus’ is also uncertain. Incidentally, there is no
published record of the finding of dorsal vertebrae of Gurjuiniu.
Hughes (1963) writes of Dongusiu that ‘The vertebra in question may belong to
Erythrosuchus . . . but such fragmentary material is really generically indeterminate
. .’ In his list on p. 235 he leaves Dongusiu incertae sedis.
Young (1964) cannot accept that Dongusz’u is congeneric with Erythrosuchus. H e
states that the single vertebra of Dongusia is much smaller, with many minor differences,
and that it is ‘rather characteristic’.
We do not question the close resemblance noted by Tatarinov between Dongusiu
and ‘Erythrosuchus’, nor do we doubt his observations on the true nature of von Huene’s
so-called ‘hyposphene’. But an equally great, or even greater, resemblance exists
between the Dongusiu vertebra and the anterior dorsals of Mundasuchus, which also
have the paired ‘pseudohyposphene’ described by Tatarinov ;the only difference lies in
the absence of a ventral keel on the Mandasuchus centra. It was written of Dongusiu
.
CLASSIFICATION OF THE PROTEROSUCHIA
163
(Charig, 1956: 347): ‘This vertebra bears a striking and detailed resemblance to the
anterior dorsals of Mundusuchus, in particular to the supposed fourth dorsal of specimen
no. 63’. (Actually the fifth dorsal makes a better comparison.) Mundusuchus, however
26-27:
25
-
20 -
15
-
10 -
Premoxillo
FIGURE
5. Tooth-counts in the Proterosuchia.
The tooth-counts given here are taken from what we believe to be the most reliable sources,
as follows :
Chasmatosaurits Broili & Schrijder 1934
Young 1936
Elnphrostichus
Brink 1955
Ga+z‘nia
Ochev 1958
Tatarinov 1961
Erythrosuchus
von Huene 1911
Brink 1955
Young 1964 (text on p. 127, not the very different figures given in the
Shansisuchus
comparative Table 11 on p. 147).
(see von Huene, 1956; Charig, in press), is certainly not congeneric with Erythrosuchus;
it is not even a proterosuchian. It is therefore apparent that a great degree of homogeneity exists among the vertebrae of Thecodontia and that Tatarinov’s conclusionsthat the ‘anterior dorsal’ of Dongusiu is in fact a posterior dorsal of Erythrosuchus-are
quite unjustified.
A. J. CHARIG AND 0.A. REIG
164
In any case, the entirely inadequate nature of the Dongusia material and, in particular,
the lack of any evidence that the genus possessed three-headed ribs, must lead to its
being placed incertae sedis (following Hughes). Indeed, the name Dongusia might
better be regarded as a nomen dubium.
Cuyosuchus = Erythrosuchus? The opinions of Tatarinov (1961) and Hughes (1963)
on the synonymy of Cuyosuchus with Erythrosuchus are cited in the ‘Historical introduction’ to the full account of Cuyosuchus by Reig & Charig (in press). Our opinions
on the suggested synonymy are given in the same paper.
Dasygnathoides = Erythrosuchus? Hughes (1963) also suggests the possible inclusion
in the genus Erythrosuchus of the Upper Triassic reptile described as Dasygnathus
Huxley 1877; which name, incidentally, is not a nomen nudum-as stated by Hughesbut a junior homonym of Dasygnathus Macleay 1819, a coleopteran, for which Kuhn
proposed the new name Dasygnathoides in 1961. ‘?Dasygnathus’ is therefore included
in Hughes’ list of synonyms of Erythrosuchus.As mentioned above (p. 139), however,
Walker (1964) disagrees with Hughes’ opinions on Dasygnathoides and places the genus
in the synonymy of OrnithosuchusNewton 1894; which latter, in his view, is not even
a thecodont but a primitive saurischian dinosaur.
Shansisuchus heiyuekouensis. Another nominal species of erythrosuchid merits consideration in this review. Young (1964) describes and discusses a second species of
Shamisuchus,S.heiyuekou&, the relationships of which seem a little difficult to understand. The holotype includes 17 vertebrae (most of the dorsals, the two sacrals and the
first two caudals), both ends of one humerus, one complete femur with part of the other,
and the proximal parts of both tibiae; the associationof the limb bones with the vertebrae
as parts of one individual is not absolutely certain. Referred to the same species as paratypes are nine collectionsoffragments,one of whichincludessomeskullmaterial.Young’s
reasons for referring these to S.heiyuekouensis,however, seem rather unsatisfactory ;and
the descriptions and illustrations show that, where comparisons with the holotype are
possible, the paratypes are often quite different from the holotype and/or different from
each other (contrast the humeri, fig. 40 A-D, fig. 42 A, B). Yet it is upon these paratypes
rather than upon the holotype that the more significant of the supposed differences
between S. shansisuchus and S. heiyuekouensisare based; the only respects in which the
holotype of S.hezyuekouensis differs from S. shansisuchus lie in its rather smaller size, the
presence of a broad sagittal groove on the ventral side of the anterior dorsal centra, and
the more sigmoid shapeof the femur. One instance of an unsatisfactoryparatype concerns
two elongated cervical vertebrae (Young’s fig. 38 B, C) referred to S. heiyuekouensis
simply on a basis of size; Young considers that they are either too small or too large for
any of the other thecodonts described from the Ehrmaying Series and, therefore, that
their ‘belonging. to the present new species is almost certain’. But these vertebrae are
quite unlike cervicals of either Shansisuchus shansisuchus or Erythrosuchus; they seem to
be far closer (as Young himself observes) to Chasmatosaurus.Further, we do not consider
that Young is justified in attaching so much significance to their size; except for their
being rather larger, they are otherwise also very like the elongated cervical vertebrae
referred by Young to his presumed euparkeriid Wangisuchusfrom the same Ehrmaying
Series (his fig. 52 A-E). Again, a ‘posterior dorsal’ vertebra (fig. 38 E-actually an
..
CLASSIFICATION OF THE PROTEROSUCHIA
165
anterior dorsal) is apparently referred to S. heiyuekouensis because it is described as
having traces of a third rib facet, which S. shansisuchus and the other Ehrmaying thecodonts do not possess. But the illustration shows that this vertebra was not provided with
three pairs of facets; the ‘lower facet’ can only be an abraded surface on the front edge of
the centrum, and it is the ‘middle facet’ which is really the parapophysis. Hence Young’s
diagnostic characters (p. 151) ‘Neck vertebrae distinctly elongated, similar to that of
Chasmatosaurus’ and ‘Traces of third articulation surface preserved [in at least some of
the dorsal vertebrae]’ cannot logically apply to S . hezyuekouensis. In the light of all this
it seems advisable to ignore S. heiyudkouensis in any systematic review until its true
diagnostic characters are known.
Conclusions
The question of the systematic position of Cuyosuchus is left aside for special
consideration in the full account of that genus by Reig & Charig (in press).
On all other matters relating to the subordinate taxa of the Proterosuchia the following
conclusions seem reasonable at present :
(1) The suborder may conveniently be classified into two families, the more primitive
Proterosuchidae and the more advanced Erythrosuchidae ; their respective diagnostic
characters have been listed above (pp. 141-142). Further division of theErythrosuchidae
into two subfamilies, one based on Erythrosuchus and one on Shansisuchus, would
seem to be unjustified as yet.
(2) The Proterosuchidae include the following genera:
Proterosuchus
Archosaurus
Chasmatosaurus
Chasmatosuchus
Elaphrosuchus
It may be that Proterosuchus is a senior synonym of Chasmatosaurus (see Addendum,
pp. 167-168)’ but this question cannot be resolved on the evidence published hitherto.
(3) The Erythrosuchidae include the following genera:
Ery throsuchus
Garjainia
Shansiswhus
Vjushkovia
Vjushkovia might be congeneric with Erythrosuchus, but this cannot be proved one way
or the other on the evidence at present available.
(4) The following generic names, applied to material of Lower Triassic or probably
Lower Triassic age which is likely to be proterosuchian but is extremely scrappy,
should be regarded as nomina dubia:
Ankistrodon
A rizonasaurus
Dongusia
Ocoyuntaia
Seemannia
12
A. J. CHARIG AND 0. A. REIG
166
( 5 ) The only genera of which more than one species has been described are
Chasmatosaurus (4), Chasmatosuchus ( 3 ) and Shumisuchus (2). The possible
conspecificity of Chasmatosaurus vanhoepeni and C . alexanderi is discussed in detail,
d
ui
ui
ui
5
-I
6
bl
6
N
FIGURE
6. The Proterosuchia: a highly speculative correlation of the stratigraphical positions
of the various genera, and an even more speculative, greatly simplified scheme of evolution.
in so far as it affects the characters of the genus as a whole (and perhaps of the family
and suborder), but no conclusions are drawn from this. The claims to separate status
of other non-type species are not considered.
CLASSIFICATION OF THE PROTEROSUCHIA
167
(6) The advanced proterosuchid Elaphrosuchus and the primitive erythrosuchid
Garjainia bridge the evolutionary gap between their respective families, at least in
some particulars (see pp. 149-150, 161-162).
SUMMARY
The earliest archosaurs (Upper Permian and Lower Trias) have been classified in
many different ways. All classifications introduced during the period 1945-67 are
compared and are themselves classified. They are then evaluated in detail; in some
cases this has necessitated reconsideration of the descriptions in the literature and,
where practicable, the fossils themselves have been re-examined.
The typical characters of these earliest archosaurs are listed. Most of them together
form a single taxonomic unit which should be ranked as a suborder and called the
Proterosuchia. A few Lower Triassic archosaur genera should be excluded, and there
is no justification for including any Middle or Upper Triassic genera.
The Proterosuchia may conveniently be classified into two subordinate taxa, the
characters of which are listed. These should be ranked as families and called Proterosuchidae and Erythrosuchidae respectively. The composition of each family is considered and, in particular, the placing of severalgenera in the synonymy of Erythrosuchus
is rejected. Lists are given of the genera in each family, and of those generic names which
should be regarded as nomina dubia.
The possible conspecificity of Chasmatosaurus vanhoepeni and C . alexanderi is also
considered, albeit inconclusively.
A highly speculative, greatly simplified scheme of evolution of the Proterosuchia
is drawn up.
ACKNOWLEDGEMENTS
In May 1968 Dr A. D. Walker (Department of Geology, University of Newcastle
upon Tyne) visited Munich, where he made detailed observations on the skull of
Chasmatosaurus vanhoepeni which Broili 8c Schroder had described in 1934; he also
photographed it in several views. We should like to thank Dr Walker for his kindness
in allowing us access to his unpublished notes and photographs and in giving us the
benefit of his opinions, with permission to publish whatever we wished.
We should also like to thank Dr H. W. Ball, Keeper of Palaeontology in the British
Museum (Natural History), who kindly read the manuscript of this review.
ADDENDUM
Since this paper was accepted for publication the senior author (A. J. C.) has received
from Dr A. R. I. Cruickshank of Johannesburg a letter dated 26 January 1970.
This letter states :
(a) that the unique specimen of Proterosuchus fergm', hitherto believed lost, has
been found in the South African Museum (Cape Town);
(b) that the holotype of Chasmatosaurus vanhoepeni could not be found in the
Transvaal Museum (Pretoria) ;
168
A. J. CHARIG AND 0. A. REIG
that it seems to the writer (A.R.I.C.) that the palate of P.fergusi-virtually the
only part well enough preserved to allow any comparisons-is the same as those
of the various specimens referred to C. vanhoepeni (all the specimens together
forming a growth series); and
(d) that it seems probable that P.fergusi and C. vanhoepeni are congeneric but not
conspecific.
Cruickshank's forthcoming publication will enable us to examine the evidence for
his opinions (c) and (d). Should we accept them, Proterosuchus and Chmmatosaurus
would become synonyms; Proterosuchus would be the senior of the two and hence
would be used in place of Chasmatosaurus.
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CLASSIFICATION OF THE PROTEROSUCHIA
ABBREVIATIONS USED IN FIGURES
a
aof
ar
bo
bs
d
e
ec
en
f
fm
in
iP”
1
1
lmf
?Is
Itf
m
n
OP
or
angular
antorbital fenestra
articular
basioccipital
basisphenoid (including rostrum)
dentary
epipterygoid
ectopterygoid
external naris
frontal
foramen magnum
internal naris
interpterygoid vacuity
jugal
lachrymal
lateral mandibular fenestra
llaterosphenoid
lower temporal fenestra
maxilla
nasal
opisthotic
orbit
P
Paf
Pf
Pl
Pm
PO
popr
PP
Pra
Prf
PS
Pt
Ptf
9
qf
qj
sa
SOC
sof
sq
stf
utf
V
parietal
parietal foramen
post frontal
palatine
premaxilla
postorbital
paroccipital process
poetparietal
prearticular
prefrontal
parasphenoid
pterygoid
post-temporal fenestra
quadrate
quadrate foramen
quadratojugal
surangular
supraoccipital
suborbital fenestra
squamosal
aubtemporal fenestra
upper temporal fenestra
vomer
171