Zoological Journal of the Linnean Society, 62: 161-177.With 13 plates and 1 figure
February 1978
The pes of Erythrosuchus africanus Broom
A. R. I. CRUICKSHANK
Bernard Price Institute f o r Palaeontological Research,
University of the Witwatersrand, Johannesburg, South Africa
Accepted for publication March 1 9 7 6
The pes and ankle of the proterosuchian thecodont Erythrosuchus africanus Broom are
described in detail and it is shown that the ankle in particular is of an advanced type, derived
from an Euparkeria-like ancestor and n o t capable itself of giving rise t o any other.
Eryrhrosuchus was probably tending towards digitigrady in its hind feet. Erythrosuchus and
Euparkeria can be placed in different families within the Proterosuchia and because of their
advanced morphology are probably very late Lower Triassic proterosuchians.
CONTENTS
. . . . . . . . .
Introduction
Material
. . . . . . . . . .
The foot of Erythrosuchus afn’canus Broom
Discussion
. . . . . . . . .
Summary and conclusions
. . . . .
Acknowledgements
. . . . . . .
References
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161
161
162
174
176
176
177
INTRODUCTION
Previous descriptions of the pes of Erythrosuchus have been based largely on
incomplete material, but one specimen in the Bernard Price Institute for
Palaeontological Research is essentially complete and will form the basis of the
present description (von Huene, 1915; Hughes, 1963).
The animal itself is large, with a skull about 1 m in overall length, and the
limb-bones proportionately massive. However the ankle is of a bizarre pattern
when compared with other primitive (Lower Triassic) archosaurs and in view of
the other work in progress on the evolution of the early Archosaur ankle,
(Cruickshank, in prep.) a separate, full account of the whole foot was deemed
the best way of handling the matter.
MATERIAL
(a) B.P.I. F. 2096/M. 405. An almost complete right foot found in a nodule
with the digits flexed against the metatarsals, but whose tarsal bones had been
considerably disturbed during preservation. I t lacks metatarsal I and all of the
161
162
A. R. 1. CRUICKSHANK
phalanges of that digit. From Winnaarsbaken Burghersdorp, Upper Beaufort
Cynognatkus zone.
(b) B.M.N.H. 3592, ex D.M.S.W. R 525 (Figured Hughes, 1963: fig. 4 ) . A
left foot comprising the distal ends of the epipodials, the tarsus and the
proximal ends of all the metatarsals. Metatarsal I the most complete lacking
only a small portion distally. The B.P.I. specimen was prepared by vibro-tool
with sketches and photographs being taken at intervals to establish the relative
position of the individual bones in the nodule.
The British Museum specimen was also apparently preserved in a nodule and
was prepared by Hughes (1963: 230) in acetic acid. I t is almost dimensionally
identical to the B.P.I. specimen.
As the originals were of a variable surface colour, each bone or association of
bones (as in the case of digits 111 and IV) was cast in Plaster of Paris several
times. The casts were then painted in neutral grey primer and arranged in
groups for photography This seems to be a convenient method for illustrating
complex shapes of variable surface colour such as this material, but allowance
has to be made for the existence of minor flaws in the casts when looking at
the photographs.
T H E FOOT O F ERYTHROSUCHUS AFRICANUS BROOM
(Table 1)
The existing descriptions of the foot of Erythrosuchus are not adequate. Von
Huene (1915: 495-496, fig. 16) discusses the calcaneum thus: “Through the
kindness of Mr D. M. S. Watson . . . I (figure). . . the calcaneum of Erythrosziclius africanus Broom which is also enlarged but in another way than in
crocodiles and Episcoposaurus. I t does not possess a tuber, but is a broad and
thick plate rather similar to primitive reptiles.” However after making. general
comparisons with the calcaneum of “other Parasuchia” and concluding that
“
. . . this calcaneum . . . is a distinct development by itself”, continues,
correctly to identify it as . . . I suppose . . . a left one. The tuber (my italics)
extending laterally backwards and upwards is flat from the latero-anterior side
and has a cushion-like thickening at the postero-medial side for fixation of the
tendons.”
Although von Huene figured this specimen (1915 ) in correct orientation, his
descriptions are difficult to associate with the figures.
Hughes (1963: fig. 6) figures the whole of this foot as it was after he
prepared the nodule in acetic acid. Although he orientates his diagram as it
were a right foot (for comparative purposes no doubt) it is in fact a left one.
His descriptions are brief, but the conclusions valid “ . . . a specialized
derivative from the Chasmatosaur pattern: it has no resemblance to the foot of
later pseudosuchians” (Hughes, 1963: 230).
The ankle has a superficial resemblance to that of Etiparkeria (Ewer, 1965)
and is probably more likely to have been derived from that pattern rather than
directly from a proterosuchian as will be discussed below
However the foot in general differs in several important respects from that of
Euparkeria, the first being that the combined breadth of the proximal tarsals is
considerably less than the distance across the ends of the epipodials (Plates 1 to 4;
‘ I
163
PES O F ER YTHROSUCHUS AFRICANUS
Table 1. Principal measurements of B.P.I. F. No. 2096
~
Max. diameter distal end (mm)
Tibia
Fibula
107
72
96
47.5
Transverse diameter (mm)
Astragalus
Depth antero-posterior ( m m )
63.6
72
Transverse width (mm) Depth medially (mm)
Calcaneum
71
Max. length
(mm)
Metatarsal
Metatarsal
Metatarsal
Metatarsal
I1
111
1V
V
100.8
108
97.8
77.8
Depth laterally ( m m )
53.8
35.1
Max. diameter (mm)
Min. diameter ( m m )
38.5
54.5
33
40.5
Distal tarsal 3
Distal tarsal 4
Metatarsal 1 (B.M. 3 592)
~~
Min. diameter distal end (mm)
Max. length
as preserved (mm)
Max. width
proximally (mm)
54
60
Min. width
of shaft (mm)
32
Max. width
Max. width
Max. depth
Max. depth
proximally (mm) distally (mm) proximally (mm) distally (mm)
67.5
56.5
50
66
44.8
37
33.7
35.7
36.9
25.1
24.2
37.2
33
27.9
21.5
20.5
Estimated*
length (mm)
____
Digit 11
111
IV
V
110
92
77
34.5
__
~
Max. length
(rnm)
Digit 11
Phalanges 1
2
45
31
3
-
Digit 111
Phalangcs 1
2
3
4
-
42.7
21.8
17.3
-
Max. width
Max. width
Max. depth
Max. depth
proximally (mm) distally (mm) proximally (mm) distally (mm)
__
36
26.8
17.8
32
22
31.3
20.5
16.7
11.0
26.8
22
14.4
-
-
33.6
24.2
17.6
23.3
17.2
29.5
20
14.9
12.3
18.4
23.1
9.8
~
~
164
A. R. 1. CRUICKSHANK
Digit I V
Phalanges 1
2
3
4
34.5
18.8
13.7
9.4
25.2
1 7 .9
13
8 .2
28
1 6 .4
12
6 .8
22
13.1
9 .2
7
13
8.3
6.7
4.5
Digit V
Phalanx 1
34.5
25.2
1 9 .8
1 7 .8
11
DigitlMetatarsal Ratio
Digit II'* - 110
- 109%
M.T. 11
100.8
~
Digit 111.'
~
M.T. I11
Digit IV**
-
92
108
77
_ _ - -~
M.T. IV
97. 8
Digit V
__
M.T. V
= _ -
34.5
77. 8
-
85%
- 79%
-
- 44%
* As reconstructed (Fig. 14)
* * Based on estimated length of digit.
Plate 1 . A. Tibia in anterior view. B. 'Tibia in cnd view. All scalcs in centimctres. All photographs
are of B.P.I.F. No. 2096, and arc of the right limb.
PES O F ER YTHROSUCHUS AFRICANUS
Plate 2. A. Fibula in anterior view. B. Fibula in end view.
Plate 3. A. Asnagalus in anterior view. The arrow marks the position of the astragalar
component of the perforating foramen. Stereo. B . Astragalus in posterior view. The arrow
marks the position of the astragalar component of the perforating foramen. Stereo.
165
166
A. R. I . CRUICKSHANK
Plate 4. A. Calcaneum in anterior view. Medial end uppermost. Stereo. B. Calcaneum in
posterior view. Medial end uppermost. Stereo. C. Calcaneum in proximal view. Medial end
uppermost. Stereo.
Fig. 1). The distal end of the tibia (Plate 1 ) is massively round and that of the
fibula not much less, although it is oval in section. A small lateral process on
the tibia and a corresponding mark on the fibula (Plate 2) showed where the two
met, although it seems that the process on the tibia could have been enhanced
through post-mortem pressure. The ends of these two bones are slightly
hollowed and finished in rough bone.
The astragalus is a rough ovoid, almost totally devoid of character (Plate 3).
However it has at least two features which enable it to be orientated in the
reconstruction. These two features are namely an oval concave area covered
with finished bone pierced by nutrient foramina and a “Y”-shaped set of
grooves diametrically opposite. These two features correspond t o the same
areas on the anterior and posterior of the astragali of Proterosuchus and
167
Figure 1 . Reconstruction of the right pes of Erythrosuchusafricanus Broom. Based o n B.P.I. F.
No. 2096 with metatarsal I from B.M. 3 5 9 2 . In anterior view.
168
A. R. 1. CRUICKSHANK
Euparkeria, and might indicate that this bone in fact corresponds to the lateral
part of the normal proterosuchian astragalus (Cruickshank, in prep.). An
indication of the astragalar component of the perforating foramen can be seen
on the lateral surface.
The calcaneum is very similar to that of Euparkeria, but the medial portion
is even more removed from the proterosuchian condition than is seen in that
form (Plate 4). No indication of the perforating foramen is preserved on this
bone.
In anterior view the bone is sub-rectangular with a surface largely made of
finished bone and pierced with nutrient foramina. The medial portion is
produced into a deepened inverted pyramid, very similar in shape to that of
Euparkeria, but there is no distinct articular surface for either the astragalus or
the fibula. There is however a slight bevelling of the proximo-medial corner
which can be interpreted as an area of contact with the fibula. It is also quite
clear from the proportions of the various elements of this foot and their
relationships that a considerable portion of the ankle was filled with cartilage,
especially towards the medial side. The reconstruction has in fact been drawn
to show this as best as can be judged with the present material.
A slight angling on the latero-distal edge of the calcaneum might indicate the
proximal articulation of the fifth metatarsal, although in general terms this
might be expected to occur more medially on the distal surface. Therefore an
equivocal position has been shown in the reconstruction. I t is also clear that
there was no excavation on the proximal surface similar to that known in
Euparkeria. (C.M.Z. T 692, Museum of Zoology, Downing Street, Cambridge)
and interpreted there as being the insertion of the pedal retractor muscle.
The two distal tarsals are as is usual in thecodonts, with “four” being the
larger and articulating proximally with the calcaneum opposite the deepest
development of the postero-medial projection (Plate 5 ) . Laterally it abuts
against a large contact on the fifth metatarsal and distally number “three”
intervenes between it and metatarsals three and four to a certain extent.
All five metatarsals are available for study-the first being reversed from the
British Museum left foot in this reconstruction. This first metatarsal is not
quite complete and there are no associated phalanges of this digit with either
foot. Therefore the reconstruction has been made using the best available
evidence.
Metatarsal one (Fig. 11, is a short, stumpy bone with its proximal face
hollowed towards its anterior to take, in association with the second
metatarsal, the rounded astragalus. From the nature of this hollow, which is
finished in a good surface, a minimum of cartilage could have interfered here
and the articulation was a clearly movable one. Distally the articular face for
the first phalange twists through an angle of about 40” in an anti-clockwise
direction when viewed on the distal face, so that the axis of the digit would be
directed medially .
The second metatarsal (Plate 6) is the most robust of this series with a heavy,
rectangular proximal end. The proximo-medial surface is a facet for the first
metatarsal and confluent with the astragalar facet on the first metatarsal is the
corresponding portion of this its neighbour, again towards the anterior.
Distally, the condyle for the first phalange is transversely rectangular and its
long axis makes a large angle with the long axis of the proximal end. The
PES O F ER YTHROSUCHUS AFRICANUS
169
Plate 5. A. Fourth distal tarsal in three views. B. Third distal tarsal in two views.
relative rotation is once again anti-clockwise, but the digit is directed almost
straight out along the axis of the metatarsal. The shaft of the bone contracts t o
a minimum about three-quarters of its length from the base and there is no
marked arching of the bone. The latero-distal portion of the bone is excavated
slightly, the medio-distal portion is a smoothly rounded tubercle. The distal
face is only slightly grooved.
The third metatarsal (Plate 7) is very similar t o the second, being slightly
longer but otherwise very much more lightly built. The narrowest part is near
the midpoint and the proximal end is hollowed, almost symmetrically, for
distal tarsal three. The shaft is slightly arched.
Metatarsal four (Plate 8) is much more lightly built than the preceding two
and its shaft is highly arched with the narrowest portion also about its
midpoint. It is almost the same length as metatarsal 111. The proximal end is
oval, with a facet for the distal tarsals. The distal articulation also makes an
angle with the long axis of the proximal end, but it is also oval, as opposed to
being rectangular as in numbers two and three. The fifth metatarsal (Plate 9 ) is a
heavy club-shaped bone with a prominent “hook”, very much like that of
Eupurkeriu. The proximal end has two facets; a small one for meeting the
calcaneum and another, making an angle of about 130’ with the first, for
articulating with the fourth distal tarsal. The shaft of the bone twists slightly to
170
A . R . I . CRUICKSHANK
Plate 6. Metatarsal I1 in anterior (left) lateral (right), proximal (upper) and distal (lower) views.
Plate 7. Metatarsal I11 in anterior (left), lateral (right), proximal (upper) and distal (lower)
views.
PES O F ER YTHROSUCHUS AFRICANUS
171
Plate 8. Metatarsal I V in anterior (left), lateral (right), proximal (upper) and distal (lower)
views.
Plate 9 . Metatarsal V in anterior (left), lateral (right), proximal (upper) and distal (lower) views.
direct its digit towards the posterior of the foot. The distal face is an oval
slightly wider medially than laterally.
As already noted there are no phalanges of the first digit in either specimen.
The first phalange of the second digit (Plate 10) is a very substantial bone, quite
typical in all respects. There are both medial and lateral muscle insertions on
the distal, rounded condyle. The proximal end is round and concave. The
172
A. R . 1. CRUICKSHANK
Plate 10. Digit 11. Phalanges 1-3 in anterior view (left) and lateral (right) views. The centre row
shows phalanges 1 and 2 in proximal and distal views and the ungual phalanx ( 3 ) in proximal
view only.
Plate 11. Digit 111. Phalanges 1-4 in anterior view (left) and lateral view (right). Phalanx 1 in
proximal view only (centre upper)
second phalange seems t o have been able to be hyper-extended, and certainly
more so than in the equivalents in digits three and four. The second phalange
on the second digit has a sub-triangular proximal end, which is also hollowed. I t
is smaller than the preceding bone. The distal articulation has a median groove
and the tendon insertions face very largely anteriorly. The articulation with the
ungual phalange extended far onto the posterior surface. This last phalange is
PES O F ER YTHROSUCHUS AFRICANUS
173
the largest of the preserved unguals, but even then seems to be a very small
bone for a thecodont. I t is incomplete. Its proximal end is triangular, with the
apex pointing to the posterior surface, and divided into two unequal areas for
contact with the second phalange. The axis of the bone seems to have been
twisted so that the point of the claw would have been directed medially.
The first phalange of the third digit (Plate 11) is almost exactly the same
length as its counterpart of the second digit, but is considerably slimmer. Apart
from the apparent lack of an ability to hyperextend its next phalange, it seems
to be very similar to the preceding first phalange. The second phalange is a
slightly smaller edition of its counterpart of the second digit, and the third
phalange of this digit continues the trend. The ungual is a very small claw
which is incompletely preserved. Like the others, its tip may have been directed
slightly medially .
The trends established in the second and third digits are repeated in the
fourth, to a more marked degree (Plate 12). The principal effect of this is to
make all the phalanges of this digit very much smaller than their equivalents in
the other two digits. Thus, the fourth phalange, which might be expected under
normal circumstances to support a claw, is so small that it is impossible to
believe that it could have done so, although one is indicated in the
reconstruction. Of the fifth digit, (Plate 1 3 ) only the most proximal phalange is
Plate 12. Digit IV. Phalanges 1-4in anterior view (left) and lateral view (right). Phalanx 1 in
proximal view only.
Hate 1 3 . Digit V. Sole preserved phalanx in anterior view (left), lateral view (right), proximal
view (upper) and distal view (lower).
12
174
A. R. 1. CRUICKSHANK
preserved. It is about the same size and proportion as its counterpart in the
fourth digit although it is antero-posteriorly narrower. I t does not have a
groove on the distal condyle and it is conceivable therefore that it did not
support any further phalanges. This idea is supported by observations made on
the hind feet of other early thecodonts where the distal phalanges of the fifth
digit are reduced in size, or even not present at all. The digital formula is ?, 3 ,
4, 4 (5), ? l .
In general terms this foot (Plate 14) differs from that of Euparkeria in the
much modified astragalus, the simplified calcaneum and a possible lack of
phalanges two and three on the fifth digit. (Ewer, 1965; Cruickshank, in prep.)
In Euparkeria the digits seem to be either sub-equal to the metatarsals, or
slightly longer than them. In Erythrosuchus the digits at very best are only just
sub-equal to the metatarsals. It is seen in more generalized thecodonts that the
digits usually exceed their metatarsals in length e.g. Proterosuchus and
Euparkeria (Cruickshank, 1972: fig. 10; Ewer, 1965: fig. 13).
Charig (1972: 146) concludes“The foot of the ‘sprawler’ . . . is also primitive in structure with each
phalangeal series much longer than its metatarsal and with digit IV the
longest. Pseudosuchians . . . and crocodilians. . . show a reduction in the
length of the digits, for the phalangeal series are generally no longer (or
even shorter) than the corresponding metatarsals; they also show the
beginning of a trend towards a bilaterally symmetrical foot with digit IV
slightly shorter than digit 111 and digit V greatly reduced”.
which confirms the idea that Erytlzroszichus represents a developmental stage
beyond that of Euparkeria.
In both Euparkeria and Erythrosuchus the effective joint between leg and
foot must have been mesotarsal, notwithstanding Ewer’s evidence (1965: 426)
to the contrary. I t just does not seem possible to effect any movement between
calcaneum and astragalus as would be required by her analysis. In fact,
reappraisal of the unnumbered specimen figured by both her and Broom (Ewer,
op. cit. plate 34, fig. 30) shows that the astragalus and calcaneum are still
locked together in a natural relationship and only the fibula has moved
significantly. I t is also of interest to note that in NM C 3016 (Proterosuchus) a
similar post-mortem disjointing of the ankle took place. The astragalus and
calcaneum are still in their original articulation, but the fibula has rotated on
the astragalus away from the calcanear contact. The only conclusion that this
can lead to is that in the Proterosuchia whereas the fibular-calcanear joint was
weak, both proximal tarsals moved as a unit.
DISCUSSION
In the past Euparkeria and Erythrosuchus have been considered to be very
closely related genera (Ewer, 1965; Cruickshank, 1972: 117), but in detail their
lineal relationships have not been discussed except by Hughes (1963: 230)
where he states that the ankle was a specialized derivative from the
Chasmatosaur (sic) pattern and bore no resemblance to the foot of later
pseudosuchians. Cruickshank noted in passing (1972: 117) that the Euparkeria
ankle could be considered as a derivative of that of Erythrosuchus, on the basis
of comparative size only. However it is clear from a closer study of the ankle of
PE S 0 F ER YTHR 0s UCH US AFRICA NUS
175
these two genera that Euparkeria is the more generalized of the two and that
the Erythrosuchus ankle represents if anything a specialization of the
Euparkeria pattern, with a recognizable but reduced calcaneum comparable to
that of other proterosuchians and a highly specialized and reduced astragalus
corresponding to the lateral portion only of the proterosuchian equivalent. In
considering other features of the skeleton of these two genera a similar
comparison can be made. The braincase of Euparkeria is closely comparable to
that of Sphenodon and probably does not possess a laterosphenoid (Cruickshank, 1971) but the braincase of Erythrosuchus does possess an anterior
ossification which is undoubtedly a laterosphenoid (Walker, pers. comm. ). The
vertebrae of Erythrosuchus show a tendency to be “sculptured” in a manner
analogous to later thecodonts and dinosaurs, whereas those of Euparkeria are
very simple in their architecture. Finally, the digits of Erythrosiicliirs are
relatively shorter than those of Euparkeria. Thus in four basic characters
Euparkeria is less advanced than Erythrosrichus and hence must represent a
stage through which the ancestor to Erythrosuchus may have passed. The ankle
of Erytlirosiicliiis is even more specialized than that of Sliansisiichzrs (Young,
1964: fig. 34, 35) and the pes in the latter shows distinct differences
confirming this i.e. the proportions of phalanges to metatarsals. Otherwise
Shansisiichiis is clearly related to Erythrosiicliiis.
Eiiparkeria can therefore be regarded as quite distinct from Er~~tlirosirclirw
and Sliaiisiszicliiis and should be placed in a separate family from those two
genera. However all three belong in the sub-order Proterosuchia which in
summary can be considered to contain the following families and genera.
1. Proterosuchidae
- Proterosudius, Archosaurus
2. Erythrosuchidae
- Erythrosuchus
Shansisuchus
3. Euparkeridae
- Euparkeria
4. Proterochampsidae - Cerritosaurus, Gualosuchus
Chanaresuch us, Pro terochampsa
Some of the Chinese material has been omitted because of the lack of
certainty as to its affinities (e.g. Fennhosuchus).
One final point which emerges, is that Euparkeria and particularly
Erythrosucliiis show advances over the earliest Proterosuchia i.e. the Proterosuchidae. These latter are presumed to be of Uppermost Permian-Lowermost
zone and its equivalents
Triassic age, or zone IV of Russia and the L~~strc~saurzrs
in Africa and other Gondwanaland countries (Anderson & Anderson, 1970:
charts 4, 5, 21). The age equivalents of these zones within the Scythian (= L.
Triassic = Bunter) is presumed to be Lower Scythian (Griesbachian) at the
latest. The Cynogtiathus zone (in which occurs both Eiiparkeria and Erytlirosiicliirs) is placed according to Anderson & Anderson (1970) as Upper Induan
(Dienerian). However their acceptance of the L~~strosairruszone as being
uppermost Permian (Upper Tartarian) is open to question on a number of
grounds and it is more usual to consider the Lj’strosaurirs zone as being very
low in the Triassic (e.g. Haughton, 1969) and by implication of Induan age.
The difference in morphological structure between the Lystrosairrirs zone and
Cjxogriatliirs zone proterosuchians might then point o t the latter being of very
late Lower Triassic age. This point was covered in another context
A. R. I. CRUICKSHANK
176
(Cruickshank, 1967: 204) where it was noted that specimens of Kannemeyeria
simocephalus Weit, a typical Cynognathus zone anomodont species of South
Africa occurs in East Africa in association with a Middle Triassic assemblage of
thecodonts, cynodonts and rhynchosaurs. The grade of evolution of the
Euparkeria ankle is almost identical to that of Chanaresuchus (Romer, 1972)
from the Ischichuca Formation (= Chanares Formation) which is of late Middle
Triassic age (Cruickshank, in prep.). It might be reasonable to assume on all of
those grounds that the Cynognathus zone is therefore more likely t o be of late
Lower Triassic age or even early Anisian (Table 2).
Table 2. Suggested stratigraphical position of the South African Cynognathus
and Lystrosaurus zones
In Europe
Russia
“Standard
stages”
S. Africa Middle and
Upper Beaufort.
Anderson & Anderson
(1970)
South African
Middle and Upper
Beaufort.
This paper
M. Triassic
Anisian
Anisian
Anisian
__-_____
L. Triassic
Scythian
Olenekian
Spathian
Smithian
Dienerian
Griesbachian
Cynognathus zone
Induan
U. Permian
U. Tartarian U. Dzulfian
Cynognathus zone
Lystrosaums zone
Lystrosaurus zone
SUMMARY AND CONCLUSIONS
(1) The foot and ankle of the advanced proterosuchian Erythrosuchus
africanus Broom is described in detail for the first time.
(2) I t is shown that this pattern of foot and ankle is specialized and probably
derived from a condition similar to the other Cynognathus zone
proterosuchian, Euparkeria.
( 3 ) Functionally the Erythrosuchus foot shows a tendency towards the
digitigrade condition because of the ratio of digit length to metatarsal
length and in the metatarsals all being sub-equal in length.
(4) From a brief consideration of the relative stages of morphological
advancement, it is postulated that the Cynognathus zone proterosuchians
are so much more specialized than their Lystrosaurus zone forebears as to
probably represent genera of very late Lower Triassic or perhaps even
earliest Middle Triassic age.
ACKNOWLEDGEMENTS
I am indebted to Drs A. D. Walker and C. E. Gow for the critical reading of
early drafts of this paper and in particular to the former for much stimulating
discussion of matters pertaining to archosaur evolution in general. Mr Gerard
Smith drew the reconstruction of the foot and took the photographs of the
individual bones of the foot.
PES O F ERYTHROSUCHUS AFRICANUS
177
Financial assistance is gratefully acknowledged from the University of the
Witwatersrand and the C.S.I.R.. Pretoria.
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