Zoolugical Journal ofthe Linnean SocieQ (1984), 82: 159-1 75. With 6 figures
The teeth of Archaeopteryx and a
reinterpretation of the Eichstatt
specimen
M. E. HOWGATE
Department of <oology, Universip College London,
Gower Street, London W C I 6BT
Receiaed Jvouemher 1983, accepted for publication January 1984
A full description is given of the dentition in the London, Berlin and Eichstatt specimens of
Archaeopteryx lithographica. Definite differences in tooth shape are noted between the Berlin and
Eichstatt specimens. The teeth of the Berlin specimen are stout and peg-like, with a flatly conical
recurved tip; the teeth of the Eichstatt specimen are more gracile and evenly recurved. This is most
probably associated with a difference in food preference.
Four competing hypotheses are considered to explain these and other skeletal dijrerences: ( 1 )
Sexual dimorphism; (2) Ontogenetic differences; 13) The Eichstatt specimen is distinct at the
specific or generic level from the other specimens; (4) Polymorphism within the species A.
lilhographica. It is concluded that the most parsimonious interpretation of the osteology is that the
Eichstatt specimen is distinct from the other (Berlin, London and Maxbergj specimens definitely at
the species level and most probably at the genrric level. A new species is therefore proposed to
accommodate the Eichstatt specimen-Archaeopteryx
r e c u r v a sp. nov. T,ie teeth of
Archaeopteryx do not provide evidence of a close relationship to crocodilians.
KEY WORDS:-teeth
relationships.
-
diet
~
Eichstatt specimen
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Archaeopteryx recwrva sp. nov.
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CONTENTS
Introduction .
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Teeth of the Berlin specimen .
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Teeth of the Eichstatt specimen
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Teeth of the London specimen .
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Dietary hypothesis.
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Competing hypotheses on the relationship of thr Eichstatt specimen to other specimens of
Archaeopteryx . . . . . . . . . . . . . . . . . . .
Sexual dimorphism
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Ontogenetic difference. .
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Phylogenetic difference
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Polymorphism
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Conclusions .
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Archaeopteryx r e c u r v a sp. POV.
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The supposed crocodilian relationship of 4rchaeopleryx--evidence from the teeth . .
Acknowledgements
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References.
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002&4082/84/090159+ 17 S03.00jO
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0 1984 The Linnean
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M . E. HOWGATE
160
INTRODUCTION
I n the area of the Southern Franconian Alb known as the Altmuhltal, the
lower Tithonian rocks are represented by very fine-grained limestones which
were deposited in a quiet lagoon-the famous Solnhofen limestone series. It is
particularly the upper division of this series, the ‘Ober Solnhofen Plattenkalk’,
which has produced the best preserved vertebrate fossils, including those under
discussion here, the bird Archaeopteryx lithographica von Meyer and the small
coelurosaurian dinosaur Compsognathus longipes Wagner. Of the six known
specimens of Archaeopteryx, one is a single feather and two others, the Maxberg
(Heller, 1959) and Teyler (Ostrom, 1972) specimens, do not have any
indication of the dentition. Another, the London specimen (Figs 4, 5 ) ) has five
teeth on two broken and disarticulated jaw bones regarded by de Beer (1954)
and others as a premaxilla, but identified by Wellnhofer (1974) as a premaxilla
containing a single tooth and a maxilla with four teeth. Wellnhofer however
attributes both elements to the same (left) side of the jaw ramus, whereas the
maxilla is from the right jaw ramus and exposes the teeth in lingual aspect.
Finally there are two specimens which are preserved fully articulated and have
the teeth of the maxilla and premaxilla displayed in a comparable fashion.
These are the Berlin specimen (Figs lA, 2)) considered by all workers to be a
fully adult individual, and the Eichstatt specimen (Figs lB, 3 ) described by
Wellnhofer (1974) and Ostrom (1976) as a juvenile, or at most a sub-adult
specimen. Also considered in this study is Compsognathus longipes, as its tooth row
Table 1. Dimensions of the teeth of three Archaeopteryx specimens
Dimensions ( m m )
Length of tooth row
(tip of snout to last
maxillary tooth)
Upper jaw
Lower jaw
Premaxillary teeth
Number
Length of row
Max. crown ht
Max. crown dia.
Length of root
Maxillary teeth
Number
Length of row
Max. crown ht
.Max. crown dia.
Dentary teeth
Number
Max. crown ht
Max. crown dia.
Berlin
Eic hsta t t
London
14.0
14.5
12.0
14.5*
3
4
4.0
I .2
0.5
4
4.0
0.9
0.4
3
8(9)§
10.0
I .o
0.7
8
10.5
0.8
0.5
(2111
11
?
3
0.5
0.5
3
(2)t
4.5t
1.1:
0.6:
1.6:
3(6)7
10.0y
I .5
0.9
*Summation of lengths of left premaxilla and right maxilla taking no account of
possible overlap or incomplete preservation of the right maxilla.
t Only onc tooth preserved in the left premaxilla, but space present for at least four
teeth.
Measuremcnts from the isolated premaxillary tooth.
4 According to Dames (1884a, b) one tooth was broken off.
li Inrluding empty alveoli.
11 Number visible.
’I EETH OF .lR(’HalEOPTERYX
161
provides a useful functional comparison with those of the Archaeopteryx
specimens. This comparison does not imply any phylogenetic relationship
between Archaeopteryx and coelurosaurian dinosaurs. All numerical data on the
teeth of the three specimens are given in Table 1.
TEETH OF T H E REKI.1N SPECIMEN
‘ h e teeth of the Berlin specimen (Figs lA, 2), which were first noticed by
Karl Vogt and 0. C. Marsh, were fully prepared out and described by Dames
( I 884a), who noted that there were I 3 peg-like teeth along the right upper jaw
ramus, of which 12 remain. Of these, he ascribed six to the intermaxillary
(premaxilla) and seven to the maxilla. His reason for so doing is that a distinct
step is visible just behind the sixth tooth and the area above this ‘step’ is very
fractured. Wellnhofer (1974) also ascribes five or six teeth to the premaxilla on
what appear to be similar grounds. However, there is a distinct suture which
slants down at a shallow angle from the ventral margin of the external narial
opening to midway between the fourth and fifth tooth (Fig. 2 ) . Thus the upper
dentition is in this respect similar to that of the Eichstatt specimen (Fig. 3 , Table
1 ), which has four premaxillary teeth.
However, Dames correctly described what he saw of the overall structure of
the teeth, “These twelve teeth are almost of equal size and sha:pe, measuring
1 mm in length and 0.5 mm in width; the upper part [apical] is cylindrical, and
the lower half [occlusal] tapers rathcr abruptly to a point, the sharp point bends
rather under and inwards [posteriorly curved]. Their surfaces arc polished and
smooth, and show no ribs or furrows” (Dames, 1884b: 422).
Since the discovery of the Eichstatt specimen and its description by
Wellnhofer (1974) it has been tacitly assumed that the teeth of the Berlin
specimen were much the same as those of the more accessible Eichstatt
specimen. This misconception was aided by the drawings of the skull of the
Berlin specimen produced by Damcs (1884a, b), Petronievics (1925) and
Heilmann (1926)) which depicted the teeth as more evenly recurved than is in
fact the case. So much so that when Brodkorb (1971) suggested that
Archaeopteryx had peg-like teeth (he also gave a greatly overeslimated tooth
count of six premaxillary and 15 maxillary teeth), Ostrom came back with the
rejoinder that the teeth were not peg-like and referred Brodkorb to the Eichstatt
specimen for confirmation. B u t even in photographs of the whole skull i t is
evident that the teeth of the Berlin specimen are distinct from and more peg-like
than the teeth of the Eichstatt specimen and hence less theropod-like! [See
especially Ostrom (1976: 130) for a comparison of the two dentitions at this level
of resolution.] At higher magnification the differences between the teeth of the
Berlin and Eichstatt specimens are even more pronounced.
The teeth, which are fully displayed in labial view along the upper jaw
ramus, are isodont and appear to be set in distinct sockets. T h e most obvious
differences along the jaw ramus are due to differential tooth wear, breakage and
partial eruption of some of the teeth. T h e first five teeth, i.e. the four
premaxillary and the first maxillary tooth, are all of the same size and slightly
prognathous, while the more posterior teeth have an alternating replacement
pattern and are more or less vertical. A typical tooth is completely smooth and
translucent; in several cases the pulp cavity can be seen in outlinc. There is no
I62
M . E. HOWGA'IE
Figure 1, A, T h e jaw ramus of the Berlin specimen ofArchaeopteryx lithogruphica van Meyer. B, The jaw
ramus of the Eichstiitt specimen of Archneoptecyx, herein renamed Archaeopteryx recurva sp. nov.
indication of striations, carinae, banding or any other surface ornamentation
except on the fifth maxillary tooth, which is only partially erupted and exhibits
a distinct, slightly distally recurved carina medially on the labial surface. The
average tooth crown emerges from the socket without any visible constriction at
the root, appearing smoothly cylindrical in labial view. There may be a slight
'waist' about half-way u p the crown which gives the mesial and distal edges a
slightly sigmoidal shape; lhis is most evident in the premaxillary teeth. Towards
TEETH OF ilRCHAE0PTERY.Y
163
.
u
1 rnm
Figure 2. 'l'he teeth of the B d i n spccimen of Archaeopteryx lithographim von Meyer. AOF, Antorbital
fcnestra; DENT, dentary; ENO, external riarial opening; MX, maxilla; P-XIX. premaxilla.
the occlusal tip, between two-thirds and three-quarters of the distance from the
cervix, the crown becomes squatly conical with the most pronounced curvature
at the mesial edge, producing a distinctive distal offset to the asymmetrical tip of
the crown. This is most prominent in the posterior maxillary teeth, less so in the
antrrior maxillary teeth in which the tip is in line with the distal margin of the
tooth crown. The tip is least asymmetrical in the premaxillary teeth in which
the well-rounded and perfectly preserved tip is shifted slightly medial to the
distal margin. This is most noticeable in the most anterior premaxillary tooth
crown.
The exceptions to this general trend are the second and fifth maxillary teeth:
the former, which may be only partially erupted, has both mesial and distal
margins equally curved to produce a medial tip, and the latter has a smoothly
convex mesial margin coupled with a more pronouncedly concave distal margin
to give the tip a recurved profile.
1 EETH OE T H E CICHSTA TT SPECILMEN
T h e teeth of the Eichstatt specimen (Figs IB, 3 ) are similar to those of the
Berlin specimen in that they are all smooth, without surface striaticns or carinae
(except possibly on the ninth dentary tooth), translucent and often with visible
indications of the pulp cavity. Unlike the Berlin specimen, howeter, the tooth
crowns are evenly recurved and exhibit a pronounced alternating replacement
pattern. The premaxilla is well preserved and is ornamented with numerous
pits, presumably foramina for nerves to a sensitive snout area. Wellnhofer
(1974) noted that the majority of the teeth of the upper jaw had rounded tips
and were distinctly curved posteriorly, due to the anterior border being more
curved than the posterior border, but only "the fifth maxillary tooth has a sharp
164
M . E. HOWGATE
point”. O n close examination the rounded tips of some of the teeth appear to be
due to wear and a distinct wear facet can be seen a t the tip of the second
premaxillary tooth. Unworn tips can be seen on the third and fourth
premaxillary teeth as well as the fifth maxillary. These are quite distinctive as
just before the tip the smoothly curved mesial and distal margins are reflected
medially to produce a sharp but obtusely angled cone. As Wellnhofer has
observed, the first two premaxillary teeth are distinctly prognathous, as are all
but the last two teeth of the dentary, and the anterior teeth of both jaw rami are
relatively robust. The most posterior teeth are small, squat, obtuse cones. I was
unable to confirm Wellnhofer’s statement that three of the teeth of the lower jaw
are to be seen in medial (lingual) view. Although the fourth, eighth and ninth
dentary teeth appear to be curved anteriorly rather than posteriorly, I was
unable to convince myself that this was not just an artefact of the limited
preparation of the deeper-lying dentary teeth. Neither could I confirm or deny
the presence of an anterior carina on the ninth dentary tooth.
TEETH O F THE LONDON SPECIMEN
T h e five teeth (Table l ) , which are present on what appears to be a V-shaped
bony fragment in the centre of the counterslab, were first noticed by Sir John
Evans. He brought them to the attention of Owen who figured them in his
monograph (1863) and considered them as premaxillary teeth, probably of a
fish. Evans in his later paper (1865) declined to express a definite opinion as to
exactly which jaw element was involved, but was convinced that the dentigerous
bones were really a part of the Archaeopleryx skeleton.
Owen’s opinion that the jaw fragments represent one bone only, the
premaxilla, has in the main persisted. De Beer (1954) interpreted the bones
I mrn
Figure 3. The teeth ofthe Eichstatt specimen ofilrchaeopleryx, herein renamed Archaeopteryx recurva
sp. nov. See Fig. 2 lor explanation of abbreviations.
TEETH OF’ .JRCH.~lEOPTEK2”Y
165
(Fig. 5E) as a complete but crushed left premaxilla, and reconstructed them
(Fig. 5F) as a very deep bone unlike the premaxilla of either the Berlin or the
then undiscovered Eichstatt specimens. I n so doing he arrived at a tooth count
of seven for the premaxilla of the London specimen (four fully erupted teeth in
their sockets and at least three other distinct alveoli), this is as against a
supposed six for the Berlin specimen and four for the Eichstatt specimen.
Edmund (1 960), although recognizing that the main tooth-bearing fragment
was to be seen in lingual view, maintained de Beer’s reconstruction of the
fragments as representing a premaxilla (Fig. 5G). Wellnhofer (1’374) partially
corrected this misinterpretation. He regarded the main toothed element as the
left maxilla which had partially overridden the left premaxilla (which had space
for at most four teeth), but makes no mention of the fact that the maxillary
teeth are to be seen in internal view. Piveteau (1955) and most recently Martin,
Stewart & Whetstone (1980) describe the teeth as being associated with
fragments of a maxilla.
A detailed examination of the two fragments (Figs 4, 5A) indicates that
Wellnhofer was correct in supposing that the major toothed element was a
maxilla. However, and more interestingly, Edmund was also correct in noticing
that the teeth were displayed in lingual (internal) aspect. The left premaxilla,
the upper bone in Fig. 5A, carries one poorly exposed, relatively small and
mitre-shaped partially erupted replacement tooth, exposed in labial aspect. This
is probably the third of four premaxillary teeth. Above and anterior to the tooth
the bone is embellished with numerous foramina exactly like those on the
premaxilla of the Eichstatt specimen (Fig. 3 ) . This confirms that the supposed
fracture surface of the bone in de Beer’s restoration is indeed the ventral margin
of the premaxilla. Anterior to this third premaxillary tooth is at least one other
indistinct alveolus.
T h e lower bone in Fig. 5A bearing three teeth is a portion of the right maxilla
seen in lingual view. The teeth lie on a pronounced labial ridge and appear to
lie in distinct crater-like sockets. This is best seen in de Beer’s ultra-violet
photograph (1954: pl. 9, fig. 4) where the teeth can be seen to be surrounded by
large masses of poorly structured ankylosing bone. The mode of insertion could
therefore be said to be sub-thecodont rather than thecodont. T h e ankylosing
bone is quite distinct from the tooth root itself as is evident from the perfectly
preserved isolated premaxillary tooth (Fig. 5B) which lies just in front of the
maxilla. It is the presence of these large masses of bone surrounding each tooth
and masking the point of insertion into the alveolus which gave Evans (1865:
419) the impression that the teeth were set upon “a more bony base which
widens out suddenly into a semi-elliptical form, so that at the line of attachment
to the jaw, the base of one tooth comes into contact with that of the next”.
Of the maxillary teeth the best preserved are the first and third :Fig. 5C, D),
both of which are prognathous, appear flattened and bear terminal wear facets
which indicate an overbite by the upper jaw, at least partial occlusion with the
teeth of the lower jaw and a probable durophagous diet. I n other respects they
appear similar to the teeth of the Berlin specimen in being peg-like in outline,
translucent and devoid of surface ornamentation. A more important
consideration in establishing the similarity of the teeth of the London specimen
to those of the Berlin specimen is also provided by the isolated tooth lying in
front of the maxilla in the London specimen. This is identical in outline to the
166
M. E. HOWGATE
Figure 4. l ' h e anterior portions of the left premaxilla and right maxilla of the London specimen of
Archaeopteryx lilhoyapkica von bleyei-.
premaxillary teeth already described for the Berlin specimen, i.e. the apical twothirds of the crown is peg-like with shallowly sigmoidal medial and distal
margins, while the occlusal third is recurved sharply distally such that the tip is
in line with the distal margin. However, the exposed lingual surface is much
flatter than the well-rounded surface of the Berlin specimen. This is particularly
so in the recurved portion of the crown where an almost vertically oriented wear
facet can be seen just distal to the tip.
The root of this tooth is the only one fully exposed in any of the specimens of
Archaeopteryx and indicates that contrary to the opinions of Martin et al. (1980),
there is no constriction at the base of the crown and the root is not unduly
expanded apically. There is, as Martin et al. (1980) pointed out, a well
developed oval resorption pit in the lower half of the root. T h e 2.5 mm tooth
length given by Evans (1865) is probably of this tooth and includes the root
length (see Table 1 ) . A full tooth count cannot be given but it is most probable
that there were four teeth in the premaxilla, as in the other specimens. The
maxilla has three teeth preserved in situ and the ultra-violet photograph in de
Beer (1954) suggests that at least three others a t one time occupied now vacant
alveoli; this also accounts for the exaggerated interdental distance of 5 mm given
by Evans (1865).
Figure 5. T h e teeth ofthe London specimen ofArchaeopteryx lzthographzca von Meyer. A, Premaxilla and
maxilla as drawn from the counterslab; B, isolated premaxillary tooth showing sub-terminal wear facet,
root and resorption pit; C , maxillary tooth crown I ; D, maxillary tooth crown 3 showing terminal wear
facets and asymmetriral cross-sertion: E, line drawing and F, reconstruction as a crusher premaxilla; G,
Edniund's (1960) reconstructionofthe'premaxilla'; D, E,afterdeBeer (1954);C, afterEdmund (1960).
TEETH OF zlRCHdlEOPTER1p,\'
167
I rnm
F
168
M. E. HOWGATE
DIETARY HYPOTHESIS
Two alternative hypotheses can be formulated on the basis of the new
information presented above: that the subthecodont style of insertion and
unserrated teeth are plesiomorphic for the class Aves, in which case they have
remained unchanged from a presumably proterosuchian ancestor. Alternatively,
as Martin et al. (1980: 89) suggest is the case with the Cretaceous bird
Hesperornis, the teeth of Archaeopteryx may be neotenous. If so they may be
regarded as a stage in the evolution of a typical thecodont dentition into that
seen in Cretaceous birds. If this is the case then the most obvious conclusion from the differences in tooth architecture between the Berlin and
Eichstatt specimens is that they reflect a difference in diet. Among nonpiscivores a n isodont peg-like dentition is often associated with an insectivorous
diet and this is generally accepted as the preferred diet of Archaeopteryx. The
evidence of the lingual wear facets on the upper dentition of the London
specimen adds further weight to this contention. However, the Eichstatt
specimen departs from this pattern in that it has distinctly recurved teeth in
which the first two premaxillary teeth are prognathous, the upper and lower
teeth interdigitate rather than occlude, and the lower dentition is markedly
more prognathous than the upper. This is analogous in some respects to the
dentition of Compsognathus longipes (Stromer, 1934; Ostrom, 1978), which has
prognathous, peg-like and distinctly bent anterior teeth. The teeth of the midjaw are more compressed, smoothly recurved, often with a distinct distal carina
but lacking denticulations. Only on the most posterior teeth, which are small
and unrecurved, are denticles found. As seems to be indicated both by the style
of .the dentition and the well-preserved remains of Bauarisaurus cf. macrodact_ylus
within the body cavity (Ostrom, 1978), Compsognathus was able to take quite
large prey items and ingest them whole. I t seems that the Eichstatt and Berlin
specimens represent two stages along the route from an obligate carnivore to an
obligate insectivore. The Eichstatt specimen, still somewhat adapted to ingesting
whole large prey, lacks the sharp carinae and denticulations necessary to tear up
its prey, while the Berlin specimen appears better adapted to a more
insectivorous diet. The following evolutionary scenario is tentatively proposed.
( 1 ) The original tooth style is that common to pseudosuchian thecodonts and
theropods, namely an isodont dentition of moderately recurved and serrated
teeth, suited to cutting up prey into manageable pieces.
(2) A stage with a Compsognathus-like dentition, in which all the teeth are
strongly recurved and there is a fang-like development of the most anterior teeth
designed to force whole prey down the throat. Serrations are preserved as nonfunctional ‘atavisms’ only on the most posterior teeth.
(3) A stage corresponding to that seen in the Eichstatt specimen. The teeth
are stouter, sub-cylindrical, but with sharp points and distinctly recurved. T h e
anterior teeth of the upper jaw and most of the teeth of the lower jaw are
prognathous and the teeth interdigitate. T h e relict and non-functional
serrations have disappeared from the posterior teeth. The Eichstatt specimen
appears still to be a facultative ‘whole-body’ carnivore but is becoming adapted
to a more insectivorous diet.
(4) T h e final stage, corresponding to the Berlin specimen. The teeth are not
recurved but peg-like, with bluntly conical tips. They occlude, producing steep
wear facets and appear to be adapted to crushing and slicing up insects. They
can no longer be used to ingest large whole prey.
TEETH OF dKL‘fLIPOPTERYX
169
COMPETING HYPOTHESES ON ‘I‘HE RELXI‘IONSHIP OF ‘THE EICHS’I‘AI‘I’ SPECIbILN T.3
OTHER SPECIMLNS O F IIKCHAEOPTPKYX
Sexual dimorphism
In birds and reptiles sexual dimorphism is generally confined to differences in
.body size, plumage, head ornament and combative appendage:;. Among the
birds, only in the recently extinct Huia (Heteralorcha acutirostris Gould) of New
Zealand does sexual differentiation extend to dietary preference and foodgathering apparatus. The male Huia has a strong starling-like beak suited to
chipping at tough bark, while the female has a thin, curved probing beak suited
only to tackling soft wood (Greenway, 1967). Of sexual dimorphism in extant
and fossil reptiles Dodson (1976: 936) suggests that it is “generally poorly
expressed and difficult to identify”, particularly so with fossils where it is
difficult to get a large enough sample for statistical work. I n his work on
Protoceratops based on 24 skulls, Dodson proposes that sexual differences may
have existed in the masticatory apparatus, the putative females havirig a lower
coronoid process, and that this “would have increased the breadth of the niche
occupied by Protoceratops, allowing use of a wider range of resourcm than would
be possible for a monotypic species” (1976: 939). But among all hi:; data Dodson
makes no reference to any difference in tooth structure between the two sexual
morphotypes. Similarly with the species Igiinnodon bernissartensis Dollo, Norman
(1980: 81), “. . . despite a thorough survey of the numerous Bernissart
specimens”, can find little variation in the skull that could be attributed to
sexual dimorphism other than a minor difference in the number of teeth. He
also concludes that the theory that “ I . bernissartensis and I. rriantdli are sexual
forms of a single species . . . is unfounded” (1980: 81).
The only cases of sexual dimorphism affecting the dentition in fossil reptiles
are inferred among the rhynchosaurs a n d heterodontosaurs. In both groups the
difference is that the putative males 1iaL.e diagnostic caniniform tusks which the
females lack, mirroring the condition known in several species of extant small
deer. In neither reptile group is the rest of the dentition Itnown to be
significantly different between the sexes. I t is therefore considered unlikely that
the tooth difference exhibited within the genus i l r c h a e o p t e ~ xcan be assigned to
sexual difference. T h e only line of cvidence which suggests this explanation is
the smaller size of the Eichstatt specimen. It is 30°;, smaller than the Berlin
specimen, but this is generally ascrihed to the supposed juvenile condition of the
Eichstatt specimen. Other osteological differences discussed below also militate
against this hypothesis.
Ontocgmrtic dgtv ence
‘I’he most common explanation of the osteological differences between the
Eichstatt and other specimens of ilrrharopt~r_px(absence in the Eichstatt specimen
of a furcula, lack of fusion of the metatarsi, the short pubic symphysis and small
size) has been that the Eichstatt specimen is a juvenile. If so it must then be
assumed that the difference in tooth structure is associated with a change in dirt
from juvenile to adult. This is often the caxe among reptiles, where juveniles are
much smaller than their parents. Thus juveniles tend to be more insectivorous
than their parents (Webb, Manolis & Buckworth, 1982), but usually tooth
structure is altered only by the dentition becoming more robust Mith age.
170
M E HOWGATE
However, instances do exist where there is a distinctive change in tooth
morphology which can be associated with a change in dietary preference during
the life cycle. Such is the case with Varunus niloticus Kuhl (Rieppel & Labhardt,
1979) in which insectivorous/piscivorous conical teeth are replaced, particularly
at the rear of the jaw ramus, by button-like teeth suited to the durophagous diet
of the adult. Two lines of evidence might be taken to indicate that this took
place in Archaeopteryx: the teeth of the Berlin specimen are more robust than in
the Eichstatt specimen, and there seems to have been a slowing in replacement
of the teeth in the Berlin specimen, as is evident from the full eruption of all the
premaxillary teeth. This latter point could possibly be ascribed to old ageoligophyodonty. Edmund (1969) notes that although this phenomenon has been
observed in Sphenodon and the acrodont agamid lizards, in non-acrodont reptiles,
such as crocodiles, although there is a tendency for replacement to slow down
and become more irregular it is still active even in old age.
Among other reptiles failure of tooth replacement is regarded as pathological.
It would also be expected that if tooth replacement did slow significantly in
adulthood then there would be signs of increased general tooth wear as well as
that associated with particular facets, especially at the tips. This is not evident
on the premaxillary teeth of the Berlin specimen, in which the tips of all the
teeth are perfectly preserved, but can be seen on the second premaxillary tooth
of the ‘juvenile’ Eichstatt specimen. O n the first point above, it is possible to
assume almost any tooth variation within limits as the result of changes taking
place during ontogeny. However, if I am right in suggesting that the Eichstatt
dentition is more carnivorous and the Berlin dentition more insectivorous, we
have the strange picture of a carnivorous juvenile giving rise to an insectivorous
adult.
Phylogenetic dzfference
The marked differences in osteology between the Eichstatt specimen and the
Berlin, London, Maxberg and Tyler specimens are generally attributed to the
supposed juvenile nature of the Eichstatt specimen. However, those ‘juvenile’
features are associated with others which tend to indicate that the Eichstatt
animal was an adult. Martin el ul. (1980) regard the supposed thecodont
implantation of the teeth in Archaeopteryx as an indication of the adult status of
all the specimens since they would expect a juvenile dentition to be set in a
constricted groove. The subthecodont insertion seen in the largest specimen
(London) does not invalidate their argument but emphasizes it.
Similarly the lack of an ossified furcula in an otherwise complete specimen,
the unfused condition of the metatarsi and the short pubic symphysis (Ostrom,
1976) are interpreted as evidence of incomplete ossification due to the juvenile
status of the Eichstatt specimen. But other bones which one would expect to be
poorly ossified in a juvenile bird are as well preserved and complete in the
Eichstatt ‘juvenile’ as in the other adults. Not only are the ends of the limb
bones, the extremities of the pelvic and pectoral girdles and the fine tips of such
elements as the cervical ribs fully ossified, but other bones appear to be more
robust and better ossified in the Eichstatt specimen than in the Berlin
specimen-most notably the gastralia and the expanded foot at the distal end of
the conjoined pubes (Ostrom, 1976: 127). Only in the case of the lack of fusion
TEETH OF ARCHAEOPTERYX
171
of the metatarsi does it appear that an indisputable juvenile character is present,
but fusion of the three main metatarsals has only been proved in the Maxberg
specimen (Heller, 1959) and de Beer (1954) considers that the mel.atarsals of the
London specimen are not fused. Finally, the ascending process of the calcaneum,
regarded by Martin et al. (1980) as a very late ossification which occurs after the
fusion of the proximal tarsals, is a prominent bone in the Eichstatt specimen.
T h e other major difference between the osteology of the Eich!;tatt specimen
and the other fully preserved skeletons is in the orientation of the pubis. It is
almost vertical in the Eichstatt specimen rather than markedly opisthopubic as
seen in the Berlin and London specimens. This has been the subject of a great
deal of controversy (Ostrom, 1973, 1974, 1975, 1976; Tarsitano & Hecht, 1980;
Hecht & Tarsitano, 1982; Walker, 1980), with Ostrom proposing that the
correct position of the pubis is that seen in the Eichstatt specimen, and Walker,
Hecht and Tarsitano championing the Berlin/London orientation, Each side of
the debate has then to reorient the pubis of the ‘distorted’ specimen.
From my own examination of the two most easily comparable specimens, the
Berlin and Eichstatt specimens, in neither is there any significanl. post-mortem
dislocation of any other bones in the vicinity of the pelvis. Even the heads of the
opposing femurs of the Eichstatt specimen are displaced only in so far as they do
not lie directly opposite each other (Wellnhofer, 1974: 196, fig. 10). The slight
twisting which the pubis has undergone in both specimens is no doubt due to
the resistance to diagenetic compaction of a vertically oriented springy bone.
Unlike the flat plate-like ilium and ischium, which are undistorted though the
ilium may be crushed against the sacrum, the pubes are cylindrical bones,
strongly fused distally and diverging proximally. Under pressure the pubis
would resist compaction more than the ilium and ischium, spring loose from the
acetabulum, skew round about the symphysial axis to offset the .vertical stress,
and on one side, as can be seen in the Berlin specimen, slightly override the
ilium. I t thus seems a more parsimonious interpretation of the osteology to
regard the differences in orientation of the pubes as real phylogenetic
differences, and not as artefacts of preservation.
Similarly the differing proportions of the limb bones are indicative of
phylogenetic difference rather than differential growth during ont’ogeny. This is
particularly noticeable in Wellnhofer’s table 7.5 (1974: 211) in which the
Eichstatt specimen falls outside the range of the Berlin, London and Maxberg
specimens. The most interesting of Wellnhofer’s data are the hind limb ratios,
femur: tibia: foot (Table 2), which indicate that the Eichstatt :specimen was
more cursorial than the other specimens. (The Haarlem data are at best an
estimate as the femur and tibia are both incomplete.)
Probably the reason why those features which I have outlined above have
never before been regarded as of phylogenetic significance is the overcaution
Table 2. Ratio of femur : tibia : foot (metatarsal II+digit 111),after Wellnhofer
(1974 : 196)
Eichstatt
London
Berlin
I : 1.42 : 1.67
1 : 1.33 : 1.47
I : 1.30: 1.43
Maxberg
I : 1.38 :
~
Haarlem
1 : 1.48:-
172
M. E. HOWGATE
instilled by the history of' the various attempts to separate the Berlin and
London specimens at the specific, generic and even familial levels. Seeley (1881)
proposed that the Berlin specimen was a distinct species purely due to its slightly
smaller size. Dames (1884a) at first dismissed these differences as due to age
and/or sex, but later (1897) on the basis of differences in the teeth and pelvis he
erected the new species Archaeopteryx siemensii for the Berlin specimen.
Petronievics (1927, 1950) suggested on very poor evidence not only a generic
difference between the Berlin (Archaeornis siemensii) and London (Archaeopteryx
lithographica) specimens, but also concluded that they were in different families
and gave rise to the carinates and ratites respectively. Following de Beer (1954)
it is now generally thought that the two specimens are conspecific, a conclusion
that is further reinforced by the similarities in their teeth noted above.
The differences in tooth structure between the Eichstatt specimen and the
London and Berlin specimens could conceivably be interpreted in the light of
any of the preceding hypotheses with varying degrees of probability. However,
the tooth difference is such that, in a less contentious taxon, they would be
assigned to different species. This, together with the other osteological
differences and lack of firm evidence of sexual dimorphism and/or juvenile
characters, indicates that the Eichstatt specimen should be at least assigned to a
distinct species if' not a new genus.
Polymorphism
I t is possible that all the differences noted above are the result of
polymorphism within the single species Archaeopteryx lithographica. Such a
situation could have occurred if Archaeopteryx was invading an unoccupied niche
or a niche in which potential competitors were at an overwhelming
disadvantage. Under such circumstances the release of effective selection
pressure could produce a wide variety of' morphotypes within the basic flightadapted structure. Such a breakdown of homeostasis has been noted in various
lineages of molluscs in sediments around Lake Turkana (Williamson, 1981 ) and
described as an example of punctuated speciation. As Fryer et al. (1983) have
pointed out such a process cannot be described as a speciation event but is a
good example of the release of the normally present constraints on natural
polymorphism within the species. They also describe a n even more spectacular
example of the breakdown of homeostasis in the Marsh Fritillary butterfly
(Ford, 1945) in which what would normally be hugely disadvantaged
morphotypes were represented in the population for a short period of time. It
would, however, be unusual to say the least to expect polymorphism within a
species to extend to major functional complexes involving feeding, running and
flying.
CONCLUSIONS
Archaeopteryx recurvu sp. nov.
I t is proposed that the Eichstatt specimen be distinguished from all the other
specimens referred to Archaeopteryx lithographica at least at the specific level. The
question as to whether the differences merit separation at the generic level will
‘I‘EKI’H O F dRCHAEOPTER1;Y
173
be discussed elsewhere. The following major differences serve to identify the new
species.
( 1 ) The teeth are more gracile and recurved.
(2) The specimen is one-third smaller than the other specimens of
Archaeopteryx.
13) T h e distal elements of the pes are proportionately longer.
(4) The pubic symphysis is short.
The following more problematic differences, if confirmed, would serve to
establish a distinct genus for the Eichstatt specimen.
(5) The pubis is very slightly opisthopubic or vertical.
(6) The lack of a n ossified furcula.
These differences indicate that the Eichstatt specimen was probably a
representative of an evolutionary precursor stage to A . lithograph’ca,although it
was a stratigraphic contemporary, and was also a poorer flyer and a more
cursorial species. T h e specific epithet refers to the recurved style of the dentition.
T h e supposed crocodilian relationships of Archaeopteryx-evidence j?om the teeth
Martin et al. (1980) proposed that the structure of the teeth of Archaeopteryx
and the Cretaceous birds lchthyornis and Hesperornis supported Walker’s ( 1972)
contention that birds were more closely related to crocodiles than to any other
group of archosaurs. In support of their claim they show convincing
comparisons between the teeth of Alligator mississippiensis Daudin and Ichthyornis
viclor Marsh, and they are indeed strikingly similar. However, no matter how
similar are the teeth of Cretaceous birds and of crocodiles, there is little
similarity of either to the teeth of Archaeopteryx. Of the four characters supposedly
indicative of close relationship only one is present, namely lack of serration. But
not only do some crocodiles have theropod-like serrations, other archosaur
groups have lost the serrations presumably present in their pseudosuchian
ancestor, notably the pterosaurs, and even the coelurosaurian dinosaur
Compsognathus only retains serrated teeth in a non-functional position at the rear
of the jaw. Of the other similarities between crocodilian and bird teeth
(triangular crowns, separation of an expanded root from the crown by a distinct
waist, and an oval to circular resorption pit rather than an elongate resorption
pit) none is present in Archaeopteryx. Therefore on this evidence it would be just
as parsimonious, if not more so, to derive the teeth of Archaeopteryx from either a
theropod or a pseudosuchian ancestor.
The tooth crowns of A. recurva arc triangular only in SCI far as most
thecodontian teeth can be said to bc triangular. T h e tooth crowns of A .
lithographica are conically triangular as illustrated by Martin et al. (1980: 90)
only at the rear of the jaw ramus; elsewhere they are peg-like with obtusely
conical recurved tips. They are asymmetrical in cross-section, flat internally and
rounded externally, very unlike the teeth of crocodiles or theropod dinosaurs.
‘I‘here is no evidence of waisting at the cervix of the teeth of Archaeopteryx recurva;
this is particularly clear in the dentary teeth which are almost parallel-sided on
entering the alveolus. In Archaeopteryx lithographica the one tooth which shows the
root in full, the isolated premaxillary tooth of the London specimen, shows quite
clearly an unconstricted passage from crown to root and that the root is not
174
M. E. HOWGATE
notably inflated (Fig. 3B). The one easily recognizable replacement pit, on the
isolated premaxillary tooth of the London specimen, is distinctly elongate and
hence on the evidence presented by Martin et al. (1980: 91) more like that of a
theropod dinosaur.
As Stromer (1934) has pointed out, it is very difficult to draw any taxonomic
conclusions from the structure of the teeth of carnivorous dinosaurs. The same
could be said of this attempt to adduce evidence of a nearest neighbour
relationship between birds and crocodiles on the evidence of a supposed
similarity in tooth architecture. The evidence from Archaeopteryx in fact points
the other way; the absence of a constriction at the base of the tooth crown, the
straight root and the elongate resorption pit indicate that the ancestor of
Archaeopteryx was an animal with a pseudosuchian or theropod dentition rather
than a crocodilian dentition. The similarity then between the teeth of
crocodilians and Cretaceous birds is a case of evolutionary convergence.
ACKNOWLEDGEMENTS
I would like to thank Dr Alan Charig of the British Museum (Natural
History), London, Dr Hermann Jaeger of the Museum fur Naturkunde, East
Berlin, Dr Giinter Viohl of the Jura Museum, Eichstatt and Dr Peter
Wellnhofer of the Bayerische Staatssammlung fur Palaontologie und historische
Geologie, Munich, for allowing me to examine the specimens in their charge,
Prof Kenneth Kermack for bearing with me in this diversion from Kirtlington,
and Dr Susan Evans for playing the devil’s advocate to all my theorizing. This
project was in part financed by a grant from the Central Research Fund of
London University.
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