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Home , Pythonomorpha, Reptile, Sauropsida, Testudinata

ON THE PHYLOGENETIC ARRANGEMENT OF THE .

DR. G. BAUR, YALECOLLEGE MUSEUM, NEW HAVEN,Cam. Cope' has given the following classification of the Reptilia :- A. Extremities not differentiated in form beyond proximal segment. I. 0s quadratum immovably articulated to squamosal, etc. Tubercular and capitular -articulations present and distinct. I. . A.A. Elements of extremities differentiated. 11. 0s quadratum immovably articulated, capitular and tubercular rib-articulations distinct. ARCHOSAURIA. Pubis and ischium united, and with little or no obturater foramen ; one posterior cranial arch ; limbs ambulatory ; a procoracoid. 2. Theromovpha. Ischium and pubis distinct, the latter directed forwards, back- wards, or downwards ; two posterior cranial arches ; limbs am- bulatory ; no procoracoid. 3. Binosauria (+) . Ischium and pubis united ; two postcranial arches ; anterior limbs volant. 4. Omithosauria. 111. 0s quadratum closely united to cranial arches ; but one rib-articulation. SYNAPTOSAURIA. Distinct hyposternal and postabdominal bones ; joining each two vertebrae, and generally forming a carapace ; one pos- terior cranial arch. 5. . Hyposternal and postabdominal bones not distinct ; two pos- terior cranial arches ; ribs attached to one ; a ; ? no procoracoid. 6. Rhynckocephalia. Cape, E. D. On the of the vertebrata, progressive and retrogressive. Amer. Naturalist, March, 1885, pp. 245-246. 94 BAUR. POL. I.

Hyposternal and postabdominal bones not distinct ; two pos- terior cranial arches; ribs attached to one centrum; no ster- num ; a procoracoid. 7. .

IV. 0s quadratum attached only at the proximal extremity, and more or less immovable; ribs with one head. STREPTO- STYLICA.

Brain case membranous in front of proijtic bone; trabecula not persistent. 8. Lacevtilia.

Brain case with osseous walls anterior to prootic ; a scapular arch and sternum. 9. Pythonomorpka.

Brain case with osseous walls anterior to proijtic ; no scapular arch nor sternum ; trabecular grooves of sphenoid and pre- sphenoid bones. 10. .

The phylogeny of the Reptilia is expressed by Cope in the following way :-

Dinosauria Testudinata. . Lacertilia. opbidia. (Crocodilia) . \ I / I

\IPythonomorpha. Pterosauria. \ \ I /

Theromorpha. No. I.] ARRANGEMENT OF THE SAUROPSfDA. 95

CRITICISM OF THIS CLASSIFICATION. Ichthyopterygia. The Ichthyopterygia are separated by Cope from the rest of the Reptilia because of the non-differentiation of the extremities in form beyond proximal segment. That the Ichthyopterygia stand in the same relation to one or the other group of as the Cetaceans do to the Ungulata and Carnivora seems to me unquestionable. Prof. Haeckel expressed this idea twenty ago in his celebrated work:

‘I Generelle Morphologie der Organismen.” Vol. I., pp. I 84- 185. Berlin, 1866. Of the Halisauria (= Enaliosauria = Ichthyopterygia + Sau- ropterygia), he says, -

Ihre vielfachen Ahnlichkeiten mit den Fischen und insbeson- dere mit den Ganoiden haben zu der Annahme gefiihrt, dass sie diesen niher als den iibrigen Reptilien venvandt seien, und man hat selbst neuerdings versucht, die Ganoiden, Ganocephalen, Labyrinthodonten, Ichthyosaurier und Sauropterygier als fort- laufende Glieder einer einzigen Entwicklungsreihe darzustellen. Indessen ist es viel wahrscheinlicher, hss diese k’knZichkeiten mehr Anpassungs ahnlichkeiten sind, und dassdie Halisaurier sich zu den iibrigen Reptilien verhalten, wie die Cetaceen zu den Saugethieren.”

In 1881 Prof. C. Vogt’ expressed the same opinion. Quite lately I have brought forward new proofs for the cor- rectness of this view? Therefore it is impossible to separate the Ichthyopterygia from the rest of the Reptiles ; it would be the same as to sepa- rate the Cetaceans from the . Weber3 has shown, in a very important memoir, that the Cetaceans descended from a group of Mammals, probably ancestral to both the Ungulata and the Carnivora.

’Revue scientifique. 12. Mlirz, 1881; Kosmos, Vol. 9, 1881,pp. 318-319. Baur, G. Bemerkungen iiber SIuropterygia und Ichthyopterygia. Zool. Anz., NO. 221. 1886. 3Weber, Max. Studien iiber Singethiere. Ein Beitrag ZUT Frage nach dem Ursprnng da Cetaceen. Jena, 1886. 96 BAUR. [VOL. I.

The question now is, from which group of Reptiles descended the Ichthyopterygia ? The shows characters of the Rhynchocephalia, the oldest () and the ; but it is still more generalized than in these groups. This is proved espe- cially by two bones, - the opisthotic and the supratemporal. The opisthotic is separate as in the Testudinata.’ Huxley a speaks of a flattened bone between the postorbital, postfrontal, and the squamosal; this bone (temporal, Cuvier - prosquamosal, Owen), according to Huxley, does not appear to have any precise homologue among other Reptilia. I shall show, in another paper, that this peculiar bone is

nothing else than the supratemporal I’ of the Lacertilia, and the

‘I squamosal ” of the Stegocephali ; that the (( squamosal ” of the Stegocephali is really the supatemporaZ, the supra-

temporal ” of the Stegocephali, the squnmosal, of the Reptilia. The Ichthyopterygia, therefore, are the only Reptiles, so far as now known, which have a supratemporal, like that of the old Stegocephali. Another character common to the Rhynchocephalia, a few and Dinosauria, the oldest Crocodilia (Belodon), and Sa~ropterygin,~is the presence of the postorbital and the post- frontal in a separate condition. The scapular arch of The Ichthyopterygia is Lacertilian or Rhynchocephalian. The ribs are two-headed, like those of the Crocodilia, Dinosauria, etc. They are different from the ribs of all other known Reptiles, because they are never connected with the neurapophyses; they never leave the body of the vertebra (according to Owen’s figures). Abdominal ribs are developed, as in the Rhynchocephalia and Sauropterygia. Therefore we have combined characters of the Rhynchoce- phalia, the oldest Crocodilia and Sauropterygia. To-day we do not know a group of Reptiles showing such characters;

1 Cope, E. 0. On the homologies of some of the cranial bones of Reptilia, and on the systematic arrangement of the . Proc. Amer. Assoc. Adv. Sc., Vol. XIX., p. 199. 1871. ”uley, T. H. A manual of the of vertebrsted . London, 1871, p. 246. 3 In Sirnorourus these two bones have already united. No. 1.3 ARRANGEMENT OF THE SAUROPSIDA. 97 but that the Ichthyopterygia must have taken their origin from such a one I have no doubt.' The Sauropterygia and Testudinata. This group of Reptiles is classified by Cope with the Synapto- sauyia, which have but one rib articulation. This is not correct; the oldest Sauropterygia, the Lariosauridae and , and even Plesiosaums, have two-headed ribs in the cervicals and the former families even in the anterior dorsals. The posterior dorsals have the capitulum and tuberculum united, and therefore are morphologically two-headed. It always seemed difficult to determine the systematic position of the Sauropterygia. Huxley considered this group allied to the Crocodilia, especially to the Teleosauride ; Owen cbmpared it with the Testudinata. That they descended from land-living reptiles is certain? The Sauropterygia begin in the with the Lario- sauridae and Nothosauridae. They are in no direct relation to the Ichthyopterygia. The skull and shoulder-girdle are entirely different in both. The skull is very characteristic. It resembles the Rhyncho- cephalia and old Crocodilia (Belodon, ) ; the parietal foramen is present. The postorbital is free or united with the postfrontal. The whole shape (at least of some forms) resembles very much the skull of the Crocodilia; but one character shows at once the specialization of the Sauroptery- gian skull; it is the absence of the lower temporal arch, as in the Lacertilia; a quadratojugal seems never to be developed. Another resemblance to the Rhynchocephalia consists in the structure of the abdominal ribs. If we compare these elements in the Lariosauridae and Nothosauridae with those in Sphenodon we find exactly the same condition. In and Sphenodon they are entirely identical, as the figures of Deecke prove.3

'The Baptanodontia (Sauranodontia), Marsh, are specialized forms of the Ichthy- opterygia, like the Mystacoceti among the Cetacea, and the Pteranodontidse among the Ornithosauria. 'Barn, G. Bemerkungen iiber Sauroptetlrgia und IchthpptetYgia. Zool. Am., No. 221, 1886. a Deecke, W. uber Lariosaurus und einige andere Saurier der 1ombardischenTrias. Zcitschr. Deutsch. Geol. Ges. Bd. 38. P1. 1x1. Fig. I. BAUR. POL. I.

There seem to be the larger number of connections with the Testudinata. The cervical ribs of the Testudinata are entirely rudimentary. Hoffmann ' has shown that they are developed in the . In the adult Testudinata there are often well-developed dia- pophyses and parapophyses in the anterior cervicals. The former are connected with the neurapophyses, the latter with the body of the vertebra; both touch each other. Therefore we have a real para-diapophysis, and, consequently, if a rib should be developed, a rib with a capitulo-tuberculum. That the an- cestors of the Testudinata had well-developed ribs on the cervicals is shown, not only by Hoffmann's researches, but also by the still developed para-diapophyses. The pelvic arch of the Nothosauridz' is only comparable with that of the Testudinata. The shape of the pubis is very much alike in both. The obturator foramen is usually present in the Nothosauridz, but is generally situated at the border of the bone. In the Testudinata the obturator foramen is generally wanting. Rudiments of it I find, however, in a specimen of Eretmoclzel'ys imbricata, and I do not doubt that a close exami- nation of the pubic bones in the oldest Testudinata will show its rudimentary presence. The ischia are very much alike. The femur of , according to H. v. Meyer, is only comparable to that of the Testudinata. The humerus of the Lariosauridze and Nothosauridae has the ectepicondylar foramen, like the Lacertilia, Rhynchoce- phalia, and Testudinata. Other resemblances are to be found in the sacral and caudal vertebrz, in the condition of the chevrons, etc. The sacral vertebrz of both the Sauropterygia and Testudi- nata have well-developed para- and diapophyses, to which the sacral rib is connected ; the same is to be found in the anterior caudals ; in the posterior caudals the para-diapophyses become rudimentary. In all the Sauropterygia the chevrons are at- tached only to the posterior part of the vertebrze, not between two vertebrz, as in the Rhynchocephalia, Crocodilia, etc. The same ha2 place in the Testudinata; if chevrons are de-

'Hoffmann, C. K. Uber das Vorkommen von Halsrippen bei den Schildkroten. Beitrage zur verzleichenden Anatomie der Wirbelthiere, pp. 138-150. Leiden-Leipzig, 1879. No. I.] ARRANGEMENT OF THE SAUROPStDA. 99

veloped, they are mainly connected with the posterior part of the vertebrze. Another proof of the affinity of the Testudinata and Saurop- terygia is given by Parker.‘ He says: “There is one thing of great importance to be noted in the development of the , and that is the number of its body-segments at various stages, their rapid increase at first, and then the suppression or of several after- wards. ‘t In embryos a little more than a quarter of an inch in length there are about 27 muscle-plates or somatomes. ‘‘ In embryos ranging from 6% to 9 lines there are 5 I of these divisions of the bbdy visible externally. -Now, in the adult I can only find 41developed vertebrae, viz. : 8 cerv., 10dorsals, 2 sacr., 21 caud., -41 in all. “But in the third and fourth stages there are at least 15 somatomes in the cervical region ; in the dorso-lumbo-sacral, 12 (as in the adult), and 24 in the caudal, - 5 I in all. Thus we miss in the adult 7 in the cervical and 3 in the caudal,- 10in all. ‘‘ This free suppression of segments suggests a great secular modification by shortening of a form not unlike a PZesiosaur.” If it seems from the foregoing that the Testudinata are more or less related to the Sauropterygia, the question arises, which is the group of Reptiles ancestral to both? It is none of the known groups, and we can only admit that we do not know any- thing of the ancestors of the Testudinata and Sauropterygia; that it was a group allied to the Rhynchocephalia is probable. The Testudinata have an epipterygoid (columella), and it may be that the plastron of Testudinata was developed from or on abdominal ribs of a form like Sphenodon. RhynchocephaZia, LacertiZia, , Ophidia. Prof. Cope puts the Rhynchocephalia in one group, with the Testudinata and Sauropterygia. I do not find that natural. I find it very much more natural to combine the Rhynchocephalia with the Lacertilia, Pythonomorpha, and Ophidia. The Rhynchocephalia are the most generalized of these ;

‘Parker, W. K. Report on the Development of the Green Turtle (Chelone viridis Schneid). The Voyage of H.M.S. Challenger. Zaol., Vol. I., p- 47. I00 BAU.. POL. I.

they still have the complete lower cranial arch, lost in the other groups; they still have the intercentra, two Centralia in the carpus, and the proatlas. Their shoulder-girdle is entirely Lacertilian. It is probable that the Homceosauria must be put together with the Rhynchocephalia ; the shape of the jugal' shows that the lower arch was complete in Hommxaurus. I do not doubt that Homczosaurus had intercentra between all vertebrz. The Rhynchocephalia, together with the , to which they are allied, are certainly the most generalized group of all Reptiles, and come nearest, in many respects, to that of Reptiles from which all the others took their origin. The embryology of Sphenodon (Hatteria) would be of the highest importance for the understanding of the phylogenesis of the Reptilia.

The I' Simadosauria." DoZZo.

The I' Simedosauria," containing the and eocene form, Chainpsosa~~us,Cope, are considered by Dollo as a dis- tinct order.2 I have to consider , as Lydekker did, as a specialized member of the order Rhynchocephalia. My principal proofs for that are, besides the common char- acters given by Dollo (1. c., p. 158): -

First. The loose condition of the otic bones4 Second. The condition of the rib-articulation. Third. The articulation of the ribs in Champsosaurus is only comparable with that of Sphenodon and . The ribs of Champsosaurus are never placed entirely on the neura- pophysis, as in the dorsals of Crocodilia, Dinosauria, Sauroptery-

I Ammon, L. V. Uber Homowsaurus Maximiliani. AbhandIungen d. K. Bayr. Akad. d. Wiss. 11. C1. XV. Bd. 11. Abth., Miinchen, 1885, p. 12, 'Dollo, L. Premiere note sur le Simcedosaurien dErqutlinnes. Bull. Mus. Roy. d'Hist. Nat. Belg. Tome III. 1884. The loose condition of the otic hones, as described by Lemoine, is only found, in a similar way, in Sphcnodon. In young specimens, and even in old ones, the sutures between the three bones are entirely distinct. Lemoine, L. Etude sur les caractkres gdndriques du Simaedosaure. Reims, 18%. NO. 1.3 ARRANGEMENT OF THE SAUROPSIDA. I01

gia, etc.; the same is to be found in Sphenodon. The differ- ences between Champsosaurus and Sphenodon, given by Dollo (1. c., p. 159)~are results of specialization of a Sphenodon-like form. Champsosaurus retains the neurocentral suture, which is lost in the adult Sphenodon. Dinosauria -CrocodiZia - Ornithosauria -Aves.

These four “orders ” certainly form a natural group of the Sauropsida. The Dinosaurs are the oldest of these. It is not probable that Protovosaurzu from the is a , as Huxley ’ was inclined to suppose, and as Seeleya has quite lately suggested. The Dinosauria form three well-distinguished group^.^

A. Carnivorous Dinosaurs,’ Harpagosauria, Haeckel, I 866. I. Goniopoda, Cope, I 866 (, Marsh, 1881). B. Herbivorous Dinosaurs, Themsauria, Haeckel, I 866. 11. Orthopoda, Cope, 1866. I. , Marsh, 1881. 2. , Marsh, 1877. C. Crocodilian-like Dinosaurs, , Marsh, I 878. 111. Opisthocdia, Owen, 1859.~ It is possible that the Ornithosauria took their origin from true Dinosaurs ; but at present we do not know such a group from which they could have originated. It may be that the Dinosaurs and Ornithosauria had a common ancestor. ‘Huxley, T. H. On the classification of the Dinosauria, with observations on the Dinosauria of the Trias. Quart. Joum. Geol. SOC.,Vol. 26, 1870,p. 37. SSeeley, H. G. T. Philipps. Manual of geology, theoretical, and practical. Part I. London, 1885, p. 515. 31 omit here the “ Dinosauria ” described by Owen in “Descriptive and illus- trated catalogue of the fossil Reptilia of South Africa, in the collection of the British Museum, London, 1876.” Owen creates a new group, Trcfospondyla : Tapinoccphalus with notochordal vertebra In the family Serrafiahtia he puts the genera Parciasnurus and . shows characters of the Sauropoda; Anfhodon such of the Stegosauridze. But from the present material the exact position of these forms cannot be determined. ‘Baur, G. Der Tarsus der Voegel und Dinosaurier. Morph. Jahrb., Bd. VIII., 1882, p. 452. I retain the first name proposed by Owen, who put those ‘I Saurians ” among the Crocodilia. It is a fact that these forms show more characters common to the Croco- dilia than to the Orthopoda. I02 BAUR. POL. I.

The oldest CrocodiZes, the Belodontidz, and Aethosauridz are very much allied to the Zanclodontidae and the Sauropoda, and I feel quite sure that Crocodiles and Dinosaurs converge in the lower Triassic. The , and among those the Ratitz with teeth, went off from the Ovnithopoda,' but not from any known form. Probably they started from some Ornithopoda-like form in the Triassic, because I do not doubt that some of the footprints in the Connecticut sandstone are made by true Birds. The Orthopoda and Birds are the only Sauropsida in which the pubis is directed backwards ;2 a fact of great importance. Arclzaopteryx is not on the direct line, but is a very much specialized member of a collateral branch. The Tlzeromorpha. Prof. Cope includes the Theromorpha in the group con- sisting of the Dinosauria (Crocodilia) and Ornithosauria. I can- not agree with that proposition. The Theromorpha form a natural group, like that containing the Crocodilia, Dinosauria, Ornithosauria, and Birds. They are limited to the Permian and Triassic. This group is characterized by the absence of the postorbito- squamosal arch, the presence of the entepicondylar foramen, and the peculiar structure of the scapular arch. The Pelycosauria, including Owen's Theriodontia, form the original stage, having the centra of the vertebrae notochordal and the intercentra present ; the Anomodontia are very much special- ized ; the centra are not notochordal, the intercentra wanting, and the in a rudimentary condition. Prof. Cope considers the Theromorpha as the ancestors of all other Reptilia with, possibly, the exception of the Ichthyopterygia. He also con- siders the Pelycosauria as the ancestors of the Mammalia. I tried to show in a lately published paper that the Theromorpha are already too much specialized to be the ancestors of Mammals.

'Baur, G. Note on the Pelvis in Birds and Dinosaurs. Amer. Nat., Dec., 1884, P. '274- -Bemerkungen fiber das Becken der Vogel, und Dinosaurier. Morphol. Jahrb., Bd. 10,1885, pp. 613-616. 'Baur, G. 2001. Anz., No. 216, 1886. 3 Banr, G. Uher die Kanaele im Humerus der Amnioten. Morph. Jahrb., Bd. XII., 1886, pp. 299-305. No. I.] ARRANGEMENT OF THE SAUROPSIDA. 103

The same I should like to say in regard to the Reptilia. I can- not see how the Testudinata, Lacertilia, Nothosauridze, etc., with the ectepicondylur foramen in the humerus, could be devel- oped from the Theromorpha with the entepicondyZar foramen. It is true we know some Permian Reptiles which possess both the canals in the same way as Sphenodon ;but whether these forms are Theromorpha or Rhynchocephalia is a question. I think it is very much more probable that the Theromorpha and Rhynchocephalia had a common reptilian ancestor below the Permian in the . Cope2 has described a fossil from the Carboniferous of Brazil, which he considers as Batrachian, with query. I have shown that it is probably a Reptile3 allied to the Rhynchocephalia. This fossil, which Professor Cope calls Stereosternum turni- durn, has notochordal vertebrae, and the humerus with an epicondylar foramen ; but the principal character of this consists in the presence of five distinct tarsal bones in the second row. This seems to me of very high importance. No , living or extinct, has inore than four tarsal bones in the second row ; the fourth and fifth digit is always supported by a single bone,- single even in the . The Rynchocephalia, the Protorosauria, the Pelycosauria, all have only four tarsal bones in the second row. This one character, if it is true, seems to be strong enough to allow the formation of a new order of Reptiles, which con- tains Stereosternum; for this order I propose the name Pro- ganosauria. But can we consider the Proganosauria as the ancestors of the other Reptiles? Possibly we may if we take the Proganosauria in a general . Stereosterum itself is certainly not on the direct line ; it is a specialized member of the Proganosauria, like Echidna, a specialized member of the Prototheria (Monotre- mata). In some later time I hope to give more detailed commu- nications on the philogeny of the single groups of Sauropsida. NEWHAVEN, CONN., Sept. 26, 1886.

H. v. Meyer. Reptilien aus dem Kupfersandstein des West Uralischen Gouvei ments Orenburg. Paleontographica, Bd. 15, Cassel, 1865-68, pp. 97-1 30. *Cope, E. D. A Contribution to the of Brazil. (P before the American Phil. SOC.,Apr. 17, 1885.) Pal. Bull., No. 40. 3Baur, G. Die zwei Centralia im Carpus von Sphenodon . . . Zool. P No. 219. 1886. 104 BAUR. POL. I.

The ideas brought forward in this paper may be expressed in the following diagram : -