Hyperodapedon Gordoni Further Observations Upon

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Quarterly Journal of the Geological Society

Further Observations upon Hyperodapedon Gordoni.

T. H. Huxley

Quarterly Journal of the Geological Society 1887, v.43; p675-694. doi: 10.1144/GSL.JGS.1887.043.01-04.51

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Notes

ON HYPERODAPEDON GORDONL 675

47. FcR~n~l~ O~S~RVAT][O~S upon ~EIYPERODAPEDOI~ GORDON][. By Prof. T. tI. HvxL~, F.R.S., F.G.S. (Read May 11, 1887.) [PLA~ES XXYL & XXVII.] IT is now twenty,nine years since, in describing those remains of Stagonolepis t~obertsoni from the Elgin Sandstones which enabled me to determine the reptilian nature and the crocodilian affinities of that supposed fish, I indicated the occurrence in the same beds of a Laeertilian reptile, to which I gave the name of Hyperodapedon Gordoni. I laid stress upon the " marked affinity with certain Triassic reptiles" (e. g. _Rhynchosaurus)of Hyperodapedon, and I said that these, "when taken together with the resemblance of Stagonolelois to Mesozoic Crocodilia," led me "to require the strongest stratigraphical proof before admitting the Palmozoic age of the beds in which it occurs ,' % Many Fellows of the Society will remember the prolonged dis- cussions which took place, in the course of the ensuing ten or twelve years, before the Mesozoic age of the reptiliferous sandstones of Elgin was universally admitted. Hyperoda~edon was destined to play no inconsiderable part in the coutroversy. Some ten years after the discovery of the original specimen, remains referable to the same genus were found in strata of unquestionably Triassic age in Central and Southern England; and, about the same time, I received abundant evidence of the occurrence of Hyperodapedon, associated with Dicynodonts, Crocodilia, and Labyrinthodonts, in certain Indian rocks which, on other grounds, were strongly sus- pected to belong to the oldest Mesozoic series. An account of these new materials, together with a full description of the original specimen of Hyperodapedon, was read before the Society and published in the ' Quarterly ~Iournal' for 1S69 t. Unfortunately the type specimen, now in the :Elgin Museum, was in very bad condition; and though, by careful study of the fossil itself, it was possible to make out all the most important features of the skeleton, the work of the artist employed to figure it turned out so unsatisfactory, that I abstained from publishing the two plates which were prepared for the Memoirs of the Geological Survey, thinking it wiser to wait until better materials should make their appearance. My discretion has been justified by the event, as a second specimen, of almost exactly the same dimensions as the first, was discovered in the Lossiemouth Quarries, and became the property of the British Museum some timeago. It has been worked out with a skill which my old experience of the nature of the matrix of these Elgin fossils enables me fully to appreciate, by Mr. Hall, and my friend Dr. Woodward has been so good as to place it in my hands for descript.ion. * Quart. Journ. Geol. See.vol. xv. 1859, p. 460. t " On Hy2erod~l~ed~n,"Quart. Journ. Geol. See. 1869, vol. xxv. p. 138. ~2 Downloaded from http://jgslegacy.lyellcollection.org/ at University of Virginia on October 5, 2012

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676 PROF. T. H. HU~LEr~OBSERVATI01~S

I am glad to be able to say that, so far as it goes, the account of the structure of the skeleton of Hyperodapedon which I gave in 1869 needs no correction; but the new material enables me to make large and important additions. Moreover, several specimens of .Rhynchosaurus articeios in the Pal~eontologieal Collection of the :British Museum render it possible to make a full comparison of l~hynchosaurus with Hyperodapedon, and to put an end to any doubts which may have been entertained as to the generic distinction of the two. Finally, the full evidence now accessible permits us to obtain a clear view of the relations of both these extinct genera with the recent Sphenodon, a point to which I drew particular attention in 1869 *. These relations, both of resemblance and of difference, are so interesting and important, in/'act, that I shall give my account of ttyperodapedon mainly in the form of a comparison between that genus and Sphenodon. The present specimen of Hyperodapedon Gordoni has been exposed by the splitting of a large block of sandstone into two slabs, along a plane which corresponds roughly with thai of the imbedded skeleton. I have no information respecting the relative position of these slabs in the rock before it was quarried ; but, supposing that slab which contains the larger part of the skeleton and the entire skull to have been uppermost, the animal lay flat upon its belly with its limbs standing out, very much as those of a dead Lizard ordinarily do, when it was buried in the sands of the Elgin shore. The skull, the vertebral column as far as the root of the tail, slightly curved towards the right side, almost the whole of the bones of the left (and part of the right) fore limb, with those of the right hind limb, are preserved in almost their natural relations. The following table gives a view of the actual dimensions of HyTerodapedon and of the proportions of its parts compared with a specimen of Sphenodon :~ .Measurements, in millimetres. HyperodaTed~. SThenodon. Total length ...... (Probably over 2000) 460 End of premaxilla to end of second sacral vertebra ...... 900 208=(4.5: 1) Skull, end of premaxilla to edge of occiput ...... 160 55=(3 : 1) Skull, greatest breadth of the occipital region ...... 210 34=(7: 1) Total length of humerus + radius ...... 210 56=(4: 1) Total length of femur + tibia .. 200 66=(3: 1) Supposing the tail of Hyperodapedon to have been as long in proportion as that of S_phenodon, this specimen will have had a length of between six and seven feet, or rather more than four times as long as the specimen of Sphe~odon. Hence it would appear that the *Loc. cit. p. 147. Downloaded from http://jgslegacy.lyellcollection.org/ at University of Virginia on October 5, 2012

UPON HYPERODAPEDON GORDONI. 677

skull and the hind limbs were relatively shorter in the extinct reptile, but otherwise it must have had much the general aspect of its ~ew- Zealand ally--only, as I shall have occasion to point out more fully by-and-by, the skull was relatively much broader and more massive and the feet were shorter and stouter in Hyperoda2edon. There are certainly 23 prmsacral vertebrm in Hyperodapedon, perhaps 24, but I think not more; S2henodon has 25. In both genera there are two sacral vertebrae. In the first specimen, such of the thoraco-lumbar vertebrm as were preserved were split through the middle vertically and longitudinally. The sections of the centra showed that they were well- ossified throughout, and they appeared to be terminated by slightly concave contours. In the present specimen, the ventral faces of the cervical, and of some of the anterior thoracic, vertebrm are exposed and are almost uninjured ; but from that which I reckon to be the 13th (though it may be the 14th)to the 20th, they are split horizontally and longitudinally, the dorsal halves lying in the upper slab and the ventral halves in the lower. The 2ist, 22nd, and 23rd are similarly split, but they are much injured. ~ow the ends of several of these centra, notably the 13th, 14th, 18th, and 20th, present a sectional contour, which in front is more or less convex; while behind it is similarly concave. The anterior ends of the centra of the 4th (cervical) vertebra and of the 10th and 11th (thoracic) vertebrm appear to be strongly convex from side to side and their posterior faces correspondingly concave. Combining these appearances with those seen in the longitudinal section, I can only suppose that the surfaces must have been slightly eylindroidal, convex from side to side in front, and concave in the same direction behind; and thus that they approximated, though very distantly, to those of ordinary birds. The remains of the slightly displaced atlas (Plate XXVI. fig. 7) are seen immediately behind the skull. It has the form of a ring 26 millim, wide and 20 millim, in vertical height. Traces of the os odontoideum are visible immediately in front of the ventral portion of the ring, which lies horizontally, with its ventral region turned backwards. The front half of the second cervical vertebra is broken away, but its centrum appears to have been about 20 millim. long. The ventral faces of the third and fourth are well displayed. Each is about 20 millim, long and 17 millim, wide at the ends, but not more than 13 millim, at the middle. On each side of the anterior end a short broad tubercle, which represents the transverse process, is developed. I can find no indication of the existence of intercentral ossifications. :Each vertebra possesses a pair of strong ribs (Plate XXVI. fig. 8). These lie at the sides of the centra of the vertebrm and parallel with their length ; so that, at first sight, the cervical region has a crocodilian look. The first rib on the right side is well seen. It is a straight styliform bone, 40 millim, long and 3 millim, wide. On its dorsal side, and, more or less hidden by it, lies the second rib, the remains of which have about the same width and length. However, neither of these ribs Downloaded from http://jgslegacy.lyellcollection.org/ at University of Virginia on October 5, 2012

678 PROF. T. tl. HUXLEY-~OBSERYATIONS

is complete at its extremities. The right rib of the third cervical vertebra is 38 millim, long and 10 millim, wide at its head, but it gradually tapers to a point at its ventral end. The fourth cervical vertebra has a rib of similar dimensions, but curved somewhat in the shape of an italic f. This great development of all the anterior cervical ribs is a point of contrast between Hyperoda2edo~ and Sphe- nodon, in which last only rudiments of such ribs are discoverable. The fifth cervical vertebra is almost completely hidden under the shoulder-girdle, behind which a vertebra makes its appearance, which I take to be the 9th, though it may be the 10th. The centrum of this vertebra is 20 millim, long, 25 millim, wide between the ends of the transverse processes in front, and ] 7 millim, wide in the middle of its length; and the centra of the three vertebrre which follow it have similar dimensions and appear to have concave posterior faces. These vertebrae have strong but short transverse processes. That of the llth vertebra, on the right side, shows a rounded surface for the articulation of the head of the rib. The vertebral end of this rib is also well displayed ; it is broad, measuring 20 millim, from its dorsal to its ventral margin, which is concave and thick, while the dorsal margin is thinner and convex (Plate XXVI. fig. 9). The vertebral end of a similar rib is visible on the right side, close to the 16th vertebra, and there are less well-preserved remains of others. These ribs are very similar to the corresponding ribs of Sphenodon. Nearly the whole length of the rib which belongs to the 12th or 13th vertebra is shown; it is about 12 millim, broad, flattened and truncated at the sternal end; it measures 153 millim, along the chord of the arc of its curvature. The vertebral end is not completely exposed. A thin flat plate of bone, 20 millim, long by 14 millim, wide, is seen on the right side, overlying the remains of two vertebral ribs, opposite the 14th vertebra. I suspect that this is a "procossus nncinatus" such as those which occur in S_phenodon. The position of the skeleton is unfavourable for showing such bones, if they were preserved, and they would readily become detached. Portions of eight ribs, in undisturbed series, corresponding to the vertebrae from the 18th to the 22nd inclusively, are seen on the right side. It is possible that these may be the ends of vertebral ribs ; but I incline to the supposition that they are sternal ribs, because the inner truncated end of each is in close relation with a bundle of five or six lateral abdominal ossieles, of which the central ossicles in each bundle are nearly straight, while the anterior and posterior describe elliptical curves. If these are really sternal ribs, they are very different, in form, from those of St)henodon% It is by no means easy to arrive at a clear notion of the nature and arrangement of the abdominal ossicles, which extend over the ventral surface between the sternum and shoulder-girdle in front, and the pelvis behind. In front there is an area covered by ossicles of a V shape, the point Dr. Baur has stated that the abdominal ossicles of Sphenodon are connected by ligament in pairs with the sternal ribs, but I have not yet been abl~ to satisfy myself of the ihct. Downloaded from http://jgslegacy.lyellcollection.org/ at University of Virginia on October 5, 2012

UPON HYPERODAPEDON GORD0~I. 679 of the V being turned forwards. The most anterior two of these are 4-5 millim, broad in the middle; but, behind, they become narrower in the middle and taper off to mere threads of bone at their outer and posterior ends. This area of V-shaped ossicles can be traced back for 90 millim, and is fully 120 millim, wide. Between the 15th and 20th vertebrm, narrow and nearly straight, bands of bone appear to extend across the abdominal wall, and either to end in, or be connected with, the lateral ossicles already mentioned. The width of the area occupied by the abdominal ossicles, in this region, is not less than 220 millim. In front of the right pubis there are three broad curved plates, the inner ends of which turn forwards, and which fill up the space between the pr~epubic process and the position which would be occupied by the epipubie cartilage, if such existed. The posterior abdominal ossicles in Crocodiles are, as is well known, closely connected with the pubis. S phenodon requires re-examination in relation to this point. The sacral vertebrae are, unfortunat,ely, much injured; but the centrum of the first (Plate XXVI. fig. 10) appears to be amphi- eoelous, the convex posterior face of the 23rd (or 24th) centrum fitting into it in front, and the convex anterior face of the second sacral fitting into it behind. The rib of the first sacral vertebra measures 18 mfllim, transversely, and its expanded outer end 23 millim. In the form of the articular surfaces of the eentra, in the great development of the cervical ribs, and in the absence of intereentral ossifications, the skeleton of the trunk of Hyperodapedon departs from Sphenodon more widely than in any other particular. The skull has been completely detached from the matrix, and all its most important characters are beautifully displayed. Viewed from above (Plate XXVI. fig. 1), its contour presents the form of a broad-based isosceles triangle. The base, represented by the occipital region, measures 210 millim. ; while the distance from the centre of that region to the rounded apex, formed by the conjoined premaxillary bones, is 160 millim. The hinder moiety of the dorsal region of the skull displays the great supratemporal foss~e (s.t), which are somewhat rounded (50 millim, wide and 58 miUim, long), and are separated by the relatively narrow parietal region of the skull (20 millim, wide), which presents no parietal foramen. In the front moiety, the orbits (or.), of a half-oval shape (50 millim, long and 30 miIlim, wide), are separated by the broad frontal portion of the skull, which is 40 millim, wide. In front of these, again, and of the broad and short nasal bones, is the single anterior nasal aperture (a.n), which is triangular, with the apex forwards, and is 20 millim, broad by 24 millim, long. In the living animal, this opening would have been divided into two by the nasal septum ; but, no doubt, this was entirely cartilaginous, and hence, in the fossil, the aperture appears single. Laterally, it is bounded by a strong ascending process of each premaxilla. In this respect there is a very marked difference between Hyperodapedon and Sphenodon. In the latter, the median end of Downloaded from http://jgslegacy.lyellcollection.org/ at University of Virginia on October 5, 2012

680 PROF. T. H. HUXLEY--OBSERVATIONS

each premaxilla sends up a broad and strong process, which, united with its fellow, ascends in front of the nasal septum to the nasal bones, and thus the two nasal apertures become widely separated by bone. Laterally, on the other hand, the premaxill~e are united with the maxillee by a short process, which has no ascending branch. In HyperodaTedon, as in Sphenodon, the median end of the oral face of each premaxilla is elongated downwards into a recurved process (Plate XXVI. figs. 2, 3, 5, r.p); and the two processes, closely applied together by their inner surfaces, form the beak, or rostrum, in which the upper jaw terminates. In Sphenodon, these rostral processes are broad and flattened from before backwards. Their broad truncated ends descend but little beyond the dentary edge of the mandible, when the mouth is shut, and present two tooth-like eminences. Moreover, their inner sides, closely applied through the greater part of their length, diverge so as to leave a median notch below. In Hyperodapedon, the rostral processes are thick and semicircular in section, the inner, mutually applied, sides being flat and the outer faces convex. Each tapers to its extremity, and the apices of the two are conjoined to form the sharp conical extremity of the beak. The rostrum, as a whole, is much more curved than in S_phenodon, and descends far lower in front of the mandibular symphysis. There is no dentary substance upon any part of the rostrum of Ityperodapedon ; and the aspect of its external surface leads me to believe that it was coated with a horny sheath. In Sphenodon, the anterior end of the mandible lies altogether behind the broad premaxillary rostrum, when the mouth is shut. In Hyperodapedon, on the contrary, the rostrum is received between the restful processes of the mandible. The lateral view of the skull (Plate XXVI. fig. 2) shows that the orbits looked more upwards in Hyperodapedon than in Sphe- nodon; the lateral temporal foss~e (l.t) are relatively much smaller and have a very peculiar ear-like contour, while the bony boundaries of these parts are much stronger. In Hyperodapedon, I can find nothing but bone in the region which should be occupied by the posttemporal lessee. The contour of the alveolar edge of the maxilla in Sphenodon is slightly convex downwards and slighbly concave inwards. In Hyperodapedon, the contour is very strongly convex both downwards and inwards, and this feature, combined with the great length and recurvature of the premaxillary rostrum, confers a very peculiar aspect on the skull (see figs. 1 & 3, p. 682). In the under view of the skull of Sphenodon (fig. 6, p. 683), the maxillaryand palatal regions present little difference from those of ordinary Lizards. The palatal area slowly widens from before backwards, and its maxillary boundaries are slightly concave inwards. Running parallel with the posterior half of each of these is the dentigerous ridge of the palatal bone, bearing a single series of some seven or eigh~ teeth, which, like those of the maxilla, are acutely conical. Between these and the posterior maxillary teeth is the deep groove Downloaded from http://jgslegacy.lyellcollection.org/ at University of Virginia on October 5, 2012

UPON HYPERODAPEDON GORDONI. 681 into which the mandibular teeth are received. The palatal and maxillary teeth of opposite sides are separated by the widest part of the palatal area, formed by the pterygoid bones in the middle, and the palatals at the sides. The long oval posterior nares are wide and conspicuous, occupying, as they do, the greater part of the space between the anterior end of the palatal series of teeth and the premaxillary rostrum (see fig. 6, p. 683). In Hyperodapedon (Plate XXVI. fig. 3) the alveolar edges of the maxillae describe a curve which is strongly convex towards the middle line, and correspondingly concave outwards. Their posterior ends are very far ap~rt, but in the anterior halves of their extent they approach so closely as to leave only a narrow palatal area. At their anterior ends they again slightly diverge. Behind, three longitudinal rows of obtusely conical teeth are set between the groove for the mandible arid the outer margin of the maxilla, but only one of these rows is continued forwards along the anterior half of the length of the maxilla (see fig. 4, p. 683). The space included between the mandibular groove and the curved posterior boundary of so much of the dentigerous area of the palatal bones as is left visible in the specimen by the dislocated mandible is occupied on each side by four rows of obtusely conical teeth, which take a direction roughly parallel with one another and with the series of maxillary teeth. Only one of these series of teeth is continued fbrward alongside of the single part of the series of maxillary teeth. The palatal bones are undistinguishably united, either with the pterygoids, or over them, in the anterior narrow part of the palate, which ends in a semilunar margin, concave forward. The space between this and the posterior face of the root of the premaxillary beak is, for the most part, filled by a broad plate of bone which represents the vetoers. The posterior nares must have been very small; but, on the left side, between a concave edge of this vomerine plate, on the inner side, the premaxilla, in front, and the maxilla, externally, there is a small aperture, which I take to be the posterior nasal opening (Plate XXVI. fig. 3,p.n). The articular con- dyles of the quadrate bones are elongated from side to side, and present eylindroidal surfaces. They lie about 25 millim, behind a vertical line drawn from the oceiput, when the roof of the skull is horizontal. In Sphenodon (see fig. 3, p. 682) the rami of the mandible appear nearly straight in the greater part of their length, both in the lateral and the ventral aspects. In the latter, their anterior ends present a sudden incurvature towards the symphysis, which is not longer than in ordinary Lizards ; and, as in them, the union of the rami is effeeted by ligament. The eontom's of the alveolar edges of the rami have an upward concavity, which is so slight as to be hardly perceptible ; and, viewed from above, they form a narrow arch with nearly straight sides. The inner and superior angle of the symphysial end of each ramus is separated by an interspace from its fellow, above the symphysis. The surface of the ramus at this part is tooth-like in aspect, from the density of the bone of which it is composed. Externally, just where the bent portion of the ramus passes into the Q.J.G.S. No. 172. 3 A Downloaded from http://jgslegacy.lyellcollection.org/ at University of Virginia on October 5, 2012

682 ~oP. ~. 5. trUXL~Y--0BS~,RVATI0~S

Figs. 1-6.--Diagram~nativ views of she Skulls of Hyperodapedon, ~roportion$

Fig. 1.--Skull of Hyperodapedon, side view.

Fig. 2.--Incomplete Skull of Rhynehosaurus, side view. (

Fig. 3.--Skull of l~phenodon, side view.

straight part, there is a strong conical tooth, the base of which is imbedded in the substance of the ramus. This is followed by a series of distinct, acutely conical, teeth (also ankylosed to the jaw); these increase in size backwards up to the last three, which gradually diminish. The anterior six or seven of these teeth are very close set, but quite separate. In Hylaerodapedon, the mandibular rami are extremely massive, and are ankylosed together in front, throughout their long symphysis Downloaded from http://jgslegacy.lyellcollection.org/ at University of Virginia on October 5, 2012

uPo~ rrve~aou,t~,~Do~r aoR~o~rI. 683

Rhynchosaurus, and Sphenodon, illustrating the variations in their and form. Fig. 4.--Skull of Hyperodal~edon , under view.

Fig. 5.--Skull of tthynchosaurus, under view.

Fig. 6.--Skull of Sphenodon, under view.

(Plate XXVI. fig. 4). The anterior and superior angle of each is prolonged into a" rostraI" process (r.m), which passes upwards, outwards, and forwards. The two thus leave a wide V-shaped interval, 3A2 Downloaded from http://jgslegacy.lyellcollection.org/ at University of Virginia on October 5, 2012

684 PROF. T. lt. ItUXLEY--OBSERVATION'S into which the end of the premaxillary beak is received when the mouth is shut. These mandibular rostral processes were probably clothed, like the premaxillary rostrum, with horn; and, with the interlocking premaxillary beak, must have constituted a pair of pincers of great strer, gth. Behind this forked mandibular beak, the upper contour of each ramus is strongly concave upwards, in correspondence uit h the maxillo-palatal convexity, and its close-set teeth are worn to a sharp scissor-edge, which fitted into the fore part of the mandibular groove of the upper jaw. Throughout the symph.~sial region, the two rami lie close together and form a parallel-sided body of the width of the fore part of the palate: but, behind, the rami diverge, sweep outwards in a curve which corresponds, at first, with that of the mandibular groove in the broad part of the palate, and then pass to their articulation with the quadrate. The angle of the ramus appears to have extended cor~siderably behind this articulation, but its exact length and shape cannot be determined. The alveolar edges of the rami begin to show teeth rather behind the middle of the symphysis, and the series of teeth extends for 60 millim, behind this point. In the front part of the series, the teeth are so close-set as to form a palisade-like continuous ridge, worn upon the two face~ to a sharp edge. There are about 6 teeth in a l~n~th of 10 millim., and each tooth is 5 millim, high, but at about 7 millim, from the hinder end of the series the teeth become separate. :Here they present rounded summits and their outer surfaces are convex and unworn (Plate XXVI. fig. 6). Measurements of_parts of the ,Skull of gyperodapedon in millimetres. Nasal aperture, 27 long by 24 broad at, the base. Orbit, 48 long, 35 wide. Narrowest par~ of interorbital region, 40. Supratemporal fossa .. 50 long, 45 wide. Parietal region ...... 20 wide. Lat, eral temporal fossa . 23 wide, 41 in perpendicular depth. Premaxillary rostrum . 25 thick at the base from before backwards. ,, ,, 30 broad from side to side. ,, ,, 35 in a straight line from base to apex. Extreme width of dentigerous area ...... 93 ,, length ,, ,, ...... 82 Width of alveolar face of posterior end of maxilla .... 14 ,, ,, .... palatal .... 24 Diameter of the bases of teeth ...... 3 to 4 Length of symphysis of mandible ...... 56 Breadth of middle of symphysis of mandible at narrowest ~ 23 between the anterior parts of the dentary edges .... J Depth of the rami at this part ...... : ...... 30 Length of each half of the mandibular rostrum from base. 20 Greatest depth of ramus from the dentary edge to the ~ 45 lower border ...... J Total length of ramus, probably ...... 190 Posterior nares ...... 6 wide by 4 long. Downloaded from http://jgslegacy.lyellcollection.org/ at University of Virginia on October 5, 2012

UPON HYPERODAPEDON GORDONI. 685

Fig. 7.--Hyperodapedon Go~'doni. Fig. 8.--Hyperodapedon Gordoni. Mr. Grant's specimen. Mr. Grant's specimen. Left side. Right side.

Dr. Woodward has afforded me the opportunity of examining a very instructive, though fragmentary, specimen of the fore part of the skull of a large Hyperodclpeclon, the property of Mr. Grant, of Lossie- mouth. The premaxillary rostrum is nearly entire and in connexion with the facial bones, as far as the anterior boundary of the orbit on the left side. The anterior end of the left ramus of the mandible, with its rostral process nearly entire, is almost in place (fig. 7), and on the opposite side of the matrix there is the almost complete impression of the right mandibular rostral process (fig. 8). Moreover, a cast of the outer surface of the left rostral process of the premaxilla is preserved in one of the halves of the matrix. The left rostral process itself is quite free, and can be lifted out and examined on all sides. In- cluding the anterior extremity, of which only the impression remains, it is 57 millim, long, 23 millim, deep, and 13 millim, thick at its proximal end. The anterior face is more strongly curved than the posterior, and somewhat flattened, and it is rather obtusely pointed at its free end. The inner face is flat, and was evidently closely applied to that of the opposite rostral process in the greater part of its extent ; but, in the course of fossilization, a thin layer of matrix has been interposed between the two. About the posterior third, the inner face of each rostral process slopes sharply outwards, and the upper margin becomes rounded as it bounds the external nares. Both the inner and the outer surfaces of the bony substance of the rostral processes are marked by fine close-set longitudinal grooves, and the surfaces of the rostral processes of the mandible present similar markings. The convex face of the left premaxillary restful process fits closely into the concavity of the east, to which I have referred, and presents fine longitudinal ridges which answer to the grooves on the surface Downloaded from http://jgslegacy.lyellcollection.org/ at University of Virginia on October 5, 2012

686 PROF. T. H. HUXLEY--OBSERV&TION8 of the bone. I conclude, therefore, that the soft parts and any horny sheath that may have existed must have decomposed and left the bone bare before the sandy matrix set round the imbedded skeleton. Of the bones which enter into the composition of the shoulder- girdle of Hyperodapedon, the specimen presents remains of the interclavicle and the clavicle, the coraeoid, and the scapula. The interclavicle is a long narrow bone, thin and spatulate towards its posterior end. The anterior end bends somewhat sharply towards the dorsal side ; but the shape of its extremity, and whether it was provided with transversely elongated lateral processes or not, cannot be ascertained. On the left side it is in connexion with a strong and long curved bone, which is obviously a clavicle. Nothing more than the edge of a bone which I take to be the scapula can be seen, but the left coracoid is well preserved. It is a cheesecutter-shaped bone, with a broad blade and a comparatively narrow neck, which widens out again to the glenoidal extremity. In Sphenodon, the anterior end of the interelavicle is not bent upwards, and is produced into two strong transverse arms, with which the clavicles are articulated. The scapula and the coracoid very early became undistinguishably united; while, in Hyperodapedon, they appear to have remained, as usual, separate. The principal bones of the left fore limb are seen nearly in their natural relations (Plate XXVI. fig. 11). The humerus has a widely expanded proximal end of a rhomboi- dal shape. In the middle, the shaft is rounded for a short distance and then expands into the broad and thick distal end, the ventral face of which presents a deep intercondyloid fossa. On the inner side there are indications of a "median" canal. The ulna is stout, with a prismatic olecranar prominence, and is somewhat curved longitudinally so as to be concave to the interosseous space. The radius is more slender and nearly straight. The structure of the carpus is not recognizable. The five metacarpals are preserved in various conditions of completeness. The most remarkable feature about them is that they do not seem to have differed to any notable extent in length (17 millim.) ; but while the first, second, and third are proportionally very broad (about 10 millim.), the fourth has a width of not more than 7 millim., and the fifth of 5 millim. The humerus, radius, and ulna in Sphenodon, though more slender, are very similar; but the ulna is longer in proportion to the radius ; the first metacarpal is considerably shorter and at the same time thicker than the second, while the second and fourth are a little shorter than the third, and the fifth is about as long as the first ; and all have much slenderer proportions than those of Hyperoda- pedon. The fore foot of the extinct Lizard must in fact have been remarkably short and thick in its proportions. Downloaded from http://jgslegacy.lyellcollection.org/ at University of Virginia on October 5, 2012

UPON HYPERODAPEDON GORDONI. 687

Meazurements of the Shoulder-girdle and Fore Limb in millimetre$. HyTerodapedon. SThenodo~. Interolavicle, length ...... 90 (about) 31 ,, greatest width .... 17 3 Clavicle ...... 100 (about) 20 Coraeoid, length ...... 58 7, breadth ...... 42 11 Humerus, length ...... 130 33 ,, width at proximal end ...... 62 11 at distal end.. ? 11 ,7 shaft in the middle.. 20 2"5 Radius, length ...... 74 20 ,, width, proximal ...... 20 4 distal ...... 13 4 Ulna, length ...... 74 25 ,, width, proximal ...... 30 5 ,, ,, distal ...... 20 5 Metacarpals :-- ...... 6.5 ii. I ...... 9"5 iii. ~ ...... 17 11'0 iv. [ .. 10"0 v.) ...... 6.0

The right half of the pelvis is exposed ; but the pelvic bones are a good deal crushed, and it is difficult to arrive at an unquestionable interpretation of the appearances they present. There is no doubt, however, as to the posigon of the obturator foramen, bounded in front by the pubis and behind by the ischium. The former bone (P1. XXVI. fig. 12, pb) is transversely elongated, and somewhat narrow in the middle ; it widens out at both ends. At the inner extremity it is flat and thin, and presents a convex symphysial contour. At the outer extremity it is developed forwards into a strong prepubie process and backwards into a thick acetabular portion. The bone is therefore quite Lacertilian. The thick acetabular portion of the ischium (Plate XXVI. fig. 12, is) is in connexion with that of the pubis, and the concave obturator margin of the bone can be well made out. The difficulty is to say how much of the mass of bone which lies behind this point (x, fig. 12) belongs to the ischium and how much to the ilium, which seems to be crushed down upon the ischium. If, as appears probable, the posterior contour of the ischium is indicated by the curved depression (a a, fig. 12), the ventral half of the pelvis will be quite like that of ordinary Lizards, and the rest of the bony matter belongs to the ilium. On the other hand, the form of the ischium in l~hynchosaurus rather leads to the supposition that the ischium was expanded inwardly and prolonged further backward, so as to be unlike that of Sphenodon. The chief bones of the right hind limb (Plate XXVI. fig. 12) are Downloaded from http://jgslegacy.lyellcollection.org/ at University of Virginia on October 5, 2012

688 PROF. T. H. HUXEEY~OBSERVATIONS fairly well seen. The femur is directed forwards, outwards, and dorsad, its proximal end being close to the acetabnlum. The bones of "the leg are sharply bent at the knee, where they lie close to the distal end of the femur, but slightly dislocated backwards. At their distal ends they are in close proximity to the remains of the tarsus and metatarsus. The femur is a short and stout bone, bent so as to lie slightly concave on the ventral and convex on the dorsal surface. The proximal end is a good deal injured, but it obviously expanded to its articular surface and was quite Lizard-like. The middle of the shaft is rounded and little more than half the diameter of the ends of the bone. The inner condyle is stouter than the outer, and between the two there is a deep intercondyloid depression. At about the junction of the middle with the proximal third, the ventral face exhibits a longitudinal elevation, which I take to be the commence- ment of a strong trochanterie ridge, such as exists in Sphenodon. The tibia and fibula are not fully exposed, but the former must have been much shorter than the femur; the distal end is trihedral; the middle of the shaft is flattened, and the proximal end somewhat expanded. The fibula seems to have had a similar form, but it was much more slender. Only fragments of the tarsal bones are preserved. There are indications of five metatarsals, only three of which are represented in Plate XXVI. fig. 12. They increase in length from the first to the third, if not to the fourth. The first is 17 millim, long, the second 35 miIJim., the third 45 millim., and each has a breadth of about 10 millim. Of the fourth only an imperfect impression of the proximal half remains. These four metatarsals lie close together and parallel with one another. The fifth digit was set at a distance from the fourth, as is usual in Lizards, but only the impression of the characteristically broad basal end of the fifth metatarsal is preserved ~ The first phalanx of the first digit is 14 millim, long, and the second seems to have had about the same length. There are two fragmentary phalanges of the second and third digits respectively. Measurements of the Pelvis and Hind Limb. Hyperodapedo~. Sphenodon. Pubis from acetabulum to medial edge ...... 74 19 Femur, length...... 121 40 ,, breadth, proximal end .... 41 8 ,, ,, middle ...... 23 3 distal end ...... 36 8"5 Tibia, length ...... 80 26 Fibula, length ...... 80 (about) 25"5 Metatarsal i ...... 17 8 ,, ii ...... 35 12"5 ,, iii ...... 45 15 The indications of the structure of the metatarsus which I have int~erpreted as above, are somewhat obscure. ]~ven with large-sized figures, their value could hardly be estimated without examination of the original, Downloaded from http://jgslegacy.lyellcollection.org/ at University of Virginia on October 5, 2012

UPON HYPERODAPEDON GORDONI. 689

It is obvious, even from these imperfect data, that the hind foot of Hyperodapedou was longer than the fore foot, though shorter in proportion than that of Sphenodon. It seems also in the gradation of the digits to have departed less from the ordinary Lacertilian foot than the fore foot does.

The comparison of all parts of the skeleton, which has now been made, leaves no doubt as to the close relations between Hyperodapedon and S2henodon. At the same time it makes clear the existence of a number of differences, of which the following appear to me to be the most important :m 1. The centra of the prmsacral vertebrae are ossified throughout and more or less opisthoecelous, especially in the cervical region. Moreover there are no intercentral ossifications. 2. The anterior cervical vertebrm have long and strong ribs. 3. The external nares are not separated by bone. 4. The conjoined premaxillary processes form a long, conical, curved, pointed rostrum, which is received between two rostral processes of the mandible. All these were devoid of teeth, and probably ensheathed in horn. 5. The palatal area is very narrow in front and wide behind, with strongly curved lateral boundaries. 6. The posterior maxillary and palatal teeth are multiserial. 7. The rami of the mandible are united in a long symphysis, behind which they diverge widely, and their dentigerous edges are strongly concave upwards as well as outwards. 8. The mandibular teeth are set into a close, apparently continuous palisade in front, and they become distinct and conical only at the posterior end of each series. 9. The fore foot is remarkably short and stout, with metacarpals of equal length. I find no evidence of the existence of an " eet-epi- condylar foramen" in the humerus.

Rhynchosaurus, although allied to tTyperodctpedon, is sharply distinguished from the latter by its vertebral and cranial characters ; and, in some respects, it occupies an intermediate place between H~perodapedon and Sl)]~e~odon. A specimen in the British Museum (to which I shall refer as No. 1) shows the head and trunk in almost undisturbed relation, thoughmuch damaged in some parts. The length, from the snout to the sacrum, could not, have exceeded 280 millim. ; so that the animal was only a little larger than the specimen of ~henodon of which the measurements are given above ; and, as the skull was about 80 millim, long, it had about the same proportion to the trunk as in S phenodon. The centra of the thoraco-lumbar vertebrae are about 10 millim. long and amphiccelous. They present, at each end, a hemispherical concavity, each of which occupies about a fourth of the length of the centrum, the two middle fourths being occupied by bone. No specimen which I have seen shows the characters of the centra of the cervical or sacral vertebrae, nor throws any light upon the question Downloaded from http://jgslegacy.lyellcollection.org/ at University of Virginia on October 5, 2012

690 PROF. T, H. HUXLEY--OBSERVATIONS of the existence of anterior cervical ribs. There is no evidence of the occurrence of intereentral ossifications. The abdominal ossicles, so far as they are visible, resemble those of Hyperodapedon and Slohenodon, but no specimen I have seen enables tbeir details to be satisfactorily made out. The skull, in its general characters, resembles that of both Hypero- dapedon and of Sphenodon. In contour, it is intermediate between the two, having the occiput relatively somewhat broader than in •Thenodon and much narrower than in Hyperodapedon. The anterior nasal aperture is single, as in Hyperodapedon, and the strong recurred premaxillary rostrum has essentially the same structure, and probably was ensheathed in a horny envelope. On the other hand, the dentary edge of the maxilla is but very slightly convex downwards; and, viewed from below, there is a corresponding difference from ttyperodapedon. The outward lateral concavity and inward convexity of the dentary edges of the maxiUm are very slight, and consequently there is no such anterior narrowing and posterior widening of the palatal surface as in Hyperodapedon. The palatal bones are not fully exposed in any specimen, but in one there is evidence that they bear certainly not more than two longitudinal rows of teeth, perhaps only a single row ; consequently they are narrow, as in SThenodon ; and, as in the latter genus, leave the anterior portions of the pterygoid bones, which lie between them, un- covered (Plate XXu fig. 1,pt). The symphysis of the mandible is relatively short, and the rami do not curve outwards as they do in Hyperodapedon. The mandibular rostral processes, between which the premaxillary rostrum is received, are short and obtuse (see fig. 2, p. 6s~). Thus the skull of t~hynchosaurus resembles that of Hyperoda- pedon and differs from that of Sphenodon, in its single anterior nasal aperture, its premaxillary and mandibular rostral processes, and, perhaps, in possessing more than one series of palatal teeth ; but, m general form, and in the shape of the maxillae, palatal bones, and rami of the mandible, it departs fax less from S2henodon than Ityperodapedon does. In another respect, Rhynchosaurus appears to differ from both Hyperodapedon and Sphenodon, in that no distinct teeth are discernible on the dentary edges either of the maxillae or of the mandible. Without microscopic examination of sections of the parts, it is impossible to say whether the maxillm and the mandible of tChynehosaurus were really edentulous or not. If they were, this genus will present an interesting approximation to the Anomodontia. Two other specimens (No. 2, and its counterpart, No. 3) display the coracoids (co) in place (Plate XXVII. fig. 3). These bones are broad and expanded, 34 millim, long and 20 millim, wide, and have convex median edges. Close to this edge of the right coracoid (in No. 2) lies the interclavicle (i.cl.), 30 millim, long. It is narrow, blade-like, and bent dorsad at its anterior end. Here it expands transversely into two arms, which are short, but are not improbably broken. The clavicles are wanting, unless the part marked vl. in fig. 3 represents one. In the specimen of tChynchosaurus to which I have already referred Downloaded from http://jgslegacy.lyellcollection.org/ at University of Virginia on October 5, 2012

UPON HYPERODAP~DON GORDONio 91 as No. 1, much of the skeleton of the right fore limb is preserved. The right humerus is 40 millim, long, and has widely expanded proximal and distal ends. The radius has about the same length. There are more or less well-preserved remains of five metacarpals. The first has about half the length of the second, which is about equal to the third. In the specimen (No. 2) all five digits of the manus are displayed. The fifth metacarpal, which is broad and short, as in St)he. nodon, and three or four of the phalanges of the fifth digit are in place (Plate :XXVII. fig. 3). In all respects, this foot is more like that of ~phenodon than that of Hyperodaloedon. The impressions of the ischia are very well shown in No. 3 (Plate XXu fig. 4, is). They are broadly triangular in shape, with the angles rounded off. The symphysial side is 25 millim, long; while, from the symphysis to the acetabulum, transversely, the bone measures 20 millim. In front of the left ischium there is seen, in the place which ought to be occupied by the pubis, the impression of a broad fiat plate (Plate XXVII. fig. 4, 2b), 25 millim, from side to side by 10 antero-posteriorly, the posterior edge of which is, for its inner two thirds, in close contact with the front edge of the ischium, leaving only a small space to represent the obturator foramen. I cannot take this impression to represent anything but the pubis, though its form and position are somewhat unusual. The femur is 57 millim, long, and the shaft is curved like an ~. The tibia and fibula are each 50 millim, long. The astragalus and calcaneum are separate (as in Sphenodon), and have the ordinary Lacertilian form. A large distal tarsal bone (as in Sphenodon) affords an articular surface for the fifth metatarsal, which, with the four phalanges of its digit, is preserved (Plate XXVII. fig. 4, v). This digit differs but little in size and form from the corresponding digit in Sphenodon ; and it is therefore remarkable that the fourth metatarsal of I~hyncho- sauru# is very much broader than that of Sphenodon, and half as long again. The third and second metatarsals are nearly as broad, but shorter. The first is relatively shorter and thicker (Plate XXVII. fig. 5). Two imperfect series of tail-vertebrae show that, in the anterior caudal region, the vertebrae were provided with long and strong chevron bones (Plate XXVII. fig. 2). The evidence which has now been adduced appears to me to prove that Hyperodapedon, Rhynchosaurus, and Sphenodon constitute a peculiar group of Lacertilia, the skeletons of which are distinguished from those of all other recent or extinct known forms by the com- bination of the following characters, namely :--the premaxillary rostra ; the longitudinal series of palatal teeth, bounding a groove, between which and the maxillary teeth the hinder mandibular teeth are received ; the abdominal ossicles ; and the absence of proccelous pr~esacral vertebrm. This group of Sphenodontina falls into two families, the Rhynchosaurid~ and the Sphenodontid~. The Rhynchosauridce have a single external nasal aperture; Downloaded from http://jgslegacy.lyellcollection.org/ at University of Virginia on October 5, 2012

692 PRel~. T, H. HUXLEY--OBSERVATIONS edentulous premaxillary and mandibular rostra, probably covered with horn, the former received between the latter; sometimes more than one series of palatal teeth ; and either amphiccelous, or more or less opisthoccelous, pr~esacral vertebrm. This family contains Hyperodapedon and Rhynchosaurus, readily distinguished by the crani~al, vertebral, and dental differences given above. The S phenodontidce have divided external nares; a toothed premaxillary rostrum, not horn-covered, nor received between mandibular rostral processes ; a single series of palatal teeth ; and amphi- coelous vertebrm. It is very interesting to observe that, so early as the Triassic epoch, the group of the Sphenodontina had attained its highest known degree of specialization, Hyperodapedon being in all respects a more modified form than S phenodon. It appears a probable conclusion that in the :Permian epoch or earlier, Lacertilia existed which were less different from ,SLphenodon than either Hyperodapedon or ~hynchosaurus. I am unable to discover any feature in the organization of either Hyperodapedon or t~hynchosattrus which supports the supposition, sometimes entertained, that these reptiles departed from the types of structure found among existing Lacertilia in any greater degree than these (e. g. Monitor, Chamv~leo,Gecko, Sphenodon) do from one another, or that they present any approximation to other Orders of Reptilia. The evidence now offered concurs with that afforded by the structure of Telerpeton, in establishing the belief that the Lacertilian type of organization had, in the Triassic epoch, attained perfectly clear definition from all others; and it further shows that, in H~perodapedon, the type had attained a degree of specialization on a level with that exhibited by any modern Lizard. The relations of the Sphenodontina with other groups of Reptilea of approximately the same age, in which the anterior ends of the jaws tend to assume the characters of a beak, with or without palatal teeth (Dicynodon, Endothiodon), and with such forms as Placodus, cannot, I think, be profitably dealt with until more is known of the organization of the latter. I may add that I am unable at present to see any good grounds for the approximation of Simcedosaurus to Hyt)erodapedon. In his valuable account of the Indian species of HyperodaTedon (' Indian Pretertiary Vertebrata,' eel. i. 1885), Mr. Lydekker assigns various detached bones to this genus on very fair grounds of probability. The absence of intervertebral ossifications in H. Gordoni, however, would seem to diminish that probability so far as the vertebrae are concerned.

EXPLANATION OF THE PLATES. PLATE XXVI:--ttyperodapcdon Gordoni. Fig. 1, 2. Upper and lateral views of the skull. ~ nat. size. 3. The palatal surface of the skull, so far as the adherent mandible permits it to be seen. ~ nat. size. Downloaded from http://jgslegacy.lyellcollection.org/ at University of Virginia on October 5, 2012

UPON HYPERODAPED0~ 00RDONI. 693

Fig. 4. Under view of the mandible. 89nat. size. 5. Front view of the premaxillary rostrum and the anterior nares. .~ nat. size. 6. Series of mandibular teeth : a, anterior, p, posterior end[ :Nat. size. 7. The remains of the atlas, and fig. 8, the succeeding cervical vertebrm. Nat. size. 9. Prmsaeral vertebrm, with the proximal end of a rib. Nat. size. 10. The remains of the first sacratvertebra. ~at. size. 11. The left fore limb. ~ nat. size. 12. The right hind limb. 88nat. size.

PLATE XXu articeps. Fig. 1. Under view of an imperfect skull lXIat,size. 2. A series of caudal vertebra. 1Nat. size. 3. The right shoulder-girdle, ventral aspect (No. 2), and the ]eft fore limb, dorsal aspect (No. 3). 1Nat. size. It is doubtfifl whether cl is really the clavicle. 4. Impressions of the left pubis and ischium, and remains of the bones of the left hind limb as they lie in No. 3. Nat. size. 5 Right hind foot, ventral aspect (No. 1). :Nat. size.

I)isevsslo~. The P~ESIDW~ remarked that he felt he only expressed the sen- t[ments of all the Fellows present in welcoming back their past President to the scene of his former triumphs. The type specimen of Hyperodapedon was so imperfect that it was marvellous the characters ascribed to the genus required so little modification in conse- quence of the far more perfect specimen now described. Mr. ]~VL~E could only re-echo the President's congratulations on the reappearance of Prof. Huxley. He could but admire the clear manner in which this very interesting reptile had been described by him. Dr. GEIKIE recalled the early controversies about the age of the :Elgin Sandstones, and pointed out that no satisfactory stratigraphical solution of the puzzle had yet been found. A line between the beds with Mesozoic Reptilia and those containing ttoloptychius would never have been drawn but for the extraordinary contrast of the organic remains. By physical characters it was not possible to separate them. Prof. SnE~E~ said that caution was necessary in concluding that such types were limited to one system. The Reptiles of South America associated with Lepidodendron and Schizodus, partly described by Prof. Cope, have close affinity with some from South Afl'ica which are usually regarded as Triassic. The form of articulation of the vertebrm being merely generic ia Amphibia, it is not surprising to find that some reptiles have opisthoccelous vertebrm. Some recent lizards also show peculiar forms of the abdominal ribs, as in Plesiosaurns, which are present in many Triassic reptiles, though enveloped with matrix, so as to form abdominal rods like those seen in this fossil. In conclusion, he spoke of the satisfaction he experienced in once more hearing :Mr. tIuxley. Mr. LYI)~a noticed the occurrence of Hyperoclaloedon in India associated with Parasuchus and Belodon; but the associated ver- Downloaded from http://jgslegacy.lyellcollection.org/ at University of Virginia on October 5, 2012

694 ON HYPERODAPEDON 60RDONI. tebrm are amphiccelous. The maxillo-palatines appeared perfectly similar, more so than he at first believed ; indeed there was scarcely apparent specific difference between those described by him and those of the new Elgin specimen. Mr. Wm~AX~R wished to thank Prof. Huxley for the good lesson given by the absence of dogmatism in his paper. Dr. BAva inquired as to the development of the parietal foramen. Prof. HUXLEY said that he could not find a trace of any such foramen in Hyperodapedon. Dr. BAUR said that this showed the specialization of Hyperoda- pedon. Simwdosaurus or Champsosaurus must have some relation to Sphenodon, but it is also a specialized form. Ire pointed out some vertebral points of similarity between the former and SThenodon. With regard to the systematic position of Hyperodapedon and its allies he would prefer putting them under the Rhynchocephalia apart from Lacertilia as a group equivalent t~ Ophidia and Mosasauria. Dr. BL~Fo~ described the relative position of the Hyperoda- Tedon-beds in India, showing that they were, in all probability, later than the Dicynodon-beds, and closely allied, if not identical, with the beds containing fishes of Liassic type. He also noticed that Uromasti.v, an agamoid lizard which shows some points of resemblance in dentition to Hyperodalvedon, is exclusively herbivorous. Prof. BOrD DAwxI•s said that Mr. Charles Moore's examination of the Rhmtie strata which overlie the Hyperodapedon-beds of Elgin, proved that the latter occupied the samet~al~ontological horizon below the Jurassic series as the Hyperodapedon-beds of India mentioned by Dr. Blanford. The P~ESIl)~NT ssid, the difficulty about the position of the :Elgin beds was not so great as was often supposed. In the Old Red- Sandstone quarries fish-remains are byno means rare, but in the exten- sive quarries whence the reptiles have been procured no fishes are found, and recently the reptiliferons beds have been shown to overlie unconformably the Holoptychian beds. The whole of the strata are greatly faulted and covered with drift, ttyperode~edonand Dicyno- don certainly occurred together, and the specimens of the latter were being worked out by Dr. Traquair. The Rh~etic fossils obtained by Mr. Charles Moore were from a boulder. Prof. HuxLeY, in reply, said he remembered the time when pal~eontological papers were not received with such general consent. He begged leave to thank the President and :Fellows for the very cordial reception they had given him. He was unable to agree with Dr. Baur's views as to the classification of lizards and their allies, and considered that it was undesirable to multiply great groups too much. The Rhynchocephalian forms did not appear to him to have any real affinity with Sim~dosaurus, nor were ~hey so much generalized as, for instance, Telerpeton. Probably in Car- boniferous times the gap between Labyrinthodonts and Lizards was bridged over, and intermediate forms occurred.