Downloaded from http://jgslegacy.lyellcollection.org/ at University of Virginia on October 5, 2012 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 Email alerting click here to receive free service e-mail alerts when new articles cite this article Permission click here to seek permission request to re-use all or part of this article Subscribe click here to subscribe to Quarterly Journal of the Geological Society or the Lyell Collection Notes © The Geological Society of London 2012 Downloaded from http://jgslegacy.lyellcollection.org/ at University of Virginia on October 5, 2012 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 speci- men 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 pro- perty 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 .. ..... '~i~. ~'~i~~ i Downloaded from http://jgslegacy.lyellcollection.org/ at University of Virginia on OctoberQuart. 5, 2012 goum. Geol. Soc.Vot. XLIII. P1. XKtrff. pb-- "4 '~ 9]r ,{~ v Itr II lr M{m.~er'r~ l~oe; nnp. RI-FfN CH0~AURU$ AI%TICEPS . Downloaded from http://jgslegacy.lyellcollection.org/ at University of Virginia on October 5, 2012 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 verte- bral 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 pre- served 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 pro- portion 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 longitu- dinally. 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 horizon- tally 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 appear- ances 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.