Geological Society, May 11

Nature (May 1887)

[94] –Prof. J.W. Judd, F.R.S., President, in the chair.–The following communcations were read:–Further observations on Hyperodapedon gordoni, by Prof. T. H.Huxley, F.R.S. The author briefly noticed the circumstances under which he first described the occurrence of Lacertilian and Crocodilan fossils in the Elgin sandstones, and the confirmtion which his views as to the Mesozoic age of these remains had received from the discovery of Hyperodapedon in English Triassic rocks and in India. The original type of Hyperodapedon gordoni from Elgin was, however, in bad condition, and the receipt at the British Museum of a second much better preserved skeleton, found in the Lossiemouth quarries of the same neighbourhood, had enabled him to add considerably to the known characters of the genus, and to compare it more thoroughly both with the recent Sphenodon (or Hatteria) of New Zealand and with the Triassic Rhynchosaurus articeps, several [95] specimens of which are in the British Museum palæontological collection. The recently discovered Hyperodapedon skeleton was of nearly the same size as that formerly described, and must have belonged to an individual about 6 or 7 feet in length. The specimen was exposed by the splitting of a large block of sandstone, and comprised the skull, the vertebral column as far as the root of the tail, all the bones of the left and of part of the right fore—limbs, and those of the right hind-limb, the whole almost in their original relations. The bones were described in order and compared with those of Sphenodon, the most important differences in Hyperodapedon being the following–(1) The centre of the presacral vertebræ are ossified throughout and more or less opisthocœlous, especially in the cervical region. (2) The anterior cervical vertebræ have long and strong ribs. (3) The external nares are not separated by bone. (4) Conjoined pre-maxillary bones form a long, conical, curved, pointed rostrum, which is received between the rostral processes of the mandible. All these were devoid of teeth and probably sheathed 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 the dentigerous edges are strongly concave upwards as well as outwards. (8) The mandibular teeth in front are set into a close, apparently continous palisade, and become distinct and conical only ast the posterior end of the series. (9) The fore-foot is remarkably short and stout, with metacarpals of equal length. The relations of Rhynchosaurus to Hyperodapedon and Sphenodon were then dealt with, the first-named being shown to occupy in some respects an intermediate place between the two other. The skull of Rhynchosaurus resembles that of Hyperodapedon in its single anterior nasal aperture, its premaxillary and mandibular rostral processes, and its having more than one series of palatal teeth; but in general form and in the shape of the maxillæ, palatal bones, and rami of the mandible it departs far less from Sphenodon than Hyperodapodon does. Some comparisions of the limb-bones were also made. The three genera mentioned were shown to form a particular group, which, however, had no claim to ordinal distinction, and appeared to form a family, Sphenodontidæ, of the Lacertilia, comprising two sub-families, Rhynchosaurinæ (including Rhynchosaurus and Hyperodapedon) and Sphenodontinæ. The fact that in this Lacertilian group the highest known degree of specialization, as shown in Hyperodapedon, was attained as early as the Triassic ephoch, showed that in Permian times, or earlier, Lacertilia existed which differed less from Sphenodon than either of the Rhynchosaurinæ did. Not only was the Lacertilian type of organization clearly defined in the Triassic epoch, but itr attained a degree of specialization equal to that exhibited by any modern lizard. The reading of this paper was followed by a discussion, to which the President, Dr. Geikie, Prof. Seeley, Mr. Lydekker, Prof. Boyd Dawkins, and others took part.–On the rocks of the Essex drift, by Rev. A. W. Rose.–On Tertiary Cyclostomatous Bryozoa from New Zeland, by Mr. Arthur W. Waters.


C. Blinderman & D. Joyce
Clark University