On Thecodontosaurus and Palaeosaurus / by H.G. Seeley.

  • Seeley, H. G. (Harry Govier), 1839-1909.
Date:
1895
Catalogue details

Licence: Public Domain Mark

Credit: On Thecodontosaurus and Palaeosaurus / by H.G. Seeley. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

    5/24 (page 145)
    vol. v. pi. xxix. figs. 1 ancl 2), Palceosaurus cylindrodon (l. c. fig. 4and Palceosaurus platyodon (/. c. fig. 5). The separa- tion of these genera has not been uniformly adopted, though they appear to have been founded upon good characters. In Tliecodontosaurus the serrations upon the cutting-margins of the teeth are inclined obliquely upward, somewhat like the condition in Dimodosaurus. In Palceosaurus the corre- sponding serrations are at right angles to the cutting-margin of the tooth, as in Megalosaurus. Therefore the dental characters suggest a possible reference of the fossils to distinct families. But the nature of the serration has not always been accurately represented, since in the British Museum Catalogue of Fossil -Reptiles, part i. p. 174, fig. 3, the lateral serrations on the tooth of Palceosaurus platyodon are shown as though they were directed obliquely upward ; and, in harmony with this figure, the species is referred to the genus Theco- dontosaurus. Messrs. Riley and Stutchbury made no attempt to divide the bones which they found between their two genera. Sir R. Owen, in 1841-42, in the Report of the British Association, recognized a resemblance between the teeth of Tliecodontosaurus, which he describes correctly, and the teeth of Rhopalodon of Fischer, which are serrated in a different way *, though there may be no implication that the serrations are identical, since, while Tliecodontosaurus is said to have the serrations directed vertically upward, the tooth-crown in Palceosaurus is said to be traversed by “ two opposite finely serrated ridges, as in Tliecodontosaurus and Rhopalodon.” The authors who first made these animals known described, in addition to teeth and jaw, vertebrae, ribs, chevron-bone, and bones which were regarded as coracoid, humerus, radius, ischium, femur, tibia, fibula, metatarsal or metacarpal bones, and claw-phalanges. Sir R. Owen (/. c.) grouped the more important bones under the genus Palceosaurus. He recog- nizes resemblances in the vertebra} to Teleosaurus and Rhynchosaurus, in the humerus to Rhynchosaurus, and in the femur to Crocodiles and Megalosaurus. The tooth in both genera is regarded as Lacertian in form, and Thecodont in implantation. The pectoral and probably the pelvic arch are regarded as Lacertian. The double-headed ribs and other vertebral characters, and the proportions of the limbs, are interpreted as Crocodilian. These animals were afterwards referred to a distinct order under the name Thecodontia; and when they were redescribed in Sir R. Owen’s 1 Palaeontology,’ ed. 2, 1861, p. 275, the * [Trans. Roy. Soc. vol. R cvi. 1894, pi, lxiii, fig. 2.]