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  Section: Anatomy of Vertebrate Animals » The Classification and the Osteology of the Reptilia
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The Protorosauria


These are the oldest known Sauropsida, their remains occurring in the Kupferschiefer of Thuringia, which is a part of the Permian formation, and in rocks of corresponding age in this country; but no more modern representatives of this group are known.

The Thuringian Lizard (Protorosaurus) does not appear to have attained a length of more than six or seven feet. The neck is remarkably long, the cervical region being equal to the dorsal in length, and it bears a skull of moderate size. The tail is long and slender, and the limbs well developed, as in the existing Monitors. Notwithstanding the length of the neck, it contained not more than nine, possibly not more than seven, vertebrae, which, except the atlas, are remarkably stout and strong. There are about eighteen or nineteen dorsal, two (or not more than three) sacral, and more than thirty caudal vertebrae. In all these vertebrae the neurocentral suture is completely obliterated, and the centra are slightly concave at each end. The side of each cervical vertebra, after the atlas, presents, near its anterior edge, a small tubercle, with which the head of a slender styliform rib articulates. The transverse processes of the dorsal vertebrae are very short, antero-posteriorly flattened, plates, and the strong ribs are articulated with them by undivided heads. The sternum has not been preserved. In the abdominal region of some specimens, numerous short and filiform bones appear to represent, and correspond with, the abdominal ribs of Plesiosauria and Crocodilia.

The spinous processes of the caudal vertebrae, up to near the middle of the tail, have the ordinary structure; but beyond this point they bifurcate, so that each vertebra seems to have two spinous processes, a peculiarity unknown in other Lacertilia.

The large chevron-bones are articulated between the bodies of the caudal vertebrae, as in the Crocodilia, but also as in some Lacertilia, such as the Geckos. The skull is preserved in one specimen only, and in that it is in such an imperfect condition that the details of its structure cannot be made out. The teeth, however, are nearly straight, conical, and sharply pointed, and seem to have been implanted in distinct sockets, though there may be some doubt upon this point.

The pectoral and pelvic arches are large and strong. The fore-limbs are shorter than the hind-limbs, and each limb bears five digits. The manus contains certainly eight, possibly nine, carpal bones, five of which correspond with the metacarpals. The number of phalanges is exactly the same as in most existing Lacertilia (2, 3, 4, 5, 3). In the pes, again, the number of the phalanges is characteristically Lacertilian (2, 3, 4, 5, 4), and so is the form of the fifth metatarsal, but the two proximal tarsal bones appear to have been less closely connected together than in existing Lacertilia, and there were, at fewest, three distal tarsal bones with which the metatarsals articulated, and by which they were completely separated from the proximal tarsals. Among existing Lacertilia an arrangement similar to this is met with only in the Ascalabota.

5-9. The great majority of existing Lacertilia belong to the procoelous kionocrania, with not more than nine cervical vertebrae, and they deviate but little in their osteology from the general type of organization which has been described.

The skull in the Platynota, or Monitors of the Old World, with the American genus Heloderma, differs from that of any other Lacertilia in the circumstance that the nasal bones are represented by a single narrow ossification.

In the genus Lacerta the bones of the roof of the skull become continued into dermal ossifications, which roof over the supra-temporal fossae. In the Chalcidea and Scincoidea, in which the body sometimes becomes elongated and snakelike, and the limbs rudimentary, the supra-and infra-temporal arcades are apt to be ligamentous, and the post-frontals and squamosals small.


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