On Protorosaurus speneri (Von Meyer) / by H.G. Seeley.

  • Harry Govier Seeley
Date:
1887
Catalogue details

Licence: Public Domain Mark

Credit: On Protorosaurus speneri (Von Meyer) / 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.

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    the forms of the articular ends of the centrum are imperfectly seen, but the condition displayed by the third vertebra of the series (Plate 14, 4) appears to show that the intercentral articulation in that vertebra, at least, was opisthocoelous. The first vertebra, which is very imperfectly preserved, has the centrum 1*9 c.m. long. The second is of the same length. The third vertebra is the longest, and measures 2-5 centims. The fourth is about a millim. shorter. The fifth measures 2 centims.; and the sixth, which is badly preserved, is about 1‘8 centim. long. In relative elongation as compared with dorsal vertebrae, these cervical vertebrae show a character which is most closely paralleled among Ornithosaurs, but is also met with in various existing Birds and Mammals. Some Chelonians have the cervical vertebrae of a similarly long form; and in the fossil the zygapophyses have a develop- ment which is scarcely equalled among Chelonians. The strong, broad, elevated neural spine is distinctive. The external layer of bony tissue in these vertebrae appears to be as thin as in an Ornithosaur, or a Dinosaur like Ccelurus, as though the centrum were occupied by an air-cell. But, although there is a small foramen in the middle of the side, in a position which might coincide with the junction of the centrum and the neural arch, it is scarcely larger than the ordinary nutritive foramen, common in such a position, and gives no indication of a pneumatic function. The forms of the articular surfaces make the inferences probable that the neck was carried or capable of being earned in a vertical position, as in the Galapagos Tortoises. Only the side of the vertebrae is exposed. In the third vertebra (Plate 14, 4) the centrum is marked with tlmee narrow, sharp, sub-parallel ridges which extend in curves between the anterior and posterior articu- lations ; they are but little elevated, and give a channelled aspect to the side of the centrum. The anterior articular ball of the centrum appears to be well ossified ; it is about 6 millims. deep, and hangs obliquely forward. There is a less obliquity in the posterior cup, which is somewhat deeper, and is defined by a sharp margin. The neural arch extends along the centrum. The anterior and posterior borders of the neurapo- physial lamina which margins the intervertebral neural foramina are concave from above downward, convex from within outward. The antero-posterior distance between them is 2 centims., and the arch, as usual, ascends from the centrum close to its anterior end, just over the anterior articulation. Fi'om the upper side of the neural canal the prezygapophysis extends forward and upward. It is 8 millims. long and 2 millims. wide, and its upper surface is 1 centim. above the base of the centrum. Immediately behind it is a strong ridge or slight transverse process which connects with the posterior zygapophysial process. Its transverse extension outward is broken away. The extreme measurement between the extremities of the zygapophyses is 3‘1 centims. The neural spine is sub-quadrate, compressed from side to side, rising about 9 millims. above the interzygapophysial ridge. The upper border is truncate, slightly rounded from the post-zygapophysis behind, as it extends forward and upward. The front border of the neural spine leans a little forward. In the fourth vertebra the
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