. Bulletin. Natural history. Text-fig. 40. Anterior portion of vertebral column of Platecarpus (YPM 24900, X %). tion, nine cervical vertebra. However, Williston and Case (1892, p. 20) state that in CUdastes the first long rib with a possible sternal connection occurs on the eighth postcranial vertebra (see also Williston, 1898b, p. 139). Osborn (1899a, p. 172), and Williston (1910, p. 538) and Huene (1911, p. 49), on the basis of excellent skeletons of Tylosaurus and Platecarpus respectively, imequivocally give the number of cervical vertebrae as seven. It is highly probable that mosa- saurs
. Bulletin. Natural history. Text-fig. 40. Anterior portion of vertebral column of Platecarpus (YPM 24900, X %). tion, nine cervical vertebra. However, Williston and Case (1892, p. 20) state that in CUdastes the first long rib with a possible sternal connection occurs on the eighth postcranial vertebra (see also Williston, 1898b, p. 139). Osborn (1899a, p. 172), and Williston (1910, p. 538) and Huene (1911, p. 49), on the basis of excellent skeletons of Tylosaurus and Platecarpus respectively, imequivocally give the number of cervical vertebrae as seven. It is highly probable that mosa- saurs have two less anterior vertebrae lacking a sternal contact than does Varaniis. The neural spine of the third cervical vertebra is slender in lateral aspect, with slightly converging anterior and posterior margins. The posterior buttress of the spine is still greatly enlarged and is almost as wide as that of the axis, though the anterior edge is very thin. A transversely oriented elliptical surface, which was capped by cartilage in life, occupies the dorsal tip of the spine. The neural spine changes its shape posteriorly so that by the time the last cervical is reached the spine is parallelogram-shaped in lateral aspect and both longer and higher. Laterally the spine also becomes very compressed, causing the posterior buttress to vanish almost completely and the dorsal edge of the spine to lose nearly all trace of a transverse elliptical expansion on the last cervical. It is thus apparent that few, if any, fibers of the M. spinalis capitis, which arises on the dorsal tip of the neural spines, can have extended behind the last cervical, and that the Mm. interspinalis, spinalis and semispinalis cervicis diminished to normal proportions in the posterior cervical region. It is interesting that these last. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may no
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