. Bulletin of the British Museum (Natural History), Geology. A REVIEW OF UPPER JURASSIC PLIOSAURS 155 The margin of the posterior articular surface is bevelled in three places—between the inferior rib facets, and on either side between the superior rib facets and the base of the neural arch. On the lateral surface there are double rib facets ; the inferior facet is oval in outline (antero-posteriorly) and the superior facet tends to be triangular with a faint ridge extending from its apex to the base of the neural arch. On the ventral surface there is a strongly developed ventral keel in the m
. Bulletin of the British Museum (Natural History), Geology. A REVIEW OF UPPER JURASSIC PLIOSAURS 155 The margin of the posterior articular surface is bevelled in three places—between the inferior rib facets, and on either side between the superior rib facets and the base of the neural arch. On the lateral surface there are double rib facets ; the inferior facet is oval in outline (antero-posteriorly) and the superior facet tends to be triangular with a faint ridge extending from its apex to the base of the neural arch. On the ventral surface there is a strongly developed ventral keel in the mid-line, with a depression on either side. There is no suggestion of rugosity along the anterior and posterior margins. Posterior cervical vertebrae. These centra are characterized by a large convex boss in the centre of their articular faces. The superior rib facets are larger than in the anterior cervicals and the inferior facets have usually disappeared, but specimen has a single rib facet on its left side and a double one on the right. On the ventral surface there is no longer a ventral keel, but the centrum is strongly convex from side to side. Dorsal vertebrae. In this part of the vertebral column the ribs are borne on the. Fig. 4. Pliosaurus brachydeirus Owen, holotype. Epipodials of hind limb, X-J. fib. fibula ; tib., tibia. transverse processes of the neural arch, and the centra are more or less cylindrical in shape but somewhat resemble a shallow pulley. Unfortunately they have no characters of diagnostic value and are useless for identification. Caudal vertebrae. Only one centrum is known from the tail region ; it has single rib facets, and, on its anterior and posterior ventral margins, four characteristic chevron bone facets. Limb bones. Owen (1841a;) described two femora with different measurements in his account of the Market Rasen skeleton, but Phillips (1871) considered the smaller of the two bones to be the humerus. However, from an examination of the
Size: 2364px × 1057px
Photo credit: © Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorbritishmuseumnaturalhistory, bookcentury1900, bookcoll
