. Bulletin of the British Museum (Natural History) Zoology. 112 CHEN Y1YU Srp Se. Fig. 4 Neurocranium in anterior view: a. Onychostoma sima b. Varicorhinus beso c. Scaphiodonichthys burmanicus which articulates the palatine; in some, such as Semiplotus semiplotus, the facet is well-developed. In Varicorhinus beso (Fig. 2 & Fig. 3) the supraethmoid is broad with a small medial anterior process. The rostral process is directed anteriorly. Compared with Onychostoma the mesethmoid is slightly longer and protrudes anteriorly below the supraethmoid; the vomer is V-shaped, thinner and laterally i
. Bulletin of the British Museum (Natural History) Zoology. 112 CHEN Y1YU Srp Se. Fig. 4 Neurocranium in anterior view: a. Onychostoma sima b. Varicorhinus beso c. Scaphiodonichthys burmanicus which articulates the palatine; in some, such as Semiplotus semiplotus, the facet is well-developed. In Varicorhinus beso (Fig. 2 & Fig. 3) the supraethmoid is broad with a small medial anterior process. The rostral process is directed anteriorly. Compared with Onychostoma the mesethmoid is slightly longer and protrudes anteriorly below the supraethmoid; the vomer is V-shaped, thinner and laterally it forms a wedge-shaped platform which provides the lower part of the preethmoid fossa. The anterior border of the vomer and the mesethmoid are concave and bear a wide groove to accommodate the rod-shaped kinethmoid. The ventral surface of the vomer lacks a palatine articulatory facet, but bears two small process on either side of the midline to which the palatine ligament attaches. In contrast to Onychostoma the lateral ethmoid wings have a concave ventral margin, lie above the horizontal plane of the vomer and are thinner (Fig. 4b). No distinct differences have been found in the orbital region between Onychostoma, Varicorhinus, Cyprinion, Scaphesthes, Scaphiodonichthys and Semiplotus. In these genera the frontals are all broad; the supraorbital bones are large; the orbitosphenoids are deep and ventro-medially they are joined to form a thick interorbital septum which contacts the para- sphenoid. The pterosphenoids provide the walls of the optic foramen and the anterior part of the posterior myodome. Posteriorly each pterosphenoid is bordered by the sphenotic and the prootic and does not contact the ascending wing of the parasphenoid. The parasphenoid is horizontally aligned; anteriorly it narrows, then widens and becomes concave where it overlies the vomer; posteriorly each broad ascending wing contacts the respective prootic. The midline ridge of the parasphenoid is well-devel
Size: 1909px × 1309px
Photo credit: © Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookcollection, bookpublisherlondonbutterworths
