Figure 18.Dorsal bones of the rostrum of †Paleopsephurusand representatives of three genera of Acipenseridae: Dorsal rostral bones
(drb) form a rectangular cover in polyodontids andHuso,but are expanded as a shield (Character 28) and accompanied by border rostral
bones (brb) extending from the jugal (j) in acipenserines (Character29).The dorsal rostral and border rostral series are separatedbyan
ampullary field (stippled circles in c) inAcipenser,but this area is filled with ampullary bones (apb) in scaphirhynchines (d; Character 40).
The pineal fontanelle (pf) is open between the frontal bones in polyodontids and Huso(a, b),but filled bypineal bones (pb)in acipense-
rids (Character 32). The pineal fontanelle is partially filled in juveniles of Acipenser oxyrinchus (b), but covered in other acipenserines (as
in d). oc= olfactory capsule opening in dermal skull.
martin jones
(Martin Jones)
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