Figure 13.Ventral hyobranchial skeleton inPsephurusand representatives ofHusoandScaphirhynchus: The skeleton is shown in oral
view Hypobranchial three (hb3)ofScaphirhychusis also shown in lateral view in the inset of (c). The first hypobranchial (hbl)is
expanded with an anterior shelf in acipenserids (heavy arrow in b, c; Character 21). It also possesses a posterior wedge contacting
hypobranchial two (hh2) in scaphirhynchines (thin arrow; Character 51). Hypobranchial three (hb3) makes double contact with ba-
sibranchial one (bb1) through a ventral process undercutting the basibranchial (inset in c) in all acipenserids (Character 22). The uni-
dentified median cartilage (ug)ofPsephurusandHusois missing in acipenserines (Character 37).hh= hypohyal,bb= basibranchial,cb=
ceratobranchial,hb= hypobranchial.
martin jones
(Martin Jones)
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