Figure 10.Palatal complex of representatives of three genera of
Acipenseridae: The palatal complex is a cartilaginous plate
bound to the palatoquadrate to expand the functional surface of
the upper jaw (top in black; Character 18). It is formed by a single
dominant cartilage inHuso,but comprises multiple large and
small cartilagesinother acipenserids.
Character 17. Basipterygial process present-Aci-
penseridaeThis basipterygial process extends from the ventral
surface of the basipterygium, flaring around the an-
terior edge of the pelvic fin musculature (Findeis
1993). It is present in all acipenserids examined.
Extant polyodontids possess a segmented basi-
pterygium different from acipenserids, but also
lacking a ventral process. The basipterygium is car-
tilaginous in adults and unknown from fossil aci-
penseriforms. Lacking †Chondrosteus and †Pei-
piaosteusas outgroups clouds cladistic analysis of
this character, but the pelvic plate of † Moythomasia
(Gardiner 1984a) is complete and lacks a ventral
process.Polypterus, Lepisosteus,andAmiapossess
differing basipterygial morphologies, but all lack a
ventral process.Character 18.Palatal complex present- Acipenseridae
The palatal complex comprises an integrated group
of flat cartilages embedded within loose skin poste-
rior to the upperjaw and opposite the ventral
tongue pad (Figure 10). This complex is attached to
and functionally linked with the palatoquadrate.
Number of cartilages forming the complex and
their individual shapes vary, but it is present in all
acipenserids examined.
The palatal complex is composed of several large
plates of cartilage unified as a wedge with thin lat-
eral arms in Scaphirhychus and Pseudoscaphi-
rhynchus(Figure 10c). The palatal complex of all
species of Acipenserexamined is deeper and more
rounded than in scaphirhynchines, and typically in-
cludes numerous small cartilages arrayed around a
large central and paired lateral plates (Figure 10b;
see Antoniu-Muigoci 1942). Huso possesses a
broad, shallow palatal complex formed by one
dominant plate with occasional thin cartilages
along the anterior edge (Figure 10a). Number of
cartilages forming the palatal complex has been
used as a character within Acipenseridae (Antoniu-
Murgoci 1936b, Sokolov 1989), but this variation
makes it dificult to polarize character states and no