Figure 9. The living North American paddlefish,Polyodon
spatthula: a – A pond-reared specimen from a commercial fish
farm in Missouri. b – Gill rakers and entrapped plankton in an
adultPolyodon.
(1992) provided a new reconstruction (Figure 6).
†Stichopterus woodwardi Reis 1910 occurs in the
Lower Cretaceous of Trans Baikal; this species was
treated in more detail by Yakovlev (1977). A second
species, †Stichopterus popoviYakovlev 1986 comes
from the Lower Cretaceous of Mongolia. Yakovlev
(1977) questioned whether †Stichopterusand †Pei-
piaosteuswarrant separate generic status. In an-
swering this question, Zhou (1992) summarized
some striking differences between the two genera,
such as the presence of an endopterygoid and palate
in †Stichopterus (not found in †Peipiaosteus) and
the presence of rhombic scales in the upper lobe of
the caudal fin in †Stichopterus(not found in †Pei-
piaosteus). All of this material warrants new addi-
tional specimen-based study.
We used published data on †Peipiaosteus pani
from Liu & Zhou (1965) and Zhou (1992) for our
analysis (see Grande & Bemis 1996 for data on †Pei-
piaosteuscollected after this paper was prepared;
two additional genera, †Yanosteus and †Spheros-
teus are treated there).
- Family Polyodontidae Bonaparte 1838
Unlike sturgeons, paddlefishes are usually regard-
ed as primary freshwater fishes (e.g., Swift et al.
1986), and although individuals may occasionally
stray into coastal marine environments (Vladykov
& Greeley 1963) all fossil paddlefishes are from
freshwater deposits. This makes the family partic-
ularly useful for biogeographic interpretation.
Grande & Bemis (1991) studied osteology and rela-
tionships among four genera of paddlefishes (†Pa-
leopsephurus,Psephurus,†CrossopholisandPolyo-
don; Table 4). Recently, a new Mesozoic genus
†Protopsephuruswas described (Lu 1994) and puta-
tively assigned to Polyodontidae. †ProtopsephurusFigure 10.A cleared and double stained juvenile specimen of be-
luga,Huso huso. Bone is stained red, cartilage stained blue. Note
the endochondral rostrum sheathed by dorsal and ventral rostral
bones, the projectile jaws, reduction of the lateral line canals to
simple tubular bones, and the series of scutes on the trunk.