Figure 12.Two North American species of Acipenser: a -A
shortnose sturgeon,Acipenser brevirostrum, being stripped by
B. Kynard and a student for captive production of eggs; b -lake
sturgeon,Acipenser fulvescensjuvenile.Graham 1997). A Lower Paleocene species from
Montana, †Polyodon tuberculataGrande&Bemis
1991, shares the elongate gill rakers.
†Pholidurus disjectus, from the Jurassic of En-
gland, historically regarded as a polyodontid
(Woodward 1895) was removed from Polyodonti-
dae by Grande &Bemis (1991). Thus, the family Po-
lyodontidae as presently known is restricted to
North America and Asia.
We used representatives of the four better known
genera of paddlefishes (†Paleopsephurus wilsoni,
Psephurus gladius,†Crossopholis magnicaudatus
andPolyodon spathula) in our phylogenetic analy-
sis. Because only a few details are available con-
cerning †ProtopsephurusLu 1994, we leave it as an
unresolved multichotomy with other paddlefishes.Grande&Bemis (1991), †Crossopholisis a modest-
ly sized polyodontid that was clearly piscivorous as
evidenced by the presence of fish in the body cavity
of several specimens. Interestingly, traces of ampul-
lary organs can be seen between stellate bones in
the paddle of some specimens.
The extant North American paddlefish, Polyo-
don spathula (Figure 9) is an intensively studied
species (see bibliographies in Grande&Bemis 1991,
Dillard et al. 1986 and Graham 1997 this volume).
Polyodonis perhaps best known for its filter-feed-
ing habit based on numerous thin, elongate gill rak-
ers unique to this genus among Acipenseriformes.
Polyodon spathulaoccurred as far north as Lake
Erie (Trautman 1981), but the species typically in-
habits large river systems, and, prior to commercial
exploitation, was common in the Mississippi River
and its tributaries (Gengerke 1986, Russell 1986,
- Family Acipenseridae Bonaparte 1831
As summarized in Table 5, the family Acipenseri-
dae includes four extant genera (Huso, Acipenser,
Scaphirhynchus and Pseudoscaphirhychus) and
one putative fossil genus (†Protoscaphirhynchus).
Other fossil and subfossil material has been de-
scribed, but most of it is fragmentary. Many pop-
ulations of sturgeons are severely depleted (e.g.,
Holcík et al. 1989, Birstein 1993 and many papers in∨
thisvolume) or extinct (e.g., Aral Sea ship sturgeon,
A. nudiventris, see Zholdasova 1997 this volume). A
thorough anatomical description of one species, the
sterlet,A. ruthenus, is available (Marinelli&Stren-