Pseudoscaphirhynchusare available in systematic
collections outside Russia and Uzbekistan, and
there has never been a modern specimen based sys-
tematic review of all three species. For example, P.
kaufmanni has been described as having two
‘morphs’ in the Amu-Darya river. with only the di-
minutive morph persisting as of the last available
information, but whether these were two separate
species is unclear (see Berg 1948a).
The genusScaphirhynchus(American shove1-
nose sturgeons) is represented by three nominal
species from North America (Figure 16). They are
restricted to freshwater rivers and prefer open,
free-flowing reaches with soft, silty bottoms.Sca-
phirhynchusdistinctively possesses an elongate, ar-
mored caudal peduncle and several osteological
characters defined by Findeis (1997). Common
shovelnose sturgeon (Scaphirhynchus platoryn-
chus) rarely exceed one meter total length, but pal-
lid sturgeon (S. albus) can be much larger (Bailey &
Cross 1954). Pallid sturgeons are endangered, and
apparently readily hybridize with common shovel-
nose sturgeons. The rare Alabama sturgeon (S. sut-
kussi) closely resembles common shovelnose stur-
geon; its status as a distinct species is debated.
A partially intact fossil from the Upper Cretace-
ous of Montana was described as †Protoscaphir-
hynchus squamosus Wilimovsky 1956. Although
Gardiner (1984b)questioned its placement within
Acipenseridae, the specimen does possess an clon-
gate caudal peduncle with armoring scales extreme-
ly similar to those of Scaphirhynchus. No features
clearly distinguish it from Scaphirhynchus, so † Pro-
toscaphirhynchusmay not warrant separate generic
status. It appears to belong in Scaphirhynchini (as
used here) indicating that the tribe was definitely
present in North America at least 65 million years
before present.
Material described as an acipenserid from the
Selma Formation of Alabama (†PropenserApple-
gate 1970) is now interpreted as portions of a coela-
canth and a pycnodont.
We used Huso huso, Acipenser brevirostrum
Scaphirhynchus platorynchus, andPseudoscaphir-
hychus kaufmanni for our phylogenetic analysis
(Table7, Figure 17).
Figure 18. Palate of Acipenser brevirostrum in anterior (aboral)
view. In the top figure, the palatoquadrate cartilage is shown
without its dermal investing bones. The only center of ossifica-
tion within the cartilage that has developed in this specimen is
the autopalatine (a) bone, a thin perichondral sheet near the
symphysis. In a few individuals, another center of ossification
develops in the region of the quadrate flange. In the lowerfigure,
the palatoquadrate cartilage is indicated with heavy stipple. It
has four investing dermal bones: dp,dermopalatine; ecpt, ectop-
terygoid, qj, quadratojugal, and enpt, entopterygoid. The entop-
terygoid bone extends on both the oral and aboral surfaces of the
palate; very light stippling demarcates the oral portion of the en-
topterygoid as seen through the palatoqudrate cartilage. Total
length of specimen: 870 mm. UMA 24- 116 - 2 - 47.Phylogenetic interpretationThis section surveys characters andinterpretations
for the generic-level phylogenetic analysis summa-
rized in Figure 17. The characters are listed or de-
scribed in the test and Table 6 and 7. All characters