nizing the International Conference on Sturgeon
Biodiversity and Conservation. Penny Jaques, Nan-
cy Ruddock and Judy Shardo helped in manuscript
and figure preparation. Vadim Birstein provided
advice and translation help for Russian papers.
Wen Jun Li and Dan Hui assisted with Chinese pa-
pers. John Waldman, Vadim Birstein and two anon-
ymous reviewers improved our manuscript. Our
work has been supported by grants from NSF (BSR
8806539 and BSR 9220938), the Whitehall Founda-
tion, and the Tontogany Creek Fund.lytype series, held in systematiccollections ineast-
ern Europe andAsia. Itwill bevital toundertake at
leastsome newfieldwork tocollect thespecimens
needed forcomprehensivestudy, butbecause of
current threats tomanyspecies ofAcipenseri-
formes, any sampling must be done insuch a way
that itdoes notfurther threatenalready diminished
populations. The effort tobetterunderstandaci-
penseridbiodiversityshould not bepostponed for
even a short period, or we may notknow intime
whichtaxa are inmost need ofconservation.
(2)Our information about living and fossil Polyo-
dontidae ismorecompletethan for any otherclade
withinAcipenseriformes.Still,there ismuch to do,
includingincorporation of the newly described
†Protopsephurusinto aphylogeneticframework,
andattentionto the functionalmorphology of feed-
ing and, inparticular,electroreception.Especially
needed are newanatomical studies ofPsephurus,
including its development.
(3) Future paleontological work On fossil Aci-
penseriformes should focus on redescription and
analysis of †Chondrosteidae and †Peipiaosteidae.
In particular, it is important to resolve whether
suggested by Yakovlev (1977). Our currently avail-
able osteological characters for paddlefish and stur-
geons will also need to be reassessed as more com-
and †Peipiaosteidae become available. Finally, it
will also be important to restudy Mesozoic and Pa-
leozoic actinopterygians, particularly †Birgeria,
†Saurichthys,and †Phanerorhynchus, to better as-
sess the sister group of Acipenseriformes.
(4) In any future studies of acipenseriform sys-
netic and individual variation. As noted above, the
documented variations in morphology, including
post-reproductive changes in ossification patterns,
mean that growth series of individuals need to be
studied.
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Acknowledgements
We thank Vadim Birstein, John Waldman, Robert
Boyle, and the Hudson River Foundation for orga-