Polypterus - Recent, Africa
† Mimia Upper Devonian, Australia
†Birgeria - Lower Triassic, Greenland
Figure4.Someliving and fossiloutgroups ofAcipenseriformes: a –Polypterusrepresents aclade generally considered to be theliving
sister group of all other living Actinopterygii .The rhombic ganoid scales are omitted in this diagram (from Dean 1895). b -†Mimia is
known from many beautifully preserved specimens (from Gardiner 1984a). c - †Birgeriafrom the Triassic of east Greenland (from
Nielsen 1949). †BirgeriasharesthreesynapomorphieswithAcipenseriformesdiscussed in the text andtables.
ies are critical topromotingawareness of agroup.
Acipenseriforms are increasingly threatened in
theirnative ranges (e.g., Birstein1993,Bemis &
Findeis1994), yet onlyrecently hasthistranslated
intomorerigorous systematic inquiry(Rochard et
al. 1991).There aremanyoutstandingsystematic
problemswhichcould influenceglobalconserva-tion efforts for thegroup. Forexample, wecannot
answerheresuchbasicquestions as: ‘is the genus
Acipensermonophyletic?’ or ‘how manyvalid spe-
cies of Acipenser should we recognize?’These
questionswillnecessarilyabsorb a greatdeal of fu-
tureresearchbecause of the broad geographic
rangeoccupied by thespecies ofAcipenseras well