Within Acipenseriformes, all workers agree that ous occur in Central Asia (Nesov & Karnyshkin
the Acipenseridae and Polyodontidae diverged pri- 1983).
or the Late Cretaceous (Berg 1948a, Yakovlev 1977, The China-western American group consists of
1986, Grande & Beinis 1991, Jin 1995, Grande & Be- Acipenser sinensis, A. dabryan us, A. medirostris,
mis 1996, Bemis et al. 1997). Within the Acipeenser- andA. transmontanus; the external morphology of
dae, the subfamily Scaphirhynchinae (Central the last two species is very similar (Findeis 1993).
Asian species ofPseudoscaphirhynchusplus North All of these species seem to have common Tertiary
American species ofScaphirhynchus) was tradi- roots (Artyukliin & Andronov 1990). The two ex-
tionally considered the sister group of all other stur- tant paddlefish species also indicate a trans-Pacific
geons (Berg 1905, Vasiliev 1985). Another interpre- pattern that is strengthened by the inclusion of fos-
tation, based on osteology, was proposed by Findeis sil taxa, such as Eocene Crossopholisand Paleo-
(1993,1997 this volume), who found thatHusolacks cenePaleopsephurus(Grande & Bemis 1991, Jin
many characters found inAcipenser,Scaphirhyn- 1995, Bemis et al. 1996, Grande & Bemis 1996).
chusandPseudoscaphirhynchusOn this basis, he The third group includes European and Amer-
considered Scaphirhynchinae as a derived group ican Atlantic sturgeons (Vladykov & Greeley 1963,
within Acipenseridae (Findeis 1997). This point of Kinzelbach 1987, Holc∨ík et al. 1989). Probably, the
view was disputed since the description of thePseu- EuropeanA. sturiohas many primitive characters
doscaphirynchus species 120 years ago (Kessler of the genus (Nesov & Kaznpshkin 1977). Once con-
1877, Berg 1905), while other researchers consid- sidered a subspecies ofA. sturio,the American At-
ered Scaphirhyninae as the oldest group within Aci- lantic sturgeons were subsequently split off as a sep-
penseridae (Bogdanov 1887). The examination of arate species, A. oxrinchus(Vladykov & Greeley
generic relationships within Acipenseriformes us- 1963). Then, two subspecies,A. o. oxyrinchusand
ing molecular phylogenetic methods was one of the A. o. desotoi,were described withinA. oxyrinchus
main goals of this paper. (Vladykov 1955, Vladykov & Greeley 1963). The
According to Nesov & Kaznyshkin (1977), extant origin and spread of the Atlantic sturgeon probably
species ofAcipenserbelong to different evolution- reflect close Tertiary links between Europe and
ary lineages which diverged long lime ago. Artyuk- North America (Artyukhin & Andronov 1990).
hin & Andronov (1990) and Artyukhin (1995)pro- The freshwater sturgeons of eastern North Amer-
posed that there were at least four main regions in ica, belonging to the fourth group, the lake stur-
which the speciation and spread of sturgeons took geon,A. fulvescens, and shortnose sturgeon,A. bre-
place: (1) the Ponto-Caspian area: (2) China-west- virostrumare possibly closely related (Vladykov &
ern America; (3) the Atlantic area: and (4) eastern Greeley 1963) and may have originated on the East-
North America the group of Ponto-Caspian spe- ern coast of North America (Artyukhin & Andro-
cies includes most of the Eurasian species (Acipen- nov 1990).
sergueldenstaedtii,A. persicrus, A. stellatus. A.ruth- Evidence for monophyly of these four groups re-
enus,A. nudiventris Huso huso, A. baerii; Berg mains uncertain, and the relationships among them
1948b, Holc∨ík et al. 1989, Pirogovsky et al. 1989, are unknown. Recently, Artyukhin (1995) publish-
Shubina et al. 1989, Vlasenko et al. 1989a, b, Soko- ed a first phylogenetic tree based on general data of
lov & Vasilev 1989a–c, Ruban 1997 this volume), as morphology, biogeography and karyology (but not
well as Amur River endemics (A. schrenckiiand the DNA content) of Acipenser. Atryukhin’s
Huso dauricus;Artyukhin 1994, Krykhtin & Svir- scheme is the first modern attempt to reconstruct
skii 1997 this volume), and, possibly, an Adriatic relationships within the genusAcipenser(see Be-
speciesA. naccarii(Tortonese 1989, Rossi et al. mis et al. 1997, for a history of the 19th century at-
1991). The origin of Ponto-Caspian species might tempts to subdivideAcipenserinto subgenera).
have been associated with brackish-water deriva- Artyukhin & Andropov (1990) wrote: ‘It is quite
tives of the Tethys Sea. The oldest extinct forms of evident that methods of biochemical genetics and
the Ponto-Caspian group from the Upper Cretace- karyology, as well as paleontological data and cur-
martin jones
(Martin Jones)
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