Preliminary historical paleobiogeographic analysis of the Austrovenus Finlay and Ameghinomya Ihering lineages (Bivalvia: Chioninae) from the Neogene of South America and New Zealand

PEREZ, D. E.; EZCURRA, M. D.

Lujan

Jornada; REUNIÓN ANUAL DE COMUNICACIONES DE LA ASOCIACIÓN PALEONTOLÓGICA ARGENTINA; 2011

Ameghinomya is an important member of the South American Cenozoic molluscan assemblages. Its phylogenetic and biogeographic relationshipshave been poorly studied. A recent phylogenetic revision of a subset of 21 chionines recovered Ameghinomya (Miocene?Recent, SouthAmerica) species within a monophyletic clade sister-group of a Protothaca clade [Austrovenus (Pliocene?Recent, New Zealand)-ProtothacaDall (three extant species, American Pacific)-Nioche (Antinioche) burmeisteri (Borchert) (Miocene, Entre Ríos)-Chionista Keen (Recent, AmericanPacific)]. Within this numerical phylogenetic framework at species level, we tested the previous proposal of a dispersal event of Austrovenusfrom South America to Australasia from an Ameghinomya ancestry during the Neogene. A tree reconciliation analysis rendered evidence(p<0.0001) supporting a monophyletic area-clade including the south Pacific as the sister-area of Australasia and the north Pacific. The northand south Atlantic areas were recovered basal to the latter ones. A Dispersal-Vicariance Analysis found within the Protothaca clade a dispersalevent from the south Pacific to the south Atlantic during the early Miocene and subsequently a dispersion from the south Pacific to thenorth Pacific and then from the north Pacific to Australasia during the Pliocene. Our results are inconsistent with the Austrovenus-dispersalhypothesis, but led to the preliminary suggestion of a new route of dispersion within these species: the south Pacific was the ancestral area forthe Ameghiniomya-Protothaca clade; and then two distinct events occurred: an eastern dispersion to the south Atlantic of Ameghinomya andNioche (Antinioche) and a counter-clockwise intra-Pacific route of dispersions of Protothaca, Chionista, and Austrovenus. More comprehensivenumerical analyses will test these preliminary results.