Phylogeny of the Neogene-Recent genera Ameghinomya and Protothaca (Bivalvia: Chioninae) in Southern America.

PEREZ, DAMIAN; DEL RIO, CLAUDIA JULIA

LONDRES

Congreso; 3° International Paleontological Congress; 2010

International Palaeontological Association

In the context of determining the fate of the Late Tertiary molluscan faunas of Southern South America and the origin of the Recent assemblages of the Southwestern Atlantic Ocean, a phylogenetic analysis of the Neogene-Recent genera Ameghinomya and Protothaca has been carried out. The study confirms the systematic validity of both genera and shows the existence of two monophyletic clades. One is constituted by the Miocene Patagonian Ameghinomya argentina (the type species of the genus), A. darwini, A. meridionalis, the Neogene Chilean A. volckmanni and´Venus" chiloensis, and the Pliocene-Recent ´Venus´ antiqua. This last taxon constitutes the only extant species of this group in the Southwestern Atlantic Ocean, and has been previously placed in Protothaca or Ameghinomya. The other clade is represented by the Recent Pacific species Protothaca thaca (type species of the genus, P. grata, P.staminea and the Australasian genus Austrovenus (Pliocene-Recent), a taxon that has been previously proposed to be derived from Ameghinomya but, according to the present results, would be more closely related with the Protothaca group than to the genus Ameghinomya.