PHYLOGENY OF THE NEOGENE-RECENT GENERA AMEGHINOMYA AND PROTOTHACA (BIVALVIA: CHIONINAE) IN SOUTHERN SOUTH AMERICA.

PEREZ, DAMIAN; DEL RIO, CLAUDIA JULIA

LONDRES

Congreso; 3° International Paleontological Congress; 2010

In the context of determining the fate of the Late Tertiary molluscan faunas of Southern South America andthe origin of the Recent assemblages of the Southwestern Atlantic Ocean, a phylogenetic analysis of theNeogene-Recent genera Ameghinomya and Protothaca has been carried out. The study confirms thesystematic validity of both genera and shows the existence of two monophyletic clades. One is constitutedby 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 theRecent Pacific species Protothaca thaca (type species of the genusj, P. grata, P.staminea and theAustralasian genus Austrovenus (Pliocene-Recent), a taxon that has been previously proposed to be derivedfrom Ameghinomya but, according to the present results, would be more closely related with theProtothaca group than to the genus Ameghinomya.