CONICET | Buscador de Institutos y Recursos Humanos

Phylogenetic relationships, systematics and taxonomic assignments of the Cenozoic Chlamydini of Argentina and Chile still remain unknown. The phylogenetic analysis performed provides the first matrix for the subfamily, based on 110 morphological continuous and numerical shell-characters scored for 37 fossil and extant species. It was used TNT 1.5 beta software, through an heuristic search of 100 replicates of Wagner trees, with space for 2000 trees in memory, followed by TBR branch swapping algorithm holding 10 trees per replicate, under implied weighting with K values between 6 and 11. The obtainedtree grouped the studied taxa into three clades. One includes the Pliocene species of Northern Chile, the other the early Miocene-middle Miocene Patagonian genera Swiftopecten, Jorgechlamys and Reticulochlamys, alone with ?Zygochlamys?nicolasi, and the other, clusters the Oligocene-middleMiocene largely misinterpreted Zygochlamys, and a new genus including Pecten actinodes (late Miocene) and Pecten aurorae (early Pliocene). Contrary to what was previously supposed, Zygochlamys is neither related to the Chilean species nor to the Pliocene-Recent circumpolar Psychrochlamys, but shows a closerrelationship with Chlamys than to any other Patagonian Cenozoic Chlamydini. As a sister group of Chlamys islandica-Chlamys rubida cluster, appears Pecten quemadensis (early Miocene), demonstrating the presence of Chlamys in Patagonia, up to now considered to be restricted to the Northern Hemisphere. Chlamys hastata is shown as the most basal Chlamys species. Finally, Psychrochlamys should not be related to these fossil genera any more, being solved as a basal group to the mentioned three clades and to the Mymachlamys-Aequipecten one.