Revision de las especies del genero Hyperdidelphys Ameghino, 1904 (Mammalia, Marsupialia, Didelphidae). Su significacion filogenetica, estratigrafica y adaptativa en el neogeno del Cono Sur Sudamericano

Abstract

All species of fossil marsupials belonging to the genus Hyperdidelphys Ameghino, 1904 (Didelphidae, Didelphinae, Didelphini) are analyzed and rediagnosed: H. inexpectata (Ameghino, 1889), H. pawula (Rovereto, 1914), H. pattersoni (Reig, 1952) and the new species H. dimartinoi. The biochron of this genus spans from the Late Miocene (Huayquerian StageIAge) to the Late Pliocene (Chapadmalalan StageIAge); al1 records referable to species of Hyperdidelphys come from central and northwestern Argentine localities. Hyperdidelphys and Lutreolina conform a monophyletic group among the Didelphini, being Lutreolina the plesiomorphic sister group of Hyperdidelphys. H. pattersoni is the sister group of a clade including two monophyletic groups: H. pawula on one side, and H. inexpectata + H. dimartinoi sp. nov. on the other. Several taxa previously referred to this genus are discussed and excluded from it: (1) «Hyperdidelphys brachyodonta» (Reig, 1952) is a junior synonym of Didelphis crucialis Ameghino,1904; (2) «Hyperdidelphys biforata» (Ameghino, 1904) is a species of Lutreolina (L. biforata n. comb.), and (3) «Paradidelphys nodosa» Ameghino, 1904 is a junior synonym of Thylophorops perplana (Ameghino, 1904) n. combo The biostratigraphic significance of the species of Hyperdidelphys in the Late Cenozoic of Southern South America remains unelear: their record in Neogene levels is unfrequent, the identification of two of the four species (H. parvula and H. inexpectata) is complex on the basis of known materials, and the biochrones of three of them are not restricted but inelude relatively wide time spans. Carnivorous adaptations of species of Hyperdidelphys correlate with the decline of Sparassodont marsupials in late Miocene-Pliocene times, a process that was previous to the arrival in South America of inmigrant placental carnivores of Holarctic origin by the stablishment of the intercontinental Panamanian land bridge.