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The giant rodent Chapalmatherium from the Pliocene of Argentina: new remains and taxonomic remarks on the family Hydrochoeridae

1998; Taylor & Francis; Volume: 18; Issue: 4 Linguagem: Inglês

10.1080/02724634.1998.10011107

1937-2809

José Luis Prado, Esperanza Cerdeño, Sergio Roig‐Juñent,

Animal Ecology and Behavior Studies

ABSTRACT Two nearly complete skulls and incomplete postcranial remains of a giant rodent of the family Hydrochoeridae are described and identified as Chapalmatherium novum. They come from the Calera Avellaneda locality, near Olavarria, Buenos Aires Province, Argentina, considered to be of Montehermosan age (early Pliocene). Diagnostic characters of the genera of Protohydrochoerinae are discussed, and synonymy between Chapalmatherium and Protohydrochoerus is proposed: the species P. perturbidus becomes Chapalmatherium perturbidum. The known data concerning Chapalmatherium species and this new material lead us to question the taxonomic validity of C. irenense and C. saavedrai; we consider them to be junior synonyms of C. novum. A cladistic analysis of the family Hydrochoeridae, with the caviid Dolichotis as the outgroup, yielded three most parsimonious cladograms. The results show that Cardiatheriinae is a paraphyletic group, Anatochoerinae is not a monophyletic subfamily, and Hydrochoeropsis must be included in Hydrochoerinae. The Protohydrochoerinae appear to be a monophyletic group, constituting the sister group of the Hydrochoerinae.