Comment on “The oldest South American Cricetidae (Rodentia) and Mustelidae (Carnivora): Late Miocene faunal turnover in central Argentina and the Great American Biotic Interchange” by D.H. Verzi and C.I. Montalvo [Palaeogeography, Palaeoclimatology, Palae

PREVOSTI, F. J. Y PARDIÑAS, U. F. J.

PALAEOGEOGRAPHY PALAEOCLIMATOLOGY PALAEOECOLOGY

ELSEVIER SCIENCE BV

Año: 2009 p. 543 - 547

0031-0182

In a recent paper (Verzi, D.H., Montalvo, C.I., 2008. The oldest South American Cricetidae (Rodentia) andMustelidae (Carnivora): late Miocene faunal turnover in central Argentina and the Great American BioticInterchange. Palaeogeography, Palaeoclimatology, Palaeoecology 267, 284–291) the potentially oldest SouthAmerican Cricetidae (Rodentia) and Mustelidae (Carnivora) have been reported from a Late Miocene(Huayquerian) assemblage located in central Argentina (Caleufú site, La Pampa province). These findingsexpand the biochron of these important families in South America 3–4 Ma earlier than previous records.However, several observations prevent us from accepting the validity of these assumptions. In this paper wediscuss the age of the Caleufú assemblage, and the assignment of the GHUNLPam 21722 to Mustelidae. TheCaleufú assemblage contains a mixture of Pliocene and Late Miocene faunal elements, and has been assignedto the Huayquerian only due to the “stage of evolution” of some rodents. The lack of isotopic orpaleomagnetic data coupled with the isolation of this locality and the absence of a local stratigraphicsuccession inhibit its correlation with other palaeontological comparable sites and a robust inference aboutits chronology. The “stage of evolution” of a taxon is not a biostratigraphic tool, thus we cannot rule out thepossibility that the Caleufú assemblage has an Early Pliocene (Montehermosan) age. The GHUNLPam 21722, apoorly preserved specimen, shows several characters (e.g., 4 lower incisors, mental foramina below theincisors absent, third lower incisor smaller than the first and second ones) that do not match with Mustelidae(or Carnivora) but instead strongly resemble those observed in didelphimorphian marsupials. The discussedcaveats regarding Caleufu assemblage chronology and taxonomy indicate that new and detailed studies areneeded before the hypotheses advanced by Verzi and Montalvo can be accepted.