Análisis cladístico, paleoecología y extinción de la subfamilia Pichipilinae (Marsupialia, Caenolestidae)

Abstract

The extinct subfamily Pichipilinae is a monophyletic group that comprise three genera and six species of small marsupials that lived on Southern South America from early Colhuehuapian (early Miocene) to Montehermosan (late Pliocene) land-mammal «ages». A cladistic analysis of the Pichipilinae was carried out using sixteen dental characters, and the six species considered as terminal taxa. Apomorphic character states were identified using the subfamily Caenolestinae as outgroup. The analysis yielded one cladogram, with 16 steps, a consistency index of 0.93, and a retention index of 0.83. In this cladogram: 1) Phonocdromus gracilis is the sister group to the other Pichipilinae species; 2) Pichipilus halleuxi + Pliolestes tripotamicus and Pichipilus rigssi + Pichipilus centinelus + Pichipilus osborni are two sistergroups, and 3) the relationship among Pichipilus rigssi + Pichipilus centinelus + Pichipilus osborni is unresolved. The results of the cladistic analysis support the previous hypothesis of a close phylogenetic relation between Pliolestes tripotamicus and Pichipilus halleuxi. It is probably that new and more complete fossil specimens of Pichipilus halleuxi allow: a) to include this species in Pliolestes; or b) to include Pliolestes tripotamicus in Pichipilus. It is possible to infer that Pichipilinae were scansorial, nocturnal and insectivorous- frugivorous mammals, that lived on wet and warm-temperate climatic conditions. Probably, its extinction was related to the climatic-environmental changes occurred on Southern South America during the middle Miocene-late Pliocene span.