Climatic-environmental changes and body mass evolution in South American mammals: The Abderitidae’s case (Marsupialia: Paucituberculata)

ABELLO, MARÍA A.; ORTIZ JAUREGUIZAR, EDGARDO

Mendoza

Congreso; ICM 10 - 10th International Mammalogical Congress; 2009

GIB-IADIZA-CONICET-IFM-SAREM

The Abderitidae are a monophyletic group of small sized marsupials, recorded in South America during Late Oligocene-Middle Miocene. They are represented by three genera (i.e., Parabderites, Abderites, and Pitheculites) and eight species, all of them showing dental specializations (e.g., plagiaulacoid molariforms) convergent with those of other mammals (e.g., burramidmarsupials, plagiaulacoid multituberculates, carpolestid plesiadapiforms). The objectives of this presentation are: (1) to understand the body mass evolution in the Abderitidae; and (2) to explore its possible linking with the climatic-environmental changes recorded in South America during the middle Cenozoic. Body mass was estimated from the area of the M2 using a linear regression equation derived from living marsupials. To understand its evolution, body mass was mapped on the Abderitidae’s cladogram using the Line Parsimony Method (LPM) implemented in Mac Clade (version 4.02). The results show that: a) Parabderites has species of small (P. minusculus, 75 g) and medium size (P. bicrispatus, 572 g); b) all the species of Pitheculites has small size (P. minimus, 32 g; P. rothi, 52 g; and P. chenche, 94 g); c) the species of Abderites occupied the range of the medium (A. crispus, 232 g; and A. meridionalis, 450g) to medium-large size (Abderites sp., 720 g); (d) only Abderites shows a clear pattern of body mass evolution across the time (from lower to higher body mass species). All these body mass changes occurred during a lapse characterized by a progressive decrease in temperatures, and an increase of aridity, that produced a reduction of the warm and wet forested environments, and the initiation of the expansion of the more open, drier and colder ones (e.g., savannas, grasslands) in southern South America. As colophon, we discuss the probable influence of these climatic-environmental changes on the body mass evolution of the Abderitidae.