Climate changes in Patagonia and Cingulata (Mammalia, Xenarthra) cladogenetic events

CARLINI A. A., M. R. CIANCIO, G. J. SCILLATO-YANÉ.

LA PLATA

Workshop; Paleogeography and Paleoclimatology of Patagonia: effects on biodiversity; 2009

FAC. CS. NATURALES Y MUSEO - DALHOUSIE UNIVERSITY

The known distibution of extant Cingulata, Dasypodidae, shows that the main clades have preferences in their distribution areas. Dasypodinae are distributed on tropical to subtropical regions, whereas the Euphractinae occur from subtropical areas to cold temperate zones in the extreme south of South America. The chronology of the main cladogenetic events of Cingulates was compared with the changes in Cenozoic mean annual sea-surface temperatures (based on [∂18O], see Zachos et al. 2001). Considering that the “peninsular” condition of Patagonia allowed the temperature changes of marine water to be more directly and immediately reflected on the inland climate, the recorded diversity of Cingulates could show it. During, late Paleocene-early Eocene, is observed the better record of most primitive Dasypodinae (Astegotheriini), at this time the warmer temperates in Patagonia are registered (“early Eocene Climatic Optimum”). Toward middle-late Eocene there was a declination in the Dasypodinae abundance, while, in contrast, increased the Euphractinae record and appeared the first Glyptodontoidea, the Palaeopeltidae. From a paleoclimatic standpoint, it is significant the presence of Euphractinae because they are frequent in temperate areas, but scarcely represented in tropical zones. The abundance of Euphractinae in these sediments might be related to a gradual decrease in mean annual temperature. This change of dasypodid diversity advances the subsequent definite prevailing of Euphractinae over Dasypodinae, at least in the South American southern tip. In the Eocene-Oligocene transition (EOT) is documented an abrupt drop of temperatures. At this moment, the decrease of the Astegotheriini both in diversity and relative abundance is stronger and the diversity and representation of Euphractinae Eutatini, medium to large sized forms with a large development of pilosity, associated to cold-temperate climate, increased notably. Coincidently, other Cingulata larger than the previous ones, are also recorded, Machlydotherium and Glyptatelinae. All these forms might be associated to preferably herbivorous diets, and are typical of open environments. Toward the middle Oligocene, there was a small increase in the temperatures until the lastest Oligocene (“Late Oligocene Warming”). Toward the early Miocene, Eutatines decrease in diversity and some peculiar taxa are recorded: one small Euphractini, with scarce pilosity, one very small species of Astegotheriini, very abundant, and one of the genus Stegotherium, also very frequent, the latter is particularly important because it would be among the most specialized Dasypodidae to a strictly insectivorous diet. Moreover, appeared the first Propalaehoplophorinae (Glyptodontidae). This set of data suggests a warmer climate than the corresponding to the previous fauna. The relative diversity of various cingulate subgroups in the paleontological record at southern South America, is strongly correlated with the changes in the oceanic paleotemperatures. PICT 1860, FCNYM N514.