CLIMATE CHANGES IN PATAGONIA AND CINGULATA (MAMMALIA, XENARTHRA) CLADOGENETIC EVENTS

CARLINI, ALFREDO A.; CIANCIO, MARTÍN R.; SCILLATO-YANÉ, G. J.

La Plata, Buenos Aires, ARG

Workshop; “PALEOGEOGRAPHY AND PALEOCLIMATOLOGY OF PATAGONIA: EFFECTS ON BIODIVERSITY”; 2009

Fac. de Cs. Naturales y Museo, UNLP

The known distibution of extant Cingulata, Dasypodidae, shows that the main cladeshave preferences in their distribution areas. Dasypodinae are distributed on tropical tosubtropical regions, whereas the Euphractinae occur from subtropical areas to cold temperatezones in the extreme south of South America. The chronology of the main cladogenetic eventsof Cingulates was compared with the changes in Cenozoic mean annual sea-surfacetemperatures (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 directlyand immediately reflected on the inland climate, the recorded diversity of Cingulates couldshow it. During, late Paleocene-early Eocene, is observed the better record of most primitiveDasypodinae (Astegotheriini), at this time the warmer temperates in Patagonia are registered(“early Eocene Climatic Optimum”). Toward middle-late Eocene there was a declination inthe Dasypodinae abundance, while, in contrast, increased the Euphractinae record andappeared the first Glyptodontoidea, the Palaeopeltidae. From a paleoclimatic standpoint, it issignificant the presence of Euphractinae because they are frequent in temperate areas, butscarcely represented in tropical zones. The abundance of Euphractinae in these sedimentsmight be related to a gradual decrease in mean annual temperature. This change of dasypodiddiversity advances the subsequent definite prevailing of Euphractinae over Dasypodinae, atleast in the South American southern tip. In the Eocene-Oligocene transition (EOT) isdocumented an abrupt drop of temperatures. At this moment, the decrease of theAstegotheriini both in diversity and relative abundance is stronger and the diversity andrepresentation of Euphractinae Eutatini, medium to large sized forms with a largedevelopment 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 preferablyherbivorous diets, and are typical of open environments. Toward the middle Oligocene, therewas a small increase in the temperatures until the lastest Oligocene (“Late OligoceneWarming”). Toward the early Miocene, Eutatines decrease in diversity and some peculiar taxaare recorded: one small Euphractini, with scarce pilosity, one very small species ofAstegotheriini, very abundant, and one of the genus Stegotherium, also very frequent, thelatter is particularly important because it would be among the most specialized Dasypodidaeto a strictly insectivorous diet. Moreover, appeared the first Propalaehoplophorinae(Glyptodontidae). This set of data suggests a warmer climate than the corresponding to theprevious fauna. The relative diversity of various cingulate subgroups in the paleontologicalrecord at southern South America, is strongly correlated with the changes in the oceanicpaleotemperatures. PICT 1860, FCNYM N514.