EVOLUTIONARY TRENDS OF PROTYPOTHERIUM LINEAGE THROUGHOUT THE MIOCENE-PLIOCENE OF SOUTH AMERICA

VERA, BÁRBARA; SCARANO, ALEJO

Brisbane

Congreso; Annual Meeting of the Society of Vertebrate Paleontology; 2019

Society of Vertebrate Paleontology

Protypotherium (Interatheriinae, Notoungulata, Mammalia) is a well-knownand very diverse genus of extinct native ungulates of South America, widelydistributed from southern to middle latitudes of Argentina, Chile, and Bolivia.This genus exhibits distinctive species throughout the different biozones fromthe Miocene to Pliocene that display an interesting size pattern. Three speciesfrom the late Early Miocene, P. attenuatum (small), P. praerutilum (medium),and P. australe (large); two species from the Middle to early Late Miocene,P. endiadys (small) and P. colloncurensis (large); two species from the LateMiocene, P. minutum (small) and P. distinctum (large); and only one speciesfrom Late Miocene-Pliocene, P. antiquum (large). The large sample ofspecimens studied during several years of research allow to us to analyze theshape and size of upper and lower molars for all the species ofProtypotherium, in order to test the hypothesis of reduction of size rangespreserving a general tooth morphology as a response to climate deterioration.Elliptic Fourier analyses (EFA) were used to capture the shape of the occlusal morphology and the centroid size (CS) was also retained for subsequentanalyses. Our results demonstrate that: 1) in general, a similar morphologicaltooth pattern is observed among all species from Miocene to Pliocene; 2) thereis a tendency to increase the size from the smallest species of the late EarlyMiocene (e.g., P. australe) to the largest one in the Late Miocene-Pliocene (P.antiquum); 3) tooth shape variation is not associated with a change in size(CS), both in upper and lower molars and between small and large species; 4)a decrease in the number of species is recorded from three in the earlyMiocene to one in the Late Miocene-Pliocene. This striking pattern could becorrelated with a global trend to lower temperatures, which indicates adeterioration of paleoenvironmental conditions. In South America, amarkedly descend of temperature occurred during Miocene times that is alsotestified by paleoflora and the marine environmental. Given thispaleoenvironmental context, a successful conservative tooth pattern, togetherwith an increase of size and a reduction in number of species were the mainevolutionary and ecological tendencies accounted in Protypotherium from theMiocene to Pliocene.