Be or not to be, that is the question?: The case of Equus neogeous (Equidae: Perissodactyla: Mammalia) as a Lujanian Stage/Age fossil guide from the Pleistocene deposits in South America

VEZZOSI, RAÚL I.; BRUNETTO, ERNESTO; AVILLA, S.L.

Córdoba

Jornada; 33º Jornadas de Paleontología de Vertebrados; 2019

CICTERRA-CONICET, APA, GOB. DE CÓRDOBA

The chronology andcontinental biostratigraphy of the South American late Cenozoic are based on fossilmammals from Argentina. Especially, the reliability of the local biostratigraphicalunits lies on the authenticity of the stratigraphic position of the fossilmammals from the Pampean region (BsAs Province) and the precision of itstaxonomic studies. Consequently, the Equusneogeus biozone is the biostratigraphical Quaternary unit representative ofthe Lujanian Stage/Age, which corresponds to Late (latest) Pleistocene/Early(earliest) Holocene. Until now, paleontological contributions had been scarce,principally consisting of reports of isolated discoveries and preliminary groupingsof mammals without a good stratigraphical context. However, the substantialnumber of geological and stratigraphical Pleistocene studies conducted in thelast years have provided a useful basis for new hypothesis in South America. Wediscuss the biostratigraphical/chronological hypothesis which sets the species E.neogeus as the fossil guide for the chronological Pleistocene Series(Lujanian Stage/Age) in lowlands. E. neogeus is herein reported since theMiddle Pleistocene (198?178 ±20.6 ka A.P., OSL dating) to Late Pleistocene fromNorthern Pampa. In this sense, the records in a suitable stratigraphicalcontext from outside the traditional Pampean Region, clearly suggest an earlyocurrence at low latitudes by SA. The new records allow establishing that E.neogeus is not an accurate regional biostratigraphical indicator to the ageLate Pleistocene sensu stricto.Therefore, the Lujanian Stage/Age should be interpreted as a local sequence forthe BsAs and should not be extrapolated to a regional framework to define andcompare lithostratigraphical sequences of Pleistocene age.