The Late Miocene mammals from the Humahuaca Basin (northwestern Argentina) provide new data on the initial stages of the Great American Biotic Interchange

CANDELA, ADRIANA M.; ABELLO, MARÍA A.; REGUERO, MARCELO A.; GARCÍA ESPONDA, CÉSAR M.; PARDIÑAS, ULYSES F.J.; ZURITA, ALFREDO E.; PUJOS, FRANCOIS; MIÑO-BOILINI, ÁNGEL R.; QUIÑONES, SOFÍA I.; GALLI, CLAUDIA I.; LUNA, CARLOS A.; VOGLINO, DAMIÁN; DE LOS REYES, MARTÍN; CUARANTA, PEDRO; ESCAMILLA, JUAN F.

San Salvador de Jujuy

Congreso; XXXIV Jornadas Argentinas de Mastozoología; 2023

Sociedad Argentina para el Estudio de los Mamíferos

In this contribution, we describe new Late Miocene mammalian specimens from the Maimará Formation (Upper Miocene to Lower Pliocene) exposed at Humahuaca Basin (23°–24°S), northwestern Argentina (NWA), and analyse their taxonomy and relevance for our understanding of the initial stages ofthe Great American Biotic Interchange (GABI). The new studied specimens from the Maimará Formation are housed at the Instituto de Geología y Minería (UNJu), Jujuy Province. The stratigraphic and geochronologic control of the studied specimens indicates a time window of c. 6.6–5.8 Ma. These data are crucial for establishing the oldest records of two emblematic groups the Holarctic immigrants of the GABI, the “heralds” of the GABI. The first record of cricetid rodents (assigned to Genus and species indet. of Sigmodontinae and represented by mandibular and maxillary fragments with teeth) from the Maimará Formation is reported. Moreover, with an age of c. 6 Ma it is the first appearance datum (FAD) of these rodents in South America. The age of the procyonid Cyonasua recorded in this unit is estimated between c. 6.6 and c. 6.4 Ma. The record of procyonids and cricetids in the same continuous sedimentary sequence suggests that the time interval between the dispersion of both groups into the continent during GABI was c. 1 Ma. Among autochthonous mammals from the Maimará Formation, the first records of litopterns (assigned to the macrauchenid cf. Windhausenia delacroixi, represented by a partial proximal end of tibia), chlamyphorid (referred to the species Doellotatus chapadmalensis and Macrochorobates scalabrinii, both represented by isolated osteoderms) and mylodontine xenarthrans (referred to cf. Pleuroestodon, represented by a lower molariform), and caviomorph rodents (including new species of Octodontidae and Caviidae, represented by mandibular and maxillary fragments with teeth) are described. FADs of immigrant and autochthonous mammals in NWA suggest a major faunal turnover during GABI at the Messinian, probably linked to global climatic changes and the tectonic activity that affected the Humahuaca Basin at that time. Hypsodonty, a dominant feature among Maimaran mammals, may be related to a landscape strongly influenced by the Andean uplift.