Population structure of the gomphothere Stegomastodon waringi (Mammalia: Proboscidea: Gomphotheriidae) from the Pleistocene of Brazil

Abstract

The Quaternary fossil record of Águas de Araxá (QAA) is represented mainly by an accumulation of skeletal elements of several sizes, which are assigned to a population of Stegomastodon waringi. We analyzed 97 molars according to the wear stages of Simpson and Paula-Couto (1957), and developed a morphometric wear index. The population structure (proportion of immature, subadult, adult, mature adult and senile adult individuals) was identified, and these five age classes were compared to those of extant elephant populations and defined with social implications. The analysis made possible to establish that the population is largely composed of adults: 14.89% are immature individuals, 23.04% subadults, 27.65% adults, 17.21% mature adults and another 17.21% senile adults. Based on population structure, we do not discard the possibility that the fossil population was stable or in recovery, and/or was experiencing a high-predation period on younger individuals. The number of individuals composing the past population studied here could suggest that the occupied environment was open due to comparisons to populations of extant elephants. We consider this population as an aggregation of family units, which suggests a time of low environmental humidity. Based on literature and our findings, their extinction appears to be regional and probably related to a catastrophic event.

Extinction of a gomphothere population from Southeastern Brazil: Taphonomic, paleoecological and chronological remarks

“…The QAA N. platensis had been previously recognized as a single population (Simpson and Paula Couto, 1957;Mothé et al, 2010) and its age was established by dating a single tooth (DGM104-M) and its associated sediment, representing the dating for the entire population. This N. platensis tooth is currently housed at the paleontological collection of Departamento Nacional de Produção Mineral, Rio de Janeiro State, Brazil.…”

“…Gomphotheres fossils have been found in almost all Brazilian states, but the Quaternary of Águas de Araxá (QAA) outcrop is noted for its great abundance of dental and postcranial fossils of N. platensis (Simpson and Paula Couto, 1957;Mothé et al, 2010). Previous studies suggested that the gomphothere remains from the QAA outcrop represents a single N. platensis population (Simpson and Paula Couto, 1957;Mothé et al, 2010). These papers are the basis for several other studies that investigated aspects of the taphonomy and paleoecology of South American gomphotheres (e.g.…”

Climate and humans set the place and time of Proboscidean extinction in late Quaternary of South America

“…Following this idea, the biomass of herbivore communities is closely regulated by food availability (i.e. habitat's carrying capacity; see a study with African ungulates in Fritz and Duncan, 1994) and, in accordance with Mothé et al (2010), the family structure of Notiomastodon is analogous to those from current African elephants (Loxodonta africana). Also, Thomas et al (2008) show that summer home range (environmental requirements) of current African elephants is four times wider than its winter one.…”

Lagoa do Quari (São Raimundo Nonato, Piauí): Palaeoenvironment and wetland archaeology in Northeastern Brazil

“…Width reaches 75 mm at the level of the third raw, 67 mm at the fourth and 47.5 mm at the heel.This gomphothere had the mass of an Asian elephant. It is reported from several Brazilian sites such as Águas de Araxá (Minas Gerais) (Mothé et al, 2010), Lagoa São Vitor (Piauí) and Lagoa Uri de Cima (Pernambuco state) (Faure & Guérin, 2013, Figures 3 and 4). Recently, Mothé et al (2020) observed some traces of projectile points on a Gomphothere calf skull from Lapa do Caetano (Lagoa Santa region, Minas Gerais state).…”