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.

Evidence of scavenging on remains of the gomphothere Haplomastodon waringi (Proboscidea: Mammalia) from the Pleistocene of Brazil: Taphonomic and paleoecological remarks

“…However, even a large pack of hypercarnivorous canids would need to spend excessive energy to hunt such a large prey as an adult H. waringi. Mothé et al (2010) estimates that around 40 individuals represented the gomphothere population from QAA. According to Simpson and Paula-Couto (1957) and Mothé et al (2010), the QAA gomphothere fossil bones can be assigned to a mass death event related to a environmental low humidity period, with scarcity of water and food resources (Fig.…”

“…Mothé et al (2010) estimates that around 40 individuals represented the gomphothere population from QAA. According to Simpson and Paula-Couto (1957) and Mothé et al (2010), the QAA gomphothere fossil bones can be assigned to a mass death event related to a environmental low humidity period, with scarcity of water and food resources (Fig. 6A); under such conditions, proboscideans tend to suffer mass mortality near water refuge (Haynes, 1991).…”

“…Simpson and Paula-Couto (1957) argued that the QAA gomphotheres lived in an environment similar to a recent savanna, which is characteristic for long seasons of drought followed by torrential rain in the summer. According to Mothé et al (2010) during this period of extreme drought, associated to the shortage of water and food resources, these gomphotheres suffered a mass mortality.…”

“…Especially problematic are the dynamics of communities that included proboscideans such as gomphotheres (Gadens-Marcon, 2007, 2008; Mothé et al, 2010). In this paper, we interpret carnivore tooth marks and other evidences from a Brazilian find of bones of mostly adult gomphothere in order to explain the formation of the site's fossiliferous deposit and reconstruct aspects of an extinct Pleistocene ecosystem.…”

First record of Eremotherium laurillardi (Lund, 1842) (Mammalia, Xenarthra, Megatheriidae) in the Quaternary of Uberaba, Triângulo Mineiro (Minas Gerais State), Brazil

“…The works started with the pioneering contributions of Peter W. Lund and Herluf Winge (e.g., Lund, 1950), who studied thousand of specimens recovered from natural karstic caves filled with PleistoceneeHolocene sediments (see Cartelle, 1994Cartelle, , 2002, from different localities from the center and north of Minas Gerais. Later on, especially since the second half of 20th Century, several contributions enlarged considerably the Quaternary studies of Minas Gerais State (e.g., Price, 1944;Simpson and Paula Couto, 1957;Paula Couto, 1979;Cartelle and Lessa, 1988;Cartelle, 1989Cartelle, , 1994Cartelle, , 1999Monteiro, 1998;Neves et al, 1999;Hadler et al, 2009;Mothé et al, 2010).…”