Yukon to the Yucatan: Habitat partitioning in North American Late Pleistocene ground sloths (Xenarthra, Pilosa)

Abstract

The late Pleistocene mammalian fauna of North America included seven genera of ground sloth, representing four families. This cohort of megaherbivores had an extensive geographic range in North America from the Yukon in Canada to the Yucatan Peninsula in Mexico and inhabited a variety of biomes. Within this latitudinal range there are taxa with a distribution limited to temperate latitudes while others have a distribution restricted to tropical latitudes. Some taxa are better documented than others and more is known about their palaeoecology and habitat preferences, while our knowledge of the palaeoecology of taxa more recently discovered remains limited. In order to better understand what aspects of their palaeoecology allowed their dispersal from South America, long–term success in North America and ultimately the underlying causes for their extinction at the end of the Pleistocene more information is needed. A summary overview of the differences in the palaeoecology of the late Pleistocene sloths in North America and their preferred habitats is presented based on different data sources.

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

“…JUY‐P‐0345 is assigned to Proscelidodon based on the following morphological characteristics: (1) skull with the anterior region of the parietals bulging transversely; (2) lacrimal lacking contact with the nasal because the maxilla is interposed (McDonald 1987; Montalvo et al . 2020).…”

Paleobiology of Jefferson’s Ground Sloth (Megalonyx jeffersonii) derived from three contemporaneous, ontogenetically distinct individuals recovered from Southwestern Iowa, U.S.A.

“…Megalonyx jeffersonii was widely distributed and its paleoecological associations were variable, but it is frequently associated with a non-analog, spruce-dominated, mixed conifer-hardwood forest present across the northern U.S.A. (Schubert et al, 2004; Hoganson and McDonald, 2007). With a hypselodont dentition composed entirely of dentine, it was a browser (McDonald, 2021). Megalonyx is unique among all the North American ground sloths for having plantigrade hind feet, a primitive characteristic for sloths.…”

First Shasta Ground Sloth (Nothrotheriops; Xenarthra) from the Eastern Great Basin, Nevada

“…Although the recognized distribution of N. shastensis has its northernmost occurrence at approximately 40°N in northern, mountainous California (Potter Creek, Hawver, and Samwel caves; a less understood specimen occurs in Merrill, Oregon, at 42°N; Table 1, Fig. 1), N. shastensis may have been inhabiting a modern Mediterranean climate within a nonanalog biotic community (McDonald 2021). All previous records of the Shasta ground sloth in the Great Basin are from its southernmost margin, making the Smith Creek Cave record both the northernmost (39.2°N) and highest (1963 m) record for the Great Basin; it is also among the greatest records of both parameters for the species in general (Fig.…”

“…Overall, Nothrotheriops shastensis was the most xeric-adapted of all North American ground sloths based on the dietary reconstructions from plants obtained from dry-preserved dung found in multiple caves in the Southwest (Laudermilk and Munz 1938, Hansen 1978, Thompson et al 1980, Poinar et al 1998, Mead et al 2021, McDonald 2022). However, it was clearly able to inhabit less xeric habitats and process different vegetation based on its co-occurrences with other ground sloths (e.g., Megalonyx and Paramylodon ) in southern, more coastal California (McDonald 2021, Fig. 1).…”