Posts Tagged ‘eremotherium laurillardi simultaneous die off in Ecuador’

At Least 1 Species of Giant Ground Sloth (Eremotherium laurillardi) Lived in Groups

February 28, 2020

Some scientists have long suspected at least 1 species of giant ground sloth lived in groups.  The bones of Eremotherium laurillardi are often found in intergenerational assemblages, and there is a large degree of sexual dimorphism within the species.  Animals with large males and small females or vice-versa tend to live in social groups.  Lions are an example of this.  However, most of the sites where mixed-age assemblages of E. laurillardi occur were difficult to interpret–scientists were unable to determine whether the collection of bones came from a simultaneous die-off or accumulated over a long period of time.  But a site in southwestern Ecuador known as Tanque Loma does contain bones of E. laurillardi that clearly resulted from a simultaneous die-off.

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Photo of the Tanque Loma excavation from the below reference.

Scientists excavated 575 specimens of E. laurillardi from at least 22 individuals at the Tanque Loma site.  They found less than 100 bones of other species including  gompothere (a type of mastodon), glossotherium (a smaller species of ground sloth), pampathere (a very large armadillo), horse, and deer in the same genus as white tail deer.  The bones of E. laurillardi come from individuals of different ages and sexes, suggesting it was a social group. Sloth coprolites and stomach contents were found as well, but the plant remains have not been identified or if they have the results have not been published yet.  Tanque Loma was a temporary marshy pond that apparently dried up during dry seasons, then periodically refilled during rainy season.  This region of Ecuador was a tropical grassland during the Last Glacial Maximum, similar to modern day East Africa.  The remains are estimated to be between 18,000-23,000 years old, but the conditions of this site make radiocarbon dating less reliable.  Humidity and the presence of tar interfere with accurate radio-carbon dating.  It was not a tar pit trap because the tar seeped into the deposit after the animals had been dead for a long time.  The bones were preserved when they were quickly buried in a low oxygen environment.

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Replica skeleton of Eremotherium laurillardi mounted at a museum on Skidaway Island.  They were common along the Georgia coast during interglacials.  They reached 20 feet in length and weighed over 4 tons.  They may have been hairless like elephants and unlike other ground sloths.

The authors of this study believe this group of sloths died when the marsh shrank and the sloths fouled the water with a concentration of their own fecal matter.  The high nitrogen input may have caused a toxic algal bloom that poisoned the group, the members of which died within a few weeks.  Large mammal die-offs like this occur in East Africa today, especially among hippos when they are congregated around shrinking water holes.

E. laurillardi ranged into Florida and coastal Georgia during warm interglacials, but they disappeared from the region at least 30,000 years ago.  They were not as well adapted to temperate climates as Harlan’s ground sloth and Jefferson’s ground sloth (which occurred in Alaska).  These latter 2 species had furry coats and dug deep burrows.  Eremotherium may have been hairless and may not have dug deep burrows.  The temperate species of ground sloths didn’t become extinct in North America until men wiped them out.

Reference:

Lindsay, Emily; et. al.

“A Monodominant Late-Pleistocene Megafauna Locality from Santo-Elena, Ecuador: Insight on the Biology and Behavior of Giant Ground Sloths”

Paleogeography, Paleoclimatology, Paleoecology 544 April 2020