Paleontologists Find 3.58-Million-Year-Old Ground Sloth Fossil

Thursday, February 4, 2021

Life reconstruction of Megatherium. Image credit: Sebastián Rozadilla.

Paleontologists in Argentina have discovered what they say is one of the oldest-known fossils of the ground sloth Megatherium.

Megatherium is an extinct genus of ground sloths that lived in South America from the Early Pliocene epoch (5 million years ago) through the end of the Pleistocene epoch (11,700 years ago).

The earliest and smallest known species of the genus is Megatherium altiplanicum from Pliocene of Bolivia.

But it is best known for the elephant-sized Megatherium americanum, sometimes called the giant ground sloth, native to Argentina, Uruguay and Bolivia during the Pleistocene.

It was up to 10 times the size of living sloths reaching weights of up to 4 tons.

It was able to stand and walk on its hind legs, making it the largest bipedal mammal of all time.

Megatherium overlapped with humans in time as their fossils have been found with cut marks on them, suggesting that these creatures were on the menu thousands of years ago.

Footprints attributed to Megatherium americanum dating to around 14,000 years old have been found in Argentina.

These animals lived mostly in groups, but they may have lived singly in caves.

They probably had mainly a browsing diet in open habitats, but also they probably fed on other moderate to soft tough food.

There even have been suggestions that their long claws and strong forelimbs may have allowed them to hunt other animals.

The 3.58-million-year-old skull of Megatherium from the San Eduardo del Mar locality, Argentina. Image credit: Museo Municipal Punta Hermengo, Miramar.

Megatherium remains are very common in almost the entire Argentine territory, however, it is the first time that the remains of such high antiquity have been found, which is only comparable to a find made a few years ago in Bolivia,” said Dr. Nicolás Chimento from the Museo Argentino de Ciencias Naturales ‘Bernardino Rivadavia’-CONICET and his colleagues from the Museo Municipal Punta Hermengo, Miramar, the Universidad MaimónidesCICYTTP-CONICET, and CIC PBA-UNMDP.

The new, partial skull of a Megatherium was discovered at the locality of San Eduardo del Mar in Argentina’s Buenos Aires province.

The paleontologists found that the fossil belonged to a juvenile and is at least 3.58 million years old.

The 3.58-million-year-old skull of Megatherium. Image credit: Museo Municipal Punta Hermengo, Miramar.

“This constitutes the first undoubted record of Megatherium from the Pliocene of Argentina, and one of the oldest records for the genus,” they said.

“This finding blurs previous biogeographical proposals sustaining that the genus originated in the High Andes and later dispersed to the lowlands.”

“On the contrary, present finding, together with the record of coeval Megatherium species in the Pleistocene of the Argentine Pampas, suggests a more complex paleobiogeographical scenario and indicates that the diversity of lowland Pliocene megatheriines is still underrepresented.”

The findings were published in the Journal of South American Earth Sciences.


Nicolás R. Chimento et al. A new record of Megatherium (Folivora, Megatheriidae) in the late Pliocene of the Pampean region (Argentina). Journal of South American Earth Sciences, published online October 10, 2020; doi: 10.1016/j.jsames.2020.102950