Tuesday, 27 September 2011

A New And Tiny Cousin Of The Giant Megatherium

A reconstruction of Hiskatherium santandrei from Pujos' study
Around 15 million years ago, the grasslands of South America were dominated by terror birds, sabre toothed killers, gargantuan, armoured herbivores and giant ground sloths. These giant, lazy animals are well known from many forms such as Megatherium or Mylodon. The giant bones of giant ground sloths have been found all across the Americas, from South America to the Canadian border. They were once all thought to be huge, ponderous plant eaters. However a new discovery has changed this idea.

The fossils of Hiskatherium saintandrei
Hiskatherium saintandrei was discovered in a 17 million year old, Miocene formation in Bolivia by French palaeontologists Fran├žois Pujos, Gerado de Iuliis and Bernadino Quispe. The creature is known from some rather parsimonious remains consisting of a lower jaw and four molar teeth. The length of the jaw is just 1.2 inches and could fit comfortably into a human palm even when complete. The very scant nature of the remains means that gleaning anything about this creature is difficult.

Pujos published the findings of the study in the Journal of Vertebrate Palaeontology. The team believe that Hiskatherium was related to small ground-dwelling sloths such as Hapalops which possibly possessed climbing capabilities. The name Hiskatherium is derived from the Bolivian word 'hiska,' meaning small. Its peg-like teeth suggest that it fed upon tough plant material. However the rich nature of the American grasslands means that it probably fed upon soft leaves but could eat tougher material in harder times, such as during a drought.

Soft, nutritious leaves tend to grow in the canopy layer of forests. If Hiskatherium did indeed feed upon such plants, then it would have had to have been able to climb. Its close relationship to potentially arboreal sloths such as Hapalops show that this theory is perfectly plausible. It is possible that it gave rise to the arboreal sloths, while an evolutionary cousin was the ancestor of the giant ground sloths. Hopefully, palaeontologists will discover more remains or possibly even a complete skeleton, allowing us greater insight into the life of this remarkable creature.