快猫短视频

THE megatherium, a giant ground sloth that lived in the Americas and died out
10 000 years ago, has long been thought of as a slow-moving herbivore. But now
researchers in Uruguay claim they have found evidence that this great beast,
which weighed 4 tonnes, was a carnivore. If they are correct, the sloth (
Megatherium americanum) would be the largest land-based mammalian hunter
ever to have existed.

快猫短视频s know that the sloth was capable of walking on its two hind legs.
This left its forelimbs, which were armed with vicious-looking claws, free for
other uses. It had previously been thought that the claws were used for tearing
out branches, a task that required strength.

Now Richard Fari帽a and Ernesto Blanco of the Universidad de la
Rep煤blica in Montevideo have analysed a fossil skeleton of M.
americanum and discovered that its olecranon鈥攖he part of the elbow to
which the triceps muscle attaches鈥攚as very short. This adaptation is found
in carnivores and optimises speed rather than strength. The researchers say this
would have enabled M. americanum to use its claws aggressively, like
daggers (Proceedings of the Royal Society B, vol 263, p 1725).

Other scientists are sceptical. 鈥淭his is an intriguing story based on sound
physiological arguments,鈥� says McNeill Alexander, an authority on biomechanics
at the University of Leeds, 鈥渂ut the case for carnivory doesn鈥檛 necessarily
follow.鈥� Fari帽a and Blanco do consider other possibilities for the
stabbing motion indicated by the short olecranon, such as defence or sexual
aggression.