Chris Simms in New Scientist:
Sabre teeth have very specific characteristics: they are exceptionally long, sharp canines that tend to be slightly flattened and curved, rather than rounded. Such teeth have independently evolved in different groups of mammals at least five times, and fossils of sabre-tooth predators have been found in North and South America, Europe and Asia.
The teeth are first known to have appeared some 270 million years ago, in mammal-like reptiles called gorgonopsids. Another example is Thylacosmilus, which died out about 2.5 million years ago and was most closely related to marsupials. Sabre teeth were last seen in Smilodon, often called sabre-toothed tigers, which existed until about 10,000 years ago.
To investigate why these teeth kept re-evolving, Tahlia Pollock at the University of Bristol, UK, and her colleagues looked at the canines of 95 carnivorous mammal species, including 25 sabre-toothed ones.
More here.
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