Um fóssil de 500 milhões de anos: olhos extremamente complexos e visão mais aguda do que os insetos modernos

quinta-feira, dezembro 08, 2011

An eye-opening fossil

Ancient predators had vision sharper than modern insects.

Matt Kaplan

07 December 2011

The sharp-eyed, metre-long Anomalocaris.

Armed with barbed grasping claws and a mouth full of tooth-like serrations, anomalocaridids are thought to have been the top predators in the Cambrian oceans about 500 million years ago. A cache of spectacular fossils now suggests that the ancient hunter Anomalocaris had compound eyes that gave it keener vision than many of the modern arthropods related to it.

Previous fossils have raised the possibility that it had compound eyes, but none of them has had enough surface detail to confirm this. Palaeontologist John Paterson at the University of New England in Australia, and his colleagues have now done so by studying fossils discovered in the Emu Bay Shale in South Australia. They found that thousands of tiny hardened lenses definitely made up each eye, much as they make up the eyes of modern insects and crustaceans. The fossil is described today in Nature1.

“The extraordinary detail preserved in this specimen is just fantastic,” says Robert Gaines, palaeobiologist at Pomona College in Claremont, California, who was not involved in the study.

“It has been unbelievably frustrating being able to see eyes like these at fossil sites like the Burgess Shale [in the Canadian Rocky Mountains], but not have any details. It is really refreshing to have our ideas about these animals confirmed at last,” comments Simon Conway Morris, a palaeontologist at the University of Cambridge, UK.

Moreover, it seems that the eyes of ancient anomalocaridids had even more lenses than those of most modern arthropods. Paterson and his team counted about 16,000 lenses on each eye. “This is a lot,” says Paterson. “The common housefly has only 3,200 and most ants have fewer than 1,000.” Dragonflies have up to 28,000 lenses in each eye — and extraordinary eyesight — but they are “the freaks of the arthropods”, he says.

Read more here/Leia mais aqui: Nature