The largest animal species of the Cambrian period, a marine predator with a long, segmented body and a pair of grasping appendages, lived much longer than previously thought and grew to sizes much larger than previously known.The animals, known as anomalocaridids, were thought to have gone extinct after the Cambrian period, 540 million to 500 million years ago. Now a newly discovered specimen indicates that they actually lived another 30 million years, into the Early Ordovician period.
The new specimen measures more than three feet in length; the biggest specimen previously known was about two feet long.
Derek Briggs, a paleontologist at Yale, and Peter Van Roy, a paleontologist at Ghent University in Belgium, discovered the specimen in southeastern Morocco and describe their findings in the current issue of the journal Nature.
Along with the anomalocaridid, the pair also discovered more than 1,500 fossils of other soft-bodied marine animals, including sponges, horseshoe crabs and tube-dwelling worms, at the site.
Generally, soft-bodied animals do not preserve as well as hard-shelled animals, making intact fossils a rare find. The find in Morocco was unique because the fossils were trapped in sediment clouds that preserved the bodies extremely well, Dr. Briggs said.
When anomalocaridids were first described, in the late 1800s, their scaly appendages had been found in isolation and were incorrectly thought to be the legs of a shrimp species. The animal’s disclike head was also found in isolation, and some believed it might be a jellyfish.
A century later, in 1985, Dr. Briggs published a paper that correctly described the whole animal for the first time.
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