The creature is the ancestor of all vertebrates, including humans

Mar 6, 2012 12:50 GMT  ·  By

Researchers in the United Kingdom and Canada announce the discovery of the oldest known vertebrate, a creature that lived about 505 million years ago. This finding makes the animal the ancestor of all known vertebrates that ever lived, including humans.

The fossil was discovered in the Yoho National Park, Canada, in a formation called the Burgess Shale. Thus far, this location has yielded thousands of useful fossils, which helped scientists further our understanding of Earth's ancient past.

Investigators at the University of Cambridge and the Royal Ontario Museum (ROM), in the UK, worked closely together with Canadian colleagues from the University of Toronto for this particular research.

The creature, now extinct, is called Pikaia gracilens, and is believed to be the most primitive member of the chordate family of organisms. This group includes birds, reptiles, mammals, amphibians and fish.

Details of the research appear in the March 5 issue of the British scientific journal Biological Reviews. The work is based on an in-depth analysis of 114 specimens recovered from the Burgess Shale.

The ancient creature – which developed shortly after our planet's atmosphere got a vast influx of oxygen – was first described in 1911, by American palaeontologist Charles Doolittle Walcott. However, the expert only had access to a few specimens.

He believed that P. gracilens was a primitive annelid worm, a class of organisms that now includes leeches and earthworms. Subsequent analyses of other specimens revealed the existence of a very primitive notochord in the creature.

A notochord is a flexible rod that forms in the embryos of all chordate animals. In vertebrates, the notochord goes on to form the backbone. Scientists were also able to find basic blocks of skeletal muscle called myomeres.

“The discovery of myomeres is the smoking gun that we have long been seeking. Now with myomeres, a nerve chord, a notochord and a vascular system all identified, this study clearly places Pikaia as the planet’s most primitive chordate,” says Simon Conway Morris.

“So, next time we put the family photograph on the mantle-piece, there in the background will be Pikaia,” Morris adds. He holds an appointment as a professor at the University of Cambridge, and was also the lead author of the new study.