Evolution Is Getting A Rethink After Scientists Take A Closer Look At Earth’s First Animals



By  in The Conversation.


When did animals originate? In research published in the journal Palaeontology, we show that this question is answered by Cambrian period fossils of a frond-like sea creature called Stromatoveris psygmoglena.

The Ediacaran Period lasted from 635 to 542m years ago. This era is key to understanding animal origins because it occurred just before the “Cambrian explosion” of 541m years ago, when many of the animal groups living today first appeared in the fossil record.

Yet when large fossils from the Ediacaran Period were first identified during the 20th century they included unique frond-like forms, which were not quite like any living animal. This prompted one of the greatest debates still raging in evolution. What exactly were these enigmatic fossils, often called the Ediacaran biota?

Linking Ediacaran and Cambrian fossils

By comparing members of the Ediacaran biota to a range of other groups in a computer analysis of evolutionary relationships, we found that Stromatoveris psygmoglena provides a crucial link between the older period and the animals which appeared in startling number and diversity during the Cambrian period.

Fossils of Stromatoveris psygmoglena are found in only one place in the world: Chengjiang county, China. This region is known for exceptionally well-preserved Cambrian fossils from 518m years ago.


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