A well-preserved fossilized worm dating from 518-million-years-ago resembles the ancestor of three major groups of living animals. An international team of scientists has discovered that a well-preserved fossilized worm dating from 518-million-years-ago resembles the ancestor of three major group
and unearthed in China, the fossil worm measures about half an inch long. It was a stubby creature covered in a dense, regularly overlapping array of plates on its back. It belongs to an extinct group of shelly organisms called tommotiids.
The animal kingdom consists of more than 30 major body plans categorized as phyla. Each phylum contains a unique set of features that set them apart from one another. Only a few features are shared across more than one group, which is a testament to the very fast rate of evolution during which these major groups of animals originated. This was during a period called the Cambrian Explosion, approximately 550 million years ago.
A schematic outline of how tommotiids tell us about the evolution of body plans across the tree of Life. Credit: Luke Parrybelongs to a group of Cambrian fossils that’s crucial for understanding how lophophorates evolved. They’re called tommotiids, and thanks to these fossils we have been able to understand how brachiopods evolved to have two shells from ancestors with many shell-like plates arranged into a cone or tube.
Dr. Parry added: “When it first became clear to me what this fossil was that I was looking at under the microscope, I couldn’t believe my eyes. This is a fossil that we have often speculated about and hoped we would one day lay eyes on.” “We now can see that those similarities are reflections of shared ancestry. The common ancestor of lophophorates and annelids had an anatomy most closely resembling the annelids.