“None of them had heads or skeletons. Many of them probably looked like three-dimensional bathmats on the sea floor, round discs that stuck up,” said Mary Droser, a geology professor at UCR. “These animals are so weird and so different, it’s difficult to assign them to modern categories of living organisms just by looking at them, and it’s not like we can extract their DNA — we can’t.”
Kimberella were teardrop-shaped creatures with one broad, rounded end and one narrow end that likely scraped the sea floor for food with a proboscis. Further, they could move around using a “muscular foot” like snails today. The study included flat, oval-shaped Dickinsonia with a series of raised bands on their surface, and Tribrachidium, who spent their lives immobilized at the bottom of the sea.
For their analysis, the researchers considered four animals representative of the more than 40 recognized species that have been identified from the Ediacaran era. These creatures ranged in size from a few millimeters to nearly a meter in length.
These animals likely had the genetic parts responsible for heads and the sensory organs usually found there. However, the complexity of interaction between these genes that would give rise to such features hadn’t yet been achieved.
“The fact that we can say these genes were operating in something that’s been extinct for half a billion years is fascinating to me,” Evans said.
Going forward, the team is planning to investigate muscle development and functional studies to further understand early animal evolution.
“Our work is a way to put these animals on the tree of life, in some respects,” Droser said. “And show they’re genetically linked to modern animals, and to us.”