Primitive animals, without locomotion, but capable of choosing where to live

Even without body parts to move from one place to another, some of Earth’s earliest animals managed to reside where it suited them best. This is revealed by new research.

The study was carried out by the team led by Phillip C. Boan, from the University of California at Riverside, United States.

These creatures from the Ediacaran period, about 550 million years ago, are strangely shaped soft-bodied animals that lived in the sea. The investigated species had a small, toroidal-shaped body. The Ediacaran fauna is very enigmatic because very little is known about it and because it essentially has no current evolutionary descendants, unlike, for example, the dinosaurs.

“It’s not like studying dinosaurs, which are evolutionarily related to the birds we can see today,” Boan explains. “With these animals, because they don’t have modern descendants, we’re still solving basic questions about how they lived, like how they reproduced and what they ate.”

In those distant times, the sea was a largely strange place compared to how it is today. It was dominated by microbial mats on the sea floor made up of bacteria and layers of other organic materials. Also, predatory creatures were rare.

Given the strange nature of Ediacaran Earth, the authors of the new study were surprised to find an animal that lived much like barnacles do today.

In the new study, it has been determined that this animal, Obamus coronatus, which was discovered several years ago, chose to live in specific parts of the seabed in the company of other congeners.

The animal studied had an average diameter of one and a half centimeters. It was not capable of moving on its own and probably spent most of its life embedded in its favorite place on the seabed. It was part of the Ediacaran fauna of a maritime region near what is now southern Australia.

In the foreground, an adult individual of Obamus coronatus with what it should have looked like in life. Behind, two other individuals of their species. (Illustration: Nobu Tamura. CC BY SA)

“This is really the first example of an Ediacaran creature selecting its habitat, the first example of a macroscopic animal doing this,” Boan said. “But how did they get where they wanted to go? It’s a question we don’t know the answer to yet.”

As for the motivation to do so, the research team theorizes that the Obamus were likely motivated by the need to reproduce.

The study is titled “Spatial distributions of Tribrachidium, Rugoconites, and Obamus from the Ediacara Member (Rawnsley Quartzite), South Australia”. And it has been published in the academic journal Paleobiology. (Fountain: NCYT by Amazings)