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A strange little fossil could represent the ancestor of all starfish-like animals on the planet, according to a new study.
The 480-million-year-old fossil was unearthed in the Moroccan desert over 17 years ago, but its identity and evolutionary history have remained a mystery until now. Scientists have now officially described the specimen in new research published Wednesday, January 20 in the journal Biology letters.
The new species, Cantabrigiaster fezouataensis, has the shape of a star but does not have other distinguishing features seen in either of the two starfish-like animals living today: starfish and brittle stars ( forming part of a subphylum called Asterozoa). Because the species lacked these characteristics – the long, thin arms of the fragile star and the large plates of armor around a starfish – researchers concluded that it was therefore the ancestor of both. .
“We found out exactly how the first starfish-like animal came about, and then how it evolved into the two we have today, which are almost everywhere in the sea,” said lead author of the study, Aaron Hunter, earth science paleontologist. department of the University of Cambridge. “That’s what makes him special.”
Related: Photos: A treasure of marine fossils discovered in Morocco
C. fezouataensis lived on the former supercontinent of Gondwana, a vast landmass containing parts of today’s southern continents. “You are dealing with what was perhaps closer to what we think is Antarctic today, ”Hunter told Live Science.
The ancestor lived in the early Ordovician period (around 485.4 million to 460 million years ago) on what would have been an ancient cold-water reef, surrounded by mostly alien species such than giant filter feeders called anomalocaridides. The more modern look of the ancestor of starfish would have stood out in comparison.
Researchers don’t know what C. fezouataensis Ate. Evidence from a jawbone suggests it was probably not a feeding filter like the anomalocaridids of the same period and some of today’s fragile stars. By closely analyzing the fossil, the team identified features that give clues to its ancestry.
“We sit in a room and look at every characteristic of the animal,” Hunter said. Then they compared these characteristics to those of living animals and to those already identified in the fossil record. The team then used both biology and a mathematical algorithm to place these starfish ancestors on a family tree.
Starfish and brittle stars are two of the five living groups that together form a larger group, or crown group, called echinoderms. The other three are sea urchins, sea cucumbers and Crinoidea (water lilies and feathered stars). C. fezouataensis has an arm structure similar to that of modern sea lilies, meaning that sea lilies can trace their lineage back to this ancient ancestor species.
The new analysis showed that C. fezouataensis first appeared during an important period known as the great Ordovician biodiversification event. “That’s when life really started in terms of diversity, and the starfish is one of the first animals we recognize in the sea today,” said Hunter.
Using C. fezouataensis as a starting point, it is now possible to relate animals resembling starfish from around 480 million years ago to more recent fossils and then to animals of today.
“This is an exciting study,” said Bertrand Lefebvre, paleontologist at the National Center for Scientific Research (CNRS) and the University of Lyon, in an email. Lefebvre helped collect material from the site in Morocco, known for its exceptionally well-preserved fossils, and he also edited the journal article. He was not, however, the author of the article.
“This early new sea star from Morocco provides interesting insights into the early evolution of asteroids and the origin of the crown group of echinoderms,” the larger group that includes starfish and brittle stars, as well as sea urchins , water lilies and sea cucumbers, Lefebvre said.
But more research is needed, especially on animals from the Late Cambrian Period (497 million to 485.4 million years ago), to bridge the gap between the earliest echinoderms and the five groups we see today. hui, said Lefebvre.
Originally posted on Live Science.
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