An illustration of the stylophoran sex <i>Thoralicystis</i>.
(Copyright Rich Beautiful/California Academy of Sciences)
For the past 150 years, scientists have debated a mysterious creature that lived hundreds of millions of years ago, long before the dinosaurs on Earth. And now, with the discovery of stunningly detailed fossils in Morocco, paleontologists have finally ID’d the bizarre forms of life.
The creatures, known as stylophorans, seemed flattened and armored wall decorations, that was a long arm poking out of their sides. But while it was previously unclear where they fit in the animal family tree, the new study has revealed that they are echinoderms, the old relatives of modern animals, such as sea urchins, starfish, brittle stars, sea lilies, feather stars, and sea cucumbers.
The discovery was made possible thanks to fossils with “incontrovertible evidence for an exceptionally soft parts preserved, both in the appendix and in the body of stylophorans,” said study principal investigator Bertrand Lefebvre, National Centre for Scientific Research (CNRS) researcher at the Laboratory of Geology of Lyon in France. [Photos: Treasure trove of Marine Fossils Discovered in Morocco]
The incredible fossils were found during an excavation in 2014 on the Fezouata Formation, located along the edge of the Sahara Desert in the south of Morocco. The excavation yielded a wealth of fossils, including approximately 450 stylophoran specimens, each consisting of about 478 million years ago.
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But the researchers are not immediately realize that some of the fossils preserved soft tissues. “It is only when we unpacked and looked at them under the binocular [microscope], back in the laboratory in Lyon, that we could see the soft parts,” Lefebvre told Science in an e-mail. “Their presence and identification was subsequently confirmed by SEM (scanning electron microscope) observations and analyses.”
The soft tissue found was unprecedented. Stylophoran fossils are found all over the world since the 1850s, allowing researchers to determine that these creatures lived from the middle Cambrian to the late Carboniferous periods, or approximately 510 million to 310 million years ago, when the creatures went extinct. But because the soft tissues so rarely fossilize, the stylophorans were only known from their hard skeletal parts and not their tender bowels.
“Their internal anatomy is not only entirely unknown, but also — and especially — very controversial,” Lefebvre said.
What do they look like?
Stylophorans had two major parts: a core body and a strange attachment to. The core of the body and the attachment were small, each about 1.2 inches (3 cm) long, Lefebvre said.
Previously, other researchers came up with all sorts of ideas about stylophorans.
From the years 1850 to 1950, most of the researchers think that stylophorans were the “normal” echinoderms. Their weird nipple was interpreted as equivalent to the tribe of the sea lilies.
Normal echinoderms have internal skeletons made of mineralised, calcitic plates (although this is greatly reduced in sea cucumbers ) and the so-called water vascular systems that help them move and breathe, said Peter Van Roy, a paleobiologist at the University of Ghent in Belgium, who was not involved in the study.
Most echinoderms, like starfish, have five places symmetry. They are closely related to other invertebrate group, the acorn worms, and vertebrates (animals with a backbone). Together, echinoderms, acorn worms, and vertebrates to an umbrella group known as deuterostomia, Roy said. [Deep-sea Creepy-Crawlies: Images of Acorn Worms]
Then, in the early 1960s, the Belgian paleontologist Georges Ubaghs found that the attachment of a strain, but similar to a power arm, as seen in the modern starfish.
In the late 1960s, the British paleontologist Richard Jefferies proposed a very different idea. He thought that the stylophoran main body of a head (the love of a pharynx and the brain), and that the appendix located muscles and a notochord (a kind of primitive backbone). Jefferies thought that stylophorans were the “missing link” between the echinoderms and the chordates (a group of vertebrate animals).
In the years 2000, British palaeontologist Andrew Smith proposed yet another interpretation. He said that stylophorans were probably not the “missing link” between the echinoderms and the vertebrate animals, but were more likely primitive deuterostomes, filling the gap between the acorn worms and echinoderms.
The new discovery of the fossilized soft tissue, however, has changed everything. Researchers can test, for the first time, or the soft tissue and matched what you would expect from one of these different scenarios, Lefebvre said.
The Hard evidence
The newfound fossils align most closely with Ubaghs’ interpretation. The stylophorans, ” flat bodies, intestines, and the appendix was not closed as a voice would be, and rather looked like a starfish arm. This arm is a water-vascular system that would have helped the creatures move and eat, just as the arms of the starfish to do , Roy said.
Because stylophorans are not five places to symmetry, they are likely to be lost, which means that they are more “advanced” in evolutionary terms than the other five places echinoderms, Roy added.
“This discovery is of particular importance, because it brings to an end a 150-year-old debate about the position of these bizarre-looking fossils in the tree of life,” Lefebvre said.
The study is “very thorough,” Roy said, “and I have no doubts about which of the methods used or the conclusions drawn.” In addition, stresses the importance of the well-preserved fossils of the Fezouata Formation, a spot where Roy has seen spectacular instances .
The study is published online in the February issue of the journal Geobios.
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Originally published on Live Science.