The “Sea Dragon” Circle of Mysterious History Discovered on the English Channel Coast is Defined as a New Species

Description of Thalassodraco etches. Credit: Megan Jacobs

“This animal was clearly doing something different,” says a Baylor University paleontologist.

A mysterious little sea reptile from 150 million years ago has been discovered to be a new species that can dive very deep. A well-preserved specimen was found in a late period Jurassic Deep sea bed along the coast of La Canal in Dorset, England.

According to paleontologist Megan L. Jacobs, Ph.D. in geography at Baylor University and co-author of a published study, reptiles have been identified as part of a group known as ichthyosaurs that have been training marine predators since the Late Jurassic period. in the magazine PLOS ONE.

“There are a few differences that make this ichthyosaur unique enough to have its own sex and type,” Jacobs said. “New Year’s Jurassic ichthyosaurs in England are extremely rare, because these creatures have been studied for 200 years. We knew almost immediately that it was new, but it took about a year to make a thorough comparison with all the other recent Jurassic ichthyosaurs to determine if our instincts were true. It was very exciting not to be able to find a match. ”

The sample, estimated to be about 6 meters long, was discovered in 2009 by Steve Etches MBE, who collected fossils, after a cliff collapsed by the sea. First, he saw a limestone 300 meters deep inside a slab buried in the sea surface. The sample is then housed in The Etches Collection of Jurassic Marine Life in Kimmeridge, Dorset. He named it Jacobs Thalassodraco etchesi, After Etches means “Etches sea dragon”.

“Now that the new sea dragon has been officially named, it’s time to study its biology,” said David Martill, Ph.D., a co-author of the study, and a professor of paleontology. University of Portsmouth Portsmouth, United Kingdom. “There are a number of things that make this animal special.”

Investigate the differences

“This animal was definitely doing something different compared to other ichthyosaurs. The idea is that it can be a deep dive type like sperm whales, ”Jacobs said. “Extremely deep rib cages may have allowed the larger lungs to hold their breath for longer periods of time, or the internal organs may not have been crushed under pressure. He also had incredibly large eyes, meaning he could see well in low light. This could mean diving deep in the absence of light or at night. ”

The Sea Dragon erodes the Thalassodraco Fossil

Fossil image of the sea dragon (Thalassodraco etches) (MJML K1885). Credit: The Etches Collection, Dorset, UK

With a deep rib cage, the creature looked like a lot of pipes, he said. Given their relatively small fins, they can swim in a different style than other ichthyosaurs.

The sample would have been suitable for the diet of hundreds of small teeth, squid and small fish, and “the teeth are unique in that they are completely smooth,” Jacobs said. “All other ichthyosaurs have larger teeth with striped crumbs on top, so we immediately knew this animal was different.”

Changes in history

Ichthyosaurs emerged as terrestrial lizard-like creatures and gradually evolved into dolphin / shark fossils. They turned their limbs into fins that were mostly or wide.

“They still had to breathe air on the surface and there were no scales,” Jacobs said. “Nothing is really known about the biology of these animals. We can only make assumptions from the fossils we have, but there is nothing like it today. Finally, since they could no longer land to lay eggs in order to fully adapt to living in water, they first resorted to bringing in a live young, tail. The babies inside the mother and the skeletons that were actually born were found. ”

Thalassodraco etchesi closely related to Nannopterygius, a widespread ichthyosaur genus that inhabited the Late Jurassic Seas in Europe, Russia, and the Arctic 248 million years ago, before extinction about 90 million years ago. The largest ichthyosaurs found in North America had skulls about 16 feet long.

Jacobs said the new specimen died of old age or predator attacks and then sank to the bottom of the sea.

“At that time, the sea water was incredibly soft, even soupy, which allowed you to dip your nose into the mud and bury half of it,” he said. “The back end did not sink into the mud, so they were exposed to decay and cleaners. Access to this limestone layer provided exceptional protection, including some protected internal organs and bony ligaments of the spine. ”

“It’s still great to discover new species of ichthyosis, which shows how diverse these incredible animals are,” Martill said.

Reference: December 9, 2020, PLOS ONE.
DOI: 10.1371 / journal.pone.0241700

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