A mysterious aquatic reptile referred to as sea dragon has been discovered in a Late Jurassic deep marine deposit along the English Channel coastline in Dorset, England. The reptile is believed to be the new species of ichthyosaurs.
Ichthyosaurs were streamlined marine predators from the Late Jurassic period. They were capable of diving very deeply.
The well-preserved specimen was originally was discovered in 2009 by fossil collector Steve Etches MBE after a cliff crumbled along the seaside. It is estimated to have been about 6 feet long.
Steve found it encased in a slab that would originally have been buried 300 feet deep in a limestone seafloor layer. The specimen has been housed in The Etches Collection Museum of Jurassic Marine Life in Kimmeridge, Dorset.
Paleontologist Megan L. Jacobs, a Baylor University doctoral candidate in geosciences and co-author of a study, said, “This ichthyosaur has several differences that make it unique enough to be its genus and species. New Late Jurassic ichthyosaurs in the United Kingdom are extremely rare, as these creatures have been studied for 200 years. We knew it was new almost instantly, but it took about a year to make thorough comparisons with all other Late Jurassic ichthyosaurs to make certain our instincts were correct. It was very exciting not to be able to find a match.”
Jacobs named this specimen as Thalassodraco etchesi, meaning “Etches sea dragon” after Etches.
Study co-author David Martill, Ph.D. professor of paleontology at the University of Portsmouth in Portsmouth, United Kingdom, said, “Now that the new sea dragon has been officially named, it’s time to investigate its biology. Several things make this animal special.”
This animal had an extremely deep rib cage that may have allowed for larger lungs to hold their breath for extended periods, or it may mean that the internal organs weren’t crushed under pressure. It also has large eyes so that it could see well in low light. Given its comparatively small flippers, it may have swum with a distinctive style from other ichthyosaurs.
The specimen’s hundreds of tiny teeth would have been suited for a squid and small fish diet.
Jacobs said, “All other ichthyosaurs have larger teeth with prominent striated ridges on them, so we knew pretty much straight away this animal was different.”
Thalassodraco etchesi is closely related to Nannopterygius, a widespread genus of ichthyosaurs inhabited Late Jurassic seas across Europe, Russia, and the Arctic around 248 million years ago before becoming extinct around 90 million years ago.
According to Jacobs, the specimen might have died due to its old age or attack by predators.
Jacob said, “The seafloor at the time would have been incredibly soft, even soupy, which allowed it to nose-dive into the mud and be half-buried. The back end didn’t sink into the mud, so it was left exposed to decay and scavengers, which came along and ate the tail end. Being encased in that limestone layer allowed for exceptional preservation, including some preserved internal organs and ossified ligaments of the vertebral column.”
Ichthyosaurs originated as lizard-like creatures living on land and slowly evolved into the dolphin/shark-like creature found as fossils. Their limbs evolved into flippers, most of them very long or wide.
Martill said, “It’s excellent that new species of ichthyosaurs are still being discovered, which shows just how diverse these incredible animals were.”
Journal Reference:
- Megan L. Jacobs et al. A new ophthalmosaurid ichthyosaur from the Upper Jurassic (Early Tithonian) Kimmeridge Clay of Dorset, UK implications for Late Jurassic ichthyosaur diversity. DOI: 10.1371/journal.pone.0241700