A unique find will help researchers better understand the prehistoric past of the planet
Scientists studying the prehistoric past of the Earth got an unusual find — they got their hands on a perfectly preserved Jurassic sea turtle fossil, which includes almost full skull and limbs.
About 150 million years ago, this massive-headed sea turtle was diving in the shallow tropical sea that covers what is now Europe , tells CNN.
Previously, several complete fossils of this Jurassic sea turtle, named Solnhofia parsonsi, have been discovered. Recently, however, scientists have described a remarkable fossil that has all the limbs and nearly all of the foot bones in situ, revealing for the first time the shape and structure of the turtle's limbs.
All modern species of sea turtles have elongated rigid fins that allow them to move through the ocean depths. But the limbs of the recently described fossil animal were shorter than those of modern sea turtles, compared to the size of its body. These shorter limbs suggest that the Solnhofia parsonsi turtle swam in coastal waters rather than the open ocean, scientists reported in the journal PLOS One.
The fossils of this sea turtle were first discovered in the 1970s, but new the specimen «is the best-preserved specimen of this species,» said study lead author Felix Augustin, a doctoral student in the Department of Geosciences at the University of Tübingen in Germany. – She is the first to retain a complete skull, a complete carapace, and all four limbs in their entirety”.
In life, Solnhofia parsonsi was about 30 centimeters long from nose to tail, and the prehistoric tortoise's head was «relatively large»; — the skull was about 10 centimeters long, Augustine told CNN.
Such a large skull may have been useful for chewing through the hard shells of bottom-dwelling crustaceans and molluscs, but at this point such findings are «highly speculative» as paleontologists have yet to find direct evidence of the extinct turtle's diet, notes study co-author Dr. Marton Raby. , postdoctoral researcher at the University of California.
The fossil was recovered in 2014 from a limestone quarry in southeastern Germany at a site rich in fossils from the second half of the Jurassic (199.6-145.5 million years ago). According to the study, many turtles survived there, along with fish, crocodiles, and even giant marine reptiles such as plesiosaurs and ichthyosaurs. The site has been an actively mined quarry since the 1950s, but fossil excavation only began there about 20 years ago.
Solnhofia parsonsi was described as a species in 1975 based on two nearly complete skulls found by scientists: one from Bavaria and one from Switzerland. For decades, finds of partial skeletons — all of them were found in marine deposits of the Jurassic period — gave more information about the anatomy of the prehistoric tortoise and the aquatic lifestyle. In 2000, scientists discovered a skeleton with a fuller shell than ever before. The specimen also included several bones from the rowing limbs of a reptile.
A recently described fossil gives a much more complete picture of these limbs, showing that they were very different from those of sea turtles living today.
“In modern sea turtles, the limbs are really elongated — especially the fingers and phalanges of the little fingers — to serve as fins in this marine environment”, — Augustine says. By comparison, the limbs and feet of the fossil Solnhofia parsonsi from Bavaria were less elongated, so the species was probably better adapted to swimming closer to shore rather than hundreds of miles away in the open ocean.
This hypothesis makes sense given the location where the fossil was excavated, Dr. Rabi tells CNN. In the Jurassic period, the territory of modern southern Germany was an archipelago of small islands. The habitat of Solnhofia parsonsi was probably a network of offshore reefs and lagoons. According to Rabi, turtles «have always been more or less close to the shore».
Numerous fossils from these rich and varied coastal ecosystems are found in fine-grained limestone deposits known as «plattenkalk» throughout southern Germany . Such a rock is known for preserving fossils in great detail, and the quarry where the turtle was discovered has already yielded many specimens of marine animals and plants, as well as fossils of terrestrial dinosaurs and pterosaurs, notes CNN.
But because the site is relatively new, many of these fossils have yet to be studied and scientifically described, and much remains to be learned about individual species and the coastal habitat where they coexisted millions of years ago, says Felix Augustine. “We are especially interested in the reconstruction of the ecosystem as a whole, to show the diversity — how it functioned and what different constituents of ecosystems were present in the late Jurassic,” he said.