Turtle fossil gives clues to prehistoric habitat

Perfectly preserved 150-million-year old fossil of the extinct turtle. Image: Felix Augustin / University of Tübingen

A perfectly preserved turtle fossil from Lower Bavaria has yielded important clues about a species and habitat that existed in southern Germany some 150 million years ago.

The fossil is the best-preserved specimen of the extinct marine turtle, Solnhofia parsonsi, found to date and its distinctive forelimbs and hind limbs are comparatively short, suggesting that the turtle lived near the coast. This contrasts with today's sea turtles, which have elongated flippers and live in the open sea.

"No Solnhofia individual with such completely preserved extremities has ever been described before," says Felix Augustin of the Biogeology working group at the University of Tübingen in Germany.

"The very good preservation of the fossils in the layers of limestone can be explained by the environmental conditions at the time."

Andreas Matzke, University of Tübingen

The head and carapace of Solnhofia parsonsi are also clearly preserved, showing a long, pointed jaw and a triangular head, which, at just over 9cm long, measures almost half the length of the carapace or outer shell.

"Solnhofia may have used its large head to crush hard food items such as shelled invertebrates, as we see in some modern turtles, but it does not mean these were exclusively forming its diet,” says Márton Rabi of the University of Tübingen and co-author of the study, which is published in the journal PLOS ONE.

The name Solnhofia refers to the limestone deposits of Solnhofen - a place located south of Nuremberg in the valley of the Altmühl. Famous fossils of one of the earliest birds, Archaeopteryx, and of many pterosaurs and marine reptiles have been found there.

The layers of the Solnhofen limestone, which are rich in fossils, run along the entire valley of the Altmühl. The fossil of Solnhofia parsonsi was found in a quarry west of Regensburg, where systematic digging for fossils has only been happening for about 20 years.

"The very good preservation of the fossils in the layers of limestone can be explained by the environmental conditions at the time," says Andreas Matzke of the University of Tübingen and a co-author of the study.

Some 150 million years ago, a shallow, tropical sea stretched across southern Germany. It featured many islands and reefs with lagoons protected from the open sea.

Floating particles sank to the bottom of these basins, forming layers of limestone. When marine animals died, their remains also sank to the bottom.

Due to the low exchange of the lagoon water with the open sea, the oxygen content there was so low, and the salt content so high, that dead plants and animals did not decompose. Their remains were preserved and fossilised in the limestone - often in unique detail.

The region is considered one of the world's most important sites for fossils from the Mesozoic period, which began about 250 million years ago, and lasted until the extinction of the dinosaurs 66 million years ago. The Solnhofia parsonsi fossil underscores the importance of the relatively recently discovered site in the Painten district.

The vertebrate fossils found in the limestone there are now being studied scientifically. The Dinosaur Museum in nearby Denkendorf exhibits the finds, including Solnhofia parsonsi.