Traces of a trauma 245 million years ago

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Researchers gain insight into life in an ancient sea

An injured nothosaur - of seal size hunting fish. The figure shows a pronounced
An injured nothosaur - of seal size hunting fish. The figure shows a pronounced thickening on the lower jaw, which is a healed fracture of the bone. Illustration: Jakub Zalewski .
With a broken jaw on the prowl - that seems almost impossible. But researchers have discovered an approximately 245-million-year-old nothosaur fossil on which the injury had healed. The international team, with participation from the University of Bonn, examined other marine reptile bone anomalies from a site near the town of Winterswijk in the Netherlands. The results are published in the Journal of Morphology.

In the early Middle Triassic, this part of Europe was covered by a shallow and warm sea, rich in organic life and inhabited by various marine reptiles. Today, fossilized bones of these marine reptiles can be found in large numbers. Among them are remains of nothosaurs: large marine reptiles that were top predators, hunting other creatures.

Nothosaurs had a body flattened from the back to the belly, vaguely resembling lizards, but they were not lizards. The term "nothosaur" means "false lizard" because of the superficial resemblance. An international interdisciplinary team led by Dawid Surmik of Silesian University in Katowice, Poland, and Nicole Klein of the University of Bonn, Germany, studied several bone anomalies of nothosaurs.

"Pathologies occasionally found in fossil skeletal remains give us insight into the health of extinct vertebrates and are a valuable source of knowledge about the lives of these animals," says Dawid Surmik. , "However, such pathologies are not free from misinterpretation." Many factors, such as postmortem damage and geological processes like compaction or erosion, can influence the interpretation of unusual-looking fossils in addition to actual injuries.

Clashes, predators or turf wars

Among other things, the scientists examined the lower jaw of a Nothosaurus specimen that showed signs of a healed fracture. This means that the animal survived despite the injury and was still able to hunt. "Nowadays, animals in their natural environment are exposed to injuries that can be caused, for example, by predators or turf wars. It was no different during the Triassic," says Justyna Slowiak-Morkovina of the Institute of Paleobiology at the Polish Academy of Sciences in Warsaw, Poland.

In Winterswijk in the east of the Netherlands, numerous fossils of marine reptiles have been found for more than 70 years. "This makes this site ideal for paleopathological studies, as we initially thought," says paleontologist Dr. Nicole Klein of the Institute of Geosciences at the University of Bonn. However, among thousands of bones, the researchers found only four that showed anomalies. "Which in itself is an amazing result and of course tells a story," Dr. Klein continues.

The record of pathology can show whether certain diseases, deformities, or traumas severely affected locomotion or food acquisition, and whether they could be compensated for in different ways. "This is important because, in addition to anatomy - which is sometimes difficult to interpret or insufficiently preserved - and possible parallels to modern species - which are not always perfect - it also provides us with independent clues about the lives of extinct animals," says Tomasz Szczygielski of the Institute of Paleobiology at the Polish Academy of Sciences in Warsaw, Poland.

All or nothing

These prehistoric reptiles seem to have adopted the so-called all-or-nothing strategy: "Either the hunt was successful and the prey was swallowed whole, or the prey was lucky and escaped," adds Dr. Klein. The injured nothosaur certainly couldn’t make any quick snapping movements to catch the prey for a while. Because then the lower jaw would have been constantly exposed to violent movements and would not have been able to heal, which would have resulted in the death of the animal, concludes Dr. Surmik. The animal survived, however, and the wound has healed, as evidenced by the signs of regeneration of this injury."

Benign bone tumor discovered

The researchers also found a type of benign bone tumor, in this case on a rib of another nothosaur. "This lesion is indicated by a pronounced thickening on the rib shaft. Examination of the microstructure suggests that this is not the seemingly obvious healed bone fracture, but a rare tumor-like bone lesion, osteofibrous dysplasia," comments Prof. Bruce M. Rothschild of the Carnegie Museum of Nature History in Pittsburgh (Pennsylvania, USA).