On the trail of South German primeval robbers

Reconstruction of Batrachotomus and its habitat in present-day southwest Germany. © SMNS, M. Rech

The primeval horsetail forests of what is now south-west Germany were once the domain of a monstrous predator. How exactly the up to six meter long Batrachotomus fed about 240 million years ago, paleontologists have now shed light on the basis of its teeth and traces of its victims’ fossils. Before the first predatory dinosaurs appeared, it apparently formed the top of the food chain. In addition to huge amphibians, the crocodile-like creature apparently also snapped up conspecifics, according to the fossil evidence. The team was also able to show that Batrachotomus displayed feeding behavior that has been preserved in crocodiles to this day.

If you were to travel back in time to the Triassic era, you would end up in what is now south-west Germany in a swampy forest of tall box-leaf plants. This is evident from finds at various locations in Baden-Württemberg. Numerous fossils of the fauna of that time were also discovered there. Probably the most impressive creature that roamed the forests about 240 million years ago was the dinosaur Batrachotomus kupferzellensis, of which several fossil partial skeletons have been discovered. The reptile belonging to the pseudo-suchiac group was up to six meters long and looked like a crocodile with erect limbs. Its long, sharp teeth clearly identify it as a carnivore, and its anatomical features suggest it was quite agile.

Fossil traces of the diet

In order to find out more precisely what Batrachotomus once ate, the researchers led by Eudald Mujal from the Natural History Museum in Stuttgart took another close look at the teeth of the dinosaur and also examined numerous fossils of animals that could have belonged to its victims. These were hundreds of fossils of various species of amphibians and reptiles found in the same deposits as Batrachotomus. “We carefully checked the type of bite marks, such as cuts, punctures, scratches, holes and even missing parts that were torn off, on the different fossils. We wanted to find out who was chasing and eating whom,” says Mujal.

The team reports that they frequently encountered the tooth marks of Batrachotomus, whose crowns resembled knife blades with jagged edges. “We were able to convict the perpetrator: almost all traces come from this predatory dinosaur,” reports Mujal. “That confirmed to us that he was the top hunter of the ecosystem.” It also showed again how well the name Batrachotomus, which means “amphibian slasher” means. Because the scientists were able to use the fossil tracks to make it clear that the dinosaurs also captured the super amphibian from the genus Mastodonsaurus. With a length of up to five meters, they are among the largest amphibians in the history of the earth.

Evidence of cannibalism

As the researchers continue to report, the dinosaur was apparently also a cannibal: they discovered traces of the bites of conspecifics on fossils of Batrachotomus. As they explain, most of these are found in the ribs and pelvic bones, the cracking of which provides access to the nutrient-rich intestines and muscles. “Given their location on the bones and the lack of signs of healing, these cannot represent signs of injury from a specimen that was still alive at the time,” the paleontologists write. According to them, they are therefore probably not due to intraspecific fights, but rather suggest cannibalism.

Analyzes of the tooth marks on the various victims of Batrachotomus also revealed a special pattern, Mujal and his colleagues report: although these crocodile ancestors and the dinosaurs had similar tooth shapes, there were clear differences. The bite marks of Batrachotomus were clearly similar to those of crocodiles alive today. The researchers see this as proof of the successful concepts of this group of animals, which, unlike the dinosaurs, later survived the mass extinction at the end of the Cretaceous period.

The paleontological team now wants to stay on the ball: “The current findings should form the basis for further investigations into the reconstruction of the ecosystem of that time. We want to use this to better and better understand what the world in our region looked like 240 million years ago – before the time of the great dinosaurs,” says senior author Rainer Schoch from the Natural History Museum in Stuttgart.

Source: State Museum of Natural History Stuttgart, specialist article: Palaeontology, doi: 10.1111/pala.12597

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