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Ancient amphibians swam like modern crocodiles

During the Late Permian period, about 250 million years ago, South Africa was home to a species of large predatory amphibians with bodies similar to today’s crocodiles or big salamanders. Although these animals – called rhinesuchid temnospondyls – are known mainly from skeletal remains, a team of researchers led by the University of the Witwatersrand in South Africa has recently discovered a set of trace fossils that provide key insights into how these creatures moved through their environment.

The remains were discovered in a site called the Dave Green paleosurface, in the KwaZulu-Natal Province of South Africa, on a rocky surface which was the floor of a tidal flat or lagoon of the ancient Karoo Sea during the Late Permian. By analyzing seven body impressions (resting traces), along with several tail-marks (swimming traces), the experts inferred that they were likely made by one or two two-meters-long rhinesuchid temnospondyls swimming from one resting place to another, or searching for prey.

The sinuous shapes of the tail-marks provide evidence that the amphibians propelled themselves through the water with continuous side-to-side tail motions, which is remarkably similar to how modern crocodiles and salamanders move. Moreover, the shape of their body impressions, along with a relative lack of footprints alongside the traces, suggests that they tuck their legs against their bodies while swimming, just like today’s crocodiles. Finally, these fossils indicate an active lifestyle characterized by behaviors such as swimming or bottom-walking, and are extremely valuable for better understanding the structure of Permian ecosystems.

“The findings of the study are significant because they help to fill in gaps in our knowledge of these ancient animals. The remarkable tracks and traces preserved on the Dave Green palaeosurface are a window onto the shoreline of the Karoo Sea roughly 255 million years ago, and provide direct evidence of how these animals moved and interacted with their environment. In addition to its remarkable scientific contribution, this study also demonstrates how important paleontological discoveries are often made by curious people bringing their findings to the attention of paleontologists,” the authors concluded.

The research is published in the journal PLoS ONE.

By Andrei Ionescu, Staff Writer

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