Ancient 2-meter amphibians swam like crocodiles long before true crocodiles existed, according to a study published March 29, 2023 in the open-access journal PLOS ONE by David P. Groenewald of the University of the Witwatersrand, South Africa, and colleagues.

During the late Permian period, just over 250 million years ago, South Africa was home to rhinesuchid temnospondyls, large predatory amphibians with bodies similar to crocodiles or large salamanders. These extinct animals are best known from skeletal remains, but in this study, researchers describe an exceptional set of trace fossils that provide insight into how these animals moved through their environment.

The fossils were found at what the researchers call the Dave Green palaeosurface, in South Africa’s KwaZulu-Natal province, on a rock surface that was once the bottom of a mudflat or lagoon of the ancient Karoo Sea. Researchers analyzed seven body impressions (resting marks) and a number of tail marks (swimming marks) that were deduced to have been made by a rhinesuchid temnospondyl about six feet long.

Based on the spatial arrangement of these tracks, the researchers interpret them to have been made by one or two animals swimming from one resting spot to another, perhaps in search of food.

The sinuous shape of the tail spurs suggests that these animals moved through the water with continuous side-to-side tail movements like modern crocodiles and salamanders. The shape of the body prints, as well as a relative lack of footprints next to the tracks, suggests that these amphibians pressed their legs against their bodies while swimming, also similar to crocodiles.

These fossils indicate an active lifestyle of swimming and bottom walking in these ancient amphibians, an interpretation made possible by the extraordinary preservation of locomotion tracks. This fossil site also preserves numerous traces of other tetrapods (four-legged animals), fish, and invertebrates, and is therefore an important place for understanding ecosystems of the Permian period.

The authors add: “The study’s findings are significant because they help fill gaps in our knowledge of these ancient animals. The remarkable tracks and traces preserved on Dave Green’s paleosurface are a window into the Karoo Sea coastline. , about 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 shows how important paleontological discoveries are often made by curious people who put their findings under bring it to the attention of paleontologists.”

The place can be explored on an interactive platform here:

Magazine reference

  1. Groenewald DP, Krüger A, Day MO, Penn-Clarke CR, Hancox PJ, Rubidge BS (2023) Unique trajectory along Permian Karoo coastline provides evidence of temnospondyl locomotion behaviour. PLOS ONE 18(3): e0282354. DOI: 10.1371/journal.pone.0282354