A substrate composed of microbes may have preserved a series of 255-million-year-old burrows made in a sandy South African tidal flat by a clumsy amphibian, says a new study.
The remarkable shapes reveal that the nearly 2-meter-long rhinesuchid temnospondyl stalked its prey and swam after it like a crocodile. Like a prehistoric choreographer’s diagram, the impressions are a unique window into life on ancient Earth shortly before the Permian Mass Extinction wiped out 90 percent of the planet’s species.
Read more: The Late Permian Mass Extinction Explained
“The study’s findings are significant because they help fill gaps in our knowledge of these ancient animals,” say the authors in declaration. “The notable marks and traces […] provide direct evidence of how these animals move and interact with their environment.
A shallow place
The Dave Green’s Paleosurface, named after its late discoverer and landowner, covers about 600 square meters in the Karoo Basin, a large sedimentary basin that covers about two-thirds of South Africa. About 10 centimeters of sandstone now covers the paleosurface, which is striated with ancient wave marks. This land was once part of a tidal flat or lagoon that contained fresh or salt water, according to the research team from South Africa and Europe.
While researchers have explored the Dave Green site before, this team brought drones to take pictures from 10 meters high and hand-held 3D scanners to image the rare depressions. Researchers have tried in the past to make plaster casts of long, shallow forms and failed.
The resulting images captured a prehistoric crossroads frequented by both fish and tetrapods, four-legged creatures like the rhinesuchid temnospondyl. In addition to the latter’s markings, the team found three different tracks marked by small footprints that likely belonged to smaller tetrapods that waded through the water.
Top predator
The rinzuhid creature wrapped around the entire stage, making almost right turns as it slid along the bottom. Sometimes it would idle down there and look up with the help of the eyes embedded in the top of its triangular skull. Then, when it swam along the bottom, it did so in a squiggly, sinusoidal motion that left a narrow path in the sand.
Crocodiles swim in a similar way, although they would not evolve for another 50 million years or so, during the Late Triassic. But like them, the rhinesuchid probably tucked its legs under its body when it swam, given the relative lack of footprints.
Read more: Why Dinosaurs Survived the Late Triassic Mass Extinction
Soft mats of bacteria and single-celled organisms could protect many of the depressions from erosion, the study said, especially those without wave marks. Some of the oldest living structures on earth, microbial mats have embraced countless habitats, writes biologist Gisela Gerdes in Book chapterincluding river bottoms.
South African researchers credited Dave’s role in first bringing the site to light in 1991 by contacting a professor at the University of Natal in South Africa.
The statement said the study “demonstrates how important paleontological discoveries are often made by curious people bringing their discoveries to the attention of paleontologists.”