Fossilized footprints are relatively common, but figuring out exactly which ancient creature made particular tracks has been a mystery that has long stumped paleontologists. In the latest issue of the Journal of Vertebrate Paleontology, a team of researchers overcome this dilemma for the first time, and link a fossil trackway to a well-known fossil animal.

Sebastian Voigt, a trackway expert from the Institute of Geology, Freiberg University of Mining and Technology, Germany, and David Berman and Amy Henrici of the Carnegie Museum of Natural History, Pittsburgh, who study fossil skeletons, took a close look at an exceptional fossil collection from 290-million-year-old sediments of central Germany known as the Tambach Formation. The Bromacker locality in the Tambach Formation has been famous for its fossil footprints for well over a century, but “identifying the animals that made the tracks proved challenging,” commented Voigt.

Click image for full size. Skeleton of Lower Permian diadectomorph Orobates pabsti and restoration of how it may have appeared as the trackmaker ichnospecies Ichniotherium sphaerodactylum. Artwork by Mark A. Klingler.

Fortunately, the Bromacker locality offered clues to solving the problem for the paleontologists. Superbly detailed trackways were found in concert with exceptionally preserved skeletons, in the same sediments. “To have beautifully preserved trackways and skeletons at the same site is a unique situation for paleontologists — it provides a wonderful opportunity to better understand how these extinct animals lived,” noted Berman.

The team combined their expertise in anatomy and ichnology (the study of tracks) to match up the most common tracks with their makers. Detailed measurements of the tracks, combined with measurements of the legs, feet and backbones of the skeletal material allowed the team to pinpoint the trackmakers. The two most common skeletal fossils, Diadectes absitus and Orobates pabsti, grew to approximately 3 or 4 feet. These closely related reptile-like creatures were some of the first four-legged plant eaters on land, and have no close living relatives. Their limb skeletons and size match them well to the Bromacker locality’s two most common types of trackway, scientifically named Ichniotherium cottae and Ichniotherium sphaerodactylum.

Sebastian Voigt said, “Now that we have matched the two most common skeletons to their trackways, it is time to turn our attention to the rarer animals. Our work opens new doors for delving into other paleobiological questions, including how Diadectes and Orobates walked.”

- Journal of Vertebrate Paleontology