Ichnologists in South Africa were excited to discover a fossilized long giant Cape zebra trackway - one of the few such left by ancient horselike animals in the world, The tracks are lightly outlined in chalk. Credit: Charles Helm
South Africa's southern Cape coastline is emerging as one of the best places for ichnologists to study the fossilized tracks and traces left by ancient animals and hominins. Their studies of spoor and traces left by feet, hooves, trunks and flippers have allowed them to shed more light on the movements and distribution of Southern Africa's historic inhabitants. The most recent example is the extinct giant Cape zebra (Equus capensis), reported in Quaternary Research.
At around 450kg and 1.5 meters at the withers, the back’s highest point, it was the largest hoofed equid species to be found in Africa over the past 2.5 million years, the so-called Quaternary era.
Modern zebra are around 120cm at the withers. Based on fossilized bones found mostly in arid areas, experts previously believed that the giant Cape zebra generally roamed along the western parts of southern Africa. However, the discovery of 13 sets of hoof tracks complements growing fossil bone evidence that these animals existed more widely across the region, and in its wetter areas as well.
The distance between the outer circles in the scale bars is 10 cm. Credit: Charles Helm
The tracks, made by hooves 12cm or larger in size, were left in sand which hardened into aeolianite rock over millennia. They have been discovered by members of the Cape South Coast Ichnology Project since 2007 at various rocky sites along a 350km stretch of coastline along South Africa's southern Cape coast, roughly between the holiday towns of Plettenberg Bay and Arniston.
Unique long trackway
Lead author Charles Helm, associated with the Nelson Mandela University, South Africa, says the team was especially excited to discover a 320cm trackway containing 12 tracks of an animal walking slowly. Helm says the trackway is notable because of its length, and because it was made by a single animal. It is one of only a few long fossil horse trackways known to exist worldwide.
Their size rules out the possibility that the tracks were made by the quagga (Equus quagga quagga), a smaller subspecies of the plains zebra that was hunted to extinction by the 19th century. "That they are horse/zebra tracks is clear from the unbroken hoof wall and what is known as a 'frog' towards the centre of the track," Helm explains. "Some of the tracks occurred on the original surfaces on which they were made; in other cases they were part of the layer that filled in the tracks, and thus occurred as natural casts."
Andrew Carr of the School of Geography, Geology and the Environment, University of Leicester, in the United Kingdom used an Optically Stimulated Luminescence program to date sediments from rocks close to where the trackways were made. Based on his results, the research team estimates that the tracks were left by animals between 161,000 and about 43,000 years ago.
Helm says their findings demonstrate how trace fossil records can complement body fossil records, providing new understanding of the distribution and regional prevalence of extinct species. It further shows the value of integrating ichnological studies with archaeological and paleontological body fossil investigations.
