Tens of 1000’s of years in the past, an enormous horse species walked, trotted and galloped throughout the shifting sands of what’s at the moment South Africa’s Cape south coast.
The Large Cape Zebra (Equus capensis) weighed an estimated 450 kg. Its extant family in southern Africa are far smaller: the plains zebra weighs between 250 and 300 kg and the Cape mountain zebra is the smallest of all zebra species, with a mass of between 230 and 260 kg.
The Large Cape Zebra grew to become extinct simply over 10,000 years in the past. This may increasingly have been partly due to the lack of its most well-liked habitat of in depth grasslands, as rising sea ranges flooded the huge Palaeo-Agulhas Plain. However till now it hasn’t been clear how frequent the species was on the Cape south coast as a result of its physique fossils are predominantly from southern Africa’s west coast.
That’s the place ichnology – the examine of tracks and traces – is available in. Since 2007 our workforce has documented greater than 350 fossil vertebrate tracksites alongside a 350 km stretch of the Cape south coast.
Now, by finding out the tracks left by these galloping, strolling and trotting zebra so way back, we’re capable of say that they should have been a reasonably common sight on the panorama of the Cape south coast, and had been extra frequent than was steered by the physique fossil report within the space. This confirms the capability of the physique fossil report and ichnology to enhance one another.
With the ability to look again in time on this manner doesn’t simply assist scientists to higher perceive historical landscapes. It’s additionally an necessary a part of understanding what’s modified over time and the results of local weather change and people.
In our not too long ago printed article we described how we now have recognized 26 equid tracksites – together with tracks belonging to Equus capensis – in aeolianites (cemented dunes) on South Africa’s Cape south coast within the neighborhood of cities like Nonetheless Bay and Plettenberg Bay.
That is particularly thrilling as a result of equid tracks relationship to the Pleistocene epoch, which began 2.6 million years in the past and ended about 11,700 years in the past, are uncommon. Actually, our finds imply that the Cape south coast accounts for almost all of the websites recognized globally from this time interval (different websites are in Kenya, Ethiopia, Italy, the Arabian Peninsula, and the Americas).
13 of the tracksites we discovered include tracks 12 cm or larger in size, and eight include tracks 10 cm or much less in size (within the remaining 5 circumstances we couldn’t entry the tracks for measurement). Effectively preserved equid tracks are pretty distinctive: options embody an unbroken hoof wall and what is called a “frog” in the direction of the centre of the observe.
We had been capable of attribute the massive tracks to Equus capensis, and the small tracks to the quagga (Equus quagga quagga), the plains zebra subspecies that grew to become extinct within the nineteenth century.
One of many Large Cape Zebra websites includes a single trackway containing 12 tracks. One other accommodates two possible quagga trackways that intersect at proper angles, respectively containing ten and 6 tracks. We informally dubbed this the “zebra crossing”. Such lengthy fossil equid trackways are particularly uncommon, as equids are sometimes gregarious (leading to trampled areas) and remoted trackways are uncommon.
One different African instance of a protracted equid trackway is from Laetoli in Tanzania from the older Pliocene Epoch. Sadly, the best such web site was in Nevada within the US, the place a 50,000 year-old equid trackway contained 28 tracks – but it surely was coated within the Thirties throughout jail development and is not accessible.
By means of our Optically Stimulated Luminescence relationship program, we now have established an age vary for the equid tracksites from about 161,000 years to about 43,000 years.
Trying again – and forward
Figuring out and reporting the tracks of the Large Cape Zebra permits us not solely to think about its presence on the Cape south coast many 1000’s of years in the past, but additionally reminds us of how extinction typically follows within the wake of local weather change. And it permits scientists like ourselves working in southern Africa to contribute considerably to a comparatively sparse world report of such websites.