The south coast of South Africa’s Western Cape province is a rich source of fossil tracks and traces – clues suggesting what this environment may have been like many thousands of years ago.

We’re a research group from the African Centre for Coastal Palaeoscience who have been finding and documenting these tracks since 2007. So far we have identified more than 400 tracksites left by vertebrates, including pangolins, giraffe, snakes, rock hyraxes, crocodiles and elephants. They include a variety of marks, from footprints to butt-drag impressions and even traces of sound vibrations. Some of these animals have never been found in the vicinity through the body fossil record, only from their tracks.

Most have been dated to the Pleistocene era, between 130,000 and 90,000 years in age, using a technique that measures how long ago grains of sand were exposed to light. Some of the fossil tracks and traces are the first of their kind ever found anywhere.

Our research has recently yielded two more world firsts in the fossil record:

• the only known giant tortoise tracks, and tramline tortoise trackways

• the only known tracks of a bird called the hamerkop (“hammerhead”).

These sites are in danger of being destroyed in rockfalls, but our work ensures that the traces they preserve are not lost and we can continue to build a picture of the environment back when this area – now a coastline – was a giant plain full of creatures, like today’s Serengeti.

First known fossil tracks of the hamerkop bird

The bird trackway we’ve recently found was definitely made by a hamerkop (family Scopidae). These are the first fossil tracks of this bird found anywhere in the world.

The foot of a hamerkop track is roughly similar to that of a heron or egret, except that it has substantial webbing between the toes. Members of the heron family (Ardeidae) have three forward-pointing toes, and one backward-pointing toe that is slightly offset to the side. No or minimal webbing is evident. A well-preserved hamerkop track, however, will show a similar orientation of digits, but will also have webbing.

That is exactly what we found at a tracksite on the ceiling of an overhang on a remote stretch of coastline.

We don’t know why hamerkops have webbing. Perhaps more ancient members of the lineage needed it to aid in swimming.

A couple of bones of a Pliocene hamerkop, probably about 4-5 million years old, have been identified at the South African west coast fossil site of Langebaanweg, and have been assigned to the species Scopus xenopus.

While we cannot determine if the tracks we have identified were made by the extant hamerkop (Scopus umbretta) or the extinct Scopus xenopus, a hamerkop origin is clear.

It is unusual to be able to identify a trackmaker to genus level based on just a few tracks, but a hamerkop provides a welcome exception to the rule.

The hamerkop track adds to 48 other fossil bird tracksites identified on the Cape coastline, including tracks of ostriches, storks, cranes, egrets, flamingos, guineafowl, spurfowl, oystercatchers and other shorebirds, terns, doves, and possibly cormorants, ducks and pelicans.

Bird body fossils are not common in southern Africa from this time period (from 194,000 to 57,000 years ago), but of those that have been found, most were in this coastal area.

A recurring theme in our work has been the identification of larger-than-expected bird tracks, hinting at the possibility either of extinct species or larger Pleistocene versions of extant trackmakers.

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Read more:
Fossil tracks reveal which birds once roamed South Africa’s Cape south coast

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Tramlines and giant tortoise tracks

Our team found the world’s first fossilised giant tortoise trackway in 2022 on a rugged, remote stretch of the same coast. From the size of the tracks and trackway, we estimated that its maker was 106cm long, making it 50% longer than the largest tortoise that currently inhabits South Africa, the leopard tortoise (Stigmochelys pardalis).

Tragically, within a couple of months of being found, the loose rock slab bearing the trackway of the giant tortoise had slumped down the sandy slope and disappeared into the ocean.

So we were excited to find a second set of giant tortoise tracks.

In the Walker Bay Nature Reserve we found typical “toe-tip traces” of a tortoise, and were able to estimate that the trackmaker was 98cm in length. This is, therefore, the second set of trace-fossil evidence of giant tortoises found in the world.

But first, we found three tortoise trackways showing the typical tramline pattern of smaller versions of these reptiles, with a wide “straddle” and closely spaced tracks in each line of the tramline. These fossilised tramline trackways are the first of their kind to be found in the world, and fill a notable gap in the fossil record.

One is located in the De Hoop Nature Reserve, and was probably made by a leopard tortoise. It is only rarely exposed, usually being covered by a thick layer of beach sand.

The other two are located in the Walker Bay Nature Reserve, and were probably made by the angulate tortoise, Chersina angulata.

Significance of these finds

There aren’t any body fossils of giant tortoises in southern Africa from the Pleistocene, but here we have track fossils.

Why the mismatch?

The answer may lie in the fact that the Pleistocene body fossils (of various animals) that have been uncovered in the region are mainly from caves our human ancestors inhabited. If our ancestors ate giant tortoises, it might have made more sense to butcher, cook and eat them on the spot, rather than carry a creature weighing 100kg all the way back to “home base”, which might have been as much as 10km away.

This is therefore an example of the trace fossil record delivering unanticipated findings and evidence that could not have been suspected from the traditional body fossil record.

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Read more:
Fossil treasure chest: how to preserve the geoheritage of South Africa’s Cape coast

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The hamerkop site is now threatened. An enormous rockfall from the cliffs above has obliterated a couple of tracksites just a few metres to the east, rendering the entire band of cliffs unstable and dangerous.

Our photogrammetry work (making three-dimensional models from two-dimensional images) at all the sites, however, will digitally preserve the tracks and trackways. It will also allow for the production of exact replicas which can be exhibited.

Given that these are the only known fossilised hamerkop tracks and the only remaining fossil tracks of a giant tortoise and of tramline tortoise trackways, it is reassuring to know that they will not be lost forever.