South African Coast Yields the Youngest Dinosaur Tracks Yet Reported from Southern Africa
Southern Africa has a rich record of dinosaur tracks from the Triassic and Jurassic, particularly in the Karoo Basin of South Africa and Lesotho. During these periods, the Karoo Basin was an enormous terrestrial sedimentary basin where rivers, floodplains, and other environments accumulated sediment over long periods, creating favourable conditions for the preservation of dinosaur bones and footprints. Around 182–183 million years ago, during the Jurassic Toarcian, however, extensive volcanic activity blanketed the Karoo Basin with basaltic lava flows, forming the basalts of the Drakensberg Group. At the same time, the fragmentation of Gondwana continued, and crustal extension between Africa and South America produced a series of rift basins across southern South Africa. By the Cretaceous, terrestrial sedimentary deposits preserved across southern Africa had become far more limited. As a result, even though the Cretaceous was a time when dinosaurs flourished globally, their skeletal and track records in this region became sparse and fragmentary.
A South African research team has identified a series of trace fossils in the Brenton Formation beside the Knysna Estuary in Western Cape Province. The traces are not spectacularly preserved, and some are difficult to recognise immediately as footprints. Yet they may extend the known dinosaur track record of southern Africa to approximately 132 million years ago. If the currently favoured age estimate for the Brenton Formation is correct, these may be the youngest dinosaur tracks yet reported from southern Africa.
The Brenton Formation itself is an unusual geological occurrence. It crops out only in the Knysna area and consists of sandstone, mudstone, siltstone, and claystone, with a total thickness of about 6–20 metres. The study site lies along the southern shore of the estuary, where parts of the Cretaceous succession are exposed only at low tide and submerged again as the tide rises. The actual track-bearing palaeosurface available for study covers only about 50 square metres, beside a low cliff approximately 5 metres high and 40 metres long.
The researchers divided the exposed succession into four units. Unit 1 consists of dark-grey laminated mudstone and siltstone; Unit 2 is composed of light-grey to whitish sandstone; Unit 3 is a light-brown channelised sandstone lens; and Unit 4 consists of channelised sandstone. Most of the possible tracks occur in the lowermost Unit 1, which probably represents a muddy lagoonal environment. The overlying sandstones contain features such as channel incision and cross-bedding and are interpreted as shallow-water fluvial channels and point-bar deposits within a lagoonal setting. In other words, around 130 million years ago this landscape was a low-lying mosaic of river channels, muddy flats, and lagoonal environments.
When a dinosaur stepped onto soft mud, the pressure of its foot could be transmitted downward through several sedimentary layers. The true footprint at the surface might later be eroded away, leaving only the deeper layers that had been compressed and deformed beneath it. Such a structure is known as a penetrative undertrack. The team identified one tridactyl trace measuring about 19 centimetres long and 17 centimetres wide. Its three digits are long, narrow, and nearly straight, while beneath digit III the sediment preserves longitudinal striations produced as underlying layers were bent downward by the descending foot. These characteristics are more consistent with a theropod trackmaker, although the mode of preservation itself may have distorted the apparent shape of the track. The researchers therefore regard a theropod origin as a plausible interpretation rather than a definitive identification.
Some of the footprints now stand above the surrounding surface. When a dinosaur stepped on the sediment, the material beneath its foot became compressed and more resistant to subsequent erosion than the surrounding, uncompacted sediment. Over time, the surrounding rock was preferentially worn away, leaving the compressed area beneath the original footprint projecting upward like a small pedestal. This form of preservation is known as pedestalled epirelief. Pedestalled tracks are relatively rare in the global dinosaur track record, yet the Brenton Formation preserves a substantial number of examples.
On one palaeosurface, the researchers identified at least five raised features, each roughly 30 centimetres across, arranged in a curving sequence. The mean pace length between successive features is about 38 centimetres. The individual traces are too poorly defined to identify the type of animal that made them, but their arrangement is consistent with a possible short trackway.
Nearby lies another tridactyl trace measuring about 40 centimetres long and 42 centimetres wide, with relatively blunt-tipped digits. Two additional tridactyl features, approximately 30–34 centimetres across and separated by a pace length of about 60 centimetres, occur close by. Broad tridactyl tracks with blunt digit impressions can be associated with ornithopod dinosaurs, so these traces may indicate the presence of ornithopod trackmakers. Their low-fidelity preservation, however, prevents a confident identification.
The largest traces are even more difficult to interpret. The team identified at least six large, saucer-shaped features on the exposed surface, reaching up to 60 centimetres in diameter. Some occur as paired features consisting of a large oval or rounded trace beside a smaller one, giving them a general resemblance to the hindfoot and forefoot impressions of sauropod dinosaurs. Large deformation structures are also visible in the cliff face, including examples approximately 70 centimetres in diameter with underlying layers deformed downward by as much as 30 centimetres. Their size raises the possibility that they were produced by large sauropods. Size alone, however, is insufficient to identify a sauropod track. Some of the large surface features could instead be products of weathering, while the large concave structures exposed in profile lack features such as the pronounced microfaulting sometimes associated with deeply impressed tracks. Sauropods therefore remain only one possible interpretation.
The cliff itself provides another way to view dinosaur tracks. Where erosion has cut laterally through what was once a horizontal sedimentary surface, the internal structure beneath a footprint becomes visible in cross-section. Sedimentary layers bend downward beneath the load, and in some cases the pressure was great enough to produce small faults. The researchers documented multiple concave-up deformation structures ranging from about 10 to 45 centimetres in diameter and from 4 to 25 centimetres in depth. Some traces exposed in profile also preserve possible digit impressions. One deformation structure, about 18 centimetres across, has two narrow projections extending from one end, while another, approximately 10 centimetres across, contains three narrow, tapering projections. These may represent theropod digit impressions preserved from the side after the animals stepped into soft muddy sediment.
The age of the Brenton Formation has long been debated. It was once interpreted as Late Jurassic, whereas micropalaeontological evidence has placed it in the Early Cretaceous, from the Valanginian to Hauterivian. More recent interpretations tend to favour the latter age range, and the study therefore uses approximately 132 million years as an estimated age. Dinosaur activity in the Brenton Formation may have been considerably richer than the limited exposures visible today suggest, while more extensive Cretaceous terrestrial deposits elsewhere in South Africa may still preserve additional tracks of similar age. What has long appeared to be a major gap in the Cretaceous dinosaur record of southern Africa is beginning to acquire new traces of the animals that once crossed these landscapes.
Author: Shui-Ye You
Reference:
Helm CW. (2026). Cretaceous dinosaur tracks in the Brenton Formation, Western Cape. South African Journal of Science.
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