Q&A: Western prof discovers dinosaur footprints in South Africa
Guy Plint has identified footprints of dinosaurs dating back 140 million years
A retired professor from Western University and his collaborators have identified footprints of dinosaurs in South Africa that date back to the Cretaceous period. The 140-million-year-old tracks were identified by Guy Plint, a professor emeritus of earth sciences, who travelled to the Western Cape province of South Africa in October 2023.
Plint joined London Morning to talk about the discovery with host Andrew Brown.
The following has been edited for length and clarity.
Andrew Brown: So, what took you to South Africa?
Guy Plint: It's a bit of a complicated story. I had been working for a number of years in northern British Columbia with a colleague who is originally South African. He was a medical doctor but retired from medicine to study dinosaur tracks in British Columbia and South Africa.
In doing so, he came across some rather strange rocks with peculiar deformation structures. These were Cretaceous-age rocks. Not really being a geologist, more of a medical man, he realized there was something interesting and got in touch with me. A year later, taking advantage of my retirement from Western University and my freedom to travel, my wife and I went to South Africa to examine them.
AB: What do they look like?
GP: Well, they don't look like tracks, and that's the thing. They had been previously documented in South African literature as earthquake-related formations. The layers resemble what you'd expect if someone had stepped on soft sediment—kind of squishy, deformed structures. But you don't see them in plan view; you only see them in vertical cliffs, where you get a cross-section. What you see is a kind of punch-down structure that can be over a meter across. Previous studies attributed them all to earthquakes.
AB: Whose prints are they?
GP: The size and shape of the tracks strongly suggest they were made by sauropods—those long-necked, long-tailed, massive-bodied dinosaurs with pillar-like legs. The most likely candidate is Brachiosaurus.
WATCH | Guy Plint talks dinosaur prints on London Morning:
AB: How big would a Brachiosaurus be?
GP: There's some debate about their weight, but estimates range between 20 and 50 tons—absolutely massive. If you recall the opening dinosaur scenes in Jurassic Park, they show one of these things rearing up and chewing the top off a tree, so those kind of creatures.
AB: What is the significance of finding these footprints in South Africa?
GP: The record of dinosaurs in South Africa is quite spotty. There's a good track record from the Triassic (before 200 million years ago) and the early Jurassic (up to about 180 million years ago). However, after that, South Africa was uplifted, and massive volcanic eruptions took place as South America and South Africa were splitting apart, forming the South Atlantic.
During this period, much of the land eroded, making it a poor environment for track preservation. Tracks need a subsiding sedimentary basin to accumulate layers of sediment while animals walk across it, allowing tracks to be preserved. In South Africa, most of those basins are now under the ocean. However, some portions still exist on land, and we examined one of these areas. After much deliberation, we realized we were looking at sauropod tracks in vertical cross-section, which is why they don't immediately resemble traditional tracks.
AB: That's incredible. What's it like to realize you're standing in front of such ancient tracks?
GP: These are 140-million-year-old tracks, and to be honest, I went through several cycles of self-doubt. I reviewed literature on both dinosaur tracks and earthquake structures. Earthquakes can create all sorts of unusual formations—they fracture sediments, deform them, and create features like sand dykes where material is forced upwards as water escapes.
Interestingly, those earthquake-related structures are present in the area, but mixed in with them are these distinct "punch-down" structures where sediment layers have been sharply deformed downward. It's similar to what you'd see when elephants trample soft ground at a waterhole. The layers get completely squelched and deformed—except here, we see it preserved in cross-section.
AB: Can we learn anything about dinosaur behaviour from these tracks?
GP: I think we can make some educated guesses. I'm a sedimentary geologist, not a track expert, so I had to learn about tracks as I went. The sediments were deposited in a large estuary—something like a sandy Bay of Fundy. There's no evidence of food in that environment—no trees or plants—so I suspect the dinosaurs may have wandered down the coast, gotten stuck on a sand spit, and had to cross tidal flats and channels to get back to the mainland, where the food was.
In some cases, the tracks suggest the dinosaurs were walking through abandoned, muddy tidal channels, sinking at least a meter into the sediment. Were they floundering? Having a mud bath? Wallowing in the mud? We can't say for certain, but the tracks are definitely there. What we do know is that they weren't feeding—they were playing in the mud.
AB: Relatable, isn't it?
GP: Absolutely! Some of the tracks are quite small, so maybe young dinosaurs were there too—playing in the mud, just like all kids do.