Roy Oosthuizen's fossil

Roy Oosthuizen split a nodule on Zwartkraal in the 1980s and found a braincase. Oelofsen named it for him in 1986 and filed it as a shark. In 2013, fourteen years after he died, a CT scan read the inside of it and found a chimaera - and with it the origin of the last major vertebrate group nobody could place. Nature, 4 Jan 2017.

The nodule

Roy Don Oosthuizen ran sheep on Zwartkraal and collected fossils in his own time. The district knew him as Oom Roy. [FAMILY] The farm is written both ways, Zwartkraal and Zwartskraal, and it is one place; the scientific papers use Zwartskraal.

He was a grandson of Frederik Simon Oosthuizen, the Oom Frikkie of eighty-one thousand morgen, through Oom Frikkie's son Frederick Simon, 1881 to 1963. [TREE]

The Karoo is the right place for collecting. The rock under these farms is the Karoo Supergroup, and at the bottom of it lies the Dwyka, the tillite left by an ice sheet that sat on this part of Gondwana in the Permian, when what is now the Koup was near the pole rather than in a rain shadow.

Some time in the 1980s he picked up a nodule that had weathered out of mudstone about thirty centimetres above the top of the Dwyka. He had his son hold it while he hit it with a hammer, and it broke into three.

Inside was a braincase. Not a whole animal, and not a skeleton, the cartilage of a shark does not usually survive at all, but the mineralised case that had held a brain, uncrushed, with the shape of the thing still in it.

What it was called

Burger Oelofsen described it in 1986 and named it after the man who found it: Dwykaselachus oosthuizeni. The Dwyka shark, Oosthuizen's. [SRC-175]

Oelofsen had the outside of the nodule to work from, which is to say the surfaces the break had exposed. From those he identified it as a symmoriid, an early shark. That was a reasonable reading and it stood for thirty-one years.

Roy Oosthuizen died on 20 September 1999. The specimen went to the South African Museum in Cape Town and was catalogued there.

What it actually was

In 2013 a palaeontologist named Robert Gess put the nodule through the micro-CT scanner at the University of the Witwatersrand's Evolutionary Studies Institute. He did it because Michael Coates, at Chicago, had asked him to look at this one in particular.

The scan went through the rock and read the inside of the braincase, which nobody had ever seen.

From the outside it is a symmoriid, and by some distance the most complete uncrushed symmoriid braincase anyone has found. From the inside it is not a shark at all. The arrangement of the inner ear, the shape of the space the brain sat in, the routes the cranial nerves took, and the size of the eye sockets, these are the anatomy of a chimaera.

Chimaeras are still alive. They are the ratfish and the elephantfish, the odd deep-water relatives of sharks and rays, and they had been the last major group of surviving vertebrates that nobody could place properly on the tree of life. There was no early fossil that looked like the beginning of them.

There was. It had been in a drawer in Cape Town since the 1980s, filed under sharks.

Coates, Gess, John Finarelli, Katharine Criswell and Kristen Tietjen published it in Nature on 4 January 2017. [SRC-174]

The man who found it

The first is that the fossil is about 280 million years old, and the man who found it has been dead since 1999. He was named on it in 1986, the species carries his surname and will carry it permanently, but the reason it turned out to matter was established fourteen years after he died, by a machine that did not exist in a usable form when he split the rock.

The second is about who does this work. Every account of the paper gathered here calls Roy Oosthuizen an amateur, and self-taught. He was a farmer who collected, correctly, in a place where the rock is generous and the people who know it are few. His collection also held invertebrates, an ancient lichen and a very large eurypterid, and several other fossils carry his name. He worked with the South African Museum on cataloguing what he brought in.

The rest of this history is title deeds, baptisms and who held which ground. This is where one of its farms reaches a paper in Nature, and it got there because somebody who lived on the ground paid attention to what was lying on it.

Three names, and the one he cared about

The shark is the famous one. It is not the one Roy Oosthuizen rated highest. [SRC-068]

That is worth sitting with. The find that made the journals was one he never knew was important, he thought he had a shark skull, boxed it, and sent it off. The one he was proudest of was a blastoid, which is not going to be on any magazine cover. A man who spent thirty years reading rock knew which of his finds was hard to get and which was luck.

His museum on Zwartkraal held over 3,000 fossils and was reckoned the best privately owned collection of its kind in the country. A BBC crew came out to film it. Professor John Almond visited over a shared interest in invertebrates, and what Roy said afterwards is the most revealing line anybody recorded from him:

It's like a dream come true. In the 30 years that I have been studying these fossils, I have never found anyone who shared my interest.

Thirty years, alone, on a sheep farm, getting it right.

Dr Herbert Klinger of Iziko and the museum technologist Derek Ohland called in while Judy Maguire had them out at Vrisgewaagd, and noted his good specimens of Placocystella capensis, the tadpole with horns. He left the collection to the South African Museum. Dr Roger Smith's tribute picks out the ancient lichen and "the only eurypterid ever found", a giant sea scorpion. Part of it is on permanent display at the Fransie Pienaar Museum in Prince Albert, laid out by Smith, dedicated to Roy's memory.

One claim in that source is not repeated here as fact: it also credits him with "the oldest fossil in the southern hemisphere, a mammal-type reptile". That is an extraordinary claim carrying no citation, and it is recorded in the model as not yet verified rather than told. The same source spells the shark oosthuizenae; the published name is oosthuizeni.

What this story is about

• set on Zwartkraal
• about Roy Don Oosthuizen

Sources

Everything this story rests on, with a link to the original wherever one exists. Where a citation is incomplete it says so, an incomplete citation is a research gap, not a formatting problem. If your work is here and the credit is wrong or thin, please tell us and it will be fixed.

1. Rose Willis and Doreen Atkinson, with Judy Maguire and Bruce Rubidge, "Klaarstroom: Ancient place of clear waters" (Karoo Cameos, 2021) Karoo Development Foundation, Karoo CameosKaroo Cameos, 2021view it online →
2. Coates et al., "A symmoriiform chondrichthyan braincase and the origin of chimaeroid fishes", Nature, 4 January 2017 Naturedoi:10.1038/nature20806
3. B.W. Oelofsen, original description of Dwykaselachus oosthuizeni, 1986 cited in Coates et al. 2017 (SRC-174); the original paper is not held hereOelofsen, 1986, genus and species authority for Dwykaselachus oosthuizeni
4. Rose Willis & Doreen Atkinson, "Zeekoegat: Explorations in the Koup Karoo" (2022) Karoo Development Foundation38pp cameoview it online →

Research notes

The research behind this page, kept separate from it: dated working notes, open questions, and what is not yet settled.