Ancient fossil find re-writes the record

A fossil that has been sitting in the Montagu Museum for the past twenty years has recently been identified as the oldest known intact half-jaw of a shark. The creature, an Antarctilamnid shark, lived and hunted in nearby waters 380 million years ago. That was before woody plants or vertebrate animal life existed on the land, and when Africa, South America, Antarctica and Australia were still joined together in a continental mass we now call Gondwana.
The story of the identification is almost as exciting as the find itself.
The fossil comes from the Warmwaterberg. It was part of a collection put together over many years by the late Abraham de Vries who farmed in those parts. When he retired to Montagu he donated his entire collection to the Museum. For most people it was just another fossil, although Abraham himself took it for the relic of a fish. Palaeontologists have looked it over from time to time and recognised it as the mould of a shark jawbone.
In the mid nineties Fiona Evans and John Almond made a set of latex ‘peels’ of the fossils, which take the form of natural moulds of the original remains. These are still stored in the Geological Survey office in Bellville. It was looking over these ‘peels’ quite recently that a young Wits Palaeontological student, Rob Gess, was struck by the fact that the specimen was much older and more complete than another Antarctilamnid jawbone fossil from near Grahamstown that he had been studying.
In the Grahamstown fossil all the teeth had already been shed and were scattered in the rock around, whereas in the Montagu fossil many teeth were more or less intact and aligned with the jaw much as in present-day sharks.
“This has never before been recorded from so ancient a shark jaw, so I was really excited,” Rob told us.” Shark skeletons consist mainly of cartilage, so fossils of the animal are extremely rare which is why there was such scientific excitement about the find.
“I was sure that more detail than was visible in the latex peel could be extracted from the fossil. I visited Montagu, examined the De Vries collection and obtained permission to take the jaw specimen on loan. I soon concluded that further latex peeling might cause it damage, so I decided to rather scan it at the Pelindaba nuclear reactor in Gauteng. Here, over several hours, I took hundreds of serial photographic ‘slices’, using a concentrated neutron beam. I gave these images to Michael Coates, my PhD supervisor from the University of Chicago who is one of the world’s leading and most respected experts on Devonian fish, when he was out in October 2009 exploring near the Warmwaterberg with me for more fossil sites and visiting the Montagu Museum. He asked another student of his in Chicago, Justin Lemberg, to use a computer to combine all the photographic slices to produce a three dimensional image.
“We were really impressed by the results and are now planning another set of higher resolution scans. We believe we may get even finer details of the teeth which will teach us more about the jaw architecture of early sharks.”
Ultimately a paper will be produced for publication in the world’s top scientific journals.
Rob tells us that the De Vries fossils all come from a mid-Devonian, Givetian, rock layer known as the Adolphspoort Formation which is about 380 million years old.
“The De Vries' shark lived together with other early fish in shallow coastal waters of the Agulhas Sea. Abraham’s collection consists mainly of pieces of rigid spines that supported the fins of various sharks and extinct ‘acanthodian’ fish, as well as the armoured plates of placoderm fishes, a group that became extinct about 360 million years ago. Their entire heads and bodies as far as their ‘waists’ were covered in bony armour plates. In 1980, a new species of placoderm fish, Barrydaleaspis theroni was described from earlier collected material of De Vries', which was donated to the museum in Cape Town.”
Abraham’s son Ar still lives and works in Montagu. He recalls that although not university educated on the subject of palaentology, Abraham virtually ‘lived’ for his collection. When he died and they delivered the fossils to the Montagu Museum in terms of his wishes, they filled two bakkie loads. Who knows what ancient wonders may yet surface in the collection?
Rob Gess hopes the shark jawbone fossil will some day be on display in a safe glass case in the Montagu Museum together with digital images, a copy of the scientific paper to be written about it and a short explanation in layman's terms.

Photo:
Moulded in stone - the jaw of an ancient shark, found near Montagu and identified finally by Rob Gess