In 1980 a farmer and amateur paleontologist, Roy Oosthuizen stumbled upon a fossilized skull of a primitive shark that inhabited the waters approximately 280 million years ago. Little did he know that his discovery will lead to one of the most important discoveries of the century. On Thursday, January 5th, researchers at the University of Witwatersrand revealed how modern chimaeras share their ancestry with primitive sharks.
Looking at the skull, the scientists were able to discover that chimaera skulls are remarkably similar to the one Mr. Oosthuizen discovered. Hence, telltale structure of the ancient shark’s brain case, nostrils, major cranial nerves, and inner ear are identical to what researchers are used to seeing in modern-day chimaeras, says Dr. Rob Gess with the Center of Excellence in Palaeosciences and co-author of the study.
Before the ancient skull surfaced, Dr. Gess said that specialists were able to identify chimaeras as a cartilaginous fish, related to sharks and rays. However, the origin of the chimaeras was still a mystery, since their distinctive skull also displayed striking differences from other groups of cartilaginous fish.
Roy Oosthuizen pulled out the fossilized skull from a mudstone lying just one foot above the top of the Dwyka glacial deposits. His son also helped with the discovery. The farmer asked him to hold the rock while he smashed it with a hammer.
After the fossil was extracted, the skull was deposited in a cardboard box in the Cape Town museum’s archive until 2013, when Dr. Gess finally got permission to scan the head using a micro-CT scanner the Wits Evolutionary Studies Institute obtained. The scanner allowed Dr. Gess and his team of researchers to study the intact fossil without using any invasive procedures.
The 3D map of the skull showed that the Dwkaselachus Oosthuizeni was the first specimen to reveal both features of chimaeras and primitive sharks. Hence, Mr. Oosthuizen’s fish shared multiple features of 300 million-year-old symmoriid sharks, a bizarre group of marine creatures best known for their unusual dorsal fin spines. At the same time, however, the scans also showed that the Dwkaselachus also shared some telltale anatomical structures with modern ghost sharks, which marks the specimen discovered by Roy Oosthuizen as an early chimaera.
“We can now anchor chimaeras firmly on the tree of vertebrate life”, stated Dr. Gess.
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