Ancient ‘sharks’ may have appeared 15m years earlier than previously thought

28 Sep 2022

Qianodus duplicis. Image: Heming Zhang

Teeth belonging to a newly discovered species, thought to be from the Silurian era, were found in China.

Recent fossil discoveries suggest that shark-like jawed fish could have emerged a lot earlier than previously thought.

Researchers from the UK and China found fossilised teeth belonging to a completely new species. The teeth were uncovered from rock samples in China, before being analysed by the scientists.

The teeth samples suggest that jawed fish emerged some time at the end of the Ordovician, or the beginning of the Silurian period, around 440m years ago.

Previously, the earliest jawed fish to be positively identified included species from around 424m years ago – or the upper Silurian period. These species include the placoderms, a partially armoured species, and sarcopterygians, a bony lobe-finned species found initially in China and Vietnam.

Palaeontologists had suspicions that these shark-like creatures existed much earlier than 424m years ago, getting hints from discoveries of fossil scales. Teeth would help confirm their theories, but teeth are generally a lot more difficult to locate.

“Until this point, we’ve picked up hints from fossil scales that the evolution of jawed fish occurred much earlier in the fossil record, but have not uncovered anything definite in the form of fossil teeth or fin spines,” said Dr Ivan Sansom, a vertebrate palaeobiologist and lecturer at the University of Birmingham.

Sansom is a co-author of the paper that resulted from the discoveries, which is being published today (28 September) in the journal Nature.

He said that the scale and speed with which the researchers worked to identify the fossils helped enormously to confirm that they were, in fact, belonging to a new species.

The fossils were discovered at the site of a new road being built in China’s Guizhou province. The team found lots of scales in the sample, but eventually also uncovered a number of tiny teeth between 1.5 millimetres and 2.5 millimetres long. Around 20 of the teeth turned out to be from the same species.

The researchers then used a range of techniques, including CT scanning, to establish a date for the samples, placing them in the early Silurian period.

The new species has been named Qianodus duplicis. Qian is an ancient name for Guizhou province, while odus is from the Greek for tooth. Duplicis, or double, refers to the paired rows of teeth the creature had.

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Blathnaid O’Dea is Careers reporter at Silicon Republic

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