It was a mystery that began with an egg. In 1989, scientists in Australia found a curious kind of “mermaid’s purse” – a leathery egg case, which some species of sharks lay instead of giving birth to live young. The empty egg cases had one almost unique feature – a row of prominent ridges along the top.
White and his colleagues knew the eggs recovered in the 1980s had come from a certain depth – between 410m (1,345ft) and 504m (1,640ft) – and started looking for sharks which had been caught at the same depth. The CSIRO collection had what was thought to have been a South China catshark, which turned out to have been pregnant when it was caught. The scientists dissected it and found a developing embryo inside an egg case with the same tell-tale ridges as the ones discovered years before in Rowley Shoals.
The detective work proved it was a completely new species, and the mystery that Australian shark scientists had been scratching their heads over for the last 30 years was finally solved. “It took us, like, two days to work it out,” says White. “The thing is, you’ve got to be looking specifically for it. The adults of that group, in particular, are very subtly different,” he says.
The species now has a scientific name (a common name is due to follow), and was unveiled in the Journal of Fish Biology in April 2023. This new variety of demon catshark, otherwise known as Apristurus ovicorrugatus, is thought to dwell around 700m (2,297ft) beneath the surface, laying its egg cases over coral in water too deep for sunlight to penetrate. White says this family of sharks is particularly hard to research because they are so elusive and because the differences between species can be so subtle.
“With this group, in particular, we’re actually down into looking at aspects of the digestive tract and liver shape and stuff like that. You’re definitely getting desperate when you start getting into characters like that,” White says.
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Article URL : https://www.bbc.com/future/article/20230711-why-we-keep-discovering-new-species-of-sharks