A new species of deep-water catshark has been discovered in an unusual way, identified from its egg case by researchers in northwestern Australia. Named Apristurus ovicorrugatus, it has the Western Australian Museum’s collections to thank as it was here that its egg’s true identity was revealed following a decade-long mystery.
The mystery egg was unusually ridged and didn’t fit any known species until it was matched up with two eggs at the Australian National Fish Collection, a CSIRO-affiliated organization. It wasn’t until they found a dead female in storage that they could finally fill in the blanks.
A feel of the dead female's abdomen had revealed there may be something inside and, sure enough, researchers found egg cases. Their cases were also uniquely stripey, a morphology that inspired the species name “ovicorrugatus” derived from the Latin for “egg” and “corrugated”.
The A. ovicorrugatus female had initially been misidentified as A. sinensis, but has since been given its own shiny new species name. As well as having peculiar eggs, the species has strange eyes that seem fitting for a group of catsharks nicknamed “demons”.
“The egg cases of this species have strong T-shaped longitudinal ridges on the dorsal and ventral surfaces which are unique in the genus Apristurus,” wrote the authors of a new study describing it.
The researchers also collected data on the embryos taken from egg cases, revealing some features of these demon sharks that may develop later with age including enlarged dermal denticles.
As well as its peculiar stripy eggs, the species is characterized by strange white irises that are rare among demon sharks of the Apristurus genus.
"This is not a common feature for a deepwater species and only one other species, Apristurus nakayai from New Caledonia and PNG [Papua New Guinea] shares this character," study lead author Will White from the CSIRO National Research Collections Australia told Live Science.
Demon sharks like A. ovicorrugatus are also known as ghost sharks, a group of deep-sea catsharks from the family Scyliohinidae. The Apristurus is one of the most diverse shark genera known to science, with this latest addition bringing the known number of species to 40.
As well as adding a new demon shark to the ocean’s deep-sea oddities roster, the discovery of A. ovicorrugatus is a reminder that there are all kinds of places to discover new species (sometimes, including Walmart).
“This study highlights the important contribution that egg case morphology has on oviparous elasmobranch taxonomy,” the authors concluded.
The study is published in the journal Fish Biology.