Melissa Márquez
While new species’ discoveries are often associated with field expeditions, museums hold a wealth of treasures that can reveal the hidden biodiversity of our planet. Specimens are collected over centuries, some of which remain without a name on their label. Sometimes discovering a new species can be straight-forward, especially if it appears to be unlike anything previously described.
But oftentimes identifying a new animal is no easy task—it might just start with a nagging feeling that something isn’t quite right that what they are seeing is odd… new.
That is what happened to researcher Brett Human during his volunteer work at the Western Australian Museum (WAM) in 2011. Here, he stumbled upon an intriguing discovery—an unidentified shark egg. What made it truly remarkable was its distinctive shape, adorned with longitudinal, T-shaped ridges on both the dorsal and ventral surfaces.
Among all known shark species, only one other shared this feature: the dusky catshark (Bythaelurus canescens). These deep-sea sharks, known for their cat-like eyes and dark coloration, inhabit the Southeast Pacific.
As Human carefully examined the egg, he made a startling realisation—an embryo was nestled inside! However, to his astonishment, it did not resemble the expected dusky catshark. Determined to solve the mystery, Human embarked on a process of elimination and analysed the overall structure of the specimen, a process known as gross morphology. Based on his findings, he hypothesised that this egg belonged to the Apristurus genus.
This revelation opened up a world of questions.
How was this possible?
For more than a decade, the egg remained an enigma as scientists struggled to identify to which of the eight known shark species in Australian waters it belonged. That was, until recent developments shed new light on the situation. Two more egg cases identical to Human’s intriguing find were discovered in the Australian National Fish Collection. Further investigation revealed a pregnant female South China catshark (Apristurus sinensis) within the collection, carrying an egg case that matched the others. With the well-preserved late-term embryo inside the case, the presence of this new animals belonging to the genus Apristurus was confirmed. Nevertheless, there remained a lingering doubt in the minds of the scientists involved in this discovery. There was something… odd about this shark.
The South China catshark did not entirely resemble the newfound specimen. There were notable differences, including a medium brown buccal cavity instead of jet black; ridged egg cases rather than smooth; fewer intestinal spiral valve turns; and larger pectoral fins. Interestingly, the specimen exhibited molecular similarities and shared a unique synapomorphic character, the white shiny iris, with Apristurus nakayai.
To unravel the mysteries surrounding this perplexing specimen, Dr Will White, the senior curator of the Australian National Fish Collection at CSIRO, brought his expertise into the picture. He, too, was astounded by this shark – especially the haunting eyes. “Normally, they’re always very dark — either dark green or just black eyes,” White told ABC. “It has been found only in one other deepwater shark species — a member of a closely related species from New Caledonia and Papua New Guinea.
By conducting detailed morphometrical measurements of the adult holotype and late-term embryo, Dr White confirmed the existence of a new species. This remarkable new shark was named Apristurus ovicorrugatus, a fitting title derived from the Latin terms ‘ovi,’ meaning egg, and ‘corrugatus,’ meaning corrugated, referring to its distinctively ridged egg cases.
“It’s interesting, because we often get an idea that something might be a new species, but it can take a long time for us to resolve and compare with other species,” White said, adding that the new species was found laying eggs on some coral at a depth of more than 700 metres. “We don’t see a lot of them because of the depth they occur. If you look at that coastline, where it’s usually quite steep and drops off quickly, they have a relatively narrow depth distribution. They’re probably following a habitat in which they lay their eggs on a particular coral species.”
“We just know very little about deepwater fauna in Australia. As more deepwater surveys continue, I think we’ll uncover more species records — there’s still a lot to come.”
Will White
The discovery of Apristurus ovicorrugatus highlights the critical role of egg case shape in determining species. Shark eggs provide valuable information about the biology and behaviour of these remarkable creatures, playing a crucial role in scientific research and conservation.
Recognising this significance, the UK non-governmental organisation Shark Trust has established a worldwide database that encourages public engagement in documenting and sharing images of shark egg cases. Through this citizen science initiative, individuals contribute to our understanding of shark reproduction and their connections to specific habitats. By participating in this collaborative effort, we can deepen our knowledge and promote the conservation of these fascinating creatures.
This scientific journey not only discovered a new species, but also linked it to an animal across the country. “We actually uncovered a similar species off the Gold Coast, which is closely related but a very distinct species,” White continued. “We just know very little about deepwater fauna in Australia. As more deepwater surveys continue, I think we’ll uncover more species records — there’s still a lot to come.”
The journey from a perplexing egg in a museum collection to the identification of Apristurus ovicorrugatus exemplifies the intricate process of species discovery.
Furthermore, Apristurus ovicorrugatus has opened up new research questions about a different evolutionary pathway within this group that science had not previously thought of. This new species also raises questions about potential misidentifications or overlooked species within museum collections. The scientists are now conducting extensive searches within these collections to uncover more hidden treasures, highlighting the importance of revisiting specimens and utilising advances in technology to enhance our understanding of marine biodiversity.
The journey from a perplexing egg in a museum collection to the identification of Apristurus ovicorrugatus exemplifies the intricate process of species discovery. With the public’s active participation in citizen science initiatives, such as documenting and sharing egg case findings, our collective knowledge of these enigmatic creatures will help fill the knowledge gaps.
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The Ultramarine project – focussing on research and innovation in our marine environments – is supported by Minderoo Foundation.