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7 December 2022 3 min read

Like sharks in the ocean, collaborative teams of scientists on board RV Investigator have been voyaging far and wide in recent months. They have been undertaking biodiversity surveys in some of Australia’s most remote and deepest marine environments.

Their discoveries are helping us unlock some of the mysteries of the apex predator in our oceans: sharks. They have discovered new species, a shark graveyard and teeth from an ancestor of the mighty megalodon on the ocean floor.

Naming a new shark

A team of scientists led by one of our Senior Principal Research Scientists, Dr John Keesing, is currently off Western Australia to survey marine life and habitats in the Gascoyne Marine Park. One of the many exciting finds of the voyage so far has been the collection of a specimen of a new species of shark.

Small but incredibly striking, this stripey hornshark was recognised as something special by scientists from our Australian National Fish Collection as soon as it came on board.

This species is unique to Australia and scientists have known about it for a while. However, it hasn’t yet been described and scientifically named.

As such, the specimen collected on this voyage will be incredibly important to science. We’ll use it as a holotype specimen, which is a physical example used to describe a new species.

Hornsharks, including the well-known Port Jackson shark, are generally a slow-moving species found in shallow waters. They spend most of the day camouflaged among rocks and seaweed on the seafloor, and come out at night to feed.

In contrast, this new species lives in water over 150 metres deep, and we know nothing about its behaviour.

Not mega but chubby

No one remembers second place, right? Well, Carcharocles chubutensis might have something to say about that!

Carcharocles chubutensis is sometimes called Otodus chubutensis, but we’ll just call it ‘Chubby’. It is the second-biggest shark to have ever roamed the ocean. Inhabitants of our ancient seas would definitely have been keeping an eye out for this shark.

Chubby grew to over 12 metres long. It was the ocean’s apex predator for many millions of years. Its massive size was linked to the size of its prey. Chubby ate the increasingly abundant marine mammals that were populating the ocean at the time. Marine mammals are a nutritious snack to grow big sharks.

While some refer to this species as a megalodon, it transitioned to become the megalodon shark, Otodus megalodon, during the early part of the middle Miocene. This was about 15 million years ago.

Scientists found the teeth of this massive ancient shark when surveying deep sea life in the Cocos (Keeling) Islands Marine Park. This was on our previous voyage led by Museums Victoria Research Institute. Chubby’s teeth were collected along with over 750 other shark teeth from a single seafloor survey at 5400 metres deep.

Interestingly, the teeth found during the voyage are literally on the cusp (see what we did there) of being megalodon. It is the very small side cusps – bumps at the base of the side of the tooth – that distinguish Chubby (with cusps) from mega (without cusps). The cusps on these teeth are hard to distinguish.

This shark graveyard was an astonishing abyssal find. Abyssal refers to depths of the ocean, usually between 3000 and 6000 metres down.

More data for better marine management

The discovery of these new and old sharks emphasises how little we know about our oceans. Every marine biodiversity survey makes a significant contribution to our understanding of life in our oceans. Especially surveys in deep and difficult to access environments.

This information is vital for marine park managers, such as Parks Australia, who manage the Australian Marine Parks network. This includes 60 marine parks established around the Australian continent and remote islands. These marine parks help protect our marine biodiversity now and into the future.

©  Frederique Olivier

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