During a deep-water ocean expedition off Australia, marine biologists identified over 110 new marine species — including a rare, pale "ghost shark" whose evolutionary line diverged nearly 400 million years ago, long before dinosaurs roamed the Earth

For 35 days in late 2025, a research vessel called the RV Investigator moved slowly through the deep waters off Australia’s east coast, dragging equipment thousands of metres down into places no one had ever properly looked.

By the end of the voyage, its crew had brought aboard specimens of more than 110 marine species that had never been described by science. Researchers estimate the final count, once analysis is complete, will exceed 200.

The most striking of the finds was a pale, soft-bodied fish called a chimaera. Also known as a ghost shark, ratfish, or spookfish, it belongs to an evolutionary lineage that split from sharks and rays approximately 400 million years ago — long before the first dinosaurs walked on land.

What the expedition found

The Coral Sea Marine Park sits about 1,000 kilometres east of the Queensland coast, extending across nearly one million square kilometres of ocean. It is Australia’s largest marine protected area. Most of its deep-water habitats had never been mapped or biologically surveyed before the 2025 voyage.

The RV Investigator, a research vessel operated by CSIRO (Australia’s national science agency), departed Brisbane in October 2025 and traveled as far as Mellish Reef, roughly 1,000 kilometres offshore. The expedition was a collaboration with The Nippon Foundation-Nekton Ocean Census, an international partnership dedicated to accelerating deep-ocean species discovery.

The 110-plus new species were collected at depths between 200 and 3,000 metres. They include brittlestars, crabs, sea anemones, sponges, corals, and fishes — the specific range of animals that live in the deep ocean but rarely surface anywhere near human observation.

The chief scientist of the voyage was Dr Will White, a shark and ray specialist at CSIRO. White personally identified four new fish species from the collection: two rays (a stingaree found on the Kenn Plateau and a skate), a deepwater catshark, and the chimaera.

What a ghost shark actually is

Chimaeras are among the strangest fish in the ocean, and one of the least familiar to most people.

They are related to sharks and rays but are not sharks or rays themselves. All three groups belong to a broader category called cartilaginous fishes — animals whose skeletons are made of cartilage rather than bone. But within that category, chimaeras split off very early and evolved along their own separate lineage.

Chimaeras have soft bodies, smooth skin without scales, and large dark eyes. Some species grow to nearly five feet long. They tend to move slowly and prefer the deep ocean, at depths from about 200 metres to more than 2,600 metres. Their mouths often end in a specific beak-like structure they use to crush small crustaceans and molluscs on the seafloor.

The specific new chimaera identified during the CSIRO voyage belongs to the genus Chimaera. It is soft-bodied, pale, and adapted to conditions most surface-dwelling fish could not survive.

Ghost sharks are rarely seen alive by humans. Most known species are described from specimens brought up in deep-sea fishing operations or from occasional footage captured by remotely operated submersibles. The 2025 CSIRO voyage adds another to the small catalogue of formally described species.

The 400 million years

The evolutionary depth of the chimaera lineage is worth being specific about, because it is genuinely remarkable.

Chimaeras diverged from the shark and ray lineage during the Late Silurian or Early Devonian period, roughly 400 million years ago. At that point in Earth’s history, the first plants were only beginning to grow on land. There were no trees. There were no amphibians, no reptiles, and no dinosaurs.

Chimaeras have persisted, in essentially the same body plan, for that entire span. Their surviving descendants today look and behave in ways that are recognisably similar to the fossil chimaeras preserved in ancient marine sediments.

By comparison, the earliest dinosaurs appeared approximately 230 million years ago — nearly 170 million years after the chimaera lineage was already established. The extinction of the non-avian dinosaurs, 66 million years ago, is more recent to us than the appearance of chimaeras was to the dinosaurs themselves.

Chimaeras are often described as “living fossils” for this reason. The label is somewhat misleading — modern chimaeras have continued to evolve, and there are dozens of distinct species alive today. But the underlying body plan and biological specialisation is one of the oldest continuous designs in vertebrate life.

What this tells us about the deep sea

The specific significance of the CSIRO discovery goes beyond the individual new species.

A single 35-day voyage to one region of one ocean produced descriptions of more than 110 new marine species, with hundreds more likely to follow as taxonomic workshops complete their analysis. This gives some sense of how much of the deep ocean remains genuinely unknown.

Approximately 80 percent of the world’s oceans have never been mapped in detail. The deep ocean — everything below 200 metres — is the largest biosphere on Earth by volume, and the least explored. Estimates for the total number of marine species yet to be described range from hundreds of thousands to more than a million.

The CSIRO team’s finding is the specific product of a narrow, focused effort. Most of the deep ocean is not being surveyed at all. If a single expedition to a single well-defined marine park can produce 110+ new species, the actual number of undescribed marine species across the planet’s oceans is almost certainly enormous.

Toni Moate, director of the CSIRO Marine National Facility, described the finds as adding to what she called “the ever-growing list of new species that RV Investigator’s voyages have helped to identify.” Similar patterns are being documented in other deep-sea surveys around the world — from the Chatham Rise off New Zealand to the deep trenches of the Pacific and the seamount chains of the Atlantic.

The specimens collected during the 2025 voyage have been deposited in CSIRO’s Australian National Fish Collection and other state museums. Their formal scientific descriptions, DNA sequences, and comparative work will continue for years.

Somewhere in the Coral Sea right now, more than 110 species that have just been formally identified are living their ordinary lives on the deep seafloor, mostly unbothered by the fact that anyone has finally noticed they exist. And beyond them, in the same waters, are almost certainly many more that no one has yet found.