Scientists identify New Walking Shark Species With Morse Code-like Markings

For years, people living along the coast of Papua New Guinea have known about a strange shark that strolls across shallow reefs on its fins. They even had a name for it—kadedekedewa, which roughly translates to ‘dog shark’ or ‘lazy shark.’ Yet until now, the animal has existed outside the scientific record.

A new study has changed that. Researchers have formally identified the reef-dwelling predator as a previously unknown species of walking shark, naming it Hemiscyllium dudgeonae. 

This discovery adds another member to one of the world’s most unusual shark groups—animals that have evolved to move across the seafloor using limb-like fins and can tolerate the harsh, oxygen-poor conditions of shallow reef habitats.

“New shark species don’t come along that often, and it’s most definitely the first one named after me,” Christine Dudgeon, one of the study authors and a senior research fellow at the University of the Sunshine Coast (UniSC), said.

Looking for one shark, researchers found another

The discovery emerged from a broader effort to understand walking sharks in eastern Papua New Guinea. These small sharks belong to the genus Hemiscyllium, a group restricted to waters around Australia and New Guinea. 

Unlike fast-swimming open-ocean sharks, they spend much of their lives in shallow coastal environments, hunting small animals among reefs and seagrass beds. Researchers surveyed reefs, lagoons, and coastal habitats across multiple locations in Papua New Guinea, conducting dozens of field searches using diving, snorkeling, and on-foot inspections of reef flats. 

“Survey methods included diving, snorkelling and reef walking to catch walking sharks by hand, with 70 dedicated surveys completed at 35 sites in 15 locations,” the researchers note.

Their goal was not to find a new species. Instead, they were trying to map the distribution of already known walking sharks and evaluate their conservation status. However, during a one-night survey in Milne Bay, the team encountered a shark that immediately stood out.

At first glance, it resembled other walking sharks in size and shape. However, its markings were different. Known species in the region typically display leopard-like spots, while this shark carried an unusual pattern of pale dashes and markings scattered across its body.

“The first thing that stood out was the white dashes along its brown body. These dashes were quite different to the leopard-like spots we were expecting,” Jess Blakeway, first author of the study and a PhD student at UniSC, said.

This observation alone was not enough to declare a new species. Color patterns can vary between individuals, and marine biologists have learned that appearances can be deceptive. 

The team therefore expanded its search and found additional sharks showing the same distinctive markings at nearby sites. The repeated sightings suggested they were looking at a consistent population rather than a rare individual.

DNA revealed a hidden branch of the walking shark family

To determine whether the sharks truly represented a separate species, researchers combined traditional anatomical observations with genetic analysis. This step was crucial because walking sharks are notoriously difficult to distinguish. 

DNA extracted from tissue samples revealed that the Milne Bay population was genetically distinct from all previously described members of the genus.

The result confirmed that the researchers were dealing with an evolutionary lineage that had escaped scientific recognition despite belonging to a relatively well-studied shark group.

“It wasn’t until genetic analysis of the samples back in Australia that we could confirm a new species. This is the first new species described for the genus since 2013,” Blakeway said.

The discovery also produced another surprise. Earlier research suggested that natural barriers such as deep-water channels or river systems helped isolate walking shark species from one another. 

The new surveys indicate that species ranges in eastern Papua New Guinea are more complex than previously thought. Different walking shark species can occupy overlapping regions, even though they tend not to occur in the same locations.

A new species with an uncertain future

While the discovery expands the known diversity of sharks, it also raises conservation concerns. The newly identified species appears to have an extremely limited distribution centered on Milne Bay. 

Species confined to small geographic areas face greater risks because a single environmental disturbance can affect a large proportion of their population. For instance, several walking shark species (such as Hemiscyllium strahani) are already recognized as threatened because they occupy restricted ranges, making them especially sensitive to habitat loss.

Researchers fear H. dudgeonae could face similar pressures. Its shallow coastal habitat is increasingly threatened by coral bleaching, coastal development, fishing activity, and climate-driven changes to reef ecosystems. 

The team plans to collect more data on the shark’s numbers, distribution, and ecology to support future conservation assessments. 

“We hope to collect more data on our next research trip in October to help the International Union for Conservation of Nature (IUCN) Red List assess the species as vulnerable or endangered with extinction,” Blakeway said.

The study is published in the Journal of the Ocean Science Foundation.