Four new species of shark that use their fins to walk along the seabed have been discovered off the coast of Australia.
They were identified off the coast of northern Australia and the island of Papua New Guinea during a 12 year study.
The ornately patterned sharks were the top predator on reefs during low tides when they used their fins to walk in very shallow water.
Dr Christine Dudgeon, of Queensland University, said: “At less than a metre long on average, walking sharks present no threat to people.
“But their ability to withstand low oxygen environments and walk on their fins gives them a remarkable edge over their prey of small crustaceans and molluscs.
“These unique features are not shared with their closest relatives the bamboo sharks or more distant relatives in the carpet shark order including wobbegongs and whale sharks.”
The findings reported in Marine and Freshwater Research almost doubled the total number of known walking sharks to nine. They occupy their own separate region.
Dr Dudgeon said: “We estimated the connection between the species based on comparisons between their mitochondrial DNA which is passed down through the maternal lineage.
“This DNA codes for the mitochondria which are the parts of cells that transform oxygen and nutrients from food into energy for cells.
“Data suggests the new species evolved after the sharks moved away from their original population, became genetically isolated in new areas and developed into new species.
“They may have moved by swimming or walking on their fins, but it's also possible they 'hitched' a ride on reefs moving westward across the top of New Guinea, about two million years ago.
“We believe there are more walking shark species still waiting to be discovered.”
Dr Dudgeon said future research would help researchers to better understand why the region was home to some of the greatest marine biodiversity on the planet.
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