An ancient seal tooth found at a beach in Australia suggests earless seals rolled around on sandy beaches three million years ago, scientists have said.
Researchers believe the fossil belongs to a monachine seal, an extinct sea mammal.
The specimen is thought to be only the second earless seal fossil ever discovered in the country.
The researchers said their study, published in the Journal of Vertebrate Paleontology, indicates falling sea levels were likely to have played a role in the extinction of these ancient mammals.
James Rule, a PhD candidate from Monash University’s School of Biological Sciences and study leader, said: “This tooth, roughly three million years old, tells a story similar to what occurred in South Africa and South America in the past.
“Earless monachine seals used to dominate southern beaches and waters, and then suddenly disappeared, with eared seals replacing them.
“Since seal fossils are rare globally, this discovery makes a vital contribution to our understanding of this iconic group of sea mammals.”
The team compared the tooth to other pinnipeds, a group of aquatic mammals that includes earless seals, fur seals, sea lions and the walrus.
Analysis revealed the tooth to be around three million years old and belonged to monachine seals.
Mr Rule said: “This seal lived in shallow waters close to the shore, likely hunting fish and squid.
“As monachines cannot use their limbs to walk on land, it would have required flat, sandy beaches when it came ashore to rest.”
Researchers believe drastic changes in the planet’s climate caused the beaches where the earless seals lived to disappear, contributing to the extinction of the species.
They warn that current fur seals and sea lions may face a similar threat if global warming continues.
Dr David Hocking, research fellow from Monash University’s School of Biological Sciences and study co-author, said: “These changes in the past have led to the extinction of Australia’s ancient earless seals.
“Our living fur seals and sea lions will likely face similar challenges as the Earth continues to warm, with melting polar ice leading to rising sea levels.
“Over time, this may lead to the eventual loss of islands that these species currently rely upon to rest and raise their young.”