Fossilized seal tooth found on Portland beach reveals plight of ‘real’ Australian seals

A three million year old fossilized tooth found on a southwestern Victorian beach tells two stories: that of the ancient true seals that lived on the Australian coast millions of years ago, and that of the uncertain future that awaits the fur seals and sea lions that live there today.

The fossil was picked up from a Portland beach in 1998 and donated to the Melbourne Museum, but has only recently been closely studied by a team from Monash University and the Victoria Museums.

Researcher James Rule, who examines the evolution of seals, said the extinction of “true” or earless seals could shed light on how sea level rise associated with current climate change will affect people. seals that now inhabit our coastline.

It’s all in the ears

The use of the word “true” to describe the type of seal from which the tooth comes derives from two categories which globally define different species of seal.

Seals without ears, or true seals, do not have visible earmuffs and have smaller fins, which means that it is more difficult for them to move around on land.

A crabeater seal belongs to the group of seals called earless or true seals.(

ABC News: Karen Barlow

)

Ear seals, the category to which Australian fur seals and sea lions belong, have visible ears and larger fins that allow them to move around much more easily.

“These real seals do not exist on the Australian coast today,” Mr Rule said.

“However, in the past, they were the only seals that were here.

“After their extinction, fur seals and sea lions colonized Australia and New Zealand from the North Pacific.”

Three-million-year-old fossilized seal tooth found on a beach.
This fossilized seal tooth found on a Portland beach in southwest Victoria is three million years old.(

Supplied: James Rule

)

The only other fossil showing that seals lived along the coastline millions of years ago has been found in Beaumaris, Melbourne, and has been dated to six million years ago.

Land cools altered coastal habitat

Mr Rule said higher sea levels associated with a warmer period in Earth’s history would have presented ideal habitat for true seals.

He said the climate started to cool about two and a half million years ago, which means more ice has formed at the poles and sea levels have dropped.

“It would have exposed many islands and rocky beaches along the coast, and this type of environment is perfect for fur seals and sea lions.”

An Australian fur seal in shallow water at Phillip Island
Australian fur seals like to inhabit rocky islands and beaches made up of boulders and pebbles.(

Provided: Phillip Island Nature Parks

)

“Fur seals and sea lions can actually still walk when they’re on the beach and on rocks, because they can put their hind fins out to help them.

“Unfortunately… real seals can only bounce and when they don’t have a flat beach environment to bounce on, they can’t rest on it.”

Rising sea levels could see fur seals and sea lions suffer the same fate

Mr Rule said research into the plight of ancient seals illustrated how climate change could affect seal populations, and current sea-level rise could threaten sea lion and sea lion colonies in fur in Australia.

“If the Earth continues to warm and temperatures rise, we will continue to lose ice at the poles as we are today,” he said.


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Sandy A. Greer

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