Eomonachus belegaerensis

Giant seal fossil found in New Zealand suggests they evolved in the south

By Donna Lu

An artistic impression of Eomonachus belegaerensis

Illustration by Jaime Bran for the Te Papa Museum.

The discovery of an extinct species of monk seal that lived 3 million years ago upsets what we previously knew about the seal’s evolution.

James Rule of Monash University in Melbourne, Australia and his colleagues identified the new species while studying fossil specimens found on beaches in South Taranaki on the west coast of New Zealand’s North Island.

It was named Eomonachus belegaerensis, after the fictional Belegaer Sea from JRR Tolkien’s Lord of the Rings.

advertising

Seven fossils, including a full skull, were found by members of the public between 2009 and 2016. They are the oldest evidence of monk seals ever discovered. The fossils suggest that this species was about 2.5 meters long when fully grown and weighed 200 to 250 kilograms.

Because of its teeth, the seal’s diet was likely similar to that of live monk seals, which are made up of fish, squid, and octopus, Rule says.

The discovery upsets accepted knowledge of how real seals – who are earless and are a different group from fur seals and sea lions – evolved.

“It was all thought in the past [true] Seals, including monk seals and Antarctic seals, are native to the North Atlantic, ”says Rule. “This is where most of the seal fossils were found.”

Scientists believed that these seals then crossed the equator to populate the southern hemisphere. However, the discovery of E. belegaerensis in New Zealand suggests that the ancestors of the living Antarctic, elephant, and monk seals actually evolved in the southern hemisphere.

The researchers incorporated the new discovery into an analysis of the global distribution of living and extinct seals over time. They concluded that instead, many seals evolved in the South Pacific, crossing the equator up to eight times.

“It seems to imply that real seals have wide environmental tolerances,” says Rule. “That actually makes sense when you look at the distribution of the real seals today.”

Live monk seals are found in tropical and subtropical waters, while all other species of real seals are found in polar regions.

Journal reference: Proceedings of the Royal Society B, DOI: 10.1098 / rspb.2020.2318

More on these topics: