Scientists thought these seals evolved in the north. 3-million-year-old fossils from New Zealand suggest otherwise

A fossil discovery in New Zealand has revealed a new species of monk seal it once called Australasia home. We introduce the three million year seal, Eomonachus belegaerensis, in an article published today in the Proceedings of the Royal Society B.

Eomonaco it is the first monk seal species, living or extinct, ever found in the southern hemisphere – and the oldest found anywhere.

It is rewriting everything experts thought they knew about the evolution of the “monachine”, a group of seal relatives that includes the two living species of monk seals, elephant seals and some species of Antarctic seals.

On the verge of fading

Monk seals are some of the rarest and most endangered marine mammals. Today there are fewer than 2,100 Mediterranean and Hawaiian monk seals alive. The Caribbean monk seal was hunted to extinction in the 1950s.

Conservationists are now struggling to save what’s left of Earth’s last exclusively tropical seals from disappearance.

That said, it would be wrong to assume that monk seals were fine before humans started exploiting them. It is unclear how they have fared over the past million years. We also don’t know where they originated from, as fossils are few and far between.

Scientists traditionally thought that all monk seals evolved in the North Atlantic Ocean. Before the discovery of Eomonaco, monk seals had only been found in the Northern Hemisphere.

In fact, most of the monachine fossils are found in the north, although several living monks (Antarctic seals and elephant seals) live almost exclusively in the Southern Ocean.

The unexpected discovery of Eomonaco has completely reversed the evolutionary history not only of monk seals, but of all nuns, placing all three in the southern hemisphere for the first time.

Read more: Marine species are more threatened than we thought and we only looked at 3%

A monk seal from New Zealand

The recovery of the first known Eomonaco the fossils came in the form of seven skulls discovered along the Taranaki coast in New Zealand’s North Island. The fossils were recovered from local collectors and donated to the Te Papa Tongarewa and Canterbury museums.

Eventually our team named the species Eomonachus belegaerensis. This translates to “Belegaer Monk Seal of Dawn”. Belegaer is the fictional sea located west of “Middle-earth”, the land of JRR Tolkein’s The Lord of the Rings trilogy, often associated with New Zealand.

But what were monk seals doing in New Zealand three million years ago?

Well, in the past, the southern oceans were much warmer than they are today. And ancient monk seals, just like their modern relatives, lived in subtropical waters.

But until this year, few scientific studies of extinct nuns had been conducted in the southern hemisphere. This is probably why Eomonaco scientists eluded for so long.

Read More: In a land of ancient giants, these whimsical little seals once called Australia home

The evolution of the nuns

After the inauguration of Eomonaco, we have decided to reexamine the evolution of the nuns.

Our research indicates that this group of seals did evolve in the Southern Hemisphere, after all. This is in contrast to any theory previously advanced by scientists.

If there is indeed a southern origin for the nuns, this would mean that the group has crossed the equator at least eight times in its evolutionary history.

However, warm waters at the equator are widely accepted as a difficult thermal barrier for marine mammals to cross.

If the nuns of the past jumped between the two hemispheres, they would have had wide environmental tolerances that would have allowed them to do so. And this would have allowed their dispersion in the world.

It’s hard to say definitively whether modern seals share this trait, but we know they rarely cross the equator during their lifetime.

Climate change and seal extinction

So why don’t monk seals live around New Zealand now?

About 2.5 million years ago, the marine megafauna suffered an extinction event, thought to have been caused by a drop in sea level due to the decrease in global temperature.

Previous research has theorized that this change in climate spurred the extinction of many ancient seals in the Southern Hemisphere. This would have included Eomonaco, as well as other extinct nuns.

This suggests that the last two monk seal species in the world, vestiges of what was once probably a very widespread group, are also at risk from climate change.

If sea levels continue to rise, the beaches that monk seals rely on for rest and reproduction may disappear. Rising temperatures could also disrupt food webs, making it difficult for them to find food.

While the discovery of Eomonaco it’s exciting, it can also be considered a warning.