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True live seals are the most dispersed semi-aquatic marine mammals and include geographically separate groups from the north and south. Both are believed to have evolved in the North Atlantic, with only two lineages crossing the equator thereafter. The third and oldest lineage, the monk seals, has been interpreted as exclusively Nordic and subtropical throughout their history. However, an international team of paleontologists are now describing a new species of extinct monk seal that lived during the Pliocene era in New Zealand – the first of its kind in the southern hemisphere.
An artist’s impression of Eomonachus belegaerensis. Image credit: Jaime Bran / Te Papa Museum.
The newly identified monk seal species lived in the waters around New Zealand around 3 million years ago.
Appointed Eomonachus belegaerensis, the sea creature was about 2.5 m (8.2 feet) long and weighed between 200 and 250 kg.
“This new species of extinct monk seal is the first of its kind in the southern hemisphere. Its discovery really changes the evolution of the seal, ”said lead author James Rule, Ph.D. candidate for the Biomedicine Discovery Institute at Monash University and Victoria Museums.
“Until now, we thought that all true seals came from the northern hemisphere and then crossed the equator once or twice in their entire evolutionary history.
“Instead, a lot of them seem to have evolved in the southern Pacific, then crisscrossed the equator up to eight times.”
The well-preserved specimens of Eomonachus belegaerensis. Image Credit: Rule et al.
Rule and his colleagues in New Zealand, Australia and the United States examined seven well-preserved specimens of Eomonachus belegaerensis – including a complete skull – found by local fossil hunters on the beaches of southern Taranaki in New Zealand between 2009 and 2016.
“This discovery was a triumph for citizen science,” said co-author Dr. Felix Marx, curator of marine mammals at the New Zealand Museum Te Papa Tongarewa and researcher in the Department of Geology at the University of Otago. .
“This new species was discovered thanks to many exceptionally well-preserved fossils – all of which have been found by members of the public.”
“Our results suggest that true seals have crossed the equator more than eight times in their history,” paleontologists concluded.
“Overall, they are more than double the age of the north-south dichotomy that characterizes live true seals and confirms a surprisingly recent major change in the diversity of southern true seals.
The discovery is reported in an article in Proceedings of the Royal Society B: Biological Sciences.
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James P. Rule et al. 2020. The first monk seal in the southern hemisphere rewrites the evolutionary history of true seals. Proc. R. Soc. B 287 (1938): 20202318; doi: 10.1098 / rspb.2020.2318
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