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Living true seals are the most dispersed semi-aquatic marine mammals and comprise geographically separate northern and southern groups. Both are thought to have evolved in the North Atlantic, with only two lineages subsequently crossing the equator. The third and oldest lineage, the monk seals, have been interpreted as exclusively northern and subtropical throughout their history. However, an international team of paleontologists now describes a new extinct monk seal species that lived during the Pliocene epoch in New Zealand, the first of its kind from the Southern Hemisphere.
The impression of an artist Eomonachus belegaerensis. Image credit: Jaime Bran / Te Papa Museum.
The newly identified monk seal species lived in the waters around New Zealand about 3 million years ago.
Named Eomonachus belegaerensis, the marine creature was about 2.5 m (8.2 ft) long and has a mass of between 200 and 250 kg.
“This new extinct monk seal species is the first of its kind from the Southern Hemisphere. His discovery really reverses the evolution of seals, ”said lead author James Rule, Ph.D. candidate at Monash University’s Biomedicine Discovery Institute and Museums Victoria.
“Until now, we thought that all true seals originated in the Northern Hemisphere and then cross the equator only once or twice during their entire evolutionary history.”
“Instead, many of them appear to have evolved in the South Pacific, and then crossed the equator up to eight times.”
The well-preserved specimens of Eomonachus belegaerensis. Image Credit: Rule et al.
Rule and his colleagues from 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 southern beaches of Taranaki in New Zealand between 2009 and 2016.
“This discovery was a triumph for citizen science,” said co-author Dr. Felix Marx, a marine mammal curator at the Te Papa Tongarewa Museum of New Zealand and a researcher in the University of Geology Department. Otago.
“This new species was discovered thanks to several exceptionally well-preserved fossils, all found by members of the public.”
“Our results suggest that true seals have crossed the equator more than eight times in their history,” concluded the paleontologists.
“Overall, they are more than twice the age of the north-south dichotomy that characterizes true living seals and confirms a surprisingly recent major change in the diversity of true southern seals.”
The discovery is reported in an article from 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 real seals. Proc. R. Soc. B 287 (1938): 20202318; doi: 10.1098 / rspb.2020.2318
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