San José, Costa Rica, since 1956

Unusual Fossil Found in Southern Pacific Region

A recent find by Costa Rican scientists in the country’s southwest coastal region has set a new record for the oldest land mammal found in Costa Rica: the extinct Desmostylus hesperus, a large, amphibious animal related to today’s elephants and manatees, between five and seven million years old.

Geologists Ana Lucía Valerio and César Laurito, who is also a paleontologist, recently found a fossilized tooth just over two centimeters wide from what they believe was an infant D. hesperus, according to the daily La Nación. The tooth’s unusual structure, made up of several columns, allowed the scientists to identify the animal to which it belongs.

Two U.S. specialists in the species have confirmed the find, the daily reported. It serves as the first evidence that the animal lived in tropical regions; the other fossils of this species have been found in Japan, Siberia,Mexico’s Baja California, and the U.S. states of Oregon and California. The order to which the species belongs, Desmostylia, was first described in 1888 by Othniel Charles Marsh of the United States.

Laurito said the massive herbivores, 1.8 meters long and 1.5 meters tall, may have traveled to Costa Rica on a cold ocean current. The animals spent much of their time in the water, mostly in estuaries, aided by membranes between their toes.

The tooth was found during an excavation in January that was part of Valerio and Laurito’s research, sponsored by the NationalMuseum. They’ve also found fossils of what appear to be turtles, giant armadillos, crocodiles, fish and other prehistoric creatures, and plan to publish a report on the D. hesperus in the University of Costa Rica’s Central American Geological Magazine.


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