Panama Canal Expansion: A New Era for Diverse Bats

The Panama Canal is not only a marvel of engineering, but also a treasure trove of paleontology. The recent expansion of the canal has exposed new fossils of leaf-nosed bats, a group of mammals that boasts more than 200 species with diverse diets and adaptations. These fossils are the oldest-known leaf-nosed bat fossils from Central America, dating back to 20 million years ago, when Panama was separated from South America by a wide seaway. They also challenge the prevailing idea that leaf-nosed bats originated in South America and diversified there before colonizing other regions.

A northern origin for leaf-nosed bats?

Leaf-nosed bats are named for the elaborate nose-leaf structures on their faces, which help them echolocate their prey or food sources. They are among the world’s most ecologically diverse mammals, with species that feed on insects, nectar, fruit, pollen, blood, frogs, birds, lizards and even other bats. They are mostly found in tropical and subtropical regions of the Americas, from Canada to Argentina.

It was long thought that leaf-nosed bats evolved in South America, where they had little competition from other bats and could exploit a variety of niches. However, the new fossils suggest that this may not be the case. The fossils belong to a new extinct species of leaf-nosed bat that is closely related to the big-eared woolly bat (Chrotopterus auritus), one of the largest bats in Panama today. The extinct bat lived 20 million years ago, when Panama was still part of North America and isolated from South America by a seaway that was at least 120 miles wide.

“We think they may have had a northern origin,” said Gary Morgan, curator of vertebrate paleontology at the New Mexico Museum of Natural History and lead author of the study published in the Journal of Mammalian Evolution. “They may have evolved in North America or even farther north and then dispersed southward.”

A once-in-a-century opportunity for fossil discovery

The fossils were discovered during the Panama Canal expansion project, which began in 2007 and involved widening and deepening the canal to accommodate larger ships. The project also offered a rare opportunity for paleontologists to access the canal banks, which contain layers of sedimentary rocks that preserve a rich record of ancient life.

“The canal cuts through a sequence of rocks that span about 20 million years,” said Bruce MacFadden, curator of vertebrate paleontology at the Florida Museum of Natural History and co-author of the study. “It’s a window into the past that we don’t get anywhere else in Central America.”

The researchers collected thousands of fossil fragments from the rubble left by the dynamite blasts. Among them were two jaw pieces of the extinct leaf-nosed bat, which were identified by their distinctive teeth. The teeth indicate that the bat was probably an insect-eater or a carnivore, similar to its living relative.

The fossils also shed light on one of the most important events in the history of American biogeography: the Great American Biotic Interchange. This was a massive exchange of animals and plants between North and South America that occurred after the formation of the Isthmus of Panama about 5 million years ago. The isthmus acted as a land bridge that allowed animals like sloths and armadillos to migrate northward, while horses, tapirs, bears and elephants moved southward.

The leaf-nosed bat fossils show that some groups of animals were already moving between the continents before the isthmus was complete. The researchers suggest that leaf-nosed bats may have crossed the seaway by island-hopping or flying over short stretches of water.

“The Panama Canal fossils reveal a hidden chapter in the history of biodiversity in the Americas,” MacFadden said. “They show us how ancient animals responded to changes in geography and climate over millions of years.”

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