A new study led by Museum researchers provides evidence of an interchange between the Atlantic and Pacific oceans nine to 11 million years ago despite the ongoing formation of the Isthmus of Panama.

Catalina Pimiento measures a shark tooth
Lead researcher Catalina Pimiento measures a shark tooth at the Smithsonian Tropical Research Institute.

Florida Museum photo by Jeff Gage

Seeking to provide the most complete description to date of 10-million-year-old shark and ray fossils in an outcrop on the Caribbean side of Panama, the researchers identified species that today are restricted to the Pacific Ocean, suggesting the oceans were connected at the time. The study appears in the current issue of the Journal of Paleontology.

The research has significant implications for the evolutionary history of sharks and possibly other marine animals, said lead researcher Catalina Pimiento, a doctoral candidate at the Florida Museum of Natural History on the UF campus.

“In terms of sharks, it was an important connection because it allowed the species from the two oceans to migrate from one ocean to the other,” Pimiento said.

Because urban development is quickly making the sites inaccessible, researchers sought to identify all species of cartilaginous fish from the Gatun Formation of northern Panama, an outcrop of fossils that was once a shallow bay rich in marine life.

marine fossils on ground
The Gatun Formation was a shallow bay during the late Miocene and is now rich in marine fossils like shark and ray teeth.

Florida Museum photo by Jeff Gage

Scientists studied 800 specimens of shark and ray teeth from 15 localities in the area, and identified 26 species, four of which are extinct. A similar 1984 study in the same area identified just 14 species.

“Most of the sharks we see today were also around about 10 million years ago,” Pimiento said. “This has important implications for sharks’ evolutionary history. They have lived for millions of years without many important morphological changes.”

A 2010 study by the same team showed the area was once a nursery for Megalodon, the largest and most powerful shark in history. The current study suggests the area was also a nursery for a variety of other sharks and rays.

Jan Fischer, a vertebrate paleontologist and assistant curator at the Geoskop Urweltmuseum in western Germany who was not involved in the study, said the area was essential for the survival of shark species.

Pimiento examining a fossil shark tooth
Pimiento studies a shark tooth fossil in the northern Panamanian outcrop.

Florida Museum photo by Jeff Gage

“This study is also a robust evaluation of the ancient paleoenvironment,” Fischer said. “The amount of identified taxa is impressive.”

The study is part of the Panama Canal Project of the Partnerships for International Research and Education program, funded with a National Science Foundation grant. The international project is advancing knowledge of the extinct faunas and floras of the ancient Neotropics based on new fossil discoveries along the Panama Canal while it undergoes large-scale expansions.

Study co-authors include Gerardo Gonzalez-Barba of Museo de Historia Natural, Dana Ehret of the Alabama Museum of Natural History, Austin Hendy of the Florida Museum of Natural History and the Smithsonian Tropical Research Institute, Bruce MacFadden of the Florida Museum of Natural History and Carlos Jaramillo of the Smithsonian Tropical Research Institute.

Learn more about Vertebrate Paleontology at the Florida Museum.

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