Two New 'Big-Mouthed' Fish: Discovery Triples Known Species

A rare discovery of dinosaur age fossil fish triples the number of known species belonging to the genus Rhinconichthys, a type of large-mouthed fish that swam the oceans 92 million years ago. 

Previously, there was only one known Rhinconichthys specimen, discovered in England in 2010. But a skull recently unearthed in Colorado and the re-examination of a fossil in Japan has upped that number to three.

"I was in a team that named Rhinconichthys in 2010, which was based on a single species from England, but we had no idea back then that the genus was so diverse and so globally distributed," Kenshu Shimada, a paleobiologist at DePaul University, said in a news release. 

Rhinconichthys belongs to an extinct group of bony fish called pachycormids, which contains the largest bony fish ever to have lived, researchers say. The two new species have subsequently been dubbed R. purgatoirensis (from Colorado) and R. uyenoi (from Japan). 

Like modern-day whale sharks, all three fish are equipped with expansive mouths to gulp down large amounts of plankton. However, unlike the larger whale shark, Rhinconichthys species measured only 6.5 feet in length. 

"Based on our new study, we now have three different species of Rhinconichthys from three separate regions of the globe, each represented by a single skull," Shimada noted in the university's release. "This tells just how little we still know about the biodiversity of organisms through the Earth's history. It's really mindboggling."

However, researchers are hopeful that more specimens will soon be uncovered. Their study was recently published in the journal Cretaceous Research.

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