Fish's Long Extendable Jaws Trace Back To 100 Million Years Ago

Researchers were able to trace the evolution behind the long extendable jaws that many fish possess, according to a recent study at James Cook University in Australia.

Most fish rely on their protruding (long extendable) jaws when they are catching prey. These protruding jaws quickly extend to reach and snap closes on their prey. Researchers are now exploring fish's 400-million-year history to trace its evolution of jaw protrusion, and they found that this evolution trait started about 100 million years ago, according to a news release.

"We take it for granted that all fishes can snap up elusive prey. But it wasn't like that millions of years ago," said David Bellwood of James Cook University.

By assessing the jaws of 60 living fish species, the researchers found were able to develop a method to predict fish's jaw protrusion ability based on a simple anatomical measurement. It was then possible for the researchers to predict jaw protrusion in long-lost fish of the ancient past, according to the study.

"We knew that most modern fishes could protrude their jaws," said Christopher Goatley, co-author of the study, at James Cook University. "The question was, when did this ability arise, and what anatomical features were required for protrusion?"

The researchers found that "one simple measurement of one jawbone explained almost everything." This allowed them to predict how fish feed presently and how they fed in the past, over 400 million years ago.

The researchers discovered that once the protruding jaws existed, it became more developed and fishes became superior predators over time. The proportion of fishes with jaw protrusion increased, thus spiny-rayed fishes dominated other groups and the extent of the jaw protrusion in the spiny-rayed fishes continued to increase, according to the study.

The findings revealed that this trait have played an essential role in the success of the spiny-rayed fishes in modern oceans, making them a dominant species. Their extendable jaws made prey species vulnerable to attack, according to the researchers.

"We think that over evolutionary time this drove prey to hide by becoming smaller, nocturnal, or hiding in holes," said Bellwood.

"There have been major changes in the abilities of fish to feed over time. The key to understanding this history is in the workings of a fish's head," Bellwood said. 

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