How Flying Fish First Took Off

Today's flying fish are famous for leaping into the air, gaining height from their long, wing-like fins. And now newfound fossils are providing insight into how these jumpers first took off, according to a new study.

Known as exocoetids, modern flying fish weren't the only ones that evolved gliding abilities, most likely to escape aquatic predators. An extinct species called thoracopterids, dating back 200 million years during the Triassic period, also boasted the gift of flight, possibly providing the missing link for studying modern flying fish.

"When the fish fossils were collected in the fieldwork, we had no idea what kind of fish this was," lead study author Guang-Hui Xu, a vertebrate paleontologist at China's Institute of Vertebrate Paleontology and Paleoanthropology in Beijing, told Live Science. "After painstaking specimen preparation in the lab by myself, taking about three months, I recognized that it was, unexpectedly, related to the ancestor of the thoracopterid flying fishes."

Measuring up to about two inches, Wushaichthys used to swim in the hotter surface waters of the ancient Palaeotethys Ocean approximately 235 million to 242 million years ago. Its small size probably made it easy prey for marine reptiles and large carnivorous fishes - though it likely did not rely on gliding to avoid being eaten, the study notes in the journal Biology Letters.

The remarkable ability to leap to extraordinary heights out of the water is a very energetically expensive strategy, and Wushaichthys lacked the bottom-heavy tail fin that later thoracopterids use to generate such power. What's more, the ancient thoracopterid ancestor was completely adorned with scales, a feature more modern thoracopterids lost that presumably helped improve their flight efficiency.

"Overwater gliding adaptations were gradual in nature," Xu explained.

Despite dramatic differences between extinct thoracopterids and living exocoetids, certain similarities in body shape can still help scientists shed light on the evolution of flight in modern flying fishes.

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