An artist's impression of a Ngamugawi virngarri coelacanth in its natural habitat. (Image credit: Katrina Kenny)
Ancient fish that were thought to be “living fossils” and had not changed much since the age of dinosaurs are actually evolving at a surprising rate – and their evolution accelerated during periods of more rapid continental movement, as shown by the fossil remains of a newly discovered species of coelacanth.
The study suggests that large-scale movement of continents may have driven the evolution of life, researchers reported Thursday (Sept. 12) in the journal Nature Communications.
Coelacanths are large fish that evolved about 410 million years ago. When they were known only from fossils, they were thought to be extinct until a fisherman in South Africa caught one in 1938. The modern coelacanth was called a “living fossil” and was thought to have changed little in millions of years.
The two extant species of coelacanth, Latimeria chalumnae and Latimeria menadoensis, are more closely related to other ancient fishes such as lungfish than to modern ray-finned fishes.
But the new “bridge” fossils show that coelacanths never stopped changing. The fossils, beautifully preserved in three dimensions, provide some of the best anatomical data ever on the coelacanth. Combined with other coelacanth fossils, the discovery suggests that the more active the geological environment, the more evolutionary change the fish underwent.
“Surprisingly, plate tectonic activity has had a significant impact on the pace of coelacanth evolution throughout their 400-million-year history,” says study first author Alice Clement, an evolutionary biologist at Flinders University in Australia.
The newly identified coelacanth, Ngamugawi wirngarri, was found in the Kimberley region of northwestern Australia. Today, it’s a tropical area where the landscape ranges from mountains to grasslands. But 385 million years ago, it was a thriving reef system with at least 50 species of fish, Clement told Live Science. “In a sense, it was Australia’s first major barrier reef, extending hundreds of kilometers offshore,” she added.
Two specimens of the new coelacanth species were first discovered in 2008. They were the first coelacanths from the region, Clement said, so the researchers knew they had something unique. But it took several years to prepare the fossils and analyze the finds.
Coelacanth skull bones
Sourse: www.livescience.com
