Paleontologists have long thought of the coelacanth  as a stodgy old slowpoke: Two modern-day species of the fish—considered living fossils because of their remarkable similarity to ancient coelacanths—typically swim in a slow, almost dawdling manner. As a group, coelacanths had apparently kept the same basic body plan for hundreds of millions of years. But now, researchers have found fossils of a sleeker coelacanth —one that likely was a speedy, shark-like predator in the ancient seas west of the supercontinent Pangaea about 240 million years ago. Unlike all previously known specimens, which have fleshy, three-lobed tails fringed with flexible fins, the new species (artist's reconstruction shown) had a stiff, crescent-shaped tail like modern-day tuna and barracuda, both of which are famed for their speed. The team has dubbed the new species Rebellatrix divaricerca, "the rebel coelacanth with the forked tail." Although more streamlined than previously known coelacanths, Rebellatrix, which the researchers estimate grew to reach at least 1.3 meters in length, was more thick-bodied than today's tuna and, therefore, probably slower. The new specimens, described in the May Journal of Vertebrate Paleontology, may mark the first species in a yet-to-be-discovered trove of coelacanth diversity, the researchers say. Or, the Corvette of coelacanths may have evolved to fill an ecological niche left vacant when more than 95% of the ocean's species disappeared in a mass extinction about 252 million years ago.
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