It swam slowly through the seas with a tail fin resembling those of modern sharks and side fins that stretched outward like the wings of modern birds. It's no wonder, then, that this bizarre creature, which died in what is now Mexico some 93 million years ago, has been dubbed the eagle shark. It's especially fitting as the pectoral fins on this specimen—the first of its kind to be found—gave it a "wingspan" of about 6.2 feet, which eclipsed its 5.4-foot length, lead researcher Romain Vullo of France's National Center for Scientific Research and the University of Rennes tells Live Science. A quarry worker discovered the shark's fossilized skeleton and soft tissue imprints in a slab of limestone in Mexico's Nuevo León state, which was once part of a vast inland sea, in 2012. The species is called Aquilolamna milarcae, or eagle shark of the Milarca Museum, where the fossil will be displayed.
It would've had "a unique chimeric appearance," says Vullo. But though it's classified as a shark, the eagle shark looked more like some type of ray than a great white. The fossil shows no sign of pelvic or dorsal fins—or teeth. "This previously unknown body plan represents an unexpected evolutionary experimentation with underwater flight among sharks, more than 30 million years before the rise of manta and devil rays," reads the study published Thursday in Science. Per Live Science, modern plankton-eating elasmobranchs (fish with skeletons made of cartilage) form two groups: those with traditional shark bodies and those with flatter bodies, like rays. The eagle shark is not an ancestor to rays, but was likely a wide-mouthed filter feeder that dined on plankton, as rays do today. Vullo tells AFP that rays replaced eagle sharks after most species died out around 66 million years ago. (Read more discoveries stories.)