Paleontologists have announced the discovery of an extraordinary fossil shark in Mexico. They describe Aquilolamna milarcae, a Late Cretaceous shark which was wider than long, with a curiosity slender pair of pectoral fins. This shark, far from a fierce bite, may have survived by eating plankton.
The team’s investigation was published today in Science. The authors believe A. milarcae it was a lamniform, the same order that today includes the great white shark and megamouth. But the Cretaceous shark looked completely different, with a wide mouth, flat head and 6 feet. wingspan reminiscent of rays. Although rays there are also elasmobranchs, the group of cartilaginous fish that also contain sharks and skates, A. milarcae precedes the appearance of his lookalikis, blanket and devil rays, for about 30 million years.
“Aquilolamna it is a shark; there is definitely no problem, “Romain Vullo, a paleontologist at the University of Rennes in France and lead author of the paper, said in a video call.” This lineage of sharks became extinct by the end of the Cretaceousnts. After that, the ecological niche became vacant and then a lineage of batoids — rays—evolved into manta rays “.
Vullo described the shark as a languid predator that, like other sharks, would have used his tail fin to propel itself through the shallow sea that occupied central North America. (This is another difference with respect to the rays, which wave their wing-like fins to reach from A to B.) After driving, A. milarcae he would have used those remarkable pectoral fins to make the marine equivalent of the delta gliding, coasting the seas, and perhaps swallowing the interposed plankton.
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“This is an exciting discovery” Kenshu Shimada, a professor of paleobiology at DePaul University in Chicago and an expert on ancient shark species, said in an email. “The exact taxonomic identity of this new shark is still questionable, but its body design, especially its exceptionally elongated paired pectoral fins, is unique not only within the order of Lamniform sharks, but also in the world of sharks. . “
It is not true that the shark was planktivivorous, but this is the hypothesis of Vullo and his team, based on the fact that the the fossil had no teeth. This is surprising, because most ancient sharks are identified only by their teeth, as they are better preserved. than the skin and cartilaginous skeleton. The team raises the possibility that A. milarcae or is a relative of or the same animal as Cretomanta, another elasmobranchi that it is only identified so far by its dentition.
“When you work on a single specimen, even if it’s very well preserved, you’re always missing some information, and here, the main information we’re missing is dentition,” Vullo said. “This is what I would like to answer: what was dentition Aquilolamna, and check if it is, in fact, Cretomanta“.
It is an idea of the Cretaceous Guess who?, where instead of eliminating fossil shark candidates, more come to the surface. While this would be a disaster for those who play the game, it is an advantage for paleontologists, who continue to learn more about the biodiversity of Earth’s prehistoric seas.