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A new species of shark with enlarged and slender pectoral fins has been identified from fossilized remains found in northern Mexico.
Reconstruction of the life of Aquilolamna milarcae. Image credit: Oscar Sanisidro.
The newly identified shark species, named Aquilolamna milarcae, swam in the oceans of the Late Cretaceous, about 93 million years ago.
“The complete specimen was found in 2012 in Vallecillo, Mexico, a locality producing remarkably preserved fossils,” said lead author Dr Romain Vullo of the University of Rennes and the CNRS and his colleagues.
“This site, already famous for its numerous fossils of ammonites, bony fishes and other marine reptiles, is very useful for documenting the evolution of oceanic animals.”
Aquilolamna milarcae belongs to Lamniformes, an order of sharks in the subclass Elasmobranchii.
“Elasmobranchs are the very successful group of cartilaginous fish, including sharks, skates and rays,” paleontologists said.
“They first appeared in Earth’s oceans about 380 million years ago and have since evolved to fulfill a wide range of ecological roles.”
“Modern plankton-feeding elasmobranchs are characterized by two distant clades – those with a more ‘traditional’ shark-like body shape, such as whales and basking sharks, and those with smooth, flattened bodies and winglets. Mobulidae rays. “
“To stand out among living and fossil planktivorous sharks and rays (plankton eaters) Aquilolamna milarcae lies somewhere in between. “
Fossil Aquilolamna milarcae found in limestone from Vallecillo, Mexico. Image credit: Wolfgang Stinnesbeck.
Aquilolamna milarcae exhibited many characteristics similar to modern manta rays, including long, slender fins and a mouth suitable for filter feeding, suggesting that she was planktivorous.
“It had a caudal fin with a well-developed upper lobe, typical of most pelagic sharks, such as whale sharks and tiger sharks,” Dr Vullo said.
“Thus, its anatomical characteristics give it a chimerical appearance that associates both sharks and rays.
“With his big mouth and supposedly very small teeth, he must have fed on plankton.
Aquilolamna milarcae was a relatively slow swimmer, using both his long pectoral fins and tail to glide through the water while scooping up hanging plankton using his large gaping mouth.
“His body plan represents an unexpected evolutionary experiment with underwater flight in sharks, more than 30 million years before the rise of the Mobulidae rays, and shows that the wing-shaped pectoral fins evolved independently in two clades. distant from filter-feeding elasmobranchs, ”the researchers mentioned.
The discovery of Aquilolamna milarcae is reported in a newspaper article Science.
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Romain Vullo et al. 2021. Manta-type planktivorous sharks in the oceans of the Late Cretaceous. Science 371 (6535): 1253-1256; doi: 10.1126 / science.abc1490
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