[ad_1]
A new species of shark with thin and hypertrophied pectoral fins has been identified from fossilized remains discovered in northern Mexico.
Reconstruction of life of Aquilolamna milarcae. Image credit: Oscar Sanisidro.
The recently identified species of shark, called Aquilolamna milarcae, swam in the oceans of the Upper Cretaceous, approximately 93 million years ago.
“The complete specimen was found in 2012 in Vallecillo, Mexico, a locality that produces remarkably preserved fossils,” said lead author Dr. Romain Vullo of the University of Rennes and the CNRS and colleagues.
“This site, already famous for its many fossils of ammonites, bony fish and other marine reptiles, is very useful for documenting the evolution of ocean animals.”
Aquilolamna milarcae belongs to Lamniformes, an order of sharks of the subclass Elasmobranchii.
“Elasmobranchs are the most successful group of cartilaginous fish, including sharks, rays and rays,” the 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 functions.”
“Modern plankton-eating elasmobranchs are characterized by two distantly related clades: those with a more ‘traditional’ shark-like body shape, such as whale and basking sharks, and those with smooth, flattened bodies and shark fins. wing-shaped fins of the Mobulidae stripes. “
“Standing out among planktivorous sharks and rays (that eat plankton) both living and fossil, Aquilolamna milarcae resides somewhere in between. “
Fossil of Aquilolamna milarcae found in limestone from Vallecillo, Mexico. Image credit: Wolfgang Stinnesbeck.
Aquilolamna milarcae it had many features similar to modern stingrays, notably long, slender fins and a mouth adapted for filter feeding, suggesting that it was planctivorous.
“It had a tail fin with a well-developed upper lobe, typical of most pelagic sharks, such as the whale shark and the tiger shark,” said Dr. Vullo.
“Therefore, its anatomical features give it a chimerical look that combines sharks and rays.”
“With its large mouth and supposedly very small teeth, it must have fed on plankton.”
Aquilolamna milarcae It was a relatively slow swimmer, using both its long pectoral fins and its tail to glide through the water while collecting suspended plankton using its large open mouth.
“His body plan represents an unexpected evolutionary experimentation with underwater flight among sharks, more than 30 million years before the emergence of Mobulidae rays, and shows that wing-shaped pectoral fins have evolved independently in two distant clades of filter-feeding elasmobranchs, “the researchers say. saying.
The discovery of Aquilolamna milarcae is reported in an article in the magazine Sciences.
_____
Romain Vullo et al. 2021. Planktivorous manta-like sharks in the Upper Cretaceous oceans. Sciences 371 (6535): 1253-1256; doi: 10.1126 / science.abc1490
