The fossil shark Ptychodus was first recognized 190 years in the past, however within the intervening centuries of paleontological inquiry, a complete take a look at the traditional fish has been onerous to return by. Till now. In a paper published final week within the Proceedings of the Royal Society B, a staff of researchers describe an exceptionally well-preserved Ptychodus, fossilized from its nostril to the tip of its tail.
Of their analysis, the paleontologists analyzed six near-complete Ptychodus specimens excavated from Vallecillo, Mexico, over the past decade. The specimens reveal the sharks’ skeletal elements in addition to their preserved physique outlines. The staff used the fossils to find out new details about the sharks’ anatomy and their place within the shark household tree.
“This new research offers essential info on the affinities [evolutionary relations] and the paleoecology of Ptychodus,” stated Romain Vullo, a paleontologist on the College of Rennes in France and lead creator of the paper, in an e mail to Gizmodo. “Up to now, this Cretaceous shark was solely recognized from remoted enamel, dentitions [sets of teeth], and some skeletal parts corresponding to vertebrae.”
“The entire specimens from Mexico reveal that Ptychodus was a fast-swimming open water shark (related in form to the dwelling porbeagle), which seemingly used its grinding dentition to feed totally on ammonites and sea turtles,” Vullo added.
In 2021, Vullo was the lead creator on a paper describing Aquilolamna milarcae, a bizarre-looking Cretaceous era lamniform shark that was excavated from the identical sweep of jap Mexico. Within the latest paper, the staff additionally categorised Ptychodus as a lamniform—a mackerel shark—and posit that the animal’s extinction could have occurred as a consequence of competitors with mosasaurs, an extinct group of large marine reptiles.
However the actuality could also be extra sophisticated, as Tyler Greenfield, a paleontologist on the College of Wyoming, defined to Gizmodo. As an alternative of being a mackerel shark, Greenfield suggests Ptychodus belongs to a completely totally different class.
“Sharks of the order Lamniformes have particular patterns of the configurations and dimensions of the enamel, the hole sections within the jaws that maintain the rows of enamel, and the cartilage buildings contained in the vertebrae that Ptychodus doesn’t have,” Greenfield, who will not be affiliated with the brand new paper, wrote in an e mail. “These options have been missed by the authors of the brand new paper and so they as an alternative used sure traits of the skull and jaws, which aren’t distinctive to lamniforms, to categorise Ptychodus.”
Greenfield added that, primarily based on similarities between Ptychodus and each Squalicorax and Ptychocorax (two different species of historical shark), the shark household together with Ptychodus and the one together with the latter two species should be positioned in a separate order, Anacoraciformes, or crow sharks.
“Anacoraciformes was named by different authors earlier than me, nevertheless it has not been used as legitimate since then nor has it included ptychodontids till now,” Greenfield stated, including that the enamel constructed for crushing shelled prey would seemingly have advanced outdoors of Lamniformes. “General, my speculation seeks to construct a extra correct image of the relationships and variety of prehistoric sharks,” Greenfield stated.
One would possibly assume that such immaculately preserved fossils would settle points of the shark’s phylogeny, not complicate it. However no matter how the mud settles relating to Ptychodus’ classification, it’s refreshing—and certainly, extremely lucky—that paleontologists have such well-preserved specimens to make use of in making their determinations.
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