The fossil shark Ptychodus was first recognized 190 years in the past, however within the intervening centuries of paleontological inquiry, a complete have a look at the traditional fish has been exhausting to come back 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, during the last decade. The specimens reveal the sharks’ skeletal parts 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,” mentioned Romain Vullo, a paleontologist on the College of Rennes in France and lead writer of the paper, in an electronic mail to Gizmodo. “Thus far, this Cretaceous shark was solely recognized from remoted tooth, 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 doubtless used its grinding dentition to feed totally on ammonites and sea turtles,” Vullo added.
In 2021, Vullo was the lead writer 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 current paper, the staff additionally labeled Ptychodus as a lamniform—a mackerel shark—and posit that the animal’s extinction might have occurred on account 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 completely different class.
“Sharks of the order Lamniformes have particular patterns of the configurations and dimensions of the tooth, the hole sections within the jaws that maintain the rows of tooth, and the cartilage buildings contained in the vertebrae that Ptychodus doesn’t have,” Greenfield, who shouldn’t be affiliated with the brand new paper, wrote in an electronic mail. “These options had been neglected by the authors of the brand new paper and so they as a substitute used sure traits of the skull and jaws, which aren’t distinctive to lamniforms, to categorise Ptychodus.”
Greenfield added that, based mostly 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 must 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 mentioned, including that the tooth constructed for crushing shelled prey would doubtless have developed outdoors of Lamniformes. “General, my speculation seeks to construct a extra correct image of the relationships and variety of prehistoric sharks,” Greenfield mentioned.
One may 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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