Full fossils from an infinite shark that lived alongside the dinosaurs reveal essential details about this enigmatic predator — together with it being an historic relative of the nice white shark.
The sharks, from the genus Ptychodus, have been first found within the mid-eighteenth century. Descriptions of this genus have been largely based mostly on their enamel — which may very well be almost 22 inches (55 centimeters) lengthy and 18 inches (45 cm) extensive, and have been tailored for crushing shells — present in quite a few marine deposits courting to the Cretaceous interval (145 million to 66 million years in the past).
With out the power to look at a completely intact specimen, researchers had hotly debated what the shark’s physique form may appear to be — till now.
“The invention of full Ptychodus specimens is admittedly thrilling as a result of it solves some of the hanging enigmas in vertebrate paleontology,” lead creator Romain Vullo, a researcher at Géosciences Rennes, advised Reside Science in an electronic mail.
In a research revealed Wednesday (April 24) within the journal Proceedings of the Royal Society B: Organic Sciences, researchers have described full fossils of the shark found in limestone quarries in Nuevo León, northeastern Mexico. Its define was nonetheless absolutely preserved, and its physique form suggests it hunted sea turtles — which might clarify its extinction round 76 million years in the past because it was competing with different animals that ate the identical prey.
The specimens “present an beautiful preservation,” as a result of they have been deposited in a quiet space with no scavengers, Vullo mentioned. “The carcasses of animals have been quickly buried in a mushy lime mud earlier than being fully disarticulated.”
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Evaluation of the fossils reveals this massive predator belonged to the mackerel shark group (Lamniformes), which incorporates nice whites (Carcharodon carcharias), mako, and salmon sharks. It grew to round 33 ft (10 meters) lengthy and is understood for its huge, grinding enamel, that are not like these we see in sharks at present.
It was broadly believed that Ptychodus ate up invertebrates from the seabed — the traditional kin of clams and mussels. However the brand new fossils problem that, revealing that this historic shark had a streamlined physique form, indicating it was a fast-swimming pelagic predator. “The newly found fossils from Mexico point out that Ptychodus seemed just like the dwelling porbeagle shark,” Vullo mentioned, however with “distinctive grinding dentition.”
This new data has led the researchers to consider it preyed on massive ammonites — a kind of crustacean with a tough shell — and sea turtles.
“Ptychodus occupied a particular ecological area of interest in Late Cretaceous seas,” Vullo mentioned, as a result of it was the one pelagic shark that was tailored to consuming hard-shelled prey akin to turtles. This may occasionally clarify why it died out round 10 million years earlier than the extinction occasion that ended the Cretaceous interval. “Towards the tip of the Cretaceous, these massive sharks have been probably in direct competitors with some marine reptiles (mosasaurs) concentrating on the identical prey,” he mentioned.
