Scientists have discovered remarkably preserved ancient shark fossils. The findings have revealed what the species could have looked like and why it ended up becoming extinct.
Ancient Shark Fossils
The full fossils of the ancient shark that used to live alongside dinosaurs offer important information pertaining to this predator, including its links with great white sharks.
This shark belongs to the Ptychodus genus and was first found during the mid-18th century. The genus' descriptions were largely grounded on their teeth, which could have been almost 45 centimeters wide and 55 centimeters long. Their teeth were used for shell-crushing and spotted in various marine deposits from the Cretaceous period around 145 to 66 million years ago.
Researchers have been debating the potential body shape of the shark because they cannot examine the fully intact specimen. Now, the discovery of complete ancient shark fossils could solve a long-standing, enigmatic mystery in the field of vertebrate paleontology.
The shark fossils were found in limestone quarries in Nuevo Leon, northeastern Mexico. The outline remained wholly preserved. Its body shape also suggests that it was a sea turtle hunter, which may explain how it got extinct roughly 76 million years ago, as it had other animal competitors for the same prey.
Romain Vullo, the study's lead author and a researcher from Geosciences Rennes, explains that the fossils were exquisitely preserved. They were placed in an area without scavengers. Before the carcasses were fully disarticulated, they were buried in soft lime mud.
Preying on Hard-Shell Creatures
Fossil analysis revealed that the massive predator was part of the Maniformes mackerel shark group, which covers mako, salmon, and great white sharks. It spanned up to 10 meters in length and is known to have grinding and huge teeth that are not similar to what can be seen in sharks today.
It was largely thought that Ptychodus feasted on seabed invertebrates. However, new fossils have challenged such claims, revealing that the ancient species had a streamlined body shape and was a pelagic predator that swam fast.
Vullo explains that the newfound fossils show that Ptychodus resembled a porbeagle shark with a distinct grinding dentition.
This has led scientists to think that the ancient shark preyed on sea turtles and large ammonites, a kind of hard-shelled crustacean. This confirms a lifestyle that is more actively nektonic, which was previously suggested based on the morphological features of placoid scales and vertebral centra.
Vullo notes that Ptychodus had a special ecological niche in the seas of the Late Cretaceous period. This is due to how the sole pelagic shark adapted to the consumption of hard-shelled prey. This could shed light on why it ended up dying out roughly 10 million years prior to the extinction event that marked the end of the Cretaceous period. Vullo notes that towards the end of this period, it is likely that these sharks directly competed with other marine reptiles that aimed for the same prey.
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