Shortly earlier than a mass extinction ended the Age of Dinosaurs, a reptilian, barracuda-like carnivore with a mouth like a field cutter patrolled the nice and cozy seas that when lined swaths of what’s now North Africa. A not too long ago described fossil of the ocean-dwelling beast reveals that its chunk was not like that of any of its kinfolk, within the water or onshore.
The animal was a mosasaur, an extinct, marine reptile associated to snakes and monitor lizards. Mosasaurs generally had piercing, conical enamel for gripping slippery prey or flat, crushing enamel for smashing hard-shelled animals. However this new selection had brief, serrated, squarish blades, packed tightly in collection to kind a knife’s leading edge. This mouth of razors is exclusive amongst mosasaurs, and even throughout the entirety of the tetrapod lineage, largely landlubbing vertebrates that embody amphibians, reptiles, birds and mammals.
The invention, described January 16 in Cretaceous Analysis, means that mosasaurs had been evolving experimental bodily traits and existence proper up till their abrupt extinction 66 million years in the past.
Phosphate miners in Morocco discovered the curious fossil: a piece of higher jaw studded with enamel. The jaw got here from a mosasaur dwelling on the very finish of the Cretaceous Interval. Many mosasaurs had been huge predators, some stretching longer than a faculty bus. However this fossil belonged to an animal simply over a meter lengthy, Nick Longrich, a paleontologist on the College of Tub in England, and his colleagues decided.
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Longrich says the animal’s small dimension is attention-grabbing, however that’s not what caught his eye. “These enamel are simply not like something I’ve seen in a lizard earlier than,” Longrich says. The crew named the mosasaur Xenodens calminechari — Xenodens means “unusual tooth;” calminechari is Arabic for “like a noticed.”
Longrich says the closest match for X. calminechari’s enamel look like these of modern-day dogfish sharks, which might “reduce giant bolts of flesh out as they scavenge,” he says. “Most likely these slicing enamel allowed it to course of an enormous vary of meals,” says Longrich, noting that dogfish sharks use their enamel to cut up all the pieces from fish to sea anemones. Regardless of its small dimension, X. calminechari could have been in a position to prey upon fairly giant animals or scavenge their stays, because it shared its watery dwelling with large fish and cephalopods, in addition to orca-sized, long-necked plesiosaurs.
The fossilized jaw of Xenodens calminechari was lined with a battery of slicing enamel much like razor blades, proven right here from the perimeters (high and center picture) and knife edge (backside picture) of the enamel.Nick LongrichThe fossil is “fully weird,” says Paulina Jiménez-Huidobro, a paleontologist on the College of Bonn in Germany not concerned with this analysis, noting the enamel could have been used to “slice and cube” crustaceans, shell and all.
She has doubts concerning the comparability to shark feeding strategies and food regimen primarily based solely on the tooth form, although, due to basic variations between how sharks and mosasaurs chunk prey. Shark enamel reduce into flesh on jaws that stretch outwards in the direction of prey independently of the cranium.
“This mechanism doesn’t happen in mosasaurs, even when Xenodens has a shark-like tooth form,” Jiménez-Huidobro says. “No lizard can try this.”
For Longrich, X. calminechari’sdiscovery helps paint an image of the late Cretaceous’ tropical seas as teeming with biodiversity earlier than a dinosaur-era-ending asteroid hit Earth (SN: 6/17/20). The ocean ecosystem was thriving on the time, so there could have been dozens of mosasaur species in a single habitat, he says, they usually weren’t carried out producing bizarre prototypes like Xenodens.
“The mosasaurs had been nonetheless experimenting with new methods of feeding, new morphologies, new existence simply earlier than that asteroid got here down,” Longrich says.
Studying extra about this nimble, barracuda-like sea lizard will reveal extra of the evolutionary experimentation occurring on the time, however gaining that perceive requires the invention of extra fossil materials, which may take some time, Longrich says. In half a dozen years of looking, he’s seen just one fossil of this species.
“Finally one thing has to show up, nevertheless it’s a ready sport.”