The speed at which spinosaur dinosaur teeth were replaced explains their overabundance at Cretaceous sites

Scientists have reevaluated fossil pine remains published by Viera and Torres in 1995 and found in a Lower Cretaceous site at Igea (La Rioja, Spain) in 1983. The remains represent a fragment of a left upper jaw belonging to a carnivorous dinosaur, in which 8 alveoli have been preserved. Using micro-CT techniques, they discovered the remains of multiple teeth developing simultaneously in one of these tooth cavities.

“We recognized up to three generations of teeth in the same alveolus: the functional tooth of the animal, another tooth that forms and that would replace the first, and the germ of one that would eventually replace the second,” explained Pablo Navarro of the UR.

“This indicates very rapid dentition and is probably one of the reasons why so many spinosaur teeth are found in the Iberian Peninsula during the Lower Cretaceous,” added the paper’s co-author.

To date, some species of spinosaurs — medium/large-sized carnivorous dinosaurs with elongated skulls and crocodile-like conical teeth — have been known to replace their teeth faster than other theropods in as little as two months (replacement rate estimated at 60-68 days); The research confirms that this is a trait shared across the group and provides clues as to how this change came about, ie it was made possible by the simultaneous development of multiple replacement teeth.

“Over the course of their lives, these animals grew new teeth that gradually replaced the original ones and caused them to fall out. This means that the same animal can produce multiple teeth,” said Pablo Navarro.

“These more or less conical and one centimeter large teeth were transported by rivers, accumulated in lake areas and petrified over time,” says the researcher. They are one of the most common vertebrate remains found in Lower Cretaceous (145 to 113 million years ago) Iberian sites.”

Although it is not known exactly why their teeth were replaced so often, it is believed that this meant they had a larger number of functioning teeth at all times. This was a distinct advantage when it came to withstanding the considerable effort required to hold down their prey by imprisoning it between their jaws.

In addition to these findings, research has allowed a clarification of the classification of the jaw under study: the experts do not assign it to the genus Baryonix, as previously thought, but to another species of spinosaurs very close to this one, an indeterminate baryonychid.

The paleontological studies conducted on Igea to date are significant due to the presence of numerous spinosaur skeletal remains, including partial skeletons belonging to multiple individuals. “The current research will allow us to improve our knowledge of the diversity of this unique group of carnivorous dinosaurs. It is likely that at least two different species are represented at the Igea sites,” said Erik Isasmendi and Xabier Pereda-Suberbiola, paleontologists in the UPV/EHU’s Department of Geology; Consequently, this Rioja site is one of the world’s leading sites for spinosaur research.

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