The rate at which spinosaurid dinosaur teeth were replaced explains their overabundance at Cretaceous sites

This was confirmed in the article ‘New contributions to the skull anatomy of spinosaurid theropods: Baryonychinae maxilla from the Early Cretaceous of Igea (La Rioja, Spain) ‘ published in the journal Historical Biology by Iker Isasmendi (main author) and Xavier Pereda of the UPV/EHU-University of the Basque Country, Pablo Navarro of the UR-University of La Rioja, Angélica Torices, director of the Chair of Paleontology of the UR, as well as other industry experts from the Complutense University of Madrid and the Paleontological Visitor Center of La Rioja.

The scientists have re-evaluated fossil jawbone remains published by Viera and Torres in 1995 and found in 1983 in a Lower Cretaceous web-site in Igea (La Rioja, Spain). The remains constitute a fragment of a left jawbone belonging to a carnivorous dinosaur and in which 8 cells have been preserved. Using microCT procedures, they discovered the remains of several teeth growing simultaneously in one of these tooth sockets.

“Up to three generations of teeth in the same cell: the animal’s functional tooth, another developing tooth that would replace the first, and the germ of the one that would eventually replace the second”, explains Pablo Navarro. from UR.

“This suggests a very rapid tooth replacement and is probably one of the reasons why so many spinosaurid teeth can be found in the Iberian Peninsula during the Lower Cretaceous,” the paper’s co-author added. elongated skulls and conical crocodile-like teeth – were known to replace their teeth faster than other theropods, in just two months (estimated replacement rate of 60-68 days) research confirms that this is a trait shared by the entire group and provides evidence of how this change occurred, that is, it was made possible by the development of several replacement teeth at the same time.

“Throughout of their lives, these animals have developed new d ents which gradually replaced the original ones and brought them down. This means that the same animal can generate several teeth”, said Pablo Navarro.

“These teeth, of more or less conical shape and a size of one centimeter , were transported by rivers, accumulated in lake areas and, over time, became fossilized”, explains the researcher. They are one of the most common vertebrate remains in Lower Cretaceous Iberian sites (between 145 and 113 tens of millions of years).”

Although it is not known precisely why their teeth were replaced so often, it is believed that it allowed them to have a greater number of functioning teeth at all times. It was a decisive advantage compared to the considerable effort necessary to retain its prey by trapping it between its mouth.

In addition to these discoveries, research has made it possible to clarify the classification of the jaw studied: the gurus do not attribute it, as previously thought, to the genus Baryonix, but to another type of spinosaurid very close to this one, an indeterminate baryonychid..

The paleontological studies carried out to date in Igea are important due to the presence of numerous skeletal remains of spinosaurs, including partial skeletons belonging to several individuals. “Ongoing research will improve our knowledge of the diversity of this distinctive group of carnivorous dinosaurs. It is possible that at least two different species are represented at the Igea sites”, said Erik Isasmendi and Xabier Pereda-Suberbiola, paleontologists at the Department of Geology of the UPV/EHU therefore, this locality of Riojan is one of the world’s leading web-sites in the study of spinosaurs.


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