Histology of spinosaurid dinosaur teeth from the Albian-Cenomanian of Morocco: Implications for tooth replacement and ecology

Abstract

High numbers of spinosaurid teeth found in Morocco suggest that this clade was very abundant during the "Mid-"Cretaceous in northern Africa. Several reasons have been proposed to account for this abundance of spinosaur teeth, from sampling biases to ecology. However, the number of teeth in the fossil record also depends strongly on the tooth replacement rate. So far, little is known about the tooth formation time and replacement rates in spinosaurids. Here, we analysed the histology of several spinosaur teeth to estimate tooth formation time and replacement rates, using the count of lines of von Ebner, the daily formed incremental lines in the dentine of the teeth. Line counts indicated a maximum tooth formation time of 271 days, and replacement rates were predicted to be between 59 and 68 days. These rates are faster than in other large theropods for which data are known, and, together with the rather high number of teeth in a spinosaurid dentition, might thus help to explain the abundance of spinosaur teeth in the "Mid-"Cretaceous of northern Africa.

A new theropod dinosaur from the early cretaceous (Barremian) of Cabo Espichel, Portugal: Implications for spinosaurid evolution

“…In a specimen of Tyrannosaurus only one secondary replacement tooth is present in the fourth alveolus of the right dentary [ 92 ], and in Australovenator no secondary replacement teeth appear, with even some alveoli lacking replacement teeth altogether [ 93 ]. The presence of numerous replacement teeth compared with other theropods points towards a faster replacement rate of teeth, as seen in Spinosaurus [ 94 ], and indicates that this adaptation, which could have been related to piscivory, dates back to the early evolution to the clade. The extent of the secondary replacement teeth in the anterior alveoli of the dentary means that the condition proposed by Hendrickx et al [ 29 ] as synapomorphic for Spinosauridae (“Dentary rosette of four teeth’’) can be rephrased as “Dentary rosette of at least four teeth’’ or “Dentary rosette with four alveoli”.…”

Evaluating the ecology of Spinosaurus: shoreline generalist or aquatic pursuit specialist?

“…Additionally, the recent work of Heckeberg and Rauhut (2020) demonstrates that the rate of replacement of spinosaurid teeth exceeds that of other large theropods, including those of abelisaurids and allosauroids (the clades which contain the other large-bodied carnivores of early Late Cretaceous North Africa). They note the combination of higher replacement rate and greater tooth count over all may result in spinosaurids being overrepresented in surveys of dental material with respect to their actual fraction as individual animals in the paleoenvironment.…”

Palaeohistology reveals an unusual periodontium and tooth implantation in a filter‐feeding pterodactyloid pterosaur, Pterodaustro guinazui, from the Lower Cretaceous of Argentina

“…Whereas measurement of the width between von Ebner lines has been used to infer rates of dentine formation (e.g. Dumont et al, 2016; Garcia & Zurriaguz, 2016; Heckeberg & Rauhut, 2020; Kear et al, 2017), variations in the von Ebner count between functional and replacement teeth allow the inference of rates of tooth replacement in fossil amniotes (e.g. D'Emic et al, 2013, 2019; Erickson, 1996a; Maho et al, 2022).…”