Dental histology and attachment tissues in Notosuchus terrestris (Crocodyliformes, Notosuchia): palaeobiological implications

Abstract

Notosuchia represents a highly diverse lineage of Crocodyliformes usually characterized by the presence of a heterodont dentition. Although the dental anatomy has been thor-oughly analysed in some taxa, information regarding tooth microstructure and dental attachment tissue are still poorly explored. With the purpose to obtain new data regarding feeding habits, tooth growth rates and nature of the dental attachment in notosuchians, here we describe and interpret the microstructure of the tooth and tooth attachment tissues of Notosuchus terrestris from the Late Cretaceous of Argentina (MPCA-PV 250). We found that the relative and absolute enamel thickness of Notosuchus is more similar to the one reported for carnivorous notosuchians (e.g. Baurusuchidae). The den-tine microstructure allowed us to infer that the tooth growth rates of Notosuchus are reduced in comparison with other notosuchians. The tooth attachment of Notosuchus corresponds with a typical gomphosis, which involves the presence of cementum, alveo-lar bone, and periodontal ligamentum. The spatial arrangement of these tissues exhibits the plesiomorphic condition for archosaurs and the new data supports a high degree of conservatism of this feature. The data available on the absolute and relative cementum thickness reveals that Notosuchus exhibits the highest values of absolute and relative cementum thickness among the analysed crocodyliforms. Different from other archo-saurs, in which alveolar bone is only formed by woven fibred bone, the alveolar bone of our specimen is formed by both woven and parallel fibred bone, which indicates local variations in the rates of the alveolar bone formation.