Morphological variation in the dentition of Uruguaysuchidae (Crocodyliformes: Notosuchia)

Abstract

Uruguaysuchidae was a diverse group of crocodyliforms with widespread Gondwanan distribution. Recent phylogenies recover a clade comprising six species of Araripesuchus and one Uruguaysuchus. We reviewed the morphological variation in the dentition of uruguaysuchid specimens, including unpublished fossils from the Crato (SMNK PAL 6404) and Romualdo (MN 7061-V) formations of the Araripe Basin. Dental patterns are clearly distinct between species, with important taxonomic and possible ecological implications. Neither Araripesuchus nor Uruguaysuchus have characters suggesting exclusive herbivory, even for species in which tooth-tooth occlusion is observed. New data on A. gomesii shows differences in teeth number between the new specimen MN 7061-V and the holotype, probably due to preservation. The specimen SMNK PAL 6404 has a unique combination of dental characters, which reinforces the hypothesis that it might belong to a new Araripesuchus species. The alveoli pattern of A. rattoides is very distinctive in comparison to other araripesuchids, what also suggests different taxonomic affinities. One interpretation for the morphological variation in the dentition of Uruguaysuchidae is foraging specializations for different life habits. Niche partitioning and ecological specialization could have been an important process in explaining the high taxonomic diversity and widespread spatial distribution of these animals in the Cretaceous of Gondwana.

isolated Mesoeucrocodylian tooth crown from the lower Cretaceous cerro La Isla pterosaur site in the Atacama region, northern Chile

“…Since SGO.PV.1160 was discovered in a horizon of the basal levels of the Lower Cretaceous of the Quebrada Monardes Formation (Bell and Padian 1995), whose deposition began in the late Tithonian-early Berriasian (Martínez et al 2015), the fossil may prove to belong to one of the earliest Lower Cretaceous notosuchian crocodyliforms. Considering the above mentioned three early diverging Lower Cretaceous clades, the morphology of SGO.PV.1160 is not consistent with either Uruguaysuchidae (e.g., Sereno and Larsson 2009;Figueiredo and Kellner 2021), or Ziphosuchia (e.g., Ortega et al 2000;Company et al 2005;Sellés et al 2020). Among the Peirosauridae however, species with tooth crowns bearing apicobasal ridges are quite common and most notably, some of the anteriormost teeth of Hamadasuchus rebouli from the Albian-Cenomanian of southeastern Morocco (Larsson and Sues 2007) and those of Pepesuchus deiseae from the Campanian-Maastrichtian of Brazil (Campos et al 2011) are quite similar to SGO.PV.1160.…”

“…Notosuchia is a terrestrial clade of mesoeucrocodylian crocodyliforms that showed a marked diversity in the Cretaceous of Gondwana, and particularly in South America (e.g., Pol et al 2014;Pol and Leardi 2015;Coria et al 2019;Marinho et al 2022). They are characterized by possessing heterodont dentition and a broad range of dental morphologies (e.g., Pol et al 2014;Martinelli et al 2018;Melstrom and Irmis 2019;Figueiredo and Kellner 2021). Given their fully terrestrial ecology and the fact that several taxa, such as several members of the Peirosauridae Gasparini 1982 (e.g., Larsson and Sues 2007;Campos et al 2011) and the Sphagesauridae Kuhn 1968(Pol et al 2014, possess conical premaxillary and/or anterior dentary (incisiform or caniniform) teeth that bear apicobasal ridges, Notosuchia is the main group of interest for the present study.…”