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 We reviewed the morphological variation in the dentition of uruguaysuchid specimens, including unpublished fossils from the Crato (SMNK PAL 6404) and Romualdo (MN 7061-V) formations of the Araripe Basin.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.
Highlights
The evolutionary history of Crocodyliformes is characterized by high ecological diversity, which can be traced to several episodes of radiation along the Jurassic and Cretaceous (Stubbs et al 2013, Toljagic & Butler 2013)
A further discussion on tooth morphotypes and its definitions is necessary, and here we addressed some of these issues
A wide sample of fossils were first hand analyzed for this study, consisting in the following species and specimens: Araripesuchus buitreraensis (MPCA-PV 235); Araripesuchus gomesii (DGM 423-R, AMNH 24450, MN 7061-V); Araripesuchus patagonicus (MUCPV 269, MUCPV 267, MUCPV 268, MUCPV 268b, MUCPV 270); Araripesuchus rattoides (CMN 41893, UCRC PV3); Araripesuchus sp. (MPCA-PV 236); Araripesuchus sp. (“Crato Form” SMNK PAL 6404); Araripesuchus tsangatsangana (FMNH PR 2297-2299, FMNH PR 2318, FMNH PR 2334, UA 8750, UA 8751, UA 8756, UA 8760, UA 8761, UA 8762, UA 8763); Araripesuchus wegeneri (MNN GAD 19-23, MNN GAD 26); Uruguaysuchus aznarezi (FC-DPV 2320)
Summary
The evolutionary history of Crocodyliformes is characterized by high ecological diversity, which can be traced to several episodes of radiation along the Jurassic and Cretaceous (Stubbs et al 2013, Toljagic & Butler 2013). An extensive fossil record reveals different body plans and a wide range of variation in skull morphology, notably in the shape of the rostrum, and in patterns of dentition (Riff & Kellner 2001, Ösi 2013, Wilberg 2017). Such disparity is often linked with distinct feeding habits and lifestyles, establishing a clear correlation between form and function, and their influence on the ecological roles displayed by extinct crocodyliforms is not a straightforward task (Drumheller & Wilberg 2020). Cranial-mandibular joint anatomy and dental wear facets indicate that, at least some species with specialized dentition, were capable of active oral food processing, i.e. chewing (Ösi 2013)
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