Isolated Theropod Teeth Associated With a Sauropod Skeleton From the Allen Formation (Campanian−maastrichtian, Upper Cretaceous) of Río Negro, Patagonia, Argentina.

Abstract

The discovery of theropod shed teeth associated with sauropod remains is relatively common in Cretaceous deposits of Patagonia. However, only a handful of studies have thoroughly explored the phylogenetic affinities of the theropod dental material. Here, we describe and identify twelve theropod shed teeth associated with a partially complete skeleton of a titanosaur sauropod from the Allen Formation (middle Campanian-lower Maastrichtian; Upper Cretaceous) of Paso Córdoba, Río Negro, Argentina. Using three methods, namely a cladistic analysis performed on a dentition-based data matrix, and a discriminant and cluster analyses conducted on a large dataset of theropod teeth measurements, we identify three dental morphotypes which are confidently referred to abelisaurid theropods. Whether the morphotypes represent different abelisaurid subclades or different positional entities within the jaw of the same abelisaurid species, is unknown. Such an identification, nevertheless, provides additional evidence of abelisaurids feeding on sauropod carcasses. This study highlights the importance of using combined qualitative and quantitative methodologies to identify isolated theropod teeth, especially those that can provide direct information on feeding ecology.

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“…3). The latest version of the datamatrix was published by Meso et al (2021) and includes 146 dentition-based characters scored across 107 saurischian taxa. The data generated and analysed in the contribution is available in the Supplementary_File_1 to 5.…”

“…To explore the phylogenetic distribution of RAJ/JAIS/JWGQ001, the specimen was scored in a dentition-based datamatrix focused on theropod dinosaurs created by Hendrickx and Mateus (2014). The latest version of the datamatrix was published by Meso et al (2021) and includes 146 dentitionbased characters scored across 107 saurischian taxa (Supplementary_File_1). A cladistic analysis using a fully constrained tree was performed on the datamatrix using TNT (Goloboff et al 2008) following the methodology detailed by Hendrickx et al (2020a).…”

“…Likewise, due to the putative presence of mesial denticles on the specimen (see below), character on the mesial carina (#48 and #78 for a mesial and a lateral crown, respectively), was scored as denticulated or unknown in separate analyses. As done by Hendrickx et al (2020a) and Meso et al (2021), a combination of the tree-search algorithms Wagner trees, sectorial searches, TBR branch swapping, Ratchet (perturbation phase stopped after 20 substitutions) and Tree Fusing (5 rounds), until 100 hits of the same minimum tree length were reached, were used as the search strategy. The trees were additionally subjected to a final round of TBR branch swapping.…”

“…The command we used in TNT is then: "xmult = hits 100 rss fuse 5 ratchet 20" followed by the "bb" command. Two additional cladistic analyses, one using the dentition-based dataset without constraints (Supplementary_File_3 & 5), and the second on a data matrix restricted to crown-based characters (Supplementary_File_2 & 4), were also conducted (see Young et al 2019;Hendrickx et al 2020a;Meso et al 2021).…”

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“…Collectively, these ten measurements characterize the basic geometry of a tooth. Because principle coordinate analysis (PCA) has been applied to similar problems [ 3 , 15 – 19 , 21 , 24 ], we chose to employ this technique as well. PCA ordination requires continuous variables, however, so discrete variables such as enamel ornamentation were not included in the analysis.…”