Theropoda Dinosauria

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Hendrickx, C., Mateus O., Araújo R., & Choiniere J. (2019).  The distribution of dental features in non-avian theropod dinosaurs: Taxonomic potential, degree of homoplasy, and major evolutionary trends. Palaeontologia Electronica. 22(3), 1-110. Abstractthe_distribution_of_dental_features_in_non-avian_t.pdfWebsite

Isolated theropod teeth are some of the most common fossils in the dinosaur fossil record and are continually reported in the literature. Recently developed quantitative methods have improved our ability to test the affinities of isolated teeth in a repeatable framework. But in most studies, teeth are diagnosed on qualitative characters. This can be problematic because the distribution of theropod dental characters is still poorly documented, and often restricted to one lineage. To help in the identification of isolated theropod teeth, and to more rigorously evaluate their taxonomic and phylogenetic potential, we evaluated dental features in two ways. We first analyzed the distribution of 34 qualitative dental characters in a broad sample of taxa. Functional properties for each dental feature were included to assess how functional similarity generates homoplasy. We then compiled a quantitative data matrix of 145 dental characters for 97 saurischian taxa. The latter was used to assess the degree of homoplasy of qualitative dental characters, address longstanding questions on the taxonomic and biostratigraphic value of theropod teeth, and explore the major evolutionary trends in the theropod dentition.

In smaller phylogenetic datasets for Theropoda, dental characters exhibit higher levels of homoplasy than non-dental characters, yet they still provide useful grouping information and optimize as local synapomorphies of smaller clades. In broader phylogenetic datasets, the degree of homoplasy displayed by dental and non-dental characters is not significantly different. Dental features on crown ornamentations, enamel texture and tooth microstructure have significantly less homoplasy than other dental features and can be used to identify many theropod taxa to ‘family’ or ‘sub-family’ level, and some taxa to genus or species. These features should, therefore, be a priority for investigations seeking to classify isolated teeth.

Our observations improve the taxonomic utility of theropod teeth and in some cases can help make isolated teeth useful as biostratigraphic markers. This proposed list of dental features in theropods should, therefore, facilitate future studies on the systematic paleontology of isolated teeth.

Hendrickx, C., Mateus O., & Buffetaut E. (2016).  Morphofunctional Analysis of the Quadrate of Spinosauridae (Dinosauria: Theropoda) and the Presence of Spinosaurus and a Second Spinosaurine Taxon in the Cenomanian of North Africa.. PLoS ONE. 11, e0144695., 01, Number 1: Public Library of Science Abstracthendrickx_et_al_2016_morphofunctional_analysis_of_the_quadrate_of_spinosauridae_dinosauria.pdfWebsite

Six quadrate bones, of which two almost certainly come from the Kem Kem beds (Cenomanian, Upper Cretaceous) of south-eastern Morocco, are determined to be from juvenile and adult individuals of Spinosaurinae based on phylogenetic, geometric morphometric, and phylogenetic morphometric analyses. Their morphology indicates two morphotypes evidencing the presence of two spinosaurine taxa ascribed to Spinosaurus aegyptiacus and? Sigilmassasaurus brevicollis in the Cenomanian of North Africa, casting doubt on the accuracy of some recent skeletal reconstructions which may be based on elements from several distinct species. Morphofunctional analysis of the mandibular articulation of the quadrate has shown that the jaw mechanics was peculiar in Spinosauridae. In mature spinosaurids, the posterior parts of the two mandibular rami displaced laterally when the jaw was depressed due to a lateromedially oriented intercondylar sulcus of the quadrate. Such lateral movement of the mandibular ramus was possible due to a movable mandibular symphysis in spinosaurids, allowing the pharynx to be widened. Similar jaw mechanics also occur in some pterosaurs and living pelecanids which are both adapted to capture and swallow large prey items. Spinosauridae, which were engaged, at least partially, in a piscivorous lifestyle, were able to consume large fish and may have occasionally fed on other prey such as pterosaurs and juvenile dinosaurs.

Hendrickx, C., Hartman S. A., & Mateus O. (2015).  An overview of non-avian theropod discoveries and classification. PalArch’s Journal of Vertebrate Palaeontology. 12(1), 1-73. Abstracthendrickx_etal_2015_non_avian_theropods_pjvp12_11.pdfWebsite

Theropods form a taxonomically and morphologically diverse group of dinosaurs that include extant birds. Inferred relationships between theropod clades are complex and have changed dramatically over the past thirty years with the emergence of cladistic techniques. Here, we present a brief historical perspective of theropod discoveries and classification, as well as an overview on the current systematics of non-avian theropods. The first scientifically recorded theropod remains dating back to the 17th and 18th centuries come from the Middle Jurassic of Oxfordshire and most likely belong to the megalosaurid Megalosaurus. The latter was the first theropod genus to be named in 1824, and subsequent theropod material found before 1850 can all be referred to megalosauroids. In the fifty years from 1856 to 1906, theropod remains were reported from all continents but Antarctica. The clade Theropoda was erected by Othniel Charles Marsh in 1881, and in its current usage corresponds to an intricate ladder-like organization of ‘family’ to ‘superfamily’ level clades. The earliest definitive theropods come from the Carnian of Argentina, and coelophysoids form the first significant theropod radiation from the Late Triassic to their extinction in the Early Jurassic. Most subsequent theropod clades such as ceratosaurs, allosauroids, tyrannosauroids, ornithomimosaurs, therizinosaurs, oviraptorosaurs, dromaeosaurids, and troodontids persisted until the end of the Cretaceous, though the megalosauroid clade did not extend into the Maastrichtian. Current debates are focused on the monophyly of deinonychosaurs, the position of dilophosaurids within coelophysoids, and megaraptorans among neovenatorids. Some recent analyses have suggested a placement of dilophosaurids outside Coelophysoidea, Megaraptora within Tyrannosauroidea, and a paraphyletic Deinonychosauria with troodontids placed more closely to avialans than dromaeosaurids.

Hendrickx, C., Mateus O., & Araújo R. (2015).  A proposed terminology of theropod teeth (Dinosauria, Saurischia). Journal of Vertebrate Paleontology. e982797. Abstracthendrickx_et_al_2015_theropod_teeth_svp.pdfWebsite

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Hendrickx, C., Mateus O., & Araújo R. (2015).  The dentition of megalosaurid theropods. Acta Palaeontologica Polonica. 60(3), 627–642. Abstracthendrickx_et_al_2015_theropod_teeth_app.pdfWebsite

Theropod teeth are particularly abundant in the fossil record and frequently reported in the literature. Yet, the dentition of many theropods has not been described comprehensively, omitting details on the denticle shape, crown ornamentation and enamel texture. This paucity of information has been particularly striking in basal clades, thus making identification of isolated teeth difficult, and taxonomic assignments uncertain. We here provide a detailed description of the dentition of Megalosauridae, and a comparison to and distinction from superficially similar teeth of all major theropod clades. Megalosaurid dinosaurs are characterized by a mesial carina facing mesiolabially in most mesial teeth, centrally positioned carinae on both most mesial and lateral crowns, a mesial carina terminating above the cervix, and short to well-developed interdenticular sulci between distal denticles. A discriminant analysis performed on a dataset of numerical data collected on the teeth of 62 theropod taxa reveals that megalosaurid teeth are hardly distinguishable from other theropod clades with ziphodont dentition. This study highlights the importance of detailing anatomical descriptions and providing additional morphometric data on teeth with the purpose of helping to identify isolated theropod teeth in the future.

Hendrickx, C., Mateus O., & Araújo R. (2014).  The dentition of megalosaurid theropods, with a proposed terminology on theropod teeth. XII EAVP Meeting XII Annual Meeting of the European Association of Vertebrate Palaeontologists – Abstract Book. p. 75., Torino 24-28 June 2014hendrickx_et_al_2014_megalosaurid_teeth_eavp.pdf
Mateus, O. (2014).  Gigantic Jurassic predators. 52 Things You Should Know About Palaeontology. 56-57.: Agile Libremateus_2014_gigantic_jurassic_predators.pdf
Hendrickx, C., & Mateus O. (2014).  Abelisauridae (Dinosauria: Theropoda) from the Late Jurassic of Portugal and dentition-based phylogeny as a contribution for the identification of isolated theropod teeth. Zootaxa. 3759, 1-74. Abstracthendrickx__mateus_2014._abelisauridae_dinosauria_theropoda_from_the_late_jurassic_of_portugal.pdf

Theropod dinosaurs form a highly diversified clade, and their teeth are some of the most common components of the Mesozoic dinosaur fossil record. This is the case in the Lourinhã Formation (Late Jurassic, Kimmeridgian-Tithonian) of Portugal, where theropod teeth are particularly abundant and diverse. Four isolated theropod teeth are here described and identified based on morphometric and anatomical data. They are included in a cladistic analysis performed on a data matrix of 141 dentition-based characters coded in 60 taxa, as well as a supermatrix combining our dataset with six recent datamatrices based on the whole theropod skeleton. The consensus tree resulting from the dentition-based data matrix reveals that theropod teeth provide reliable data for identification at approximately family level. Therefore, phylogenetic methods will help identifying theropod teeth with more confidence in the future. Although dental characters do not reliably indicate relationships among higher clades of theropods, they demonstrate interesting patterns of homoplasy suggesting dietary convergence in (1) alvarezsauroids, therizinosaurs and troodontids; (2) coelophysoids and spinosaurids; (3) compsognathids and dromaeosaurids; and (4) ceratosaurids, allosauroids and megalosaurids.

Based on morphometric and cladistic analyses, the biggest tooth from Lourinhã is referred to a mesial crown of the megalosaurid Torvosaurus tanneri, due to the elliptical cross section of the crown base, the large size and elongation of the crown, medially positioned mesial and distal carinae, and the coarse denticles. The smallest tooth is identified as Richardoestesia, and as a close relative of R. gilmorei based on the weak constriction between crown and root, the “eight-shaped” outline of the base crown and, on the distal carina, the average of ten symmetrically rounded denticles per mm, as well as a subequal number of denticles basally and at mid-crown. Finally, the two medium-sized teeth belong to the same taxon and exhibit pronounced interdenticular sulci between distal denticles, hooked distal denticles for one of them, an irregular enamel texture, and a straight distal margin, a combination of features only observed in abelisaurids. They provide the first record of Abelisauridae in the Jurassic of Laurasia and one of the oldest records of this clade in the world, suggesting a possible radiation of Abelisauridae in Europe well before the Upper Cretaceous.