News
March 12 2024 - New paper on the identification of isolated theropod teeth from the Kem Kem beds of Morocco published in JVP.
Hendrickx, C., Trapman, T. H., Wills, S., Holwerda, F. M., Stein, K. H. W., Rauhut, O. W. M., Melzer, R. R., Woensel, J. V. and Reumer, J. W. F. 2024. A combined approach to identify isolated theropod teeth from the Cenomanian Kem Kem Group of Morocco: cladistic, discriminant, and machine learning analyses. Journal of Vertebrate Paleontology 0 (0): e2311791.
Abstract
The Kem Kem Group of Southeastern Morocco, North Africa, is well known for theropod remains, especially isolated teeth. Here, a collection of isolated theropod teeth is assessed for diversity using a combination of linear discriminant, phylogenetic, and machine learning analyses for the first time. The results confirm earlier studies on Kem Kem theropod diversity, with teeth referred to Abelisauridae, Spinosaurinae, and Carcharodontosauridae. A single tooth is ascribed to a non-abelisauroid ceratosaur or a megaraptoran and may represent the enigmatic averostran Deltadromeus. Spinosaurine teeth are clearly differentiated by all three methodologies, whereas abelisaurid and carcharodontosaurid teeth could only be distinguished by the machine learning and phylogenetic analyses. This study shows that a combination of independent methods is most effective at providing strong evidence on theropod dental diversity in a particular assemblage, and that cladistic and machine learning analyses are the most reliable approaches to identify isolated dinosaur teeth. The methodology used here is likely to yield results in other dinosaur assemblages where isolated teeth are more abundant than body fossils.
Link
https://www.tandfonline.com/doi/full/10.1080/02724634.2024.2311791
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January 28 2024 - New paper on the evolution of dental complexity in gomphodont cynodonts published in The Anatomical Record.
Hendrickx, C., Abdala, F., Filippini, F. S., Wills, S., Benson, R. and Choiniere, J. N. 2024. Evolution of postcanine complexity in Gomphodontia (Therapsida: Cynodontia). The Anatomical Record n/a (n/a): 1–21.
Abstract
Gomphodonts form a Triassic radiation of small to medium-bodied (<0.5–2.5 m in length) quadrupedal cynodonts characterized by labiolingually expanded gomphodont postcanines. They were the dominant cynodont group in Middle and Late Triassic ecosystems from the Southern Hemisphere and the first predominantly herbivorous cynodonts to evolve. Gomphodonts were also the first therapsids to develop hypsodonty and a dentition with complex occlusal patterns, and their highly diagnostic upper and lower postcanines show many different morphologies. Here, we explored dental complexity in gomphodont cynodonts through time using geographic information system analysis and orientation patch count applied on 3D crown surfaces of upper and lower gomphodont postcanines belonging to 32 gomphodont taxa. This study reveals that the peak in postcanine complexity was reached early in the evolution of gomphodonts with the emergence in the Early Triassic of omnivorous or insectivorous forms with postcanines made of well-separated cusps and cingular cuspules. Traversodontids evolved simpler postcanines via coalescence of cusps into crests and the development of large occlusal basins, and the Middle Triassic radiation of traversodontids led to a sharp decrease in mean postcanine complexity. Simplification of the postcanines in traversodontids is interpreted as being related to a gradual increase in the consumption of plant material. Interestingly, the trend of insectivory/omnivory high postcanine complexity and herbivory low dental complexity in gomphodonts is opposite to the trend of dental complexity reported in some extant mammals, with omnivorous having low dental complexity and herbivorous higher. Postcanine complexity remained relatively stable throughout the evolution of traversodontids and only slightly diminished in the Late Triassic due to the presence of minute forms with particularly simple postcanines in the Rhaetian. The major phylogenetic diversity and taxonomic richness of Gomphodontia are represented in two periods of time: at the end of the Anisian, an age in which the postcanine complexity is simplifying, and at the early Carnian when the postcanine complexity in traversodontids, the only Gomphodontia represented, is stable.
Link
https://anatomypubs.onlinelibrary.wiley.com/doi/10.1002/ar.25386
January 6 2024 - New paper on isolated theropod teeth from the Late Cretaceous of Brazil published in the Zoological Journal of the Linnean Society.
Delcourt, R., Brilhante, N. S., Pires-Domingues, R. A., Hendrickx, C., Grillo, O. N., Augusta, B. G., Maciel, B. S., Ghilardi, A. M. and Ricardi-Branco, F. 2024. Biogeography of theropod dinosaurs during the Late Cretaceous: evidence from central South America. Zoological Journal of the Linnean Society: zlad184.
Abstract
In central South America, theropod remains are relatively scarce in comparison to the southern part of the continent, with shed teeth being the primary fossils found in this region. We examined 179 isolated teeth from the Bauru Basin, Brazil, using linear discriminant analysis (LDA; N = 178) and phylogenetic analysis (N = 174). The LDA used eight measurements, and the phylogenetic analysis used seven morphotypes. Although the results of the LDA suggest the presence of various South American theropod clades, such as Carcharodontosauridae, Noasauridae, and Spinosauridae, the phylogenetic analysis using a constrained dentition-based matrix classified the morphotypes as Abelisauridae (morphotypes I–IV, VI, and VII) and Therizinosauria (morphotype V). Given the considerable number of homoplastic characters and missing data, the phylogenetic analyses could not precisely determine the taxonomy of morphotypes V, VI, and VII in the unconstrained dataset. Morphological comparisons, nevertheless, strongly suggest that all morphotypes should be classified as abelisaurid theropods. We propose that the palaeogeographical distribution of Abelisauridae in South America was influenced by climatic conditions. These apex carnivores are likely to have adapted well to increased climate changes that led to semi-arid conditions. Our research sheds light on the evolutionary and ecological aspects of theropod dinosaurs in this region, contributing to a better understanding of the ancient ecosystems of central South America.
Link
November 14, 2023 - New paper on bite and tooth marks on sauropod bones from the Morrison Formation published in PeerJ.
Lei, R., Tschopp, E., Hendrickx, C., Wedel, M., Norell, M.A. and Hone, D.W.E. 2023. Bite and tooth marks on sauropod dinosaurs from the Morrison Formation. PeerJ 11:e16327: 1-34.
Abstract
Tooth-marked bones provide important evidence for feeding choices made by extinct carnivorous animals. In the case of the dinosaurs, most bite traces are attributed to the large and robust osteophagous tyrannosaurs, but those of other large carnivores remain underreported. Here we report on an extensive survey of the literature and some fossil collections cataloging a large number of sauropod bones (68) from the Upper Jurassic Morrison Formation of the USA that bear bite traces that can be attributed to theropods. We find that such bites on large sauropods, although less common than in tyrannosaur-dominated faunas, are known in large numbers from the Morrison Formation, and that none of the observed traces showed evidence of healing. The presence of tooth wear in non-tyrannosaur theropods further shows that they were biting into bone, but it remains difficult to assign individual bite traces to theropod taxa in the presence of multiple credible candidate biters. The widespread occurrence of bite traces without evidence of perimortem bites or healed bite traces, and of theropod tooth wear in Morrison Formation taxa suggests preferential feeding by theropods on juvenile sauropods, and likely scavenging of large-sized sauropod carcasses.
Link
http://doi.org/10.7717/peerj.16327
Media
August 12, 2022 - New paper on the exquisitely preserved integument of Psittacosaurus published in Communications Biology.
Bell, P. R., Hendrickx, C., Pittman, M., Kaye, T. G. and Mayr, G. 2022. The exquisitely preserved integument of Psittacosaurus and the scaly skin of ceratopsian dinosaurs. Communications Biology 5 (1): 1–16.
Abstract
The Frankfurt specimen of the early-branching ceratopsian dinosaur Psittacosaurus is remarkable for the exquisite preservation of squamous (scaly) skin and other soft tissues that cover almost its entire body. New observations under Laser-Stimulated Fluorescence (LSF) reveal the complexity of the squamous skin of Psittacosaurus, including several unique features and details of newly detected and previously-described integumentary structures. Variations in the scaly skin are found to be strongly regionalized in Psittacosaurus. For example, feature scales consist of truncated cone-shaped scales on the shoulder, but form a longitudinal row of quadrangular scales on the tail. Re-examined through LSF, the cloaca of Psittacosaurus has a longitudinal opening, or vent; a condition that it shares only with crocodylians. This implies that the cloaca may have had crocodylian-like internal anatomy, including a single, ventrally-positioned copulatory organ. Combined with these new integumentary data, a comprehensive review of integument in ceratopsian dinosaurs reveals that scalation was generally conservative in ceratopsians and typically consisted of large subcircular-to-polygonal feature scales surrounded by a network of smaller non-overlapping polygonal basement scales. This study highlights the importance of combining exceptional specimens with modern imaging techniques, which are helping to redefine the perceived complexity of squamation in ceratopsians and other dinosaurs.
Link
June 07, 2022 - New paper on the oldest preserved umbilical scar published in BMC Biology
Bell, R. P., Hendrickx, C., Pittman, M., O., and Kaye, T., 2022. Oldest preserved umbilical scar reveals dinosaurs had ‘belly buttons’. BMC Biology 20 (1): 132.
Abstract
Background: In egg-laying amniotes, the developing embryo is tethered to a number of extraembryonic membranes including the yolk sac and allantois that deliver oxygen and nutrients and remove metabolic waste products throughout embryonic development. Prior to, or soon after hatching, these membranes detach from the animal leaving a temporary or permanent umbilical scar (umbilicus) equivalent to the navel or ‘belly button’ in some placental mammals, including humans. Although ubiquitous in modern mammals and reptiles (including birds), at least early in their ontogeny, the umbilicus has not been identified in any pre-Cenozoic amniote.
Results: We report the oldest preserved umbilicus in a fossil amniote from a ~130-million-year-old early-branching ceratopsian dinosaur, Psittacosaurus. Under Laser Stimulated Fluorescence (LSF), the umbilicus is revealed as an elongate midline structure delimited by a row of paired scales on the abdomen. The relatively late ontogenetic stage (close to sexual maturity) estimated for the individual indicates that the umbilicus was probably retained throughout life.
Conclusions: Unlike most extant reptiles and birds that lose this scar within days to weeks after hatching, the umbilicus of Psittacosaurus persisted at least until sexual maturity, similar to some lizards and crocodylians with which it shares the closest morphological resemblance. This discovery is the oldest record of an amniote umbilicus and the first in a non-avian dinosaur. However, given the variability of this structure in extant reptilian analogues, a persistent umbilical scar may not have been present in all non-avian dinosaurs.
Link
https://bmcbiol.biomedcentral.com/articles/10.1186/s12915-022-01329-9
Media
January 06, 2022 - New paper on the non-feather integument in theropod dinosaurs published in Biological Reviews
Hendrickx, C., Bell, P. R., Pittman, M., Milner, A. R. C., Cuesta, E., O’Connor, J., Loewen, M., Currie, P. J., Mateus, O., Kaye, T. G. and Delcourt, R. 2022. Morphology and distribution of scales, dermal ossifications, and other non-feather integumentary structures in non-avialan theropod dinosaurs. Biological Reviews: 1–45..
Abstract
Modern birds are typified by the presence of feathers, complex evolutionary innovations that were already widespread in the group of theropod dinosaurs (Maniraptoriformes) that include crown Aves. Squamous or scaly reptilian-like skin is, however, considered the plesiomorphic condition for theropods and dinosaurs more broadly. Here, we review the morphology and distribution of non-feathered integumentary structures in non-avialan theropods, covering squamous skin and naked skin as well as dermal ossifications. The integumentary record of non-averostran theropods is limited to tracks, which ubiquitously show a covering of tiny reticulate scales on the plantar surface of the pes. This is consistent also with younger averostran body fossils, which confirm an arthral arrangement of the digital pads. Among averostrans, squamous skin is confirmed in Ceratosauria (Carnotaurus), Allosauroidea (Allosaurus, Concavenator, Lourinhanosaurus), Compsognathidae (Juravenator), and Tyrannosauroidea (Santanaraptor, Albertosaurus, Daspletosaurus, Gorgosaurus, Tarbosaurus, Tyrannosaurus), whereas dermal ossifications consisting of sagittate and mosaic osteoderms are restricted to Ceratosaurus. Naked, non-scale bearing skin is found in the contentious tetanuran Sciurumimus, ornithomimosaurians (Ornithomimus) and possibly tyrannosauroids (Santanaraptor), and also on the patagia of scansoriopterygids (Ambopteryx, Yi). Scales are surprisingly conservative among non-avialan theropods compared to some dinosaurian groups (e.g. hadrosaurids); however, the limited preservation of tegument on most specimens hinders further interrogation. Scale patterns vary among and/or within body regions in Carnotaurus, Concavenator and Juravenator, and include polarised, snake-like ventral scales on the tail of the latter two genera. Unusual but more uniformly distributed patterning also occurs in Tyrannosaurus, whereas feature scales are present only in Albertosaurus and Carnotaurus. Few theropods currently show compelling evidence for the co-occurrence of scales and feathers (e.g. Juravenator, Sinornithosaurus), although reticulate scales were probably retained on the mani and pedes of many theropods with a heavy plumage. Feathers and filamentous structures appear to have replaced widespread scaly integuments in maniraptorans. Theropod skin, and that of dinosaurs more broadly, remains a virtually untapped area of study and the appropriation of commonly used techniques in other palaeontological fields to the study of skin holds great promise for future insights into the biology, taphonomy and relationships of these extinct animals.
Link
July 26, 2021 - New paper on the scaly skin of the abelisaurid theropod Carnotaurus
Hendrickx, C. and Bell, P. R. 2021. The scaly skin of the abelisaurid Carnotaurus sastrei (Theropoda: Ceratosauria) from the Upper Cretaceous of Patagonia. Cretaceous Research 128: 104994.
Abstract
The integument of the theropod dinosaur Carnotaurus sastrei from the Upper Cretaceous of Argentina is here described in detail for the first time. The scaly skin of this abelisaurid is the most completely preserved of any theropod and the only example of this form of integument known outside of Tetanurae (excluding footprints). The skin is preserved in the shoulder, thoracic, tail and, possibly, neck regions and consists of medium to large (20-65 mm in diameter) conical feature scales surrounded by a network of low and small (< 14 mm) basement scales separated by narrow interstitial tissue. Contrary to previous interpretations, the feature scales are randomly distributed and neither form discrete rows nor show progressive variations in their size along parts of the body. They also show little difference in morphology along the body, although their apices are variously positioned in different body parts. Conversely, the basement scales vary from small and elongated, large and polygonal, and circular-to-lenticular in the thoracic, scapular, and tail regions, respectively. Given the presumed active lifestyle of Carnotaurus and the necessity of shedding excess heat, particularly at large body sizes (>1000 kg), we speculate that the skin may have played a vital role in thermoregulation; a role consistent with integument function in extant mammals and reptiles.
Link
https://www.sciencedirect.com/science/article/abs/pii/S0195667121002421
Media
July 26, 2021 - New paper on a new large-bodied gomphodont cynodont from South Africa
Tolchard, F., Kammerer, C. F., Butler, R. J., Hendrickx, C., Benoit, J., Abdala, F. and Choiniere, J. N. 2021. A new large gomphodont from the Triassic of South Africa and its implications for Gondwanan biostratigraphy. Journal of Vertebrate Paleontology 0 (0): e1929265.
Abstract
A partial skull (BP/1/7976) of a very large cynodont from the Middle Triassic Cynognathus Assemblage Zone (Cricodon-Ufudocyclops subzone) of South Africa is described. The specimen represents a new gomphodont taxon, Impidens hancoxi, gen. et sp. nov., diagnosed by five sectorial teeth constituting just over half of the length of the upper postcanine tooth row, and enlarged canine and incisor teeth. BP/1/8123, a skull fragment also from the Cricodon-Ufudocyclops subzone, and AMNH FARB 24421, a partial skull from the upper Fremouw Formation of Antarctica, are also referred to the new species. The presence of this taxon in both the upper Fremouw Formation and Cricodon-Ufudocyclops subzone strengthens evidence of biostratigraphic correlation between these units. Impidens hancoxi, with an inferred skull length of up to 460 mm, was a large-bodied and likely omnivorous gomphodont, and may have played the role of apex predator within the tetrapod fauna of the Cricodon-Ufudocyclops subzone.
Link
https://www.tandfonline.com/doi/full/10.1080/02724634.2021.1929265
June 7, 2021 - New paper on isolated theropod teeth from the Allen Formation of Argentina
Meso, J. G., Hendrickx, C., Baiano, M. A., Canale, J. I., Salgado, L. and Martinez, I. D. 2021. Isolated theropod teeth associated with a sauropod skeleton from the Late Cretaceous Allen Formation of Río Negro, Patagonia, Argentina. Acta Palaeontologica Polonica 66 (2): 409–423.
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.
Link
December 21, 2020 - New paper on epidermal complexity in the theropod Juravenator
Bell, P. R. and Hendrickx, C. 2021. Epidermal complexity in the theropod dinosaur Juravenator from the Late Jurassic of Germany. Palaeontology 64 (2): 203–223.
Abstract
Epidermal scales among modern reptiles are morphologically diverse and serve a variety of functions ranging from moisture balance to chemoreception. Despite being predominantly squamous-skinned (scaly), the functional implications of this type of integument have never before been explored for a dinosaur. Re-examination of the holotype of the theropod Juravenator starki (Kimmeridgian, Late Jurassic) reveals previously unseen diversity in its epidermal covering. In addition to the presence of short monofilaments on the dorsal and ventral parts of the tail, we identify distinctive scale patterns corresponding to discrete longitudinal bands of scutate, tuberculate, and ornamented scales along the length of the tail. In modern squamous-skinned amniotes, variation in scale architecture can be linked to functional differences between scale types. In Juravenator, distinctive circular nodes associated with the ornamented scales have been recently interpreted as integumentary sense organs (ISOs). We also suggest that the snake-like scutate scales on the underside of the tail likely fulfilled a role related to mechanical protection rather than locomotory function. Whereas the literature on theropod epidermal structures has been dominated by discussions on the evolution and diversity of feathers, this study highlights the complexity of squamous integument in Juravenator, which is revealed as one of the most complex among known theropods. An exploration of the epidermal structures found between Juravenator and other non-avian theropods reveals great complexity in the types and distribution of these structures across the clade, suggesting potential for the future inquiry into their taxonomic and biological importance.
Link
October 5, 2020 - New paper on sensory scales in a theropod dinosaur published in Current Biology
Bell, P. R. and Hendrickx, C. 2020. Crocodile-like sensory scales in a Late Jurassic theropod dinosaur. Current Biology 30 (19): R1068–R1070.
Link
https://www.cell.com/current-biology/fulltext/S0960-9822(20)31256-2
Media
National Geographic (also in French and Spanish)
October 17, 2020 - New paper on a new traversodontid gomphodont from the Triassic of Namibia
Hendrickx, C., Gaetano, L. C., Choiniere, J. N., Mocke, H. and Abdala, F. 2020. A new traversodontid cynodont with a peculiar postcanine dentition from the Middle/Late Triassic of Namibia and dental evolution in basal gomphodonts. Journal of Systematic Palaeontology 18 (20): 1669–1706.
Abstract
We here present a new gomphodont cynodont from the Ladinian/Carnian Upper Omingonde Formation of central Namibia. Etjoia dentitransitus, gen. et sp. nov., is a medium-sized (skull length of 88.5 mm) omnivorous gomphodont represented by an almost complete skull and a few cervical vertebrae. This new taxon is diagnosed by divergent first left and right lower incisors that bear large apically inclined denticles, a third lower gomphodont postcanine with a well-separated mesial cingulum, four distal upper and lower sectorial teeth, and a lingually offset last upper sectorial postcanine. Etjoia is particular in having a transitional dentition between basal gomphodonts and traversodontids. It shares with some non-traversodontid gomphodonts a high number of sectorial postcanines and ovoid mesialmost upper gomphodont postcanines with a centrally positioned transverse crest. Etjoia was, however, recovered as a basally branching Traversodontidae in the phylogenetic analysis performed on different data matrices. It indeed shares with traversodontids upper gomphodont postcanines with a high transverse crest, subrectangular and mesiodistally elongated lower gomphodont postcanines, and a mesially displaced transverse crest in the lower gomphodont postcanines. We explored the dental evolution in basal cynognathians based on a dentition-oriented data matrix. The acquisition of gomphodont postcanines, which allowed tooth-to-tooth occlusion, in basalmost gomphodonts was followed by a loss of shearing planes between the upper and lower gomphodonts postcanines in non-diademodontid gomphodonts, and the development of deep basins and tall transverse crests in gomphodont teeth and shearing planes between the upper and lower gomphodont postcanines in basal traversodontids. These dental transformations likely resulted from three shifts in feeding ecologies, from a carnivorous to an omnivorous diet in basalmost gomphodonts, followed by an adaptation to a specialized feeding ecology possibly made of insects and hard plant material in basalmost neogomphodonts (traditional “trirachodontids”), then an increase in the consumption of plant-material in basal traversodontids.
Link
https://www.tandfonline.com/doi/abs/10.1080/14772019.2020.1804470?journalCode=tjsp20
February 28, 2020 - New paper the dentition of Sinraptor dongi
Hendrickx, C., Stiegler, J., Currie, P. J., Han, F., Xu, X., Choiniere, J. N. and Wu, X.-C. 2020. Dental anatomy of the apex predator Sinraptor dongi (Theropoda: Allosauroidea) from the Late Jurassic of China. Canadian Journal of Earth Sciences 57 (9): 1127–1147.
Abstract
The gross dental morphology of the holotype of the theropod Sinraptor dongi from the Jurassic Shishugou Formation of China is comprehensively described. We highlight a combination of dental features that appear to be restricted to Sinraptor: i) crowns with denticulated mesial and distal carinae extending from the root, and an irregular surface texture on the enamel; ii) D- to salinon-shaped cross-sectional outline at the crown-base in mesialmost teeth; iii) mesial crowns with mesial carinae spiraling mesiolingually and lingually positioned longitudinal groove adjacent to the mesial carina; and iv) labiolingually compressed lateral teeth with weakly labially deflected distal carinae, flat to concave basocentral surfaces of the labial margins of the crowns, and horizontally elongated distal denticles showing short to well-developed interdenticular sulci. Using cladistic, multivariate, discriminant and cluster analyses, we demonstrate that the dentition of Sinraptor is relatively similar to that of ceratosaurids, megalosauroids and other allosauroids, and particularly close to that of Allosaurus. The dental anatomy of Sinraptor and Allosaurus, which mainly differs in the labiolingual compression of the lateral crowns and the number of premaxillary teeth, shows adaptations towards a predatory lifestyle, including premaxillary teeth capable of enduring bone-to-bone contact, and crowns with widely separated mesial and distal carinae capable of inflicting widely open wounds.
Link
https://www.nrcresearchpress.com/doi/abs/10.1139/cjes-2019-0231#.Xl0rBKhKjIW
April 1, 2020 - New paper on the dentition of abelisaurid theropods
Hendrickx, C., Tschopp, E. and Ezcurra, M. d. 2020. Taxonomic identification of isolated theropod teeth: The case of the shed tooth crown associated with Aerosteon (Theropoda: Megaraptora) and the dentition of Abelisauridae. Cretaceous Research 108: 104312.
Abstract
Shed teeth are usually the most abundant theropod material on a dinosaur fossil site and are constantly reported in the literature. Although new quantitative techniques have emerged to identify isolated theropod teeth with better accuracy, they remain difficult to assign to a certain family-level or genus-level taxon because of the presence of rampant homoplasy in their morphology and the lack of thorough descriptions. Here we test three methods to investigate the phylogenetic position of a tooth previously considered to be part of the holotype of the megaraptoran Aerosteon riocoloradensis (MCNA-PV-3137): a cladistic analysis performed on a dentition-based data matrix scored across 105 theropod species and using a backbone topology as constraint, as well as discriminant and cluster analyses conducted on a dataset of non-avian theropod crown measurements. Even though the cladistic technique appears to be the most reliable method to investigate the phylogenetic affinities of theropod teeth, we recommend using the three techniques conjointly to corroborate the identification of isolated dental material. The results of the cladistic and discriminant analyses support the assignment of the tooth associated with MCNA-PV-3137 to an abelisaurid theropod. It should therefore be excluded from the holotype of Aerosteon. A thorough description of the dental anatomy of Abelisauridae is also provided. The current study is the first to evaluate different methodological tools to identify isolated theropod teeth. With the added detailed description of the dental anatomy of Abelisauridae, it will also assist future authors to investigate the systematic palaeontology of isolated theropod teeth with more confidence.
Link
https://www.sciencedirect.com/science/article/abs/pii/S0195667118303860
November 25, 2019 - New paper on the distribution of dental features in theropods
Hendrickx, C., Mateus, O., Araújo, R. and 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.
Abstract
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.
Link
https://palaeo-electronica.org/content/2019/2806-dental-features-in-theropods
June 19, 2019 - New paper on a proposed terminology for the dentition of gomphodont cynodonts
Hendrickx, C., Abdala, F. and Choiniere, J. N. 2019. A proposed terminology for the dentition of gomphodont cynodonts and dental morphology in Diademodontidae and Trirachodontidae. PeerJ 7 (e6752): 1–71.
Abstract
Gomphodont cynodonts were close relatives of mammals and one of the Mesozoic lineages of cynodont therapsids that became extinct at the end of the Triassic. Gomphodonts were omnivorous to herbivorous animals characterized by labiolingually expanded postcanines, which allowed tooth-to-tooth occlusion. The morphology of the upper and lower postcanines presents important means of distinguishing among major lineages within Gomphodontia, i.e., Diademodontidae, Trirachodontidae, and Traversodontidae, but the dentition of most Diademodontidae and Trirachodontidae remain poorly documented. Here we present a comprehensive description of the dentition of each diademodontid and trirachodontid species, as well as detailed illustrations of each dental unit, after firsthand examination of material and 3d reconstructions of postcanine teeth. Based on dental morphology, Trirachodon berryi and ‘Trirachodon kannemeyeri’, considered as separate taxa by some authors are here interpreted as representing different ontogenetic stages of the same species. Likewise, Sinognathus and Beishanodon, thought to belong to non-cynognathian cynodonts and traversodontids by some authors, are referred to Trirachodontidae and Gomphodontia based on dental characters, respectively. Finally, we propose a standardized list of terms and abbreviations for incisors, canines and postcanines anatomical entities, with the goal of facilitating future descriptions and communication between researchers studying the gomphodont dentition.
Link
May 3, 2019 - New paper on isolated theropod teeth from the Isle of Skye
Young, C. M. E., Hendrickx, C., Challands, T. J., Foffa, D., Ross, D. A., Butler, I. B. and Brusatte, S. L. 2019. New theropod dinosaur teeth from the Middle Jurassic of the Isle of Skye, Scotland. Scottish Journal of Geology 55 (1): 7–19.
Abstract
The Middle Jurassic is a largely mysterious interval in dinosaur evolution, as few fossils of this age are known worldwide. In recent years, the Isle of Skye has yielded a substantial record of trackways, and a more limited inventory of body fossils, that indicate a diverse fauna of Middle Jurassic dinosaurs living in and around lagoons and deltas. Comparatively little is known about the predators in these faunas (particularly theropod dinosaurs), as their fossils are among the rarest discoveries. We here report two new isolated theropod teeth, from the Valtos Sandstone and Lealt Shale Formations of Skye, which we visualized and measured using high-resolution x-ray computed microtomographic scanning (µCT) and identified via statistical and phylogenetic analyses of a large comparative dental dataset. We argue that these teeth most likely represent at least two theropod species—one small-bodied and the other large-bodied—which likely belonged to one or several clades of basal avetheropods (ceratosaurs, megalosauroids, or allosauroids). These groups, which were diversifying during the Middle Jurassic and would become dominant in Late Jurassic, filled various niches in the food chain of Skye, probably both on land and in the lagoons.
Link
https://sjg.lyellcollection.org/content/early/2019/03/30/sjg2018-020.abstract
April 1, 2019 - New postdoc position at the Unidad Ejecutora Lillo in San Miguel de Tucumán, Argentina
Link
October 4, 2016 - New paper on the postcanine microstructure in gomphodont cynodonts
Hendrickx, C., Abdala, F. and Choiniere, J. 2016. Postcanine microstructure in Cricodon metabolus, a Middle Triassic gomphodont cynodont from south-eastern Africa. Palaeontology: 10.1111/pala.12263
Abstract
Cricodon metabolus is a trirachodontid cynodont from the Anisian (Middle Triassic) of eastern and southern Africa. It has labiolingually expanded (gomphodont) postcanines but also a sectorial tooth in the last postcanine locus. In this paper, we examine the crown microstructure of isolated sectorial and gomphodont postcanines belonging to the holotype specimen of this taxon using scanning electron microscopy. The enamel of both teeth is prismless and composed of discontinuous columnar divergence units, supporting the consistent presence of synapsid columnar enamel in cynognathians. Abundant tubules and numerous irregularly spaced incremental lines are also visible in the enamel and dentine layers in each tooth. This study reveals that the enamel thickness varies along the tooth row in Cricodon as the enamel layer of the gomphodont postcanines is 11.5 times thicker than that of the sectorial crown. This difference likely reflects occlusal stresses and fewer replacements in gomphodont postcanines relative to sectorial teeth. Approximately one hundred incremental growth lines of von Ebner are present in the dentine layer, indicating that the deposition of the dentine by odontoblasts occurred for three months before the animal’s death.
Link
January 6, 2016 - New paper on spinosaurid quadrates from the Kem Kem beds of Morocco
Hendrickx, C., Mateus, O. and 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 (1): e0144695.
Abstract
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.
Link
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0144695
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August - September 2015 - Three papers on theropods published and a postdoc position at the University of the Witwatersrand, Johannesburg
Hendrickx, C., Mateus, O. and Araújo, R. 2015a. A proposed terminology of theropod teeth (Dinosauria, Saurischia). Journal of Vertebrate Paleontology 35 (5): e982797. https://www.tandfonline.com/eprint/KDuAQViMsMguZI2NQpMj/full
Hendrickx, C., Hartman, S. A. and Mateus, O. 2015b. An overview of non-avian theropod discoveries and classification. PalArch’s Journal of Vertebrate Palaeontology 12 (1): 01–07. https://archives.palarch.nl/index.php/jvp/article/view/353
Hendrickx, C., Araújo, R. and Mateus, O. 2015c. The non-avian theropod quadrate I: standardized terminology with an overview of the anatomy and function. PeerJ 3: e1245. https://peerj.com/articles/1245/
February 25-26, 2015 - PhD thesis successfully defended and Torvosaurus gurneyi in the TV programme "Tout s'explique" on RTL-TVI (Belgian TV)
Lusodino (My supervisor's blog talks about my PhD thesis and its defense at the Universidade Nova de Lisboa)
July & August 2014 - Reconstruction of a life size model of Torvosaurus gurneyi displayed at the Dino Expo Adventure in Antwerpen (Belgium), and Torvosaurus gurneyi in the media
- Revue ATHENA (scientific magazine of Wallonia, Belgium): L'ADN de... Christophe Hendrickx Paléontologue (in French; p. 16-17).
- This View of Life: Torvosaurus gurneyi, the European T-rex (in English)
- Daily Science: Belge, scientifique et expatrié (in French)
- Expo Dino Adventure: Wereldprimeur: het allereerste model van de Torvosaurus (in Dutch)
- Deredactie.be: Het Journaal 1 (TV News in Dutch; also here)
- Flandreinfo.be: La semaine en vidéo (TV News in French)
- Ketnet: Belgische dino in Antwerpen (TV News for children in Dutch)
- Het Laatste Niews: Grootste Europese carnivoor ooit voor Antwerps Centraal Station (in Dutch)
- Rtbf: Le cousin du T-rex au "Jurassik Park" d'Hanovre et bientôt à Anvers (in French) and Parc dinosaure (TV News in French; better quality here)
- L'Avenir: Les dinosaures sont à nos portes (in French)
- Gravità Zero: Intervista a Christophe Hendrickx (in Italian)
March 27, 2014 - New paper on the dental anatomy of megalosaurid theropods
Hendrickx, C., Mateus, O. and Araújo, R. 2014. The dentition of megalosaurid theropods. Acta Palaeontologica Polonica: 1–45. DOI: 10.4202/app.00056.2013.
Abstract
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.
Link
March 5, 2014 - New paper on a new species of Torvosaurus from Portugal
Hendrickx, C. and Mateus, O. 2014. Torvosaurus gurneyi n. sp., the largest terrestrial predator from Europe, and a proposed terminology of the maxilla anatomy in nonavian theropods. PLoS ONE 9 (3): e88905.
Abstract
The Lourinhã Formation (Kimmeridgian-Tithonian) of Central West Portugal is well known for its diversified dinosaur fauna similar to that of the Morrison Formation of North America; both areas share dinosaur taxa including the top predator Torvosaurus, reported in Portugal. The material assigned to the Portuguese T. tanneri, consisting of a right maxilla and an incomplete caudal centrum, was briefly described in the literature and a thorough description of these bones is here given for the first time. A comparison with material referred to Torvosaurus tanneri allows us to highlight some important differences justifying the creation of a distinct Eastern species. Torvosaurus gurneyi n. sp. displays two autapomorphies among Megalosauroidea, a maxilla possessing fewer than eleven teeth and an interdental wall nearly coincidental with the lateral wall of the maxillary body. In addition, it differs from T. tanneri by a reduced number of maxillary teeth, the absence of interdental plates terminating ventrally by broad V-shaped points and falling short relative to the lateral maxillary wall, and the absence of a protuberant ridge on the anterior part of the medial shelf, posterior to the anteromedial process.
T. gurneyi is the largest theropod from the Lourinhã Formation of Portugal and the largest land predator discovered in Europe hitherto. This taxon supports the mechanism of vicariance that occurred in the Iberian Meseta during the Late Jurassic when the proto-Atlantic was already well formed. A fragment of maxilla from the Lourinhã Formation referred to Torvosaurus sp. is ascribed to this new species, and several other bones, including a femur, a tibia and embryonic material all from the Kimmeridgian-Tithonian of Portugal, are tentatively assigned to T. gurneyi. A standard terminology and notation of the theropod maxilla is also proposed and a record of the Torvosaurus material from Portugal is given.
Link http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0088905
Media cover (selection)
January 30, 2014 - New paper on isolated theropod teeth from the Late Jurassic of Portugal
Hendrickx, C. and 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.
Abstract
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.
Link
http://biotaxa.org/Zootaxa/article/view/zootaxa.3759.1.1
Media
May 30, 2013 - New paper on Torvosaurus embryos from the Upper Jurassic of Portugal
Araújo, R., Castanhinha, R., Martins, R.M.S., Mateus, O., Hendrickx, C., Beckmann, F., Schell, N. and Alves, L.C., 2013. Filling the gaps of dinosaur eggshell phylogeny: Late Jurassic Theropod clutch with embryos from Portugal. Scientific Reports 3. doi:10.1038/srep01924.
Abstract
The non-avian saurischians that have associated eggshells and embryos are represented only by the sauropodomorph Massospondylus and Coelurosauria (derived theropods), thus missing the basal theropod representatives. We report a dinosaur clutch containing several crushed eggs and embryonic material ascribed to the megalosaurid theropod Torvosaurus. It represents the first associated eggshells and embryos of megalosauroids, thus filling an important phylogenetic gap between two distantly related groups of saurischians. These fossils represent the only unequivocal basal theropod embryos found to date. The assemblage was found in early Tithonian fluvial overbank deposits of the Lourinhã Formation in West Portugal. The morphological, microstructural and chemical characterization results of the eggshell fragments indicate very mild diagenesis. Furthermore, these fossils allow unambiguous association of basal theropod osteology with a specific and unique new eggshell morphology.
Link http://www.nature.com/srep/2013/130530/srep01924/full/srep01924.html
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