Research

Dental evolution, feeding ecology and ecospace modelling in non-mammaliaform cynodonts 

Innovations in the dentition are a defining characteristic in the evolution of mammals. Non-mammaliaform (nm) cynodonts are a diverse group of synapsids that gave rise to mammals in the Triassic, and they epitomize how dental innovation might drive diversification and disparity in Therapsida. Yet despite their taxonomic diversity, many nm cynodont species lack a comprehensive description of their external and internal dentition anatomy and a global view of the evolution of dentition in nm cynodonts remains to be given. This project, initiated at the Evolutionary Studies Institute of the University of Witwatersrand, Johannesburg, aims to investigate morphological diversity and rates of anatomical innovation in the dentition of nm cynodonts by providing a comprehensive description of the dentition external morphology and by exploring dental disparity and complexity as well as rates of dental evolution in nm cynodonts. Results from this investigation will provide a clearer picture of morphological diversification trends in the dentition of basally branching cynodonts, illuminating macroevolutionary processes influencing the patterns of their richness throughout the Permian and Mesozoic. 

Main collaborators: Dr. Fernando Abdala (Unidad Ejecutora Lillo) and Dr. Jonah Choiniere (University of the Witwatersrand)

Selected publications:

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. 1–21.

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.

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.

Dental evolution, feeding ecology and ecospace modeling in theropod dinosaurs 

Theropods are a clade of bipedal tetrapods among which birds and all strictly carnivorous dinosaurs are found. Along with other dinosaur clades, they appeared in the Late Triassic and rapidly acquired a worldwide distribution. In the Jurassic, small theropods gave rise to birds, the only dinosaurs to survive the Cretaceous-Paleocene (K-Pg) mass extinction event 66 million years ago. After surviving the K‒Pg extinction event, birds radiated into some ecological niches left by non-avian dinosaurs. As a result, theropods are one of the most successful groups of tetrapods, and the most morphologically and taxonomically diverse clade of dinosaurs. Although toothed theropods were mostly carnivores, there is abundant evidence for substantial trophic variation within the group, including herbivory, omnivory, and piscivory. This trophic diversity resulted in many tooth shapes and dental morphologies within the group. The main objectives of this research project are to: i) identify the main evolutionary transformations occurring in the dentition of theropods; ii) investigate disparity, evolutionary rates, and dental complexity in the dentition of theropods through time, and test correlations between changes in dental disparity and complexity and different macroevolutionary variables such as species richness, body size, and angiosperm radiation; iii) assess feeding ecology in non-avialan (na) theropods using direct evidence of diet and feeding-related characters; iv) explore ecomorphospace occupation in na theropods through time and by palaeolatitudes using different ecological parameters such as paleoenvironment, habitat, body size, diet, and locomotion. 

Main collaborators: Dr. Jonah Choiniere (University of the Witwatersrand) and Dr. Octávio Mateus (Universidad Nova de Lisboa).

Selected publications:

Tschopp, E., Araújo, R., Brusatte, S. L., Hendrickx, C., Macaluso, L., Maidment, S. C. R., Rabi, M., Rashid, D., Romano, C. and Williamson, T. 2020. Dinosaurs, But Not Only: Vertebrate Evolution in the Mesozoic. In: Martinetto, E., Tschopp, E. and Gastaldo, R. A. (eds.), Nature through Time: Virtual Field Trips through the Nature of the Past, 187–208. Springer International Publishing, Cham.

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.

Hendrickx, C., Hartman, S. A. and Mateus, O. 2015a. An overview of non-avian theropod discoveries and classification. PalArch’s Journal of Vertebrate Palaeontology 12 (1): 01–07.

Integumentary structures in non-avian dinosaurs 

Unlike feathers and other feather-like structures, the scaly skin of many dinosaurs is poorly known and often succinctly described. This is particularly the case in non-avian theropods in which many preserve undescribed or briefly described skin such as Carnotaurus, Allosaurus and Juravenator. This project aims to thoroughly describe the skin of non-avialan dinosaurs, especially those that belong to the clade Theropoda and Marginocephalia, and explore the evolution of integumentary structures in Mesozoic dinosaurs.

Main collaborators: Dr. Phil Bell (University of New England) and Dr. Michael Pittman (The University of Hong Kong).

Selected publications:

Bell, R. P., 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.

Bell, P. R., Hendrickx, C., Pittman, M. and Kaye, T. G. 2022. Oldest preserved umbilical scar reveals dinosaurs had ‘belly buttons’. BMC Biology 20 (1): 132.

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 97 (3): 960–1004.

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.

Bell, P. R. and Hendrickx, C. 2020. Crocodile-like sensory scales in a Late Jurassic theropod dinosaur. Current Biology 30 (19): R1068–R1070.

Identification of isolated theropod teeth 

One of the main goals of my PhD thesis at the Universidad Nova de Lisboa was to better identify isolated theropod teeth. Very few tools were proposed to identify isolated theropod teeth at the time I started my PhD thesis in 2010 and the dental anatomy of many theropods often suffered from a lack of information. My PhD project allowed me to provide new tools to better resolve the phylogenetic position of isolated teeth and better understand the distribution of many dental features such as hooked denticles, twisted carinae and flutes. These techniques and the terminology I proposed to describe theropod teeth have now been wildly used in the literature on theropod teeth. This project led to the publication of several articles to identify isolated theropod teeth from the Middle Jurassic of the Isle of Skye, the Upper Jurassic of Portugal or the Upper Cretaceous of Argentina. The results of other projects on isolated theropod teeth from the Cretaceous of Africa and South America are yet to be published.

Main collaborators: Dr. Octávio Mateus (Universidad Nova de Lisboa) and Dr. Jonah Choiniere (University of the Witwatersrand).

Selected publications:

Hendrickx, C.*, Trapman, T. H.*, Holwerda, F. M., Stein, K. H. W., Wills, S., Rauhut, O. W. M., Melzer, R. R., Van Woensel, J. 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.

Hendrickx, C., Tschopp, E. and Ezcurra, M. d. 2020a. 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.

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.

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): 1–74.

Theropod dinosaurs from the Upper Jurassic of Portugal

One of the many chances I had when doing my PhD thesis in Lourinhã, Portugal, was to work on undescribed or briefly theropod material deposited at the Museu da Lourinhã and from the Upper Jurassic Lourinhã Formation. My first publication was on theropod embryos from this stratigraphic unit. The embryos preserved teeth and tooth-bearing bones, which allowed me to identify them as the megalosaurid theropod Torvosaurus. I then worked on several specimens belonging to very large-sized (and most likely adult) Torvosaurus individuals, which I referred to as the new species Torvosaurus gurneyi (see this page). The main goal of my PhD project was to identify isolated theropod teeth from the Lourinhã Formation, which I did with four of them using a new technique of cladistic analysis. I remain deeply interested in the theropod fauna from the Upper Jurassic of Portugal and hope to get the opportunity to work on new theropod specimens again in the future.

Main collaborators: Dr. Octávio Mateus (Unidad Ejecutora Lillo) and Dr. Ricardo Araujó (Universidad de Lisboa)

Selected publications:

Hendrickx, C. and Mateus, O. 2014a. 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): 1–74.

Hendrickx, C. and Mateus, O. 2014b. 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.

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 (1924): 1–8.