On the Authenticity of Xenodens calminechari

Nicholas R. Longrich(1), Nathalie Bardet(2), Xabier Pereda-Suberbiola(3), Anne Schulp (4,5), Nour-Eddine Jalil (2,6).

(1) Department of Biology and Biochemistry, University of Bath, Bath, UK; (2) Centre de Recherches en Paléontologie – Paris (CR2P), CNRS, Sorbonne Université, Muséum national d’Histoire naturelle, 57 Rue Cuvier, CP 38, 75005 Paris, France (3) Departamento de Geología, Facultad de Ciencia y Tecnología, Universidad del País Vasco (UPV/EHU), Apartado 644, 48080 Bilbao, Spain (4) Naturalis Biodiversity Center, Darwinweg 2, 2333 CR Leiden, The Netherlands (5) Faculty of Geosciences, Utrecht University, Budapestlaan 4, 3584 CD Utrecht, The Netherlands (6)

We would like to address the recent claims raised in a recent article published in the Anatomical Record that the mosasaurid Xenodens calminechari is based on forged material.

We would like to respond here to confirm the authenticity of the Xenodens holotype.

Our team includes the world experts in Moroccan mosasaurs. These collaborations have produced almost 20 papers and resulted in the description of 10 new mosasaurid species. Having examined literally thousands of specimens, and having conducted more than two decades of fieldwork in the Phosphates of Morocco, we are very familiar with recognizing reconstruction.

We can confirm the authenticity of Xenodens because the first author personally prepared the specimen by hand from the original matrix using a tungsten carbide needle, paintbrush and support jacket; if any reconstruction had taken place, it would have been obvious. We can furthermore state that “gummy” texture identified on the fossil as reconstructed material is simply the Paraloid B-72 consolidant applied over original bone. During preparation a tooth detached, exposing the base of the crown and interior of the root: any reconstruction would have been readily visible.

Ensuring the integrity of fossils studied is important, but accusations of forgery are also serious, and therefore should be made based on thorough study and robust evidence. Sharpe and colleagues did not examine the fossil in person, or study high-resolution photographs. Neither did they request access to study the fossil from the Natural History Museum of Marrakech (Cadi Ayyad University) where the specimen is accessioned. The study is therefore based only on second-hand observations, speculation, and misinterpretations of low-resolution published images. It is therefore surprising that Anatomical Record chose to publish this paper. Last, two new specimens of Xenodens have recently been identified, both showing the same unusual morphology as the holotype, and are now under study. We are therefore confident that further study will vindicate the validity of Xenodens.

            We also feel the need to note that western scientists have historically published on Moroccan fossils held in collections abroad. These projects have often failed to involve Moroccans, building careers while offering Morocco little in return, and the vast majority of Morocco’s important fossils have ended up outside of the country as a result. On the contrary, our collaboration involves an international team of specialists of Mesozoic marine and terrestrial reptiles as well as geologists and geochemists. This project is based on two agreements: 1) a long-term Moroccan-French Scientific Program of collaboration (since 1997) between the Muséum National d’Histoire Naturelle of Paris, the Office Chérifien des Phosphates and the Ministry of Energy, Mines, Water and Environment of Morocco, as well as the University Cadi Ayyad of Marrakech and the University Chouaib Doukkali of El Jadida; 2) a partnership between the University Cadi Ayyad in Marrakech and the University of Bath (since 2020). Both are intended to preserve Morocco’s fossil heritage for the people of Morocco and the world and have established some of the most important paleontological collections of Cretaceous and Paleogene vertebrates in the world. Discrediting this work, without first adequately researching the fossils first-hand, undermines these conservation efforts. Whilst we are confident in the robustness of our original research we note that CT scanning will give us further scientific insight into the fossil and we will be conducting this study in the coming months to be able to address the issues raised by Sharpe et al.

            Xenodens would hardly be the first time that scientists have found nature too strange to be true. Some scientists assumed that the duckbill platypus was a hoax when it was first discovered. Although the morphology of Xenodens is indeed bizarre and improbable, other unusual creatures in the phosphates— the dagger-toothed mosasaur Khinjaria, strange Stelladens, and the tube-nosed marine turtle Ocepechelon— show that the Maastrichtian was a time of wild evolutionary experimentation that produced many unbelievable species. In science one should remember that evolution is cleverer and more creative than we are, and produces things far stranger than we can imagine.

Nicholas R. Longrich

Nathalie Bardet

Xabier Pereda-Suberbiola

Anne Schulp

Nour-Eddine Jalil

Update June 9, 2025:

We have CT scans in hand and will proceed with a formal rebuttal. We are confident in the authenticity of Xenodens. We will release further details and analysis soon. —NL

References

Longrich, N.R., Bardet, N., Schulp, A.S., Jalil, N.-E., 2021. Xenodens calminechari gen. et sp. nov., a bizarre mosasaurid (Mosasauridae, Squamata) with shark-like cutting teeth from the upper Maastrichtian of Morocco, North Africa. Cretaceous Research 123, 104764.

Sharpe, H.S., Powers, M.J., Caldwell, M.W., 2024. Reassessment of Xenodens calminechari with a discussion of tooth morphology in mosasaurs. The Anatomical Record.