Reassessment of Xenodens calminechari with a discussion of tooth morphology in mosasaurs

Henry S Sharpe ¹, Mark J Powers ¹, Michael W Caldwell ¹

⁰Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada.

Anatomical Record (Hoboken, N.J. : 2007) +

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December 17, 2024

View abstract on PubMed

Summary

The mosasaurid Xenodens calminechari may be a forgery. Its holotype specimen shows artificially placed teeth, suggesting the taxon is a nomen dubium and highlighting issues in paleontology.

Area Of Science

Vertebrate Paleontology
Mosasaurid Taxonomy
Paleontological Specimen Authentication

Background

The mosasaurid taxon Xenodens calminechari was described by Longrich et al. (2021) based on a maxilla specimen (MHNM.KH.331).
The holotype was sourced from Morocco, an area known for manipulated or forged paleontological specimens.
Concerns exist regarding the scientific validity of taxa based on tooth-based holotypes, especially considering intraspecific variation and convergence.

Purpose Of The Study

To re-examine the holotype of Xenodens calminechari (MHNM.KH.331) for potential forgery.
To assess the validity of the diagnostic characters proposed for Xenodens calminechari.
To provide recommendations for the designation of mosasaurid holotypes and specimen authentication.

Main Methods

Visual examination of the holotype maxilla (MHNM.KH.331) and its associated teeth.
Analysis of tooth-to-maxilla articulation and potential use of adhesives.
Comparison of dental morphology with known mosasaurid ontogenetic variation and extant lizard dentition.
Review of established protocols for identifying artificially manipulated specimens.

Main Results

The holotype MHNM.KH.331 exhibits four tooth crowns in two apparent alveoli, with evidence suggesting artificial placement and adhesive use.
The claimed fused tooth 'roots' are identified as ankylosed periodontal ligament and alveolar bone, a common mosasaurid condition.
Dental morphology differences are explainable by ontogenetic variation within another mosasaur taxon, such as Carinodens.
At least two proposed apomorphies for Xenodens calminechari appear to be products of forgery.

Conclusions

Xenodens calminechari is argued to be a nomen dubium due to evidence of forgery in its holotype.
The specimen highlights persistent issues in vertebrate paleontology concerning commercially sourced material and inadequately tested specimens.
CT scanning is recommended for MHNM.KH.331 to definitively identify artificial additions, and revised holotype designation guidelines for mosasaurids are proposed.

Keywords:

dentition mosasaur paleontology squamate taxonomy

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