A landmarking protocol for geometric morphometric analysis of squamate endocasts

Allemand, Rémi; López‐Aguirre, Camilo; Abdul‐Sater, Jade; Khalid, Waqqas; Lang, Madlen M.; Macrì, Simone; Di‐Poï, Nicolas; Daghfous, Gheylen; Silcox, Mary

doi:10.1002/ar.25162

Cited by 3 publications

(1 citation statement)

References 66 publications

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“…This indicates that areas with a close correspondence between the brain and endocranial surface can potentially exhibit deviations in shape; however, the typical degree and pattern of such divergences remain to be tested. By employing landmark‐based geometric morphometric methods (e.g., Allemand et al, 2023; Watanabe, Gignac, et al, 2019), future quantitative assessments of brain–endocast correspondence in shape will help us to understand which brain regions are accurately or poorly approximated by the corresponding areas on squamate endocasts. Such analyses will have important implications for accurate and precise inferences of brain morphology from squamate endocasts.…”

Section: Discussionmentioning

confidence: 99%

Endocast, brain, and bones: Correspondences and spatial relationships in squamates

Allemand

Abdul‐Sater

Macrì

et al. 2023

The Anatomical Record

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Vertebrate endocasts are widely used in the fields of paleoneurology and comparative neuroanatomy. The validity of endocranial studies is dependent upon the extent to which an endocast reflects brain morphology. Due to the variable neuroanatomical resolution of vertebrate endocasts, direct information about the brain morphology can be sometimes difficult to assess and needs to be investigated across lineages. Here, we employ X‐ray computed tomography (CT), including diffusible iodine‐based contrast‐enhanced CT, to qualitatively compare brains and endocasts in different species of squamates. The relative position of the squamate brain within the skull, as well as the variability that may exist in such spatial relationships, was examined to help clarify the neurological regions evidence on their endocasts. Our results indicate that squamate endocasts provide variable representation of the brain, depending on species and neuroanatomical regions. The olfactory bulbs and peduncles, cerebral hemispheres, as well as the medulla oblongata represent the most easily discernable brain regions from squamate endocasts. In contrast, the position of the optic lobes, the ventral diencephalon and the pituitary may be difficult to determine depending on species. Finally, squamate endocasts provide very limited or no information about the cerebellum. The spatial relationships revealed here between the brain and the surrounding bones may help to identify each of the endocranial region. However, as one‐to‐one correspondences between a bone and a specific region appear limited, the exact delimitation of these regions may remain challenging according to species. This study provides a basis for further examination and interpretation of squamate endocast disparity.

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Section: Discussionmentioning

confidence: 99%

Endocast, brain, and bones: Correspondences and spatial relationships in squamates

Allemand

Abdul‐Sater

Macrì

et al. 2023

The Anatomical Record

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Approaches to studying endocranial morphology in Euarchontoglires: Assessing sources of error for a novel and biologically informative set of landmarks

Lang,

Allemand,

López-Aguirre

et al. 2023

J Mammal Evol

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First Virtual Reconstruction of a Mosasaurid Brain Endocast: Description and Comparison of the Endocast of Tethysaurus nopcsai with Those of Extant Squamates

Allemand,

Polcyn,

Houssaye

et al. 2024

Diversity

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Paleoneurological studies of mosasaurids are few and limited to old partial reconstructions made from latex casts on Platecarpus and Clidastes. Here, the brain endocasts of three specimens of the early mosasaurid Tethysaurus nopcsai from the Turonian of Morocco are reconstructed for the first time by using micro-computed tomography. Comparisons between Tethysaurus and the later Platecarpus and Clidastes show that distinct endocranial organizations have occurred within the clade through time, including differences in the flexure of the endocast and the size of the parietal eye. The physiological consequences of such variability remain unclear and further investigations are required to better interpret these variations. In addition, the endocast of Tethysaurus was compared to those of extant anguimorphs, iguanians, and snakes, using landmark-based geometric morphometrics. The results revealed that Tethysaurus exhibits a unique combination of endocranial features compared to extant toxicoferans. Contrary to previous statements, we find no strong resemblance in endocast morphology between Tethysaurus and varanids. Rather, the endocast of Tethysaurus shows some morphological similarities with each of the clades of anguimorphs, iguanians, and snakes. In this context, while a notable phylogenetic signal is observed in the variability of squamate endocasts, it is premature to establish any phylogenetic affinities between mosasaurids and extant squamates based solely on endocast morphologies.

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A landmarking protocol for geometric morphometric analysis of squamate endocasts

Cited by 3 publications

References 66 publications

Endocast, brain, and bones: Correspondences and spatial relationships in squamates

Endocast, brain, and bones: Correspondences and spatial relationships in squamates

Approaches to studying endocranial morphology in Euarchontoglires: Assessing sources of error for a novel and biologically informative set of landmarks

First Virtual Reconstruction of a Mosasaurid Brain Endocast: Description and Comparison of the Endocast of Tethysaurus nopcsai with Those of Extant Squamates

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