# Evidence of Morphological and Morphometric Differences in the Sella Turcica of Pteronotus mesoamericanus and P. mexicanus

## TL;DR

This study finds morphological and size differences in the skulls of two bat species from different regions of Mexico, suggesting possible evolutionary divergence.

## Contribution

The study provides new morphometric evidence of cranial differences between Pteronotus mesoamericanus and P. mexicanus populations.

## Key findings

- Ten measurements of the sella turcica showed significant differences between Gulf of Mexico and Pacific Coast bat populations.
- The dorsum sellae has a truncated pyramidal shape with notable variation in dimensions between the two species.
- The study suggests these cranial differences could help distinguish lineages in related bat species across the Americas.

## Abstract

Minor modifications in the structure of living beings are signs of the gradual formation of new species. In addition, studying these changes gives us scientific tools, for example, to know whether the species of one region are different from those of another area. In this work, we aim to show these subtle differences in the cranial characteristics in the populations of bats with extensive distributions in Mexico. We now know that there are differences in the populations of Pteronotus mesoamericanus of the Gulf of Mexico and P. mexicanus of the Pacific.

Morphological modifications are a potential mechanism for functional species and phylogenetic diversification. The sella turcica in mammals is a structure associated with the basisphenoid bone and serves as the receptacle for the pituitary gland; however, little is known about the morphological variation that may affect functionality in chiropterans. In this study, we provide morphological and morphometric evidence of differences between populations of Pteronotus mesoamericanus [the Gulf of Mexico] and P. mexicanus [the Pacific Coast] by describing variations in the dimensions of the dorsum sellae and the processus clinoideus caudalis of the sella turcica. We obtained 20 a priori designed measurements of the dorsum of the sella turcica from 243 skulls of both species from various locations in Mexico. The dorsum sellae were found at an average distance of 3.4 mm from the lower edge of the foramen magnum. The dorsum of the sella turcica has a truncated pyramidal shape, with the processus clinoideus caudalis located at the tip of the pyramid. Ten of the measurements obtained were found to be significant for both regions (the Pacific Coast and the Gulf of Mexico). We propose that these measurements be tested in future studies of populations from the Mormoopidae family in the Antilles, Central America, and South America for comparative purposes, and to help distinguish different lineages and functions.