Beyond the carapace: skull shape variation and morphological systematics of long-nosed armadillos (genus ).

BACKGROUND

The systematics of long-nosed armadillos (genus ) has been mainly based on a handful of external morphological characters and classical measurements. Here, we studied the pattern of morphological variation in the skull of long-nosed armadillos species, with a focus on the systematics of the widely distributed nine-banded armadillo ().

METHODS

We present the first exhaustive 3D comparison of the skull morphology within the genus , based on micro-computed tomography. We used geometric morphometric approaches to explore the patterns of the intra- and interspecific morphological variation of the skull with regard to several factors such as taxonomy, geography, allometry, and sexual dimorphism.

RESULTS

We show that the shape and size of the skull vary greatly among species, with representing a clear outlier compared to other long-nosed armadillos. The study of the cranial intraspecific variation in evidences clear links to the geographic distribution and argues in favor of a revision of past taxonomic delimitations. Our detailed morphometric comparisons detected previously overlooked morphotypes of nine-banded armadillos, especially a very distinctive unit restricted to the Guiana Shield.

DISCUSSION

As our results are congruent with recent molecular data and analyses of the structure of paranasal sinuses, we propose that should be regarded either as a polytypic species (with three to four subspecies) or as a complex of several distinct species.