Abstract

CANIZALES, Israel. Morphometric variation in skulls of the Atlantic spotted dolphin (Stenella frontalis) from Venezuela. Rev. Mex. Biodiv. [online]. 2021, vol.92, e923552.  Epub Nov 29, 2021. ISSN 2007-8706.  https://doi.org/10.22201/ib.20078706e.2021.92.3552.

The Atlantic spotted dolphin, Stenella frontalis (Cuvier, 1829), is a common species in Venezuela. The present study aims to determine the degree of variation in the cranial characteristics of individuals of S. frontalis and to show the existence of geographical differentiation or taxonomic separation of the groups. Univariate and multivariate tests of 14 skull measurements from 20 previously morphometrically characterized specimens were used to distinguish morphological groups and their variation. Roughly 78% of the variables of S. frontalis (west) showed mean values lower than those of S. frontalis (east). The variable with the highest percentage of variation between groups was the parietal width ACP = 28%. Coefficients of variation revealed significant differences (p < 0.05) between S. frontalis (west) and S. frontalis (east). Principal component analysis and cluster analysis (UPGMA) showed division between groups. These results support the recognition of two distinct morphological groups. However, the facial and cephalic indices used to differentiate the taxonomic units did not show significant differences (Kruskal-Wallis, H = 2.316; p=0.128, H = 1.576; p = 0.209); furthermore, box and whiskers diagrams on the facial, cephalic and cranial indexes commonly useful to illustrate the “75% rule” showed no differentiation between the West and East groups of S. frontalis.

Keywords : Multivariate Analysis; Differentiation; Morphometry; Stenella frontalis; Venezuela.

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