Evolutionary ecomorphology of select species of rays distributed in the Gulf of Mexico

Abstract

Bathomorphi is a diverse lineage, accounting for more than half of the chondrichthyan diversity. Yet, more than 12.3% of the species are in the “deficient data” category of the IUCN Red List of Threatened Species, indicating a gap in the knowledge of this group. In the present study, the diet and morphological variation associated with locomotion (disc) and feeding (Meckel’s cartilage and teeth) of 9 species of batomorphs were analyzed to assess trophic and morphological diversity, size, and sexual dimorphism. Comparative phylogenetic methods were used to determine the evolutionary relationship between variables. According to our results, the species selected showed a wide and intricate morphological variation. Sexual dimorphism was mainly observed in tooth morphology, where males tended to have more pointed teeth than females. Disc allometry was recorded for most species; small specimens presented a longer snout than larger specimens. Only the Meckel’s cartilage was related to the diet of the species. However, the morphological variation of the disc, Meckel’s cartilage, and teeth of the batomorphs were correlated through the evolution of the group and responded to functional patterns such as swimming and feeding, which finally, determined the ecology of the species.