Osteología comparada del esqueleto caudal y columna vertebral del género Tlaloc (Cyprinodontiformes: Profundulidae)

Abstract

Introduction: Tlaloc is a genus of freshwater fish, endemic, known only from southern Mexico and Central America; however, studies based on the analysis of osteological traits are scarce for fishes in the Profundulidae family. Objective: This paper describes the anatomy of the caudal bones and backbone of all species the genera Tlaloc. Methods: A comparative analysis was performed on 44 cleared and stained specimens to identify the differences and similarities of backbone elements and the organization of the caudal skeleton among the species. Results:  The comparison of the caudal skeleton in the four species of the genus Tlaloc, revealed a very similar pattern in the morphology of the species; however, some characters were detected that may be useful for discrimination of species of the genus; the triangular shaped hipural plate is a character that only appeared in Tlaloc labialis, while in the rest of the species (T. candalarius, T. portillorum and T. hildebrandi), the hypural plate is fan-shaped. The total number of vertebrae, including the vertebral centrum, in the four species of the genus Tlaloc ranged from 33 to 38, of which 15-17 were abdominal vertebrae and 17-21 caudal vertebrae; T. portillorum had the lowest number of total vertebrae (33); while T. labialis had the highest number of total vertebrae (37-38) Conclusions: The consistent relationship to these skeletal elements suggests that the vertebrae and caudal fin ray count is a character of fundamental nature for the profundulid fishes, giving it particular taxonomic significance in that group.