Axial skeleton morphology of the Western Palearctic aphaniid fishes (Teleostei: Cyprinodontiformes; Family: Aphaniidae)

Abstract

AbstractThe axial skeleton morphology of eighteen aphaniid species was examined for the first time by X‐ray radiography, a non‐lethal method. The number of total vertebrae in the genus Aphanius is ranged from 26 to 29, in Aphaniops, it is ranged from 24 to 28, and in Paraphanius mento, it is ranged from 26 to 27. The vertebral column in Aphanius was often slightly curved, and it is varied from almost straight (most common) to slightly or strongly curved and straight in two others. The caudal skeleton of the family Aphaniidae is characterized by a single and completely fused hypural plate, and a total number of 9–12 branched segmented soft rays, a single and elongate epural bone. All examined species of the genus Aphanius and Paraphanius mento displayed a straight epural bone in their caudal skeleton, while it was often sinuous‐like and thick in all species of the genus Aphaniops. This study supports the assumption that a sinuous epural is likely the first detected morphological synapomorphy for the “inner” clade of Aphaniops. The family Aphaniidae is closer to Cyprinodontidae, Valenciidae and Fundulidae than other cyprinodontiforms in the caudal skeleton, which is in agreement with the multigene phylogeny of cyprinodontiforms.