Morphological Variation of the Neurocranium of Eight Species of Batoids (Chondrichthyes)
Mónica González-Isáis & Héctor M. Montes D.
Systematics and anatomy studies have revealed that characteristics of the batoids skeleton show significant variability and provide relevant information on the phylogenetic relationships of this group. Within this framework, our objective is describing the neurocranium morphology in eight species of batoids. Large variations were found, mainly in the rostrum, number of fontanelles, orientation of nasal capsules, and the condition and development of the pre- and post-orbital processes. These variations allowed us to group these craniums in three morphotypes. The first, including Narcine bancroftii, has unique characteristics, such as a squared rostrum and branched anterorbital cartilages; there are no pre-or post- orbital processes, supraorbital crest or rostral appendix. The second morphotype includes Rostroraja texana and Pseudobatus lentiginosus, which have a well-developed rostrum with a rostral appendix in the anterior region, two fontanelles, jugal arches in the occipital region, and pre- and post-orbital processes poorly developed. The third morphotype includes myliobatoids species, which have small or absent rostrum, rostral appendix separated from the cranium, one fontanelle, and developed pre- and post-orbital processes. Most species have morphological variations throughout their development; therefore, when conducting phylogenetic studies, using characters from adult specimens is fundamental.