Dasyatis violacea ranges in the Atlantic Ocean from 46? N to 38? S. Pelagic longline captures have accounted for 77 of 79 records and attest to a surface-layer, open-ocean distribution. Differences between descriptive characters of D. violacea and D. purpureus support separation of the species. Tail length, presence or absence of a mediodorsal ridge on the tail, and the size or numbers of caudal spines were found to be unreliable descriptive characters for D. violacea. Anterior disc margins, the posterior edge of the nasal curtain, spination, and coloration vary among specimens. Observations are reported on eggs encapsulated in a membranous shell within the uterus, the duration of the reproductive season, and the structural and functional relation between the mother and embryo. At maturity males and females are about the same in size and number; after maturity females are larger and outnumber males by a ratio greater than 3:1. Stomach contents reveal a diet consistent with the near-surface, openocean environment of the species.
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Wilson et al. (1970) studied this question.
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