McEachran, J.D. & Konstantinou, H. (1996)
Survey of the variation of alar and malar thorns in skates: phylogenetic implications (Chondrichthyes: Rajoidei). Journal of Morphology, 228(2), 165–178
DOI: 10.1002/(SICI)1097-4687(199605)228:2<165::AID-JMOR5>3.0.CO;2-4