Batoids are a superorder of cartilaginous fish consisting of skates, rays and other fish all characterized by dorsoventrally flattened bodies and large pectoral fins fused to the head. This distinctive morphology has resulted in several unique forms of locomotion. Most Batoids exhibit median paired fin swimming, utilizing their enlarged pectoral fins. Batoids that exhibit median paired fin swimming fall somewhere along a spectrum of swimming modes from mobuliform to rajiform based on the number of waves present on their fin at once. Of the four orders of Batoidae this holds truest for the Myliobatiformes (rays) and the Rajiformes (skates). The two other orders: Rhinopristiformes and Torpediniformes exhibit a greater degree of body caudal fin swimming.[1][2]
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^Rosenberger, J.L. (2001). "Pectoral fin locomotion in batoid fishes: undulation versus oscillation". Journal of Experimental Biology. 204 (2): 379–392. doi:10.1242/jeb.204.2.379. PMID11136623.