Dictionary of Ichthyology  

mesopterygium (plural mesopterygia) = the median, elongated basal cartilage of the pectoral fins in Elasmobranchii, Holocephali and primitive Teleostomi.

Shoulder girdle and proximal part of pectoral fin of Raja, g = right half of girdle, ms = mesopterygium, mt = metapterygium, p = protopterygium, r = radii of fin, from Kingsley's "Textbook of Vertebrate Zoology, 1906. Photograph by Brian W. Coad.

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