On the anatomy and evolution of the locomotor apparatus of the nipple-tailed ocean sunfish (Masturus lanceolatus). Bulletin of the AMNH ; v. 76, article 4
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Abstract
"The purpose of this study was to discover, through a structural series from primitive percomorph to Masturus, the evolutionary changes which gave rise to the peculiar locomotor apparatus of the molids. The structural series: (1) generalized percomorph, (2) acanthurid, (3) balistid, (4) diodont, (5) molid, which was worked out by Gregory on skull structure, was adopted as a provisional basis for the present study and the present study affords additional evidence for its validity. In general the following major changes are involved in passing from generalized percomorph to molid: (1) great shortening and deepening of body; (2) extreme emphasis and vertical growth of dorsal and anal fins; (3) corresponding hypertrophy of erector and depressor muscles of dorsal and anal, involving their great extension forward and eventual atrophy and disappearance of mm. inclinatores; (4) corresponding reduction and eventual loss of the lateralis mass of metameric musculature; (5) correlated reduction and loss of undulation of the body and of the true caudal fin; (6) formation of new or pseudo-caudal fin by extension of dorsal and anal, meeting around the shortened caudal end of the column; (7) crowding of the posterior dorsal and anal pterygiophores against the seventh neural and eighth haemal spines; (8) crowding of the body cavity by forward growth of the erector plus depressor muscles of the anal fin; (9) reduction and loss of the puffing habit (will be treated more fully in a paper on Ranzania); (10) the long ligament, from supraoccipital crest to the anterior border of the dorsal fin, probably represents a vestige of the trigger mechanism of balistoids. The characters of the alimentary tract suggest that these fishes are bottom-living forms; the skin, skeleton, and the loss of the air-bladder suggest that they live in deep water and the form of the fins with their powerful muscles indicates an active existence"--P. 149-150.
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Includes bibliographical references (p. 150).