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In actinopterygians, the pelvic fin consists of two endochondrally-derived bony girdles attached to bony radials. Dermal fin rays (lepidotrichia) are positioned distally from the radials. There are three pairs of muscles each on the dorsal and ventral side of the pelvic fin girdle that abduct and adduct the fin from the body. [citation needed]
The pelvic girdle (hip) and pelvic fins of Panderichthys represents an intermediate in the fish-tetrapod evolution. During the fish-tetrapod evolution the pelvic girdle became a weight bearing structure when the ilium, meso-ventral contact of the sides of the girdle, an ilium, and a sacral rib developed.
Chondrichthyes (/ k ɒ n ˈ d r ɪ k θ i iː z /; from Ancient Greek χόνδρος (khóndros) 'cartilage' and ἰχθύς (ikhthús) 'fish') is a class of jawed fish that contains the cartilaginous fish or chondrichthyans, which all have skeletons primarily composed of cartilage.
The pelvic fin assists the fish in going up or down through the water, turning sharply, and stopping quickly. In gobies, the pelvic fins are often fused into a single sucker disk. This can be used to attach to objects [1] Pelvic fins can take many positions along the ventral surface of the fish.
The ribs attach to the spine and there are no limbs or limb girdles. The main external features of the fish, the fins, are composed of either bony or soft spines called rays which, with the exception of the caudal fins, have no direct connection with the spine. They are supported by the muscles which compose the main part of the trunk. [2]
Fins located on the median line of the fish; the dorsal, anal and caudal fins. mediolateral Between the middle and the sides. melanophore A cell (chromatophore) containing melanin or other black pigment. mesocoracoid A bone of the pectoral arch or shoulder girdle. mesopelagic Refers to the region of the open ocean between 200 m and 1000 m in depth.
In the primitive condition, the pelvic girdles have a metapterygial element supporting only one or two radials and most of the fin radials are attached directly to the pelvic plate. The derived condition differs in that there is a much higher number of radials supported by the pelvic plate.
The pelvic and pectoral girdles are both visible and the axial and cranial elements are also both present. The bowfin is a member of actinopterygii which means that the pectoral girdle is partly endochondral but mostly dermal bone. In this group of fish the fins function to maneuver, brake, and for slight positional adjustments.