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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.
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.
Fish anatomy is the study of the form or morphology of fish. ... The ribs attach to the spine and there are no limbs or limb girdles. ... Pelvic/Ventral fins: Found ...
pectoral girdle The bones to which the pectoral fin is attached. peduncle Usually referred to as the caudal peduncle, the region of the body between the end of the anal fin and the base of the caudal fin. pelagic Living on or in the open seas. pelvic girdle The bones to which the ventral fins are attached. pelvic fins
The pelvic girdle was present in early vertebrates, and can be tracked back to the paired fins of fish that were some of the earliest chordates. [ 52 ] The shape of the pelvis, most notably the orientation of the iliac crests and shape and depth of the acetabula , reflects the style of locomotion and body mass of an animal.
While the pelvic girdle of modern osteichthyans is made exclusively of endochondral bone, the pelvis of Guiyu included dermal bones as well, including paired lateral plates and an unpaired median plate. [4] The pectoral, pelvic and dorsal fins bore large spines, as seen in many placoderms and acanthodians (basal stem-chondrichthyans).
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.