The osteology of the pelvic girdle skeleton in representatives of several families of eurypterygian fishes were studied. The pelvic girdle is made up of a pair of ventral plates (basipterygia). Each plate consists of a central part, a median process, a membranous anterior process, an endochondral posterior process, wings, radials, and pelvic spines and rays. Splints are present in some primitive taxa. The central part is an ossification of the original pelvic cartilage that usually anteriorly retains a cartilage tip and posteriorly forms an articulation surface for the fin radials and rays. The membranous wings constitute an internal, an external dorsal, an external ventral, and a ventral wing. Not all the processes and wings are present in all eurypterygian fishes. It is the elaboration and orientation of wings that leads to its complexity in higher fishes. Primitively, in euteleosts, there are a number of autogenous radials. The medialmost radial is the largest and associated or fused to the base of the innermost ray and other radials are autogenous.
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