The Actinopterygii (the plural form of Actinopterygius) comprise the
class of the ray-finned fishes.The ray-finned
fishes are so called because they possess
lepidotrichia or "fin rays", their fins being webs of skin supported by bony or horny spines ("rays"), as opposed to the fleshy, lobed fins that characterize the order
Sarcopterygii. These actinopterygian fin rays attach directly to the proximal or basal skeletal elements, the radials, which represent the link or connection between these fins and the internal skeleton (e.g., pelvic and pectoral girdles).
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