Coracoid cartilage - Uko nankotsu

…There is a similar skeleton for the posterior paired limbs (pelvic fins or hind limbs), which is called the pelvic girdle (pelvis, or lower limb girdle in humans); the shoulder girdle and pelvic girdle together are generally called the limb girdle. The shoulder girdle of cartilaginous fish is a U-shaped skeleton that is not connected to the central skeleton, and consists of three parts on one side: the coracoid cartilage, the scapular cartilage, and the upper scapular cartilage, and the pectoral fin is attached to the connection between the first two. In vertebrates with hard bones, the number of bones that make up the shoulder girdle is generally more numerous in primitive species and decreases in more advanced species.

*Some of the terminology explanations that mention "coracoid cartilage" are listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…後方の有対肢(腹びれまたは後肢)に対しても類似の骨格があってこれを腰帯（ようたい）(骨盤のことでヒトでは下肢帯)とよび，肩帯と腰帯を合わせて一般に肢帯という。　軟骨魚類の肩帯は中軸の骨格とはつながらないU字形の骨格で，片側が烏口（うこう）軟骨･肩甲軟骨･上肩甲軟骨という3部分から成り，前2者の接続部に胸びれが付着する。硬い骨を備えた脊椎動物になると，肩帯の構成骨の数は一般に原始的な種類に多く，高等なものほど減少する。…

※「烏口軟骨」について言及している用語解説の一部を掲載しています。

出典｜株式会社平凡社世界大百科事典 第２版について | 情報