Spiny fish - Spiny fish

Japanese: 棘魚類 - きょくぎょるい

Acanthodii is one of the most primitive jawed fishes whose fossils have been discovered from the Silurian to Permian periods of the Paleozoic era. They are called acanthodii because they have sharp spines on their dorsal, pectoral and anal fins (some books say they are called sticklebacks, but sticklebacks are a completely different fish that belong to the Teleostei superorder of the Actinopterygii subclass of the Osteichthyes). Acanthodii were once considered to be closely related to cartilaginous fishes and were sometimes translated as echinosarcoids, but recently the theory that they are closer to the ancestors of bony fishes has gained momentum.

Source: Heibonsha World Encyclopedia, 2nd Edition Information

Japanese:

古生代のシルル紀から二畳紀にかけて化石が発見される最も原始的な有顎魚類の1綱Acanthodii。背びれ，胸びれ，しりびれなどに鋭いとげがあるので棘魚類とよばれている(トゲウオ類と書かれている本もあるが，トゲウオ類は現生の硬骨魚綱条鰭（じようき）亜綱真骨上目に属するまったく別の魚類である)。棘魚類はかつて軟骨魚類に近縁とされ，棘鮫（きよくこう）類と訳されたこともあったが，最近は硬骨魚類の祖先に近いという説が強い。

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

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