概述

盾皮鱼纲的一目.头部与身体前部均覆盖有板状骨甲，头甲与体甲以关节相连，上颌和头可以活恐鱼头胸甲侧视及前视动（下颌不能活动），故名节颈鱼.身体较宽大，口及眼均大.胸鳍或为不能活动的棘状，如有腹鳍，一般也较小.生活于淡水或海水，出现于晚志留世，泥盆纪末即灭绝.恐鱼为其代表.中国节颈目化石有产于四川中泥盆统的江油鱼（Ｋｉａｎｇｙｏｕｓｔｅｕｓ）、贵州下泥盆统的贵州鱼（Ｋｕｅｉｃｈｏｗｌｅｐｉｓ）等.Placodermi of a head. Head and body with the front were covered with a plate of bone, head and body A with A joint connected to upper jaw and head can live side-view and the former terrorist head carapace optokinetic (lower jaw is not in ), hence the name section of neck of fish. lenient body, mouth and eyes are large. pectoral fin or the spine is not in shape, if pelvic fins, generally less. live in fresh water or sea water, appeared in the Late Silurian, mud the end of the extermination of basin Ji. fear of the fish as its representative. Chinese Festival head neck fossils are produced in Sichuan's Jiangyou Devonian fish (Kiangyousteus), Guizhou, Guizhou Lower Devonian fish (Kueichowlepis) and so on.