伊克昭弓鳍鱼在华南的发现

<正> 近年来,随着地层工作的深入,在华南中生代晚期地层中,接二连三地发现了与华北中生代晚期狼鳍鱼群中的鱼化石相近的种类。继华南中华弓鳍鱼(Sinamia huananensis,苏德造,1973)、伍氏副狼鳍鱼(Paralycoptera wui,张弥曼、周家健,1977)之后,浙江省区测队在缙云县壶镇水口晚侏罗世火山岩系的沉积夹层中,又发现了伊克昭弓鳍鱼(Ikechao-amia)。这一鱼化石和内蒙的东方伊克昭弓鳍鱼(I.orientalis Liu)有些不同,我们在此简单记述,并对伊克昭弓鳍鱼属的特征作些补充,以期对我国南、北地区中生代晚期鱼群的综合研究提供些许资料。

DISCOVERY OF IKECHAOAMIA FROM SOUTH CHINA

A new species of Ikechaoamia——Ⅰ.meridionalis is described from the UpperJurassic of Zhejiang Province,south-eastern China.The only other species of thegenus——Ⅰ.orientalis Liu was known from Inner Mongolia in association withLycoptera fauna.The new species is on the whole in accordance with Ⅰ.orientalis.It differs fromthe latter in the number of vertebrae and fin rays only.Besides that,an articulatedepaxial fin-ray is present on the dorsal border of the caudal fin of the Ⅰ.meridio-nalis specimens V5805.1 and V5805.2 but is absent in the well preserved specimenV2519.1 of Ⅰ.orientalis.However,because of the scarcity of specimens,it is difficult tojudge whether this is due to individual variation or to specific difference.According to our observation,most of the scales of Ikechaoamia(Ⅰ.orientalisincluded)are rhombic.But some of the lateral line scales are enlarged and irregularin shape.The scales near the ventral border are rounded,with numerous radial linesdirected forward.At first glance Ikechaoamia is quite similar to European Jurassic Uracles in bodyproportion,jaw and opercular bones,long dorsal fin,rounded caudal fin,epaxial fin-rays,one-to-one hypural/fin-ray relationship,concentric and radial lines in scales,etc.But Ikechaoamia can be easily distinguished from the latter by the presence of fusedparietals and subdivided supratemporals.