六盘山盆地早白垩世含盐地层中石蚕巢化石

Fossil Caddisfly Cases from the Early Cretaceous Aliferous Strata in Liupanshan Basin,China

石蚕（昆虫纲：毛翅目）巢化石保存在宁夏六盘山盆地早白垩世马东山组和乃家河组含盐地层中,化石呈群栖、密集、相互平行、叠层状分布,石蚕巢为直立锥状体,长约13mm,平均直径约2.5mm.管壁具三层式结构,包括内、外暗色有机质层和中部胶结颗粒层.暗色有机质层为泥晶结构,以灰泥质为主;中部胶结颗粒层,主要由有机质球粒构成,球粒呈球形、椭球形和卵圆形等,形态大小一致,平均长0.3mm,直径0.10-0.15mm.这些有机质球粒在管壁中排列规整,长轴大多与石蚕巢生长方向垂直.依据管壁中规则排列的有机质球粒将六盘山盆地的石蚕巢化石归为Coprindusia遗迹属.通过对比各种造管生物形态学和生态学方面的特征以及现生造迹昆虫的生活环境、管体形态大小、管壁胶结颗粒组成和排列方式,综合相同层位上昆虫实体化石的分析,六盘山盆地的管状化石可能是宁夏石蛾科宁夏石蛾属房氏宁夏石蛾（Ningxiapsyche fangi）的幼虫巢.

Fossil caddisfly（Insecta：Trichoptera）larval cases have been recently discovered in the Early Cretaceous lacustine de-posits（Madongshan Formation and Naijiahe Formation）in Liupanshan basin,Ningxia.The arrays of caddisfly larval cases oc-cur as superimposed layers of vertically oriented cases.The fossils are gregarious,dense,parallel to each other and closely packed.The single larval case is conical and similar in size（generally 13mm in length and averagely 2.5mm in diameter）.The wall of the caddisfly larval cases is divided into three layers,including internal,external dark organic matter layers which have micrite structures and are composed of lime muds,and the middle layer of cemented aphanitic particles composed of organic pel-lets.The calcified organic pellets are orbicular,spheroidicity and ovate,with its size ranging from 0.10to 0.15mm wide by averagely 0.3mm long.The pellets are in regular arrangement,and their long axes are mostly perpendicular to the growth di-rection of the caddisworm cases.The larval cases in Liupanshan basin are attributed to Coprindusiain ichnology according to the pellets along the walls of the cases.By comparing the features of various tube-maker organism in morphology and bionomy,and the habitat,size and shape of cases,the composition of case-building particles,and case construction way,combining the analysis to insect body fossil from the same layers in which the caddisfly cases preserved,it seems like that the caddisfly larval cases in Liupanshan basin are Ningxiapsyche fangi from Ningxiapsychidae.