刺尾虫科三叶虫的起源和早期演化

ORIGIN AND EARLY EVOLUTION OF CERATOPYGIDAE LINNARSON, 1869 (TRILOBITA)

根据贵州东部晚寒武世早期地层内获得的刺尾虫科（Ｃｅｒａｔｏｐｙｇｉｄａｅ）三叶虫新材料，论述了具有尾侧刺和不具尾侧刺的此类三叶虫共同起源于褶颊虫目的Ｍａｐａｎｉｄａｅ，以及它们的早期演化。此外，还描述了此类三叶虫１新亚属、２新种和２新亚种及其个体发育过程中的一些变异。对于正确认识寒武纪三叶虫的分类、演化具有一定的意义。

Study on new material of Ceratopygidae from lower Upper Cambrian (the Chefu Form ation) of eastern Guizhou, South China indicates that Ceratopygidae with or with out spinose pygidium may be a monophyletic group and may have a common origin wi t h Mapania (Mapaniidae of Ptychopariida). Phylogeny of Ceratopygidae in late Middle Cambrian and early Late Cambrian is briefly discussed and shown in Text fig.1, One new subgenus, 2 new species and 2 new subspecies are established: Aplotaspis (Cataplotaspis) quadrata subgen. et sp. nov., A.(C.) spiculata subgen. et sp. nov., A.(C.) laochatianensis nobilis subsp. nov., Procerato pyge conifrons sinensis subsp. nov. Description of genera and species Family Ceratopygidae Linnarson, 1869 Genus Proceratopyge Wallerius, 1895 Type species Proceratopyge conifrons Wallerius, 1895 Remarks Palmer(1968), Henderson(1976), Shergold et al. (1976, 1982), Lisogor (in Zhuravleva et al. (1977), Lu and Lin(1980,1989),Rushton ( 1983),Jago(1987),Apollonov et al. (1984), Webby et al. (1988), and Peng ( 1992) discussed Proceratopyge and its possible subgeneric groupings and we f ollow Lu and Lin(1980,p.129;1989,p.145,259) in subdividing Proceratopyge int o three subgenera: Proceratopyge(P.) Wallerius, 1895, P.(Lopnorites) Tr oedsson, 1937 and P.(Sinoproceratopyge) Lu et Lin, 1980 based on cranidial f eatures. P. (Proceratopyge) is characterized by the subconical glabella, lon g frontal area, well developed paradoublural line(or plectral line), narrowly di verging anterior branches of facial sutures, short to moderately long (exsag.) p alpebral lobes placed centroposteriorly, subtriangular posterolateral limbs and transverse poorly segmented pygidium. P.(Lopnorites) is characterized by the subcylindrical to cylindrical glabella, short frontal area, the absence of para doublural line, narrowly diverging anterior branches of facial sutures, short pa lpebral lobes placed anteriorly, narrow fixed cheeks between palpebral lobes and long multisegmented pygidium. P.(Sinoproceratopyge) bears the closest resem blance to P.(Lopnorites) , however, it can be distinguished mainly by its wid er cranidial anterior margin, more or less longer palpebral lobes placed more ce ntroposteriorly, narrower(exsag.) strape like posterolateral limbs and more str ongly diverging anterior branches of facial sutures. Up to now more than 70 spec ies and subspecies are assigned to Proceratopyge and their new placements ar e tentatively listed in Table 1. Table Ⅰ List of species (subspecies) of Proceratopy ge with its modern taxonomic placement