寒武纪幸运期西乡化石库棘盔状化石研究

HELMET-LIKE FOSSILS FROM THE XIXIANG LAGERST?TTE(FORTUNIAN,CAMBRIAN)IN THE SOUTHERN SHAANXI,CHINA

本文对产自陕南西乡化石库的棘盔状化石进行了统计和描述,对棘盔属的属种划分进行了重新厘定。单锥形的棘盔状化石同带有多个分枝复合体的棘盔状化石的断枝在尺寸、形态和表面装饰等方面存在较大差异,因此我们把这两类具有明显不同特征的棘盔状化石归入不同的种,将单锥形、表面具有密集直刺等特征的一类归入直刺棘盔Acanthocassis orthacanthus,将分枝数量不定的多分枝复合体归入具刺棘盔Acanthocassis echinate。通过进一步的测量分析,在A.echinate种内,发现其表面装饰也存在差异。本文展示的棘盔状化石新特征丰富了对棘盔状化石的认识,为进一步探讨棘盔状化石的亲缘关系和分类提供了新的材料。

Phosphatized and three-dimensionally preserved helmet-like fossils were recovered from the Cambrian Xi-xiang Lagerst?tte,South Shaanxi.Detailed statistics and descriptions of these helmet-like fossils were carried on,and the genus of Acanthocassis was redefined.There are specific differences between the single cone-shaped helmet-like fossils and the sub-branches of the helmet-like fossils with multiple branch complexes in sizes,shapes,and surface decorations.Therefore,these two types of helmet-like fossils with distinctly different characteristics are well distinguishable into two specific,namely the single cones with dense straight spines on the surface as Acanthocassis orthacanthus,and multibranched complexes with variable number of branches as Acanthocassis echinate.Based on this,the category with multiple branches is classified as A.echinate.Through further measurement and analysis,there are also intraspecific differences in the surface decoration of A.echinate.The new features of helmet-like fossils shown in this article enrich the understanding of helmet-like fossils and provide new materials for further exploring the relationship and classification of the helmet-like fossils.