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Oktavites spiralis(Geinitz,1842)是志留系特列奇阶(Telychian)的笔石带化石,其形态特征明显,在全球范围内广泛分布,地层对比意义较强。然而,该种宽泛的化石定义以及缺乏居群变异研究,造成了对该化石延限的争议,不利于地层的精确对比。笔者对产自陕西紫阳、岚皋地区特列奇阶Oktavites spiralis带至Cyrtograptus lapworthi笔石带的45个Oktavites spiralis不同发育阶段的幼体标本进行研究,建立了较完整的发育序列,从而对该种的始部特征有了更为深入的了解,增加了描述的精确性。同时,通过始部特征的对比研究,可将Oktavites spiralis和与之共生的Oktavites contortus(Perner,1897)明确区分为2个独立的种。此外,对Oktavites spiralis和Oktavites contortus发育过程的研究,也可成为该属进一步精确厘定的主要依据之一。
The Oktavites spiralis (Geinitz, 1842) is a pen-derived fossil of the Telychian order of the Silurian. It is characterized by obvious morphological features, widespread distribution in the world and strong stratigraphic contrast. However, this broad definition of fossilism and the lack of studies on population variation have led to controversy over the delineation of the fossil, which is not conducive to accurate stratigraphic comparisons. In this paper, 45 Oktavites spiralis larvae from different stages of Oktavites spiralis to Cyrtograptus lapworthi penis from the Terezin Strait of Ziyang and Langao of Shaanxi Province were studied to establish a more complete sequence of development, Department features have become more in-depth understanding, increasing the accuracy of the description. At the same time, Oktavites spiralis and Oktavites contortus (Perner, 1897), which are symbiotic with each other, can be clearly divided into two independent species through the comparative study of the initial characteristics. In addition, the study of the development of Oktavites spiralis and Oktavites contortus may also be one of the major bases for further precise determination of this genus.