根据浙西胡乐组、鄂西庙坡组的笔石材料，结合前人研究成果，开展早期双头笔石类及其相关类群的分支系统学研究。该分支分析共选择13个生物分类单元，其中，早期双头笔石类群包括Jiangxigraptus mui，J. wuningensis，J. sextans，J. vagus，J. intortus和Dicranograptus irregularis，相关的双列笔石类群包括Undulograptus austrodentatus，U. sinicus，Archiclimacograptus caelatus，Dicaulograptus hystrix，Undulograptus ?praesextans 和 Undulograptus dicellograptoides，外类群为Exigraptus uniformis。针对该分析类群特点，共选择“始端发育及构造”、“胞管形态特征”等25个性状。另外，还特别选择“生物地层时代属性”，作为性状之一进行对照分析。分析结果显示，早期双头笔石类是一个独立的单系群，其起源经历两枝分叉—攀合—再分叉—仅始部攀合的演变过程。始部攀合、末端分叉的Dicranograptus很可能由完全分叉的Jiangxigraptus或Dicellograptus衍生而来。分类单元的地层延限分布与这一演化序列的分支节点基本相符，因此从地层发生的角度也验证了Dicranograptus的“始部攀合”是一种衍征。含与不含“生物地层时代属性”这一性状的对照分析结果基本一致，反映所选分类单元的起源先后关系与其地层记录具有较好的相关性，无“幽灵谱系”现象。该分支分析还表明，以Undulograptus dicellograptoides和Jiangxigraptus mui为代表的“两枝单列上斜”的特征在达瑞威尔期可能独立发生两次，这一现象很可能是一种趋同或重复演化，而不是系统演化关系。

Based on the graptolite materials from the Hulo Formation，western Zhejiang Province and the Miaopo Formation，western Hubei Province，a phylogenetic analysis of the early dicranograptids and their related taxa is conducted in this paper. The result of the analysis based on 13 taxa and their 25 characters. The 13 taxa include the early dicranograptids Jiangxigraptus mui，J. wuningensis，J. sextans，J. vagus，J. intortus and Dicranograptus irregularis，reletated biserial taxa Undulograptus austrodentatus，U. sinicus，Archiclimacograptus caelatus，Dicaulograptus hystrix and the disputable taxa Undulograptus ?praesextans，Undulograptus dicellograptoides，and outgroup Exigraptus uniformis. The result showed that the early dicranograptids are grouped as a monophyly, and the “uni-biserial” character state of Dicranograptus and Jiangxigraptus are homologous instead of independent origin，and Dicranograptus is likely to derive from Jiangxigraptus. This sequence basically matches the stratigraphic occurrence，indicating that the cladogram and derived tree seem to represent the true phylogeny. An alternative analysis including the biostratigraphic attribute as a character produced identical result，implying a possible correlation between age and the distance of phylogenetic relations without ghost line. The character of the “two uniserial and reclined stipes” developed in Undulograptus dicellograptoides and Jiangxigraptus mui may have independent，respectively origins in Darriwilian Stage，showing a homoplasy or an iterative evolution instead of phylogenetic evolution.

中国地质调查局项目（批准号：121201102000150010-06），现代古生物学和地层学国家重点实验室开放课题基金（批准号：163111），国家科技部项目（批准号：2013FY111000），国家自然科学基金（41725017,41590864），科技部重点研发专项（2017YFC0601505）联合资助。