The oldest known bryozoan: Prophyllodictya (Cryptostomata) from the lower Tremadocian (Lower Ordovician) of Liujiachang, southwestern Hubei, central China

A new cryptostome bryozoan, Prophyllodictya simplex sp. nov., is described from the Nantzinkuan Formation (Lower Ordovician, lower Tremadoc) of Liujiachang, central China. This antedates the previously oldest known bryozoan by several million years. Colony morphology and the phylogenetic position of Prophyllodictya within Cryptostomata are explored. Phylogenetic analysis suggests that Cryptostomata (except Prophyllodictya) can be divided into two major groups, and that Prophyllodictya occupies a basal position in the cryptostome tree, which accords with its simple morphology and antiquity. A close relationship is evident between bryozoans from the South China palaeoplate and those from Baltica.本次研究记述了采自华中地区刘家场南津关组（奥陶纪早期，特马豆克阶下部）的一新种隐口目苔藓虫（cryptostome bryozoan）——简单前叶网苔藓虫（Prophyllodictya simplex sp. nov.）。该新种的生存时代较此前已知最古老的苔藓虫早数百万年。本研究探讨了简单前叶网苔藓虫的群体形态特征及其在隐口目（Cryptostomata）中的系统发育位置。系统发育分析结果显示，隐口目（除前叶网苔藓虫属外）可划分为两个主要类群，且前叶网苔藓虫属在隐口目系统树中处于基部位置，这与其简单的形态特征及古老的生存年代相契合。华南古板块（South China palaeoplate）产出的苔藓虫与波罗的古陆（Baltica）产出的苔藓虫之间存在密切的亲缘关系。