Silurian phyllocarid crustaceans (Phyllocarida, Archaeostraca) from South China

In the Silurian, the suborder Caryocaridina of the phyllocarids was replaced by the suborder Ceratiocaridina as the dominant group. The latter did not achieve a global distribution until the late Silurian. In the early Silurian, ceratiocarids were a little-diversified group and palaeogeographically restricted mainly to Laurussia. Although previous studies have mentioned phyllocarid fossils from the Silurian of the South China plate, these have never been systematically described. This study describes three genera and four species (including one new genus, two new species, and two undetermined species), i.e. <i>Cugocaris future</i> gen. et sp. nov., <i>Gonatocaris wuhanensis</i> sp. nov., <i>Gonatocaris</i> sp. and <i>Warneticaris</i> sp., based on 38 phyllocarid specimens from the Fentou Formation in Wuhan. <i>Cugocaris future</i> gen. et sp. nov. is distinguished by an elliptic carapace ornamented by sinuous and anastomosing longitudinal striae, a styliform telson, and slender furcal rami. <i>Gonatocaris wuhanensis</i> sp. nov. is characterized by anastomosing longitudinal striae on the carapace, greatest carapace width in the centre of the carapace, and three different types of ornamentations on the surface of the abdominal segments. A phylogenetic analysis of 41 Palaeozoic phyllocarids reveals that <i>Gonatocaris</i>, <i>Rolfecaris</i> and <i>Cugocaris</i> gen. nov. form a monophyletic group. Thus, a new family, Gonatocarididae fam. nov., is proposed. This family is characterized by a carapace lacking median dorsal plate, rostral plate, a well-developed anterior carapace horn, and ornamented with prominent raised, wavy, anastomosing longitudinal striae. A palaeoecological analysis suggests that <i>G. wuhanensis</i> was a fairly active swimmer, while <i>C. future</i> was necto-benthic with relatively weak swimming abilities. This study not only extends the known morphological range of phyllocarids, but also has implications for the functional morphology, taxonomy, and evolution of archaeostracans as a whole. http://zoobank.org/urn:lsid:zoobank.org:pub:4B6B60B6-19F1-4A58-AC65-3B1AEE5D0939

志留纪（Silurian）时期，叶虾类（Phyllocarida）的Caryocaridina亚目被Ceratiocaridina亚目取代，成为彼时的优势类群。该类群直至志留纪晚期才实现全球性分布。志留纪早期，Ceratiocaridina类群多样性较低，且在古地理分布上主要局限于劳伦西亚大陆（Laurussia）。尽管此前已有研究提及华南板块（South China plate）志留纪地层中的叶虾类化石，但相关类群从未得到系统性描述。本研究基于武汉坟头组（Fentou Formation）产出的38件叶虾类标本，记述了3属4种（包括1新属、2新种及2未定种），即*Cugocaris future* gen. et sp. nov.、*Gonatocaris wuhanensis* sp. nov.、*Gonatocaris* sp. 以及*Warneticaris* sp.。*Cugocaris future* gen. et sp. nov. 的鉴别特征为：头胸甲呈椭圆形，表面饰有弯曲且相互交织的纵向细纹，针状尾节，以及纤细的尾叉肢。*Gonatocaris wuhanensis* sp. nov. 的主要特征为：头胸甲表面具相互交织的纵向细纹，头胸甲最宽处位于壳体中部，腹节表面具有三种不同类型的纹饰。对41种古生代叶虾类开展的系统发育分析显示，*Gonatocaris*、*Rolfecaris* 以及新属*Cugocaris* 构成一单系群。据此，我们建立一新科——Gonatocarididae fam. nov.，该科的鉴别特征为：头胸甲无中背板、吻板，具发达的头胸甲前角，表面饰有显著凸起、呈波浪状且相互交织的纵向细纹。古生态分析结果表明，*G. wuhanensis* 为活动性较强的游泳类群，而*C. future* 则属于游泳能力较弱的底栖游泳生物。本研究不仅拓展了叶虾类已知的形态分布范围，同时对古介形类（Archaeostraca）的功能形态学、分类学及整体演化研究均具有重要意义。http://zoobank.org/urn:lsid:zoobank.org:pub:4B6B60B6-19F1-4A58-AC65-3B1AEE5D0939