Intermediate morphologies of a new fossil crinoid shed light on the pathway by which crinoids acquired their distinctive arms. Apomorphies originating deep in echinoderm history among early nonblastozoan pentaradiate echinoderms distinguish Tremadocian (earliest Ordovician) crinoid arms from later taxa. The brachial series is separated from the ambulacra, part of the axial skeleton, by lateral plate fields. Cover plates are arrayed in two tiers, and floor plates expressed podial basins and pores. Later during the Early Ordovician, floor plates contacted and nestled into brachials, then were unexpressed as stereom elements entirely and cover plates were reduced to a single tier. Incorporation of these events into a parsimony analysis supports crinoid origin deep in echinoderm history separate from blastozoans (eocrinoids, ‘cystoids’). Arm morphology is exceptionally well-preserved in the late Tremadocian to early Floian Athenacrinus broweri new genus new species. Character analysis supports a hypothesis that this taxon originated early within in the disparid clade. Athenacrinus n. gen. (in Athenacrinidae new family) is the earliest-known crinoid to express what is commonly referred to as ‘compound’ or ‘biradial’ morphology. This terminology is misleading in that no evidence for implied fusion or fission of radials exists, rather it is suggested that this condition arose through disproportionate growth.UUID: http://zoobank.org/b383e039-3298-4472-a7e3-e81684f87cfe

中文翻译：

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Athenacrinus n. 将军 和其他早期棘皮动物分类群告知海百合起源和手臂进化

一种新化石海百合的中间形态揭示了海百合获得其独特手臂的途径。起源于早期非胚层五辐射棘皮动物的棘皮动物历史深处的变形将 Tremadocian（最早的奥陶纪）海百合臂与后来的分类群区分开来。肱骨系列通过侧板场与作为轴向骨骼的一部分的amulacra分开。盖板分两层排列，底板表现足盆和孔隙。后来在早奥陶世期间，地板接触并依偎在肱骨中，然后完全不作为立体元素表达，盖板减少为单层。将这些事件纳入简约分析支持海百合起源于棘皮动物历史的深处，与胚泡动物分开（eocrinoids，“囊样动物”）。蝼蛄新属新种。特征分析支持一个假设，即该分类群早期起源于不同的进化枝。蝼蛄n. 将军 （在 Athenacrinidae 新科中）是已知最早的表达通常称为“复合”或“双径向”形态的海百合。该术语具有误导性，因为没有证据表明存在暗示的径向融合或裂变，而是表明这种情况是通过不成比例的增长引起的。UUID：http://zoobank.org/b383e039-3298-4472-a7e3-e81684f87cfe