Twelve specimens of Eumorphocystis Branson and Peck, 1940 provide the basis for new findings and a more informed assessment of whether this blastozoan (a group including eocrinoids, blastoids, diploporites, rhombiferans) constitutes the sister taxon to crinoids, as has been recently proposed. Both Eumorphocystis and earliest-known crinoid feeding appendages express longitudinal canals, a demonstrable trait exclusive to these taxa. However, the specimen series studied here shows that Eumorphocystis canals constrict proximally and travel within ambulacrals above the thecal cavity. This relationship is congruent with a documented blastozoan pattern but very unlike earliest crinoid topology. Earliest crinoid arm cavities lie fully beneath floor plates; these expand and merge directly with the main thecal coelomic cavity at thecal shoulders. Other associated anatomical features echo this contrasting comparison. Feeding appendages of Eumorphocystis lack two-tiered cover plates, podial basins/pores, and lateral arm plating, all features of earliest crinoid ‘true arms.’ Eumorphocystis feeding appendages are buttressed by solid block-like plates added during ontogeny at a generative zone below floor plates, a pattern with no known parallel among crinoids. Eumorphocystis feeding appendages express brachioles, erect extensions of floor plates, also unknown among crinoids. These several distinctions point to nonhomology of most feeding appendage anatomy, including longitudinal canals, removing Eumorphocystis and other blastozoans from exclusive relationship with crinoids. Eumorphocystis further differs from crinoids in that thecal plates express diplopores, respiratory structures not present among crinoids, but ubiquitous among certain groups of blastozoans. Phylogenetic analysis places Eumorphocystis as a crownward blastozoan, far removed from crinoids.

中文翻译：

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胚泡真形孢子虫及其伪臂的进化意义

十二个标本孢子虫Branson 和 Peck，1940 年为新发现和更明智的评估提供了基础，以评估这种囊胚动物（包括始海白蛋白、囊胚、双孔类、菱形类）是否构成海百合类的姊妹类群，正如最近提出的那样。两个都孢子虫和已知最早的海百合摄食附属物表达纵向运河，这是这些分类群独有的明显特征。然而，这里研究的样本系列表明孢子虫根管近端收缩并在鞘腔上方的步道内行进。这种关系与记录在案的囊胚模式一致，但与最早的海百合拓扑非常不同。最早的海百合臂腔完全位于地板下方；这些扩张并直接与鞘肩处的主要鞘腔合并。其他相关的解剖特征与这种对比对比相呼应。喂食附肢孢子虫缺少两层盖板、足底盆/孔和侧臂板，这些都是最早的海百合“真臂”的所有特征。孢子虫摄食附属物由在个体发育过程中在地板下方的生殖区添加的固体块状板支撑，这种模式在海百合中没有已知的平行。孢子虫喂养附属物表达腕骨，地板的直立延伸，在海百合中也是未知的。这几个区别指向大多数喂养附件解剖结构的非同源性，包括纵向管、去除孢子虫和其他与海百合有专属关系的囊胚。孢子虫与海百合的进一步不同之处在于鞘板表达双孔，呼吸结构在海百合中不存在，但在某些囊胚动物群体中无处不在。系统发育分析场所孢子虫作为一种向冠的胚泡动物，远离海百合。