Salamon Mariusz A, Jain Sreepat, Brachaniec Tomasz, Duda Piotr, Płachno Bartosz J, Gorzelak Przemysław
Institute of Earth Sciences, University of Silesia in Katowice, Będzińska Street 60, 41-200 Sosnowiec, Poland.
Department of Geology, School of Applied Natural Science, Adama Science and Technology University, 1888 Adama, Oromia, Ethiopia.
R Soc Open Sci. 2022 Jul 20;9(7):220345. doi: 10.1098/rsos.220345. eCollection 2022 Jul.
Fossil comatulids, referred to as feather stars, are mostly known from highly disarticulated specimens. A single isolated element (centrodorsal) has been the basis for taxonomic description of a vast majority of fossil comatulids. Here, we report a nearly complete, and thus extremely rare, comatulid from the Upper Jurassic (Tithonian) of the Blue Nile Basin in central western Ethiopia that provides a unique insight into the morphology of comatulid arms and cirri. It is assigned to gen. et sp. nov. and is the first Jurassic comatulid from the African continent. The new taxon shows some similarities with representatives of the Mesozoic Solanocrinitidae but also has close resemblance with the modern family Zygometridae, exclusively known from the Holocene of western Pacific and eastern Indian Oceans. This morphologic similarity is considered to be due to convergence. The first example of pinnule regeneration in a fossil feather star is reported, which reinforces the hypothesis about the importance of predation in the evolution of these crinoids.
化石羽星类，即所谓的海羽星，大多是从高度分散的标本中得知的。单个孤立的元素（中央背板）一直是绝大多数化石羽星类分类描述的基础。在此，我们报告了一种近乎完整、因而极其罕见的海羽星，它来自埃塞俄比亚中西部青尼罗河流域的上侏罗统（提通阶），为海羽星的臂和触须形态提供了独特的见解。它被归入新属新种，是非洲大陆的首个侏罗纪海羽星。这个新分类单元与中生代茄海百合科的代表有一些相似之处，但也与仅知于西太平洋和东印度洋全新世的现代海百合科有密切相似性。这种形态相似性被认为是趋同演化的结果。本文报道了化石海羽星羽枝再生的首个实例，这强化了关于捕食在这些海百合类演化中重要性的假说。
