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| Ausichicrinites zelenskyyi Salamon, Jain, Brachaniec, Duda, Płachno & Gorzelak, 2022 DOI: 10.1098/rsos.220345 |
Abstract
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 Ausichicrinites zelenskyyi 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.
Keywords: Africa, comatulids, tithonian, predation, crinoids, Ethiopia
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| Ausichicrinites zelenskyyi gen. et sp. nov. from the upper part of the Antalo Limestone Formation (....; 2114 m elevation), 21 m above the upper Tithonian calcareous nannofossil-yielding sample 2043b, Ethiopia. Scale bar equals 10 mm (a,c,e,f,g) and 1 mm (b,d,h,i). (a,c). Specimen with centrodorsal, arms and cirri ((a) non-whitened, (c) whitened) with magnifications (b,d) of IBr2 articulation (note a ‘dotted’ suture line (red arrows) from the outer surface of the articulation (b) and a fine ridge (red arrows) on the partly exposed facet (d)). (e) Lateral view showing a centrodorsal (non-whitened). (f,g) Tomographic images of slices of the fossil comatulids showing cryptosyzygial articulation at IBr2 (red arrows). (h) Proximal pluricirral (lateral view) and isolated cirri (facet view, blue arrow). (i) Regenerating pinnules consisting of one to three pinnular plates (blue arrows). |
Ausichicrinites zelenskyyi gen. et sp. nov.
Mariusz A. Salamon, Sreepat Jain, Tomasz Brachaniec, Piotr Duda, Bartosz J. Płachno and Przemysław Gorzelak. 2022. Ausichicrinites zelenskyyi gen. et sp. nov., A First nearly complete Feather Star (Crinoidea) from the Upper Jurassic of Africa. Royal Society Open Science. 9(7); DOI: 10.1098/rsos.220345
