Exceptionally preserved soft parts in fossils from the Lower Ordovician of Morocco clarify stylophoran affinities within basal deuterostomes
Exceptionally preserved soft parts in fossils from the Lower Ordovician of Morocco clarify stylophoran affinities within basal deuterostomes
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DOI：
10.1016/j.geobios.2018.11.001
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发表时间：
2019-02-01
期刊：
影响因子：
1.6
通讯作者：
David, Bruno
中科院分区：
文献类型：
--
作者：
Lefebvre, Bertrand;Guensburg, Thomas E.;David, Bruno
已经灭绝的棘皮动物Glade Stylophora由一些已知的最奇怪的后口动物组成。茎突动物是从中寒武纪到宾夕法尼亚纪的完整、完整的骨骼遗骸中发现的，但仍然很难解释。它们奇特的形态，从一个主体延伸出一个附属物，引发了关于茎突动物系统发育意义的激烈争论，茎突动物长期以来被认为是经过改良的，但真正的棘皮动物，具有觅食附属物。最近对这种附属物的解释是一种后部的“尾巴状”结构，从字面上讲，它把动物从后面转向前面，导致人们认为茎突动物是脊索动物的祖先，或者是半趾类动物，早期棘皮动物。到目前为止，引发争论的数据仅限于对骨骼解剖的评估。在这里，我们应用新颖的元素映射技术来描述，第一次，软组织痕迹茎突结合骨骼模具。单个茎突附属物包含一个纵向管，垂直的，细长的延伸超出铰接的双纵板。这种类型的软组织与水腔相比最为有利，包括在所有典型棘皮动物中发现的水血管管和管足。方解石体和明显的水维管系统的存在支持棘皮动物而不是半硬皮动物的亲和关系。(C) 2018 Elsevier Masson SAS。版权所有。
The extinct echinoderm Glade Stylophora consists of some of the strangest known deuterostomes. Stylophorans are known from complete, fully articulated skeletal remains from the middle Cambrian to the Pennsylvanian, but remain difficult to interpret. Their bizarre morphology, with a single appendage extending from a main body, has spawned vigorous debate over the phylogenetic significance of stylophorans, which were long considered modified but bona fide echinoderms with a feeding appendage. More recent interpretation of this appendage as a posterior "tail-like" structure has literally turned the animal back to front, leading to consideration of stylophorans as ancestral chordates, or as hemichordate-like, early echinoderms. Until now, the data feeding the debate have been restricted to evaluations of skeletal anatomy. Here, we apply novel elemental mapping technologies to describe, for the first time, soft tissue traces in stylophorans in conjunction with skeletal molds. The single stylophoran appendage contains a longitudinal canal with perpendicular, elongate extensions projecting beyond hinged biserial plates. This pattern of soft tissues compares most favorably with the hydrocoel, including a water vascular canal and tube feet found in all typical echinoderms. Presence of both calcite stereom and now, an apparent water vascular system, supports echinoderm and not hemichordate-like affinities. (C) 2018 Elsevier Masson SAS. All rights reserved.