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Nature:怪诞虫头部的详细特征

摘要 : 在来自加拿大中寒武纪伯吉斯页岩的所有奇特生物中,怪诞虫(Hallucigenia)是最奇特的。尤其是,事实已经证明难以从可获得的化石材料来重建其头部区域,因此它与其他生物的关系一直是个谜。

 在来自加拿大中寒武纪伯吉斯页岩的所有奇特生物中,怪诞虫(Hallucigenia)是最奇特的。尤其是,事实已经证明难以从可获得的化石材料来重建其头部区域,因此它与其他生物的关系一直是个谜。现在,Martin Smith和Jean-Bernard Caron发表了关于新近研究的距今5.08亿年的怪诞虫化石的数据,这些数据终于以一定的详细程度显示了其头部特征。怪诞虫的奇特性在于其形状:它的嘴周围是由硬化的盘组成的一个环,它的喉咙内壁有针样的牙齿。虽然它是包括现代天鹅绒虫(有爪动物门)在内的类别当中的一员,处在节肢动物辐射的基部,但怪诞虫的头部和前肠表明,它与差别更大的动物门如线虫和“动吻动物”(kinorhynch)有演化上的联系。现在,怪诞虫为在“蜕皮动物总门”(Ecdysozoa)的最后共同祖先中可能存在的结构(这些结构以前纯属猜测)提供了确凿证据。

原文链接:

Hallucigenia’s head and the pharyngeal armature of early ecdysozoans

原文摘要:

The molecularly defined clade Ecdysozoa1 comprises the panarthropods (Euarthropoda, onychophora and Tardigrada) and the cycloneuralian worms (Nematoda, Nematomorpha, Priapulida, Loricifera and Kinorhyncha). These disparate phyla are united by their means of moulting, but otherwise share few morphological characters—none of which has a meaningful fossilization potential. As such, the early evolutionary history of the group as a whole is largely uncharted. Here we redescribe the 508-million-year-old stem-group onychophoran Hallucigenia sparsa from the mid-Cambrian Burgess Shale. We document an elongate head with a pair of simple eyes, a terminal buccal chamber containing a radial array of sclerotized elements, and a differentiated foregut that is lined with acicular teeth. The radial elements and pharyngeal teeth resemble the sclerotized circumoral elements and pharyngeal teeth expressed in tardigrades, stem-group euarthropods and cycloneuralian worms13. Phylogenetic results indicate that equivalent structures characterized the ancestral panarthropod and, seemingly, the ancestral ecdysozoan, demonstrating the deep homology of panarthropod and cycloneuralian mouthparts, and providing an anatomical synapomorphy for the ecdysozoan supergroup.

来源: Nature 浏览次数:0

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