A superarmored lobopodian from the Cambrian of China and early disparity in the evolution of Onychophora
A superarmored lobopodian from the Cambrian of China and early disparity in the evolution of Onychophora
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中国寒武纪的超级装甲叶足类动物和甲虫进化的早期差异
DOI：
10.1073/pnas.1505596112
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发表时间：
2015
期刊：
影响因子：
--
通讯作者：
Xi-guang Zhanga
中科院分区：
文献类型：
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作者：
Jie Yanga;Javier Ortega-Hernándezb;Sylvain Gerberb;Nicholas J. Butterfieldb;Jin-bo Houa;Tian Lana;Xi-guang Zhanga
古生代的足纲动物是由各种不同的蠕虫状生物组成的，它们是从各种特殊的化石沉积物中发现的，是最早发育出骨骼状身体部位以保护自己的动物之一。本文描述了一种来自华南小石巴Lagerstätte早寒武纪的甲足类动物Collinsium ciliosum gen. et sp. nov.。collinum属于一个已灭绝的超级甲足动物分支，其特征是背脊多刺，有专门的四肢用于滤食；总的来说，这些化石分类群代表了现存丝绒蠕虫谱系中一个明确的群体。尽管与其他叶足纲动物和现存的丝绒蠕虫相比，它们的形态多样性和附属物复杂性更大，但在寒武纪大爆发期间，collinum及其近亲体现了一种独特的、但最终失败的自生态。我们描述了来自中国南方早寒武纪小石巴Lagerstätte的Collinsium ciliosum，这是一种具有显著肢体分化程度的甲足类动物，包括一对天线状附属物，6对用于悬浮进食的细长硬肢和9对具有锚定功能的爪状环状腿。Collinsium属于足足动物茎群中一个高度衍生的分支，以大量的多生和生物矿化棘的背枢为特征（loolishaniidae科）。结果表明，在古生代的足纲动物中，洛里山纲动物的四肢特化程度最高，占茎类动物Onychophora总形态差异的三分之一以上，与冠类动物相比，它们的差异更大。尽管具有比其他足纲动物和现存丝绒蠕虫更高的差异和附属物复杂性，但以洛里山纲动物为代表的特殊生活方式在早古生代已经灭绝。collinum和其他超级甲足类动物在寒武纪大爆发期间利用了一个独特的古生态位。
Significance Paleozoic lobopodians constitute a diverse assemblage of worm-like organisms that are known from various exceptional fossil deposits and were among the earliest animals to develop skeletonized body parts for protection. Here, we describe Collinsium ciliosum gen. et sp. nov., an armored lobopodian from the early Cambrian Xiaoshiba Lagerstätte (South China). Collinsium belongs to an extinct clade of superarmored lobopodians characterized by supernumerary dorsal spines, and specialized limbs for filter feeding; collectively, these fossil taxa represent a well-defined group within the lineage leading to extant velvet worms (Onychophora). Despite their greater morphological variety and appendage complexity compared with other lobopodians and extant velvet worms, Collinsium and its close relatives embodied a unique, yet ultimately failed, autoecology during the Cambrian explosion. We describe Collinsium ciliosum from the early Cambrian Xiaoshiba Lagerstätte in South China, an armored lobopodian with a remarkable degree of limb differentiation including a pair of antenna-like appendages, six pairs of elongate setiferous limbs for suspension feeding, and nine pairs of clawed annulated legs with an anchoring function. Collinsium belongs to a highly derived clade of lobopodians within stem group Onychophora, distinguished by a substantial dorsal armature of supernumerary and biomineralized spines (Family Luolishaniidae). As demonstrated here, luolishaniids display the highest degree of limb specialization among Paleozoic lobopodians, constitute more than one-third of the overall morphological disparity of stem group Onychophora, and are substantially more disparate than crown group representatives. Despite having higher disparity and appendage complexity than other lobopodians and extant velvet worms, the specialized mode of life embodied by luolishaniids became extinct during the Early Paleozoic. Collinsium and other superarmored lobopodians exploited a unique paleoecological niche during the Cambrian explosion.