THE ARTHROPOD SIDNEYIA-INEXPECTANS, MIDDLE CAMBRIAN, BURGESS SHALE, BRITISH-COLUMBIA
THE ARTHROPOD SIDNEYIA-INEXPECTANS, MIDDLE CAMBRIAN, BURGESS SHALE, BRITISH-COLUMBIA
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DOI：
10.1098/rstb.1981.0164
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发表时间：
1981-01-01
影响因子：
6.3
通讯作者：
BRUTON, DL
中科院分区：
文献类型：
--
作者：
BRUTON, DL
S.的新旧标本。对未预期者进行了研究，并附有解释性的图画和照片。该动物的新重建与三维模型一起给出。体部由头、胸、腹和尾组成，头、胸、腹各有一条长的背侧双体节，胸、腹各有一条由2 ~ 3体节组成的圆柱形外骨骼。尾扇是由一对尾足动物在最后一个腹部体节的后缘形成的。头部有柄眼和口前触角，但没有行走或抓握的附属物。胸部的前4体节有成对的单支、可移动的行走腿，通过具有多刺的颚基的宽的基节附着于身体。后胸5体节上的基节较小，成对的附肢为双支，每个附肢都有一个鳃，支撑在一个皮瓣上，皮瓣的近端连接到腿的第一足节。基节-身体附着类似于现代裂口动物，并且先于三叶虫。Sidneyia可能是一种生活在底部的食肉动物，比三叶虫吃更大更硬的食物。肠道内容物包括介形虫、舌石、小三叶虫和磷酸盐碎片。Sidneyia是已知最早的可能是裂口动物的祖先的形式，但其身体计划和缺乏螯肢将Sidneyia与该组区分开来。本文重新解释了饰纹细蛾Amiella ornata Walcott，1911的正模标本，并将其与S.非预期疾病得到证实。
Old and new specimens of S. inexpectans are studied and are accompanied by explanatory drawings and photographs. New reconstructions of the animal are given together with a 3-dimensional model. The body consisted of a cephalon with a long backwardly directed doublure, a thorax of 9 articulating somites, abdomen with cylindrical exoskeleton of 2 or 3 somites and a telson. A caudal fan was formed by a pair of uropods articulating at the posterior margin of the last abdominal somite. The cephalon had stalked eyes and preoral antennae but no walking or grasping appendages. The 1st 4 somites of the thorax had paired uniramous, prehensile walking legs attached to the body by broad coxae with spiny gnathobases. The coxae were smaller on the 5 posterior thoracic somites and the paired appendages were biramous, each bearing a gill supported on a flap attached at its proximal end to the 1st podomere of the leg. The coxa-body attachment resembles that of modern merostomes and is in advance of trilobites. Sidneyia probably was a bottom-living, carnivorous animal eating larger and harder food than trilobites. Gut contents include ostracods, hyolithids, small trilobites and phosphatic debris. Sidneyia is the earliest known form which could be an ancestor to merostomes, but its body plan and absence of chelicera distinguishes Sidneyia from this group. The holotype of Amiella ornata Walcott, 1911 is reinterpreted and its synonomy with S. inexpectans is confirmed.