Early Cambrian pentamerous cubozoan embryos from South China.
Early Cambrian pentamerous cubozoan embryos from South China.
复制标题
华南早寒武世五体立方动物胚胎
DOI：
10.1371/journal.pone.0070741
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发表时间：
2013
期刊：
影响因子：
3.7
通讯作者：
Yan G
中科院分区：
文献类型：
--
作者：
Han J;Kubota S;Li G;Yao X;Yang X;Shu D;Li Y;Kinoshita S;Sasaki O;Komiya T;Yan G
现存的立方动物是贪婪的掠食者，其特征是方形，四个均匀分布的触角和发达的眼睛。在犹他州的中寒武世Marjum组和伊利诺斯州著名的石炭纪Mazon Creek组中发现了一些立方动物化石。毫无争议的立方动物化石在寒武纪早期是未知的;到那个时候，可能所有现存海洋动物门的代表，特别是那些基础动物，应该已经进化了。方法采用传统的醋酸浸渍法，从中国南方下寒武统宽川铺组磷质灰岩中提取显微化石。7个预孵化的五角体立方动物胚胎，其中每个承担5对伞下触手芽，详细分析了通过计算机显微断层扫描（Micro-CT）和扫描电子显微镜（SEM）无涂层。结果显微镜下的化石是明确的孵化前胚胎的基础上，其球形受精包膜和封闭的软组织，保留了关键的解剖特征，安排在完美的五角对称，允许详细比较与现代刺胞动物，特别是水母动物。这些特征的组合，如屏状体、生殖腺片层、悬囊和由系带悬挂的帆膜，只出现在现存立方动物的胃血管系统中，表明立方动物对这些化石的亲和力。此外，这些胚胎立方动物化石的内部解剖前所未有地展示了许多新的中隔衍生的lameparum和良好分隔的胃袋在生活立方动物中未知的发展，这意味着祖先立方动物已经进化出高度专业化的结构，显示出意想不到的复杂性在寒武纪的黎明。这些立方动物化石的发育良好的内胚层片层和胃袋发育在胚胎晚期，与现存的远洋幼年立方水母而不是无柄立方水母相当，这表明这些化石分类群中的直接发育，缺乏典型的刺胞动物后生发育的特征阶段，如无柄浮游虫和无柄息肉。
Background Extant cubozoans are voracious predators characterized by their square shape, four evenly spaced outstretched tentacles and well-developed eyes. A few cubozoan fossils are known from the Middle Cambrian Marjum Formation of Utah and the well-known Carboniferous Mazon Creek Formation of Illinois. Undisputed cubozoan fossils were previously unknown from the early Cambrian; by that time probably all representatives of the living marine phyla, especially those of basal animals, should have evolved. Methods Microscopic fossils were recovered from a phosphatic limestone in the Lower Cambrian Kuanchuanpu Formation of South China using traditional acetic-acid maceration. Seven of the pre-hatched pentamerous cubozoan embryos, each of which bears five pairs of subumbrellar tentacle buds, were analyzed in detail through computed microtomography (Micro-CT) and scanning electron microscopy (SEM) without coating. Results The figured microscopic fossils are unequivocal pre-hatching embryos based on their spherical fertilization envelope and the enclosed soft-tissue that has preserved key anatomical features arranged in perfect pentaradial symmetry, allowing detailed comparison with modern cnidarians, especially medusozoans. A combination of features, such as the claustrum, gonad-lamella, suspensorium and velarium suspended by the frenula, occur exclusively in the gastrovascular system of extant cubozoans, indicating a cubozoan affinity for these fossils. Additionally, the interior anatomy of these embryonic cubozoan fossils unprecedentedly exhibits the development of many new septum-derived lamellae and well-partitioned gastric pockets unknown in living cubozoans, implying that ancestral cubozoans had already evolved highly specialized structures displaying unexpected complexity at the dawn of the Cambrian. The well-developed endodermic lamellae and gastric pockets developed in the late embryonic stages of these cubozoan fossils are comparable with extant pelagic juvenile cubomedusae rather than sessile cubopolyps, whcih indicates a direct development in these fossil taxa, lacking characteristic stages of a typical cnidarian metagenesis such as planktonic planula and sessile polyps.
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影响因子：
1.4
作者：
Chapman, DM
通讯作者：
Chapman, DM
影响因子：
6.5
作者：
Collins, AG;Schuchert, P;Schierwater, B
通讯作者：
Schierwater, B
DOI：
10.1139/z63-046
发表时间：
1963-01-01
期刊：
CANADIAN JOURNAL OF ZOOLOGY - BACK YEAR PROJECT
影响因子：
--
作者：
BERRILL, M
通讯作者：
BERRILL, M
加拿大（不列颠哥伦比亚省）和中国（云南）寒武纪的触手化石被解释为原始后口动物
影响因子：
3.7
作者：
Caron JB;Conway Morris S;Shu D
通讯作者：
Shu D
影响因子：
3.7
作者：
Cartwright P;Halgedahl SL;Hendricks JR;Jarrard RD;Marques AC;Collins AG;Lieberman BS
通讯作者：
Lieberman BS