Cambrian sessile, suspension feeding stem-group ctenophores and evolution of the comb jelly body plan
Cambrian sessile, suspension feeding stem-group ctenophores and evolution of the comb jelly body plan
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寒武纪无柄、悬浮摄食的茎群栉水母和栉水母体结构的演化
DOI：
10.1016/j.cub.2019.02.036
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发表时间：
2019
期刊：
影响因子：
9.2
通讯作者：
Peiyun Cong
中科院分区：
文献类型：
--
作者：
Yang Zhao;Jakob Vinther;Luke A Parry;Fan Wei;Emily Green;Davide Pisani;Xianguang Hou;Gregory D. Edgecombe;Peiyun Cong
栉水母（梳水母）的起源被其有争议的系统发育位置所掩盖，最近的基因组分析将海绵或栉水母作为所有其他动物的姐妹群。化石分类群可以提供形态学证据，可以阐明不同分类群之间的衍生特征和共同祖先的起源，提供一种在系统发育树中“折断”长枝的方法。本文描述了云南澄江早寒武世生物群中的新化石材料，包括推定的刺胞动物仙光虫属（Xianguangia），新分类群戴化三琼根（Daihua sanqionggen et sp. nov.）以及维纳斯恐龙，这里非正式地称为恐龙。“恐龙”拥有一个由18个触手环绕的基萼，这些触手环绕着嘴。触手携带小羽片，每个小羽片都有一排坚硬的丝状结构，被解释为非常大的复合纤毛，其大小只有在栉水母中才知道。连同寒武纪郁金香动物Siphusauctum和装甲寒武纪scleroctenophores，他们展示的解剖学追溯栉水母到一个无柄的，息肉状的干血统。这个身体平面类似于刺胞动物的息肉状触手形态，包括由肠系膜分隔的盲胃腔。我们建议，梳行来自触角与成对套的小羽片，每个承担一行复合纤毛。硬八节水母除了具有与Dinomischus、Daihua和Xianguangia相同的有机骨架外，还具有成对的梳状列，这在Siphusauctum中也能观察到。我们制定了一个假设，栉水母从无柄，水螅状悬浮饲料，共享的相似性刺胞动物，这表明这两个门之间的密切关系，早期趋同进化的一个显着的模式，或祖先的条件下，无论是后生动物或真后生动物。
The origin of ctenophores (comb jellies) is obscured by their controversial phylogenetic position, with recent phylogenomic analyses resolving either sponges or ctenophores as the sister group of all other animals. Fossil taxa can provide morphological evidence that may elucidate the origins of derived characters and shared ancestries among divergent taxa, providing a means to "break" long branches in phylogenetic trees. Here we describe new fossil material from the early Cambrian Chengjiang Biota, Yunnan Province, China, including the putative cnidarianXianguangia, the new taxonDaihua sanqionggen et sp. nov., andDinomischus venustus, informally referred to as "dinomischids" here. "Dinomischids" possess a basal calyx encircled by 18 tentacles that surround the mouth. The tentacles carry pinnules, each with a row of stiff filamentous structures interpreted as very large compound cilia of a size otherwise only known in ctenophores. Together with the Cambrian tulip animalSiphusauctumand the armored Cambrian scleroctenophores, they exhibit anatomies that trace ctenophores to a sessile, polypoid stem lineage. This body plan resembles the polypoid, tentaculate morphology of cnidarians, including a blind gastric cavity partitioned by mesenteries. We propose that comb rows are derived from tentacles with paired sets of pinnules that each bear a row of compound cilia. The scleroctenophores exhibit paired comb rows, also observed inSiphusauctum, in addition to an organic skeleton, shared as well byDinomischus,Daihua, andXianguangia. We formulate a hypothesis in which ctenophores evolved from sessile, polypoid suspension feeders, sharing similarities with cnidarians that suggest either a close relationship between these two phyla, a striking pattern of early convergent evolution, or an ancestral condition for either metazoans or eumetazoans.