Early Cambrian pentamerous cubozoan embryos from South China.

<h4>Background</h4>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 Cr...

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Autores principales:	Jian Han, Shin Kubota, Guoxiang Li, Xiaoyong Yao, Xiaoguang Yang, Degan Shu, Yong Li, Shunichi Kinoshita, Osamu Sasaki, Tsuyoshi Komiya, Gang Yan
Formato:	article
Lenguaje:	EN
Publicado:	Public Library of Science (PLoS) 2013
Materias:	Medicine R Science Q
Acceso en línea:	https://doaj.org/article/17a534cf73b04bbba902529af689f1f7
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spelling	oai:doaj.org-article:17a534cf73b04bbba902529af689f1f72021-11-18T09:00:16ZEarly Cambrian pentamerous cubozoan embryos from South China.1932-620310.1371/journal.pone.0070741https://doaj.org/article/17a534cf73b04bbba902529af689f1f72013-01-01T00:00:00Zhttps://www.ncbi.nlm.nih.gov/pmc/articles/pmid/23950993/pdf/?tool=EBIhttps://doaj.org/toc/1932-6203<h4>Background</h4>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.<h4>Methods</h4>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.<h4>Results</h4>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.Jian HanShin KubotaGuoxiang LiXiaoyong YaoXiaoguang YangDegan ShuYong LiShunichi KinoshitaOsamu SasakiTsuyoshi KomiyaGang YanPublic Library of Science (PLoS)articleMedicineRScienceQENPLoS ONE, Vol 8, Iss 8, p e70741 (2013)
institution	DOAJ
collection	DOAJ
language	EN
topic	Medicine R Science Q
spellingShingle	Medicine R Science Q Jian Han Shin Kubota Guoxiang Li Xiaoyong Yao Xiaoguang Yang Degan Shu Yong Li Shunichi Kinoshita Osamu Sasaki Tsuyoshi Komiya Gang Yan Early Cambrian pentamerous cubozoan embryos from South China.
description	<h4>Background</h4>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.<h4>Methods</h4>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.<h4>Results</h4>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.
format	article
author	Jian Han Shin Kubota Guoxiang Li Xiaoyong Yao Xiaoguang Yang Degan Shu Yong Li Shunichi Kinoshita Osamu Sasaki Tsuyoshi Komiya Gang Yan
author_facet	Jian Han Shin Kubota Guoxiang Li Xiaoyong Yao Xiaoguang Yang Degan Shu Yong Li Shunichi Kinoshita Osamu Sasaki Tsuyoshi Komiya Gang Yan
author_sort	Jian Han
title	Early Cambrian pentamerous cubozoan embryos from South China.
title_short	Early Cambrian pentamerous cubozoan embryos from South China.
title_full	Early Cambrian pentamerous cubozoan embryos from South China.
title_fullStr	Early Cambrian pentamerous cubozoan embryos from South China.
title_full_unstemmed	Early Cambrian pentamerous cubozoan embryos from South China.
title_sort	early cambrian pentamerous cubozoan embryos from south china.
publisher	Public Library of Science (PLoS)
publishDate	2013
url	https://doaj.org/article/17a534cf73b04bbba902529af689f1f7
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Early Cambrian pentamerous cubozoan embryos from South China.

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