The first tunicate from the Early Cambrian of South China

Chen, Jun-Yuan; Huang, Diying; Peng, Qingqing; Chi, Huimei; Wang, Xiuqiang; Ming, Feng

doi:10.1073/pnas.1431177100

Cited by 119 publications

(64 citation statements)

References 12 publications

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“…To ask about the rate of miRNA acquistion in early vertebrate history, the split between urochordates and vertebrates needs to be estimated. Peterson et al (26) dated the origin of crown-group Chordata to Ϸ550 Ma, setting the maximum for this split, and the fossil record suggests that crowngroup Olfactores had arisen by the end of the Early Cambrian Ϸ520 Ma (27); the age of crown-group Vertebrata, as estimated from the fossil record, is Ϸ505 Ma (28,29). Thus, the rate of acquisition varies from 0.91 to 2.73, depending on when the speciation event occurred, and is 3-10 times higher than the rate at which they were acquired within the eutherian stem lineage (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…The following divergence times were used: Chordata, 550 Ma; Olfactores, 550 -520 Ma; Vertebrata, 505 Ma; Gnathostomata, 450 Ma; Osteichthyes, 420 Ma; Tetrapoda, 350 Ma; Amniota, 330 Ma; Eutheria, 100 Ma. The 550-Ma divergence estimate is based on a detailed molecular clock analysis (26); the rest were taken directly from the fossil record (27,44).…”

Section: Methodsmentioning

confidence: 99%

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MicroRNAs and the advent of vertebrate morphological complexity

Heimberg

Sempere

Moy

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

374

339

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The causal basis of vertebrate complexity has been sought in genome duplication events (GDEs) that occurred during the emergence of vertebrates, but evidence beyond coincidence is wanting. MicroRNAs (miRNAs) have recently been identified as a viable causal factor in increasing organismal complexity through the action of these Ϸ22-nt noncoding RNAs in regulating gene expression. Because miRNAs are continuously being added to animalian genomes, and, once integrated into a gene regulatory network, are strongly conserved in primary sequence and rarely secondarily lost, their evolutionary history can be accurately reconstructed. Here, using a combination of Northern analyses and genomic searches, we show that 41 miRNA families evolved at the base of Vertebrata, as they are found and/or detected in lamprey, but not in either ascidians or amphioxus (or any other nonchordate taxon). When placed into temporal context, the rate of miRNA acquisition and the extent of phenotypic evolution are anomalously high early in vertebrate history, far outstripping any other episode in chordate evolution. The genomic position of miRNA paralogues in humans, together with gene trees incorporating lamprey orthologues, indicates that although GDEs can account for an increase in the diversity of miRNA family members, which occurred before the last common ancestor of all living vertebrates, GDEs cannot account for the origin of these novel families themselves. We hypothesize that lying behind the origin of vertebrate complexity is the dramatic expansion of the noncoding RNA inventory including miRNAs, rather than an increase in the protein-encoding inventory caused by GDEs.genome duplication ͉ lamprey ͉ macroevolution ͉ shark ͉ chordate

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

MicroRNAs and the advent of vertebrate morphological complexity

Heimberg

Sempere

Moy

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

374

339

View full text Add to dashboard Cite

show abstract

“…Two sessile, putative urochordates, Cheungkongella and Shankouclava, have been described (38,39) as well as another Pikaia-like chordate, Yunnanozoon, which was initially described as a possible cephalochordate with a notochord, segmented trunk muscles, and an expanded pharynx with an endostyle (40). This taxon was subsequently reinterpreted as an early vertebrate (41), and it was then reinterpreted again as the earliest known enteropneust hemichordate (42).…”

Section: Fossil Recordmentioning

confidence: 99%

Evolution of centralized nervous systems: Two schools of evolutionary thought

2012

Proc. Natl. Acad. Sci. U.S.A.

112

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Understanding the evolution of centralized nervous systems requires an understanding of metazoan phylogenetic interrelationships, their fossil record, the variation in their cephalic neural characters, and the development of these characters. Each of these topics involves comparative approaches, and both cladistic and phenetic methodologies have been applied. Our understanding of metazoan phylogeny has increased greatly with the cladistic analysis of molecular data, and relaxed molecular clocks generally date the origin of bilaterians at 600-700 Mya (during the Ediacaran). Although the taxonomic affinities of the Ediacaran biota remain uncertain, a conservative interpretation suggests that a number of these taxa form clades that are closely related, if not stem clades of bilaterian crown clades. Analysis of brain-body complexity among extant bilaterians indicates that diffuse nerve nets and possibly, ganglionated cephalic neural systems existed in Ediacaran organisms. An outgroup analysis of cephalic neural characters among extant metazoans also indicates that the last common bilaterian ancestor possessed a diffuse nerve plexus and that brains evolved independently at least four times. In contrast, the hypothesis of a tripartite brain, based primarily on phenetic analysis of developmental genetic data, indicates that the brain arose in the last common bilaterian ancestor. Hopefully, this debate will be resolved by cladistic analysis of the genomes of additional taxa and an increased understanding of character identity genetic networks.The fact that some of these building stones are universal does not, of course, mean that the organs to which they contribute are as old as these molecules or their precursors.von Salvini-Plawen and Mayr (1) A ny consideration of the evolution of centralized nervous systems is inextricably linked to an understanding of the phylogeny of living metazoans, their fossil history, the vast range of complexity in their nervous systems, and the development of these nervous systems. For this reason, any attempt to reconstruct the phylogeny of metazoan CNSs must be based on all lines of evidence available. The molecular phylogenetic studies of the last 20 y are particularly important in understanding metazoan interrelationships as well as the time frame in which these animals arose and radiated, and we now have increased insights into the genetics underlying the development of CNSs.First, I will review the fossil history of the earliest putative metazoans, and then, I will discuss different comparative approaches to analyzing both molecular and morphological data: the molecular clock hypothesis, which has yielded a range of possible dates for the origin and divergence of metazoans; developmental genetics and its contribution to our understanding of the patterning of metazoan bodies, particularly patterning of the CNS; and conclusions based on the first outgroup analysis of metazoan central neural characters. Finally, I will review two hypotheses concerning the morphological complexity of the ...

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“…For example, two types of tunicate have been recorded, both from the Chengjiang Lagerstätte but otherwise distinctly different (Shu et al 2001a;Chen et al 2003). Thus, Cheungkongella is strikingly similar to extant stylid tunicates, but critics (e.g.…”

Section: The Triploblast Storymentioning

confidence: 99%

Darwin's dilemma: the realities of the Cambrian ‘explosion’

Morris

2006

Phil. Trans. R. Soc. B

152

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The Cambrian 'explosion' is widely regarded as one of the fulcrum points in the history of life, yet its origins and causes remain deeply controversial. New data from the fossil record, especially of Burgess Shale-type Lagerstätten, indicate, however, that the assembly of bodyplans is not only largely a Cambrian phenomenon, but can already be documented in fair detail. This speaks against a much more ancient origin of the metazoans, and current work is doing much to reconcile the apparent discrepancies between the fossil record, including the Ediacaran assemblages of latest Neoproterozoic age and molecular 'clocks'. Hypotheses to explain the Cambrian 'explosion' continue to be generated, but the recurrent confusion of cause and effect suggests that the wrong sort of question is being asked. Here I propose that despite its step-like function this evolutionary event is the inevitable consequence of Earth and biospheric change.

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The first tunicate from the Early Cambrian of South China

Cited by 119 publications

References 12 publications

MicroRNAs and the advent of vertebrate morphological complexity

MicroRNAs and the advent of vertebrate morphological complexity

Evolution of centralized nervous systems: Two schools of evolutionary thought

Darwin's dilemma: the realities of the Cambrian ‘explosion’

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