The oldest echinoderm faunas from Gondwana show that echinoderm body plan diversification was rapid

Smith, Andrew B.; Zamora, Samuel; Álvaro, J. Javier

doi:10.1038/ncomms2391

Cited by 60 publications

(65 citation statements)

References 39 publications

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“…Finally, Ctenocystis, Etoctenocystis, Gilcidia, and Pembrocystis are most dissimilar to Conollia, being charac-terized by double-layered marginal frames, flattened, weakly asymmetrical thecae, and differentiated ctenidial plating (Robison and Sprinkle 1969;Sprinkle and Robison 1978;Fatka and Kordule 1985;Jell et al 1985;Ubaghs 1987; Ubaghs and Robison 1988;Domínguez Alonso 2004;Rahman and Clausen 2009). Smith et al (2013) reported two ctenocystoids from Morocco (awaiting formal description) that can be compared with Conollia. Ctenocystoid gen. et sp.…”

Section: Discussionmentioning

confidence: 94%

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The youngest ctenocystoids from the Upper Ordovician of the United Kingdom and the evolution of the bilateral body plan in echinoderms

Rahman¹,

Stewart²,

Zamora³

2014

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Paleobiology, National Museum of Natural History, Smithsonian Institution, Washington DC, 20013-7012, USA; and Museo Geominero, Instituto Geológico y Minero de España, C/ Manuel Lasala, 44 -9º B, 50006 Zaragoza, Spain. This is an open-access article distributed under the terms of the Creative Commons Attribution License (for details please see creativecommons.org), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

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Section: Discussionmentioning

confidence: 94%

“…Based on its morphology and stratigraphic position, we suggest that Conollia is a derived ctenocystoid, perhaps most closely related to Jugoszovia and ctenocystoid gen. et sp. nov. 1 from Smith et al (2013).…”

Section: Discussionmentioning

confidence: 97%

The youngest ctenocystoids from the Upper Ordovician of the United Kingdom and the evolution of the bilateral body plan in echinoderms

Rahman¹,

Stewart²,

Zamora³

2014

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“…The lower member encompasses the classic lowermiddle Cambrian boundary and base of Global series 3, and is dated to approximately 517 Ma [8,16]. Helicocystis moroccoensis was collected from the Jbel Wawrmast Formation at the following three localities ( figure 1 …”

Section: Materials and Methods (A) Geological Setting And Stratigraphymentioning

confidence: 99%

“…This ontogenetic transformation reflects an evolutionary history in which originally bilaterian ancestors evolved into pentaradiate forms [3,4]. The fossil record captures a partial record of these long-extinct transitional forms, and is thus important for establishing the precise pathway followed in assembling this highly derived body plan [5][6][7] and for estimating rates of transformation [8]. However, there remain many gaps and uncertainties.…”

Section: Introductionmentioning

confidence: 99%

Cambrian spiral-plated echinoderms from Gondwana reveal the earliest pentaradial body plan

Smith

Zamora

2013

Proc. R. Soc. B.

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Echinoderms are unique among animal phyla in having a pentaradial body plan, and their fossil record provides critical data on how this novel organization came about by revealing intermediate stages. Here, we report a spiralplated animal from the early Cambrian of Morocco that is the most primitive pentaradial echinoderm yet discovered. It is intermediate between helicoplacoids (a bizarre group of spiral-bodied echinoderms) and crown-group pentaradiate echinoderms. By filling an important gap, this fossil reveals the common pattern that underpins the body plans of the two major echinoderm clades (pelmatozoans and eleutherozoans), showing that differential growth played an important role in their divergence. It also adds to the striking disparity of novel body plans appearing in the Cambrian explosion.

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“…Indeed, although there are many studies among classes of chordates (5), such comparisons are essentially unknown in any other animal taxa at this level of evolutionary comparison. Echinoderms diverged into separate classes ∼450-500 Mya in the Ordovician, but the radiation is considered to have occurred extremely rapidly, with five separate classes emerging in as few as 5 million years (14,43,44). During this rapid radiation, the classes underwent dramatic morphological change, and yet their body plans, both as adults and larvae, have remained remarkably stable since.…”

Section: Discussionmentioning

confidence: 99%

Genome-wide use of high- and low-affinity Tbrain transcription factor binding sites during echinoderm development

Cary

Jarvela

Francolini

2017

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

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Sea stars and sea urchins are model systems for interrogating the types of deep evolutionary changes that have restructured developmental gene regulatory networks (GRNs). Although cis-regulatory DNA evolution is likely the predominant mechanism of change, it was recently shown that Tbrain, a Tbox transcription factor protein, has evolved a changed preference for a low-affinity, secondary binding motif. The primary, high-affinity motif is conserved. To date, however, no genome-wide comparisons have been performed to provide an unbiased assessment of the evolution of GRNs between these taxa, and no study has attempted to determine the interplay between transcription factor binding motif evolution and GRN topology. The study here measures genome-wide binding of Tbrain orthologs by using ChIP-sequencing and associates these orthologs with putative target genes to assess global function. Targets of both factors are enriched for other regulatory genes, although nonoverlapping sets of functional enrichments in the two datasets suggest a much diverged function. The number of low-affinity binding motifs is significantly depressed in sea urchins compared with sea star, but both motif types are associated with genes from a range of functional categories. Only a small fraction (∼10%) of genes are predicted to be orthologous targets. Collectively, these data indicate that Tbr has evolved significantly different developmental roles in these echinoderms and that the targets and the binding motifs in associated cis-regulatory sequences are dispersed throughout the hierarchy of the GRN, rather than being biased toward terminal process or discrete functional blocks, which suggests extensive evolutionary tinkering.Tbrain | echinoderm | binding site affinity | ChIP-seq

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The oldest echinoderm faunas from Gondwana show that echinoderm body plan diversification was rapid

Cited by 60 publications

References 39 publications

The youngest ctenocystoids from the Upper Ordovician of the United Kingdom and the evolution of the bilateral body plan in echinoderms

The youngest ctenocystoids from the Upper Ordovician of the United Kingdom and the evolution of the bilateral body plan in echinoderms

Cambrian spiral-plated echinoderms from Gondwana reveal the earliest pentaradial body plan

Genome-wide use of high- and low-affinity Tbrain transcription factor binding sites during echinoderm development

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