The Cambrian edrioasteroid Stromatocystites (Echinodermata): Systematics, palaeogeography, and palaeoecology

Zamora, Samuel; Lefèbvre, Bertrand; Hoşgör, İzzet; Franzén, Christina; Nardin, Élise; Fatka, Oldřich; Álvaro, J. Javier

doi:10.1016/j.geobios.2015.07.004

Cited by 13 publications

(14 citation statements)

References 25 publications

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“…4a;Zhao et al, 2010, Fig. 6.7, for instance) and Early Ordovician edrioasterid edrioasteroid (Sprinkle and Sumrall, 2015;Zamora et al, 2015, et al) echinoderms (see Guensburg et al, 2020).…”

Section: Character Analysismentioning

confidence: 98%

Evolutionary significance of the blastozoanEumorphocystisand its pseudo-arms

Guensburg¹,

Sprinkle²,

Mooi³

et al. 2020

J. Paleontol.

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Twelve specimens of Eumorphocystis Branson and Peck, 1940 provide the basis for new findings and a more informed assessment of whether this blastozoan (a group including eocrinoids, blastoids, diploporites, rhombiferans) constitutes the sister taxon to crinoids, as has been recently proposed. Both Eumorphocystis and earliest-known crinoid feeding appendages express longitudinal canals, a demonstrable trait exclusive to these taxa. However, the specimen series studied here shows that Eumorphocystis canals constrict proximally and travel within ambulacrals above the thecal cavity. This relationship is congruent with a documented blastozoan pattern but very unlike earliest crinoid topology. Earliest crinoid arm cavities lie fully beneath floor plates; these expand and merge directly with the main thecal coelomic cavity at thecal shoulders. Other associated anatomical features echo this contrasting comparison. Feeding appendages of Eumorphocystis lack two-tiered cover plates, podial basins/pores, and lateral arm plating, all features of earliest crinoid ‘true arms.’ Eumorphocystis feeding appendages are buttressed by solid block-like plates added during ontogeny at a generative zone below floor plates, a pattern with no known parallel among crinoids. Eumorphocystis feeding appendages express brachioles, erect extensions of floor plates, also unknown among crinoids. These several distinctions point to nonhomology of most feeding appendage anatomy, including longitudinal canals, removing Eumorphocystis and other blastozoans from exclusive relationship with crinoids. Eumorphocystis further differs from crinoids in that thecal plates express diplopores, respiratory structures not present among crinoids, but ubiquitous among certain groups of blastozoans. Phylogenetic analysis places Eumorphocystis as a crownward blastozoan, far removed from crinoids.

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Section: Character Analysismentioning

confidence: 98%

Evolutionary significance of the blastozoanEumorphocystisand its pseudo-arms

Guensburg¹,

Sprinkle²,

Mooi³

et al. 2020

J. Paleontol.

Self Cite

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“…The analysis was rooted on a middle Cambrian edrioasteroid-like form, Stromatocystites pentangularis Pompeckj, 1896 (see Zamora et al, 2015). This taxon is here considered to approximate an archaic, pentaradiate level of organization.…”

Section: Independent Origins Of Crinoids and Blastozoans Among Early mentioning

confidence: 99%

Athenacrinusn. gen. and other early echinoderm taxa inform crinoid origin and arm evolution

Guensburg¹,

Sprinkle²,

Mooi³

et al. 2019

J. Paleontol.

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Intermediate morphologies of a new fossil crinoid shed light on the pathway by which crinoids acquired their distinctive arms. Apomorphies originating deep in echinoderm history among early nonblastozoan pentaradiate echinoderms distinguish Tremadocian (earliest Ordovician) crinoid arms from later taxa. The brachial series is separated from the ambulacra, part of the axial skeleton, by lateral plate fields. Cover plates are arrayed in two tiers, and floor plates expressed podial basins and pores. Later during the Early Ordovician, floor plates contacted and nestled into brachials, then were unexpressed as stereom elements entirely and cover plates were reduced to a single tier. Incorporation of these events into a parsimony analysis supports crinoid origin deep in echinoderm history separate from blastozoans (eocrinoids, ‘cystoids’). Arm morphology is exceptionally well-preserved in the late Tremadocian to early Floian Athenacrinus broweri new genus new species. Character analysis supports a hypothesis that this taxon originated early within in the disparid clade. Athenacrinus n. gen. (in Athenacrinidae new family) is the earliest-known crinoid to express what is commonly referred to as ‘compound’ or ‘biradial’ morphology. This terminology is misleading in that no evidence for implied fusion or fission of radials exists, rather it is suggested that this condition arose through disproportionate growth.UUID: http://zoobank.org/b383e039-3298-4472-a7e3-e81684f87cfe

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“…Echinozoans and asterozoans may have both evolved from an edrioasteroid ancestor, but though which edrioasteroids they evolved from are unknown. In order to account for this uncertainty, we use the oldest edrioasteroid, Stromatocystites walcotti , from the Cambrian Series 2 121 as the maximum bound on the divergence. The maximum bound on the divergence is thus the base of Series 2 in the Cambrian Period, which is currently set at 521 MA.…”

Section: Methodsmentioning

confidence: 99%

Cell type phylogenetics informs the evolutionary origin of echinoderm larval skeletogenic cell identity

Erkenbrack

Thompson

2019

Commun Biol

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The multiplicity of cell types comprising multicellular organisms begs the question as to how cell type identities evolve over time. Cell type phylogenetics informs this question by comparing gene expression of homologous cell types in distantly related taxa. We employ this approach to inform the identity of larval skeletogenic cells of echinoderms, a clade for which there are phylogenetically diverse datasets of spatial gene expression patterns. We determined ancestral spatial expression patterns of alx1, ets1, tbr, erg , and vegfr , key components of the skeletogenic gene regulatory network driving identity of the larval skeletogenic cell. Here we show ancestral state reconstructions of spatial gene expression of extant eleutherozoan echinoderms support homology and common ancestry of echinoderm larval skeletogenic cells. We propose larval skeletogenic cells arose in the stem lineage of eleutherozoans during a cell type duplication event that heterochronically activated adult skeletogenic cells in a topographically distinct tissue in early development.

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The Cambrian edrioasteroid Stromatocystites (Echinodermata): Systematics, palaeogeography, and palaeoecology

Cited by 13 publications

References 25 publications

Evolutionary significance of the blastozoanEumorphocystisand its pseudo-arms

Evolutionary significance of the blastozoanEumorphocystisand its pseudo-arms

Athenacrinusn. gen. and other early echinoderm taxa inform crinoid origin and arm evolution

Cell type phylogenetics informs the evolutionary origin of echinoderm larval skeletogenic cell identity

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