Evolution and Development at the Origin of a Phylum

Deline, Bradley; Thompson, Jeffrey R.; Smith, Nicholas S.; Zamora, Samuel; Rahman, Imran A.; Sheffield, Sarah L.; Ausich, William I.; Kammer, Thomas; Sumrall, Colin D.

doi:10.1016/j.cub.2020.02.054

Cited by 32 publications

(24 citation statements)

References 73 publications

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“…The same authors criticizing our approach rely on analyses that do not provide detailed delineation of character state parameters, full probing of superficial similarity, or support for why a given transformation series should be a part of a given character or carry phylogenetic signal (Kammer et al, 2013;Sumrall, 2017;Wright, et al, 2017;Deline, et al 2020;inter alia).…”

Section: Character Analysismentioning

confidence: 99%

“…The focus is primarily on feeding appendages but includes observations from adjacent skeletal anatomy as well. This analysis is based on examination of specimens hitherto unexamined by those who have suggested a sister-group relationship to crinoids for this taxon (Sheffield and Sumrall, 2019b; Deline et al, 2020). Accompanying reasoning that strongly supports a position for Eumorphocystis contrary to this recent work is presented with this analysis.…”

Section: Character Analysismentioning

confidence: 99%

“…The same authors criticizing our approach relied on analyses that do not provide detailed delineation of character state parameters, full probing of superficial similarity, or support for why a given transformation series should be a part of a given character or carry phylogenetic signal (Kammer et al, 2013; Sumrall, 2017; Wright et al, 2017; Deline et al, 2020). Approaches that differ from ours (e.g., Deline et al, 2020) leave uncited available data, or findings that undermine codings that they favor (e.g., David et al, 2000; Guensburg et al, 2010, 2016; Lefebvre et al, 2019). We prefer a different way of dealing with echinoderm phylogeny, particularly when working with fossils open to more than one interpretation.…”

Section: Character Analysismentioning

confidence: 99%

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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: 99%

Section: Character Analysismentioning

confidence: 99%

Section: Character Analysismentioning

confidence: 99%

See 1 more Smart Citation

Evolutionary significance of the blastozoanEumorphocystisand its pseudo-arms

Guensburg¹,

Sprinkle²,

Mooi³

et al. 2020

J. Paleontol.

View full text Add to dashboard Cite

show abstract

“…have never been examined under a comprehensive quantitative phylogenetic framework. Consequently, the main phylogenetic predictions of the EAT pertaining to the evolutionary relationships of Cambrian and Ordovician echinoderms, such as the origin of the crown group from edrioasteroid-like ancestors [14][15][16][17], although analysed with other homology schemes [9,11,18], have yet to be critically tested using EAT.…”

Section: Introductionmentioning

confidence: 99%

A new somasteroid from the Fezouata Lagerstätte in Morocco and the Early Ordovician origin of Asterozoa

Hunter

Ortega‐Hernández

2021

Biol. Lett.

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The somasteroids are Lower Palaeozoic star-shaped animals widely regarded as ancestors of Asterozoa, the group of echinoderms that includes brittle stars and starfish. However, the origin of asterozoans, the assembly of their distinctive body organization, and their relationships with other Cambrian and Ordovician echinoderms remain problematic owing to the difficulties of comparing the endoskeleton between disparate groups. Here, we describe the new somasteroid Cantabrigiaster fezouataensis , a primitive asterozoan from the Early Ordovician Fezouata Lagerstätte in Morocco. Cantabrigiaster shares with other somasteroids a unique endoskeletal arm organization and the presence of rod-like virgal ossicles that articulate with the ambulacrals, but differs from all other known asterozoans in the absence of adambulacral ossicles defining the arm margins, evoking parallels with non-asterozoan echinoderms. Developmentally informed Bayesian and parsimony phylogenetic analyses, which reflect the homology of the biserial ambulacral ossicles in Palaeozoic echinoderms according to the extraxial–axial theory, recover Cantabrigiaster as the earliest divergent stem-group asterozoan. Our results illuminate the ancestral morphology of Asterozoa, and clarify the affinities of problematic Ordovician Asterozoa. Bayesian inference and parsimony demonstrate that somasteroids represent a paraphyletic grade within stem- and crown-group Asterozoa, whereas stenuroids are paraphyletic within stem-group Ophiuroidea. Our results also offer potential insights on the evolutionary relationships between asterozoans, crinoids and potential Cambrian stem-group representatives.

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“…Echinoderms show complex patterns of morphological disparity and taxonomic diversity throughout their evolutionary history (Sumrall 1997; Deline 2015; Deline and Thomka 2017; Deline et al 2020) and have been suggested to respond to long-term environmental and climatic patterns (Paul 1968; Clausen 2004; Dickson 2004; Clausen and Smith 2005, 2008; Zamora and Smith 2008; Rahman and Zamora 2009). The early Paleozoic experienced large shifts in geochemical cycles (Haq and Schutter 2008; Trotter et al 2008; Rasmussen et al 2016; Albanesi et al 2019) that impacted microfossil and marine invertebrate groups (reviewed in Stigall et al 2019), suggesting that blastozoan echinoderms would have been impacted.…”

Section: Introductionmentioning

confidence: 99%

Estimating dispersal and evolutionary dynamics in diploporan blastozoans (Echinodermata) across the great Ordovician biodiversification event

Lam

Sheffield²,

Matzke³

2020

Paleobiology

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Echinoderms make up a substantial component of Ordovician marine invertebrates, yet their speciation and dispersal history as inferred within a rigorous phylogenetic and statistical framework is lacking. We use biogeographic stochastic mapping (BSM; implemented in the R package BioGeoBEARS) to infer ancestral area relationships and the number and type of dispersal events through the Ordovician for diploporan blastozoans and related species. The BSM analysis was divided into three time slices to analyze how dispersal paths changed before and during the great Ordovician biodiversification event (GOBE) and within the Late Ordovician mass extinction intervals. The best-fit biogeographic model incorporated jump dispersal, indicating this was an important speciation strategy. Reconstructed areas within the phylogeny indicate the first diploporan blastozoans likely originated within Baltica or Gondwana. Dispersal, jump dispersal, and sympatry dominated the BSM inference through the Ordovician, while dispersal paths varied in time. Long-distance dispersal events in the Early Ordovician indicate distance was not a significant predictor of dispersal, whereas increased dispersal events between Baltica and Laurentia are apparent during the GOBE, indicating these areas were important to blastozoan speciation. During the Late Ordovician, there is an increase in dispersal events among all paleocontinents. The drivers of dispersal are attributed to oceanic and epicontinental currents. Speciation events plotted against geochemical data indicate that blastozoans may not have responded to climate cooling events and other geochemical perturbations, but additional data will continue to shed light on the drivers of early Paleozoic blastozoan speciation and dispersal patterns.

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Evolution and Development at the Origin of a Phylum

Cited by 32 publications

References 73 publications

Evolutionary significance of the blastozoanEumorphocystisand its pseudo-arms

Evolutionary significance of the blastozoanEumorphocystisand its pseudo-arms

A new somasteroid from the Fezouata Lagerstätte in Morocco and the Early Ordovician origin of Asterozoa

Estimating dispersal and evolutionary dynamics in diploporan blastozoans (Echinodermata) across the great Ordovician biodiversification event

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