Divergent evolution of medusozoan symmetric patterns: Evidence from the microanatomy of Cambrian tetramerous cubozoans from South China

Fossilized embryos afford direct insight into the pattern of development in extinct organisms, providing unique tests of hypotheses of developmental evolution based in comparative embryology. However, these fossils can only be effective in this role if their embryology and phylogenetic affinities are well constrained. We elucidate and interpret the development of Olivooides from embryonic and adult stages and use these data to discriminate among competing interpretations of their anatomy and affinity. The embryology of Olivooides is principally characterized by the development of an ornamented periderm that initially forms externally and is subsequently formed internally, released at the aperture, facilitating the direct development of the embryo into an adult theca. Internal anatomy is known only from embryonic stages, revealing two internal tissue layers, the innermost of which is developed into three transversally arranged walls that partly divide the lumen into an abapertural region, interpreted as the gut of a polyp, and an adapertural region that includes structures that resemble the peridermal teeth of coronate scyphozoans. The anatomy and pattern of development exhibited by Olivooides appears common to the other known genus of olivooid, Quadrapyrgites, which differs in its tetraradial, as opposed to pentaradial symmetry. We reject previous interpretations of the olivooids as cycloneuralians, principally on the grounds that they lack a through gut and introvert, in embryo and adult. Instead we consider the affinities of the olivooids among medusozoan cnidarians; our phylogenetic analysis supports their classification as totalgroup Coronata, within crown-Scyphozoa. Olivooides and Quadrapyrgites evidence a broader range of life history strategies and bodyplan symmetry than is otherwise commonly represented in extant Scyphozoa specifically, and Cnidaria more generally.Key words: development, embryo, Cnidaria, Scyphozoa, Kuanchuanpu, Cambrian. et al. 2015), the tempo of early animal evolution is astonishing given the scale of innovation achieved (Erwin et al. 2011): the establishment of all phylum-level body plans that are sufficiently distinct that they are effectively defined by the limits of comparative anatomy (Bengtson 1986). Insights into the processes that brought about this remarkable episode in evolutionary history are afforded through comparative embryology of living animals, facilitating inference of the embryology of ancient ancestors and, indeed, into the evolution of development that brought about the origin of animal bodyplans. Inevitably, this approach is confused by the subsequent developmental evolution that serves to conflate homologies and convergences. Hence, the discovery of a fossil record of embryology from early in animal evolutionary history affords a more direct insight into the embryology of ancient ancestors, free from the confounding effects of half a billion years of subsequent evolutionary history. T H O U G H there remains considerable debate over the timing of ori...

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“…) and Quadrapyrgites (Han et al . in press). Tomographic analyses of the post‐embryonic thecate stage by Yasui et al .…”

Section: History Of Research Into Olivooidesmentioning

confidence: 99%

“…() and Han et al . (in press) described the pattern of development of Quadrapyrgites , which they revealed to be like Olivooides in all respects, with the exception that it is tetramerous rather than pentamerous. Liu et al .…”

Section: History Of Research Into Olivooidesmentioning

confidence: 99%

Developmental biology of the early Cambrian cnidarian Olivooides

Vargas

Cunningham

et al. 2016

Palaeontology

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“…In spite of the micro CT 3D imaging of the Brioverian specimens, symmetric and geometric structures similar to the ones revealed by Synchrotron Radiation microCT on submillimetric Cambrian ‘medusoids’ from South China (Han et al . ) were impossible to identify in this study.…”

Section: Discussionmentioning

confidence: 81%

First evidence of Ediacaran–Fortunian elliptical body fossils in the Brioverian series of Brittany, NW France

Néraudeau

Dabard

Albani

et al. 2018

LET

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Body fossils are described for the first time from the Upper Brioverian (Ediacaran–Fortunian) deposits of Central Brittany (NW France). The material consists of a dozen of specimens preserved on two slates, recently collected in a quarry in Saint‐Gonlay. The fossils, centimetric in size, have an elliptical and acuminated outline, with a peripheral bulge but without conspicuous concentric or radial lines. These body fossils are preserved in slates that are locally rich in grazing traces, sometimes associated with microbial mats. The sedimentological characteristics of these deposits correspond to a shallow marine shelf environment, with a low to moderate hydrodynamism. Such findings, in concomitance with previous ichnological discoveries, unravel the potential of the Brioverian strata from Brittany as a new locality to provide answers on Ediacaran and early Cambrian biocenoses.

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“…), or a cubozoan (Han et al . ). Review of the lengthy debates on the affinities of these early radial animals is beyond the scope of the present work, as this matter has been addressed in several recent papers (Dong et al .…”

Section: Discussionmentioning

confidence: 97%

“…Olivooides was first interpreted as a fossil embryo in 1997, proposed as a coronate scyphozoan (Bengtson & Yue ; Yue & Bengtson ) and later re‐interpreted as an echinoderm (Chen ), a cubozoan (Han et al . , b), a stem‐group cycloneuralian (Steiner et al . ) or a diploblastic stem‐group eumetazoan (Yasui et al .…”

Section: Discussionmentioning

confidence: 99%

A new scyphozoan from the Cambrian Fortunian Stage of South China

et al. 2017

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Animals with radial symmetry are abundant in the Cambrian Fortunian Stage of South China, but with relatively low diversity: representatives include Olivooides, Quadrapyrgites, carinachitiids, hexangulaconulariids and Pseudooides. Here, we report a new radial animal, Qinscyphus necopinus gen. et sp. nov., from the Fortunian small shelly fauna of southern Shaanxi Province, South China. Qinscyphus necopinus has a cup-shaped profile, with slightly raised annuli and five groups of triangular thickenings in pentaradial symmetry. This organism has a comparable morphology to, and thus a close affinity with, Olivooides and Quadrapyrgites, and is interpreted as a coronate scyphozoan. This discovery adds a new crown-group cnidarian to the Cambrian Explosion.

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Divergent evolution of medusozoan symmetric patterns: Evidence from the microanatomy of Cambrian tetramerous cubozoans from South China

Cited by 35 publications

References 46 publications

Developmental biology of the early Cambrian cnidarian Olivooides

Developmental biology of the early Cambrian cnidarian Olivooides

First evidence of Ediacaran–Fortunian elliptical body fossils in the Brioverian series of Brittany, NW France

A new scyphozoan from the Cambrian Fortunian Stage of South China

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