Ontogeny in the fossil record: diversification of body plans and the evolution of “aberrant” symmetry in Paleozoic echinoderms

@inproceedings{Sumrall2007OntogenyIT,
  title={Ontogeny in the fossil record: diversification of body plans and the evolution of “aberrant” symmetry in Paleozoic echinoderms},
  author={Colin D. Sumrall and Gregory A. Wray},
  booktitle={Paleobiology},
  year={2007}
}
Abstract Echinoderms have long been characterized by the presence of ambulacra that exhibit pentaradiate symmetry and define five primary body axes. In reality, truly pentaradial ambulacral symmetry is a condition derived only once in the evolutionary history of echinoderms and is restricted to eleutherozoans, the clade that contains most living echinoderm species. In contrast, early echinoderms have a bilaterally symmetrical 2–1–2 arrangement, with three ambulacra radiating from the mouth… Expand
Genomic insights of body plan transitions from bilateral to pentameral symmetry in Echinoderms
TLDR
It is determined that the last common ancestor of echinoderms contained an organized Hox cluster and endoskeleton genes, and it is suggested that cooption of bilateral development genes was involved in evolution of the pentameric body plan. Expand
Deciphering The Early Evolution of Echinoderms with Cambrian Fossils
TLDR
Pentaradial echinoderms diversified rapidly from the beginning of their history, and the most significant differences between groups are recorded in the construction of the oral area and ambulacra, as well as the nature of their feeding appendages, which provides a clear narrative of the early evolution of the echinoderm body plan. Expand
The Youngest Ctenocystoids from the Upper Ordovician of the United Kingdom and the Evolution of the Bilateral Body Plan in Echinoderms
During the early Palaeozoic, echinoderm body plans were much more diverse than they are today, displaying four distinct types of symmetry. This included the bilateral ctenocystoids, which were longExpand
Oral Region Homologies in Paleozoic Crinoids and Other Plesiomorphic Pentaradial Echinoderms
TLDR
Newly recognized oral region homologies are presented, based on the Universal Elemental Homology model for skeletal plates, in a wide range of fossil taxa for exploring branching order among stem groups on the echinoderm tree of life. Expand
A hexamer origin of the echinoderms' five rays
TLDR
It is proposed that the predominant five‐ray structure is derived from a hexamer structure that is grounded directly in the structure of the bilaterally symmetric larva, which implies that the adult echinoderm body can be derived directly from the larval bilateral symmetry and thus firmly ranks even the adults echinoderms among the bilaterians. Expand
The oldest echinoderm faunas from Gondwana show that echinoderm body plan diversification was rapid.
TLDR
The discovery of two new echinoderm faunas from the early part of the Cambrian of Morocco (West Gondwana) indicates that considerable diversification had already taken place by 510 Ma, and suggests that a rapid rate of morphological divergence took place during the initial stages of echinoderms evolution. Expand
Testing for homologies in the axial skeleton of primitive echinoderms
  • C. Paul
  • Biology
  • Journal of Paleontology
  • 2017
TLDR
The range of variation in echinoderms with fewer than five ambulacra implies that both the ‘branch’ and ‘stop’ instructions acted independently in all five rays, and terminal addition of plates, spacing of brachioles/pinnules, and lack of musculature to open cover plates all suggest that ‘cystoids’ had extensions of the water vascular system in their ambulanceacra. Expand
Taphonomy and ontogeny of early pelmatozoan echinoderms: A case study of a mass-mortality assemblage of Gogia from the Cambrian of North America
TLDR
This study demonstrates that taxonomic studies of gogiids should, wherever possible, consider a large number of specimens encompassing a range of sizes in order to clearly distinguish between ontogenetic and interspecific morphological variation. Expand
Fixed, free, and fixed: the fickle phylogeny of extant Crinoidea (Echinodermata) and their Permian-Triassic origin.
TLDR
These analyses tend to support the hypothesis that the Crinoidea group is a radiation from a small clade that passed through the Permian-Triassic extinction event rather than several lineages that survived. Expand
Generic revision of the Holocystitidae of North America (Diploporita, Echinodermata) based on universal elemental homology
TLDR
The Holocystites Fauna is an enigmatic group of North American diploporitans that presents a rare window into unusual middle Silurian echinoderm communities and shows a conservative peristomial bordering plate pattern that is shared among all described genera. Expand
...
1
2
3
4
5
...

References

SHOWING 1-10 OF 79 REFERENCES
Evolution of the chordate body plan: new insights from phylogenetic analyses of deuterostome phyla.
TLDR
The nesting of the pterobranchs within the enteropneusts dramatically alters the view of the evolution of the chordate body plan and suggests that the ancestral deuterostome more closely resembled a mobile worm-like enteropNEust than a sessile colonial pterOBranch. Expand
The pre‐radial history of echinoderms
TLDR
Carpoids, a highly contentious group of extinct deuterostomes with a plated calcite skeleton, display many of these basal characters and provide critical evidence for how the latest common ancestor of hemichordates and echinoderms was transformed into a pentaradiate crown-group echinoderm. Expand
Are homalozoans echinoderms? An answer from the extraxial-axial theory
TLDR
The Extraxial-Axial Theory (EAT) identifies body-wall homologies, common ontogenetic patterns, and major events in bodyplan evolution and strongly suggests that the bizarre asymmetry of homalozoans is a derived characteristic, and not indicative of plesiomorphic morphology for either chordates or echinoderms. Expand
Radical alterations in the roles of homeobox genes during echinoderm evolution
TLDR
The expression domains in echinoderms of three important developmental regulatory genes ( distal-less, engrailed and orthodenticle ), all of which encode transcription factors that contain a homeodomain are reported, demonstrating the evolutionary lability of regulatory genes that are widely viewed as conservative. Expand
The Early Phylogeny of Chordates and Echinoderms and the Origin of Chordate Left–Right Asymmetry and Bilateral Symmetry
TLDR
The history of the echinoderm stem group is reconstructed and left–right asymmetry in Dexiothetica results mainly from dexiothetism—an episode in their ancestry when an animal resembling the Recent pterobranch Cephalodiscus lay right-side-downwards on the sea floor. Expand
A critical reappraisal of the fossil record of the bilaterian phyla
  • G. Budd, S. Jensen
  • Medicine
  • Biological reviews of the Cambridge Philosophical Society
  • 2000
TLDR
It is shown that the prospect of lineage diversification occurring early in the Proterozoic can be seen to be unlikely on grounds of both parsimony and functional morphology, and this analysis points to the requirement for a careful application of systematic methodology before explanations are sought for alleged patterns of constraint and flexibility. Expand
A critical reappraisal of the fossil record of the bilaterian phyla.
TLDR
It is shown that the prospect of lineage diversification occurring early in the Proterozoic can be seen to be unlikely on grounds of both parsimony and functional morphology, and this analysis points to the requirement for a careful application of systematic methodology before explanations are sought for alleged patterns of constraint and flexibility. Expand
The A/P axis in echinoderm ontogeny and evolution: evidence from fossils and molecules
SUMMARY Even though echinoderms are members of the Bilateria, the location of their anterior/posterior axis has remained enigmatic. Here we propose a novel solution to the problem employing threeExpand
A phylogenetic test of the calcichordate scenario
TLDR
The calcichordate scenario of Jefferies and colleagues purports to explain the origin and early evolution of the phyla Echinodermata and Chordata is tested, finding that it fails the erection of scenarios and fossils are unable to dictate the relationships among phyla. Expand
Chapter 5 Evolution of Primitive Echinoderms
TLDR
Primitive echinoderms have the most complex morphology of any phylum and they are second only to the vertebrates in the intimacy of the relationship between soft and hard anatomy. Expand
...
1
2
3
4
5
...