A soft-bodied mollusc with radula from the Middle Cambrian Burgess Shale

Caron, Jean‐Bernard; Scheltema, Amélie H.; Schänder, Christoffer; Rudkin, David M.

doi:10.1038/nature04894

Cited by 141 publications

(101 citation statements)

References 33 publications

(28 reference statements)

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“…Some paleontologists and zoologists have argued that these animals are mollusks and therefore are yet another representative of the placophoran grade of organization. Others argue that while they are closely related to mollusks and other lophotrochozoan groups such as annelid worms or perhaps brachiopods, they are not members of the Mollusca (see Vinther and Nielsen 2005;Caron et al 2006;Butterfield 2006 for a sampling of both pro and con arguments).…”

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confidence: 99%

Monoplacophorans and the Origin and Relationships of Mollusks

Lindberg

2009

Evo Edu Outreach

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The story of the discovery and study of the Monoplacophora (or Tryblidia) and how they have contributed to our understanding of the evolution of the Mollusca highlights the importance of integrating data from the fossil record with the study of living forms. Monoplacophora were common in the early Paleozoic and were thought to have become extinct during the Devonian Period, approximately 375 Mya. In the mid 1950s, they were recovered from abyssal depths off of Costa Rica and were immediately heralded as a "living fossil." The living specimens confirmed that some of the organs (kidneys, heart, and gills) were repeated serially, just like the shell muscles that had been observed in fossil specimens. This supported the hypothesis that they were closely related to other segmented organisms such as annelids and arthropods. Today, there are 29 described living species and a growing body of work examining their anatomy, phylogeny, and ecology. Additional fossil specimens have also been discovered, and what was once thought to be a possible missing link between annelid worms and mollusks now appears to be a highly specialized branch of the molluscan tree that tells us little about the ancestral mollusk condition. However, some assumptions and generalizations from those early days still remain-such as the abyssal nature of the living species. A large part of the evolutionary history of the lineage remains to be discovered and will likely prove more complicated and interesting than afforded by the living fossil designation.

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confidence: 99%

Monoplacophorans and the Origin and Relationships of Mollusks

Lindberg

2009

Evo Edu Outreach

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“…Significant extracellular secretion is indicated by the residual three-dimensionality of teeth [8]. As iterated by Caron et al [2,7], the mouthparts comprise symmetrical transverse rows of solid teeth that are distinct from, but embedded in, a radular membrane; the rows pass round the end of a supporting apparatus, are sloughed anteriorly and replaced from the posterior, and contain more teeth when they are larger. But where Caron et al identified two denticulate teeth per row [2,7], this study recognizes each 'denticle' as a separate articulating tooth.…”

Section: Discussion (A) Reconstructionmentioning

confidence: 99%

“…The soft-bodied organisms Odontogriphus omalus and Wiwaxia corrugata from the Middle Cambrian Burgess Shale (Series 3-505 Ma) seem to represent early members of this group [1,2]; if so, they provide our best constraint on the ancestral mollusc. However, it has been suggested that Wiwaxia is more closely related to the annelid worms [3][4][5], and that Odontogriphus could have diverged from a lineage ancestral to both the molluscs and the annelids [4,5].…”

Section: Introductionmentioning

confidence: 99%

“…They closely resemble the betterunderstood Odontogriphus feeding apparatus. According to Caron et al [2,7], this consists of two (occasionally three) bilaterally symmetrical tooth rows, with the posterior row usually wider than the anterior. The teeth, which have a consistent relative position even when isolated from the body, are held to have been embedded in or on a non-fossilized radular membrane.…”

Section: Introductionmentioning

confidence: 99%

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Mouthparts of the Burgess Shale fossils Odontogriphus and Wiwaxia : implications for the ancestral molluscan radula

Smith

2012

Proc. R. Soc. B.

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The Middle Cambrian lophotrochozoans Odontogriphus omalus and Wiwaxia corrugata have been interpreted as stem-group members of either the Mollusca, the Annelida, or a group containing Mollusca þ Annelida. The case for each classification rests on the organisms' unusual mouthparts, whose two to three tooth-rows resemble both the molluscan radula and the jaws of certain annelid worms. Despite their potential significance, these mouthparts have not previously been described in detail. This study examined the feeding apparatuses of over 300 specimens from the 505-million-year-old Burgess Shale, many of which were studied for the first time. Rather than denticulate plates, each tooth row comprises a single axial tooth that is flanked on each side by eight to 16 separate shoehorn-shaped teeth. Tooth rows sat on a grooved basal tongue, and two large lobes flanked the apparatus. New observations-the shape, distribution and articulation of the individual teeth, and the mouthparts' mode of growth-are incompatible with an annelid interpretation, instead supporting a classification in Mollusca. The ancestral molluscan radula is best reconstructed as unipartite with a symmetrical medial tooth, and Odontogriphus and Wiwaxia as grazing deposit-feeders.

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“…This is on the dual supposition of the similarities of the sclerite microstructure to annelidan chaetae (Butterfield, 1990; see also Conway Morris and Peel, 1995) and the inferred transformation of the scleritome into parapodial bundles capable of locomotion and defense (Conway Morris and Peel, 1995;Struck, 2011). Arguments, especially on the nature of the radula-like mouthConway Morris et al-Burgess Shale-type taxa parts (Smith, 2012) and similarities to Odontogriphus (Caron et al, 2006) on the other hand point to a molluscan affinity (see also Smith, 2014). By itself, W. herka can add nothing material to this discussion, but it is worth emphasizing that if the wiwaxiids belong to a stem-group identified as the halwaxiids (Conway Morris and Caron, 2007) then shoe-horning them into a given phylum may serve to obscure how crucial anatomical transitions were achieved among which end-results are the setae of annelids (and brachiopods) or radula of mollusks.…”

Section: Genus Wiwaxia Walcott 1911amentioning

confidence: 99%

New records of Burgess Shale-type taxa from the middle Cambrian of Utah

Morris

Selden

Gunther³

et al. 2015

J. Paleontol.

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Abstract.-Cambrian strata of the Laurentian craton contain numerous examples of Burgess Shale-type faunas. Although displaying a more or less concentric distribution around the cratonal margin, most faunal occurrences are in present-day western North America, extending from the Northwest Territories to California. Nevertheless, the soft-bodied and lightly skeletalized fossils in most of these Lagerstätten are highly sporadic. Here, we extend knowledge of such Middle Cambrian occurrences in Utah with reports of four taxa. An arthropod from the Marjum Formation, Dytikosicula desmatae gen. et sp. nov., is a putative megacheiran. It is most similar to Dicranocaris guntherorum, best known from the younger Wheeler Formation, but differs primarily in the arrangement of pleurae and overall size. Along with a specimen of ?Yohoia sp, a new species of Yohoia, Y. utahana sp. nov., is described. It differs from the type and only known species, Y. tenuis, principally in its larger size and shorter exopods; it is the first description of this genus from outside the Burgess Shale. A new species of a stem-group lophotrochozoan from the Spence Shale, Wiwaxia herka sp. nov., possesses a palisade of dorso-lateral spines that are more robust and numerous than the type species of Wiwaxia, W. corrugata. Another notable taxon is Eldonia ludwigi from the Marjum Formation, which is interpreted as a primitive ambulacrarian (assigned to the cambroernids) and a new specimen of the ?cnidarian Cambrorhytium from the Wheeler Shale is illustrated.

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A soft-bodied mollusc with radula from the Middle Cambrian Burgess Shale

Cited by 141 publications

References 33 publications

Monoplacophorans and the Origin and Relationships of Mollusks

Monoplacophorans and the Origin and Relationships of Mollusks

Mouthparts of the Burgess Shale fossils Odontogriphus and Wiwaxia : implications for the ancestral molluscan radula

New records of Burgess Shale-type taxa from the middle Cambrian of Utah

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