The Early Cambrian Radiation of Mollusca

Parkhaev, P. Yu.

doi:10.1525/california/9780520250925.003.0003

Cited by 62 publications

(39 citation statements)

References 47 publications

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“…Bars correspond to 95% credibility intervals. Fossil constraints were set on nodes A-E: node A, 231 Ma (Leptochiton davolii [66]); node B, 505 Ma (Plectronoceras cambria [67]); node C, 475 Ma (Glyptarca serrata, Arenigian [68]); node D, 530 Ma (Fordilla troyensis from the Tommotian of Siberia [69 -71]); node E, 418 Ma (Sublitoidea [72]). We used 550 Ma (ca Terreneuvian; see [41]) to set a prior density on the root age using a maximum soft bound with 2.5% tail probability.…”

Section: (B) Relationships Within Major Gastropod Cladesmentioning

confidence: 99%

Phylogenomic analyses of deep gastropod relationships reject Orthogastropoda

et al. 2014

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Gastropods are a highly diverse clade of molluscs that includes many familiar animals, such as limpets, snails, slugs and sea slugs. It is one of the most abundant groups of animals in the sea and the only molluscan lineage that has successfully colonized land. Yet the relationships among and within its constituent clades have remained in flux for over a century of morphological, anatomical and molecular study. Here, we re-evaluate gastropod phylogenetic relationships by collecting new transcriptome data for 40 species and analysing them in combination with publicly available genomes and transcriptomes. Our datasets include all five main gastropod clades: Patellogastropoda, Vetigastropoda, Neritimorpha, Caenogastropoda and Heterobranchia. We use two different methods to assign orthology, subsample each of these matrices into three increasingly dense subsets, and analyse all six of these supermatrices with two different models of molecular evolution. All 12 analyses yield the same unrooted network connecting the five major gastropod lineages. This reduces deep gastropod phylogeny to three alternative rooting hypotheses. These results reject the prevalent hypothesis of gastropod phylogeny, Orthogastropoda. Our dated tree is congruent with a possible end-Permian recovery of some gastropod clades, namely Caenogastropoda and some Heterobranchia subclades.

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Section: (B) Relationships Within Major Gastropod Cladesmentioning

confidence: 99%

Phylogenomic analyses of deep gastropod relationships reject Orthogastropoda

et al. 2014

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“…Whether these fossils are monoplacophorans or gastropods is debatable based on several lines of inference, and there remains some controversy as to what are and what are not monoplacophorans in the fossil record (see Signor 1985;Runnegar 1996). For example, whereas Pojeta and Runnegar (1976) and Peel (1991) considered almost all Cambrian cap-shaped taxa as well as the coiled Helcionelloida and some, if not all, of the bellerophontiform taxa to be monoplacophorans, other workers, including Knight and Yochelson (1960), Golikov and Starobogatov (1988), and Parkhaev (2002Parkhaev ( , 2008, limit the diagnosis of Monoplacophora to cap-shaped taxa and consider the remaining Helcionelloida and bellerophontiform taxa to be members of other univalved or gastropod groups. Because these positions are based on the interpretations of a small suite of muscle insertion characters and cartoonlike reconstructions of possible water-flow patterns, it is difficult to test either position.…”

Section: Fossil Monoplacophoramentioning

confidence: 99%

Monoplacophorans and the Origin and Relationships of Mollusks

Lindberg

2009

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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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“…The origin of Images not to scale the phylum dates back to at least the Early Cambrian some 540 million years ago, but is most likely rooted deep in the Precambrian (Vendian) era (Parkhaev 2008 ).…”

Section: Introductionmentioning

confidence: 99%