Monoplacophorans

@misc{knight1960monoplacophora1,
    author = "Knight, J. B. and Yochelson, E. L",
    title = "Monoplacophora",
    year = "1960",
    howpublished = "P. I77-I84, in Moore, R. C., ed., Treatise on Invertebrate Paleontology: p. I1-I351",
    note = "talkorigins\_source = {true}; raw\_reference = {Knight, J. B., and Yochelson, E. L., 1960, Monoplacophora: P. I77-I84, in Moore, R. C., ed., Treatise on Invertebrate Paleontology: p. I1-I351.}"
}

FIGURE 1. Representatives of monoplacophorans and polyplacophorans from below 2000 m. A, dorsal view of the holotype of Neopilina galatheae Lemche, 1957 from the East Pacific, off Costa Rica (09°23'N, 89°32'W), 3590 m (photo by G. Brovad, Zoological Museum, University of Copenhagen). B, C, Left lateral (B) and dorsal view (C) of the holotype of Ferreiraella tsuchidai Saito, 2006 (National Science Museum Tokyo Mo 73601) from the Philippine Basin between Mindanao Island and Palau Islands (05°30.8'­05°28.0'N, 130°20.2'­130°19.9'E), 5567 m (photos by H. Saito, National Science Museum Tokyo).

@misc{schwabe2008figure,
    author = "Schwabe, Enrico",
    title = "FIGURE 1 in A summary of reports of abyssal and hadal Monoplacophora and Polyplacophora (Mollusca) *",
    year = "2008",
    publisher = "Zenodo",
    abstract = "FIGURE 1. Representatives of monoplacophorans and polyplacophorans from below 2000 m. A, dorsal view of the holotype of Neopilina galatheae Lemche, 1957 from the East Pacific, off Costa Rica (09°23'N, 89°32'W), 3590 m (photo by G. Brovad, Zoological Museum, University of Copenhagen). B, C, Left lateral (B) and dorsal view (C) of the holotype of Ferreiraella tsuchidai Saito, 2006 (National Science Museum Tokyo Mo 73601) from the Philippine Basin between Mindanao Island and Palau Islands (05°30.8'­05°28.0'N, 130°20.2'­130°19.9'E), 5567 m (photos by H. Saito, National Science Museum Tokyo).",
    url = "https://zenodo.org/record/183816",
    doi = "10.5281/zenodo.183816"
}

A consensus on molluscan relationships has yet to be achieved, largely because of conflicting morphological and molecular hypotheses. Monoplacophora show marked seriality of ctenidia, atria, muscles and nephridia and this has been interpreted as plesiomorphic for Mollusca, reflecting a segmented ancestry. More recently this seriality, also partly seen in Polyplacophora, has been seen as a derived condition. Analysis of the first published monoplacophoran DNA sequence from Laevilipilina antarctica Warén & Hain, 1992 [Giribet, G., Okusu, A., Lindgren, A.R., Huff, S., Schrödl, M., Nishiguchi, M.K., 2006. Evidence for a clade composed of molluscs with serially repeated structures: Monoplacophorans are related to chitons. Proc. Natl. Acad. Sci. USA 103, 7723-7728. 10.1073/pnas.0602578103], showed Monoplacophora inside Polyplacophora. These taxa were then grouped under the name Serialia, reflecting the hypothesis that their seriality is a synapomorphy. Subsequent examination revealed that part of the L. antarctica published sequence was the result of contamination with Polyplacophora (Giribet, Supplementary Material S1). We collected and sequenced another monoplacophoran, Laevipilina hyalina McLean, 1979, resulting in the first multi-gene dataset representing all molluscan classes. Our analyses did not show unambiguous support for Serialia. Model-based approaches strongly supported Serialia as a clade, however, parsimony analyses under dynamic and static homology did not resolve the position of Monoplacophora. Although our study provides support for Serialia and none for Conchifera, it appears that further resolution of molluscan relationships will require large increases of data.

@article{doi101016jympev200907028,
    author = "Wilson, Nerida G and Rouse, Greg W and Giribet, Gonzalo",
    title = "Assessing the molluscan hypothesis Serialia (Monoplacophora+Polyplacophora) using novel molecular data.",
    year = "2010",
    journal = "Molecular phylogenetics and evolution",
    abstract = "A consensus on molluscan relationships has yet to be achieved, largely because of conflicting morphological and molecular hypotheses. Monoplacophora show marked seriality of ctenidia, atria, muscles and nephridia and this has been interpreted as plesiomorphic for Mollusca, reflecting a segmented ancestry. More recently this seriality, also partly seen in Polyplacophora, has been seen as a derived condition. Analysis of the first published monoplacophoran DNA sequence from Laevilipilina antarctica Warén \& Hain, 1992 [Giribet, G., Okusu, A., Lindgren, A.R., Huff, S., Schrödl, M., Nishiguchi, M.K., 2006. Evidence for a clade composed of molluscs with serially repeated structures: Monoplacophorans are related to chitons. Proc. Natl. Acad. Sci. USA 103, 7723-7728. 10.1073/pnas.0602578103], showed Monoplacophora inside Polyplacophora. These taxa were then grouped under the name Serialia, reflecting the hypothesis that their seriality is a synapomorphy. Subsequent examination revealed that part of the L. antarctica published sequence was the result of contamination with Polyplacophora (Giribet, Supplementary Material S1). We collected and sequenced another monoplacophoran, Laevipilina hyalina McLean, 1979, resulting in the first multi-gene dataset representing all molluscan classes. Our analyses did not show unambiguous support for Serialia. Model-based approaches strongly supported Serialia as a clade, however, parsimony analyses under dynamic and static homology did not resolve the position of Monoplacophora. Although our study provides support for Serialia and none for Conchifera, it appears that further resolution of molluscan relationships will require large increases of data.",
    url = "https://pubmed.ncbi.nlm.nih.gov/19647088/",
    doi = "10.1016/j.ympev.2009.07.028",
    pmid = "19647088"
}

Molluscs are a diverse animal phylum with a formidable fossil record. Although there is little doubt about the monophyly of the eight extant classes, relationships between these groups are controversial. We analysed a comprehensive multilocus molecular data set for molluscs, the first to include multiple species from all classes, including five monoplacophorans in both extant families. Our analyses of five markers resolve two major clades: the first includes gastropods and bivalves sister to Serialia (monoplacophorans and chitons), and the second comprises scaphopods sister to aplacophorans and cephalopods. Traditional groupings such as Testaria, Aculifera, and Conchifera are rejected by our data with significant Approximately Unbiased (AU) test values. A new molecular clock indicates that molluscs had a terminal Precambrian origin with rapid divergence of all eight extant classes in the Cambrian. The recovery of Serialia as a derived, Late Cambrian clade is potentially in line with the stratigraphic chronology of morphologically heterogeneous early mollusc fossils. Serialia is in conflict with traditional molluscan classifications and recent phylogenomic data. Yet our hypothesis, as others from molecular data, implies frequent molluscan shell and body transformations by heterochronic shifts in development and multiple convergent adaptations, leading to the variable shells and body plans in extant lineages.

@article{doi1011552013407072,
    author = "Stöger, I and Sigwart, J D and Kano, Y and Knebelsberger, T and Marshall, B A and Schwabe, E and Schrödl, M",
    title = "The continuing debate on deep molluscan phylogeny: evidence for Serialia (Mollusca, Monoplacophora + Polyplacophora).",
    year = "2013",
    journal = "BioMed research international",
    abstract = "Molluscs are a diverse animal phylum with a formidable fossil record. Although there is little doubt about the monophyly of the eight extant classes, relationships between these groups are controversial. We analysed a comprehensive multilocus molecular data set for molluscs, the first to include multiple species from all classes, including five monoplacophorans in both extant families. Our analyses of five markers resolve two major clades: the first includes gastropods and bivalves sister to Serialia (monoplacophorans and chitons), and the second comprises scaphopods sister to aplacophorans and cephalopods. Traditional groupings such as Testaria, Aculifera, and Conchifera are rejected by our data with significant Approximately Unbiased (AU) test values. A new molecular clock indicates that molluscs had a terminal Precambrian origin with rapid divergence of all eight extant classes in the Cambrian. The recovery of Serialia as a derived, Late Cambrian clade is potentially in line with the stratigraphic chronology of morphologically heterogeneous early mollusc fossils. Serialia is in conflict with traditional molluscan classifications and recent phylogenomic data. Yet our hypothesis, as others from molecular data, implies frequent molluscan shell and body transformations by heterochronic shifts in development and multiple convergent adaptations, leading to the variable shells and body plans in extant lineages.",
    url = "https://pmc.ncbi.nlm.nih.gov/articles/PMC3856133/",
    doi = "10.1155/2013/407072",
    pmcid = "PMC3856133",
    pmid = "24350268"
}

Relationships among the major lineages of Mollusca have long been debated. Morphological studies have considered the rarely collected Monoplacophora (Tryblidia) to have several plesiomorphic molluscan traits. The phylogenetic position of this group is contentious as morphologists have generally placed this clade as the sister taxon of the rest of Conchifera whereas earlier molecular studies supported a clade of Monoplacophora + Polyplacophora (Serialia) and phylogenomic studies have generally recovered a clade of Monoplacophora + Cephalopoda. Phylogenomic studies have also strongly supported a clade including Gastropoda, Bivalvia, and Scaphopoda, but relationships among these taxa have been inconsistent. In order to resolve conchiferan relationships and improve understanding of early molluscan evolution, we carefully curated a high-quality data matrix and conducted phylogenomic analyses with broad taxon sampling including newly sequenced genomic data from the monoplacophoran Laevipilina antarctica. Whereas a partitioned maximum likelihood (ML) analysis using site-homogeneous models recovered Monoplacophora sister to Cephalopoda with moderate support, both ML and Bayesian inference (BI) analyses using mixture models recovered Monoplacophora sister to all other conchiferans with strong support. A supertree approach also recovered Monoplacophora as the sister taxon of a clade composed of the rest of Conchifera. Gastropoda was recovered as the sister taxon of Scaphopoda in most analyses, which was strongly supported when mixture models were used. A molecular clock based on our BI topology dates diversification of Mollusca to ~546 MYA (+/- 6 MYA) and Conchifera to ~540 MYA (+/- 9 MYA), generally consistent with previous work employing nuclear housekeeping genes. These results provide important resolution of conchiferan mollusc phylogeny and offer new insights into ancestral character states of major mollusc clades.

@article{doi101038s4159801956728w,
    author = "Kocot, Kevin M and Poustka, Albert J and Stöger, Isabella and Halanych, Kenneth M and Schrödl, Michael",
    title = "New data from Monoplacophora and a carefully-curated dataset resolve molluscan relationships.",
    year = "2020",
    journal = "Scientific reports",
    abstract = "Relationships among the major lineages of Mollusca have long been debated. Morphological studies have considered the rarely collected Monoplacophora (Tryblidia) to have several plesiomorphic molluscan traits. The phylogenetic position of this group is contentious as morphologists have generally placed this clade as the sister taxon of the rest of Conchifera whereas earlier molecular studies supported a clade of Monoplacophora + Polyplacophora (Serialia) and phylogenomic studies have generally recovered a clade of Monoplacophora + Cephalopoda. Phylogenomic studies have also strongly supported a clade including Gastropoda, Bivalvia, and Scaphopoda, but relationships among these taxa have been inconsistent. In order to resolve conchiferan relationships and improve understanding of early molluscan evolution, we carefully curated a high-quality data matrix and conducted phylogenomic analyses with broad taxon sampling including newly sequenced genomic data from the monoplacophoran Laevipilina antarctica. Whereas a partitioned maximum likelihood (ML) analysis using site-homogeneous models recovered Monoplacophora sister to Cephalopoda with moderate support, both ML and Bayesian inference (BI) analyses using mixture models recovered Monoplacophora sister to all other conchiferans with strong support. A supertree approach also recovered Monoplacophora as the sister taxon of a clade composed of the rest of Conchifera. Gastropoda was recovered as the sister taxon of Scaphopoda in most analyses, which was strongly supported when mixture models were used. A molecular clock based on our BI topology dates diversification of Mollusca to \textasciitilde 546 MYA (+/- 6 MYA) and Conchifera to \textasciitilde 540 MYA (+/- 9 MYA), generally consistent with previous work employing nuclear housekeeping genes. These results provide important resolution of conchiferan mollusc phylogeny and offer new insights into ancestral character states of major mollusc clades.",
    url = "https://pmc.ncbi.nlm.nih.gov/articles/PMC6952402/",
    doi = "10.1038/s41598-019-56728-w",
    pmcid = "PMC6952402",
    pmid = "31919367"
}

@incollection{crossref2023monoplacophora,
    title = "Monoplacophora, n.",
    year = "2023",
    booktitle = "Oxford English Dictionary",
    url = "https://doi.org/10.1093/oed/1170386942",
    doi = "10.1093/oed/1170386942"
}

@incollection{crossref2024class,
    title = "Class Monoplacophora",
    year = "2024",
    booktitle = "Shells of the World",
    url = "https://doi.org/10.2307/jj.7657712.5",
    doi = "10.2307/jj.7657712.5",
    pages = "34-35"
}

@incollection{crossref2024monoplacophora,
    title = "MONOPLACOPHORA",
    year = "2024",
    booktitle = "Shells of the World",
    url = "https://doi.org/10.1515/9780691248257-004",
    doi = "10.1515/9780691248257-004",
    pages = "34-36"
}