The scaphopod foot is ventral: more evidence from the anatomy of<i>Rhabdus rectius</i>(Carpenter, 1864) (Dentaliida: Rhabdidae)

Sigwart, Julia D.; Sumner‐Rooney, Lauren; Dickey, James W. E.; Carey, Nicholas

doi:10.1080/13235818.2016.1257970

Cited by 7 publications

(3 citation statements)

References 33 publications

(45 reference statements)

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“…This pair of unequal sister taxa contradicts the Cyrtosoma concept uniting Gastropoda and Cephalopoda (plus Monoplacophora by the original definition 10 ; reviewed by Kocot 22 ). Interestingly, a close relationship of Scaphopoda and Gastropoda was proposed based on the pronounced dorsoventral axis 47 and recent work has confirmed the morphological ventral position of the scaphopod foot 48 . Examination of published molluscan morphological data matrices 20,21,49 reveals obvious symplesiomorphies shared between these taxa (e.g., external univalved shell), but we find no clear morphological synapomorphies for the gastropod-scaphopod clade.…”

Section: Resultsmentioning

confidence: 95%

New data from Monoplacophora and a carefully-curated dataset resolve molluscan relationships

Kocot

Poustka

Stöger

et al. 2020

Sci Rep

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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. Mollusca is the second most diverse animal phylum whose members exhibit an incredible array of body shapes and sizes. Many molluscs have important ecological roles in marine, freshwater, and terrestrial environments and others are culturally and/or economically important as a source of food, jewellery, or dye 1. Despite their diversity and importance, understanding of early molluscan evolution remains incomplete and several conflicting phylogenetic hypotheses 1-9 have been proposed regarding relationships among the eight major clades (i.e., classes): Bivalvia (clams, scallops, oysters, etc.), Caudofoveata (Chaetodermomorpha), Cephalopoda (octopuses, squids, and Nautilus), Gastropoda (snails and slugs), Monoplacophora (Tryblidia; deep-sea, limpet-like molluscs), Polyplacophora (chitons), Scaphopoda (tusk shells), and Solenogastres (Neomeniomorpha). Within Conchifera (Bivalvia, Cephalopoda, Gastropoda, Monoplacophora, and Scaphopoda), the clade of molluscs with uni-or bivalved shells, the deep-sea limpet-like Monoplacophora has long been thought to be important to understanding early molluscan evolution 5,10-...

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Section: Resultsmentioning

confidence: 95%

New data from Monoplacophora and a carefully-curated dataset resolve molluscan relationships

Kocot

Poustka

Stöger

et al. 2020

Sci Rep

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“…Another situation that masks the real diversity of Scaphopoda is the scarcity of researchers studying the alpha-taxonomy of these mollusks worldwide. In the last decades, the knowledge about phylogenetics, comparative anatomy, ecology and development of Scaphopoda has grown tremendously (e.g., Steiner & Dreyer, 2003;Simone, 2009;Faller et al, 2012;Sumner-Rooney et al, 2015;Smith & Spencer, 2016;Dantas et al, 2017;Sigwart et al, 2017;Vilela et al, 2019), which is excellent but little attention has been given to regional taxonomic revisions.…”

Section: Discussionmentioning

confidence: 99%

New records and a new species of Scaphopoda (Mollusca) from the southwestern Atlantic Ocean

Souza

Caetano

Scarabino

et al. 2020

Iheringia, Sér. Zool.

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“…Although sexual dimorphism is classically punctuated as scarce in Mollusca (Purchon 1977;Webber 1977;Hughes 1986), recent studies have shown that it does not seem to be as uncommon as it has been described for most classes. There are recent examples of sexual dimorphism in Cephalopoda (Bolstad 2006), Bivalvia (Yoshimura et al 2019), Scaphopoda (Sigwart et al 2017), and Gastropoda (Minton and Wang 2011). Among gastropods, sexual dimorphism has long been stressed as a remarkable characteristic of eulimid snails (Purchon 1977;Webber 1977), but it has commonly been exclusively observed in terms of shell length (e.g., Lutzen 1972;Matsuda et al 2013).…”

Section: Introductionmentioning

confidence: 99%

Sexual dimorphism in the parasitic snail Nanobalcis worsfoldi: a histological and morphometric approach with insights for the family Eulimidae

Sales

Queiroz

2021

Can. J. Zool.

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Sexual dimorphism has long been stressed as a remarkable characteristic of Eulimidae snails. This idea is so common for this family that, even without information on the soft parts, some species were already identified as male or female, as observed in Nanobalcis worsfoldi Warén, 1990. Here, we investigated whether larger and smaller individuals of N. worsfoldi are female and male, respectively, and what are the most useful characteristics to differentiate the sexes. We analyzed shell morphology and morphometry, along with coloration of the soft parts of large and small individuals, and crosschecked our findings through histological analysis. Our results confirmed that (i) larger and smaller individuals are females and males, respectively; (ii) shell morphology is not useful, while morphometry is important to address sexual dimorphism; (iii) since shell length and width showed the most remarkable differences, they are considered the best parameters to predict the sex. Furthermore, conchological characteristics associated with histological analysis suggest that this species could be the first non-sessile eulimid known as a sequential hermaphrodite (protandric) with environmental sex determination, but this remains to be confirmed. Considering that most studies on eulimids are based on shells, the morphometric parameters used here may support future ecological/biological analyses in the family, such as parasitological prevalence, or parasitic burden related to sex.

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The scaphopod foot is ventral: more evidence from the anatomy ofRhabdus rectius(Carpenter, 1864) (Dentaliida: Rhabdidae)

Cited by 7 publications

References 33 publications

New data from Monoplacophora and a carefully-curated dataset resolve molluscan relationships

New data from Monoplacophora and a carefully-curated dataset resolve molluscan relationships

New records and a new species of Scaphopoda (Mollusca) from the southwestern Atlantic Ocean

Sexual dimorphism in the parasitic snail Nanobalcis worsfoldi: a histological and morphometric approach with insights for the family Eulimidae

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