Brachiopods: origin and early history

Harper, David A. T.; Popov, Leonid E.; Holmer, Lars E.

doi:10.1111/pala.12307

Cited by 58 publications

(53 citation statements)

References 116 publications

(180 reference statements)

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“…According to our comparative analysis, the spermatozoon may have evolved along three different paths in brachiopods (Figure 9). This inference regarding spermatozoon evolution is consistent with brachiopod phylogeny based on morphological and molecular analysis and suggests the presence of three main lineages within brachiopods: Linguliformea, Craniiformea, and Rhynchonelliformea (Harper et al, 2017), but rejects "articulate" and "inarticulate" brachiopods as taxonomically valid clades. (h) the space between the acrosome and nucleus is filled with fibrillar material.…”

Section: Organization Of Mature Spermatozoa In Brachiopodssupporting

confidence: 78%

“…Williams, Carlson, Brunton, Holmer, and Popov (1996) suggested a supraordinal classification of brachiopods with three subphyla: Linguliformea, Craniiformea, and Rhynchonelliformea. The relationship between these three groups is still unclear (Cohen, 2013;Harper, Popov, & Holmer, 2017;Helmkampf, Bruchaus, & Hausdorf, 2008;Sperling, Pisani, & Peterson, 2011). According to Williams et al (1996), craniiforms and rhynchonelliforms are sister taxa.…”

Section: Introductionmentioning

confidence: 99%

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Spermatogenesis in the deep‐sea brachiopod Pelagodiscus atlanticus and the phylogenetic significance of spermatozoon structure

Temereva

Kuzmina

2018

Journal of Morphology

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Details of spermatogenesis and sperm organization are often useful for reconstructing the phylogeny of closely related groups of invertebrates. Development in general and gametogenesis in particular usually differ in shallow water and deep‐sea invertebrates. Here, the spermatogenesis and ultrastructure of sperm were studied in the deep‐sea brachiopod Pelagodiscus atlanticus. The testes of P. atlanticus are voluminous sacs located along the lateral sides of the body. Germ cells develop around the blood capillaries, contact the basal lamina, and contain germ plasm, numerous mitochondria, Golgi apparatus, lipid droplets, and centrioles of the rudimentary cilium. During spermatogenesis, several proacrosomal vesicles appear at the posterior pole of the cell; these vesicles then fuse and migrate to the anterior pole. The spermatozoon has a head with an acrosome, nucleus, eight mitochondria, proximal and distal centrioles orthogonally arranged, and a long tail. Comparative analysis suggests that the spermatozoon of P. atlanticus can be considered the most ancestral among all brachiopods. Such an organization indicates that fertilization is external in this deep‐sea species. Spermatozoa of other brachiopods should be regarded as derived from this ancestral type. The transformation of brachiopod spermatozoa might have occurred in three different ways that correspond to the three main clades of recent brachiopods: Linguliformea, Craniiformea, and Rhynchonelliformea.

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Section: Organization Of Mature Spermatozoa In Brachiopodssupporting

confidence: 78%

Section: Introductionmentioning

confidence: 99%

Spermatogenesis in the deep‐sea brachiopod Pelagodiscus atlanticus and the phylogenetic significance of spermatozoon structure

Temereva

Kuzmina

2018

Journal of Morphology

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“…This position of hyoliths close to the basal node of Brachiopoda, in the context of outgroup taxa, resolves the polarity of certain characters within the brachiopod lineage, clarifying the position of some otherwise enigmatic brachiopod groups [29]. We recognize paterinids, Salanygolina, chileids and kutorginates as successive stem groups to the rhynchonelliforms (figure 4).…”

Section: Affinity Of Hyolithsmentioning

confidence: 51%

Hyoliths with pedicles illuminate the origin of the brachiopod body plan

et al. 2018

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Hyoliths are a taxonomically problematic group of Palaeozoic lophotrochozoans that are among the first shelly fossils to appear in the Cambrian period. On the basis of their distinctive exoskeleton, hyoliths have historically been classified as a separate phylum with possible affinities to the molluscs, sipunculans or lophophorates—but their precise phylogenetic position remains uncertain. Here, we describe a new orthothecide hyolith from the Chengjiang Lagerstätte (Cambrian Series 2 Stage 3), Pedunculotheca diania Sun, Zhao et Zhu gen. et sp. nov., which exhibits a non-mineralized attachment structure that strikingly resembles the brachiopod pedicle—the first report of a peduncular organ in hyoliths. This organ establishes a sessile, suspension feeding ecology for these orthothecides and—together with other characteristics (e.g. bilaterally symmetrical bivalve shell enclosing a filtration chamber and the differentiation of cardinal areas)—identifies hyoliths as stem-group brachiopods. Our phylogenetic analysis indicates that both hyoliths and crown brachiopods derived from a tommotiid grade, and that the pedicle has a single origin within the brachiopod total group.

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“…One set of organisms whose scleritomes exhibit an intriguing similarity with those of halkieriids are the camenellan tommotiids, a group that is implicated in the earliest ancestry of brachiopods 40–43 . The scleritome of the kennardiid camenellan Dailyatia 35 has been reconstructed as comprising median and peripheral fields (Fig.…”

Section: Discussionmentioning

confidence: 99%

Orthrozanclus elongata n. sp. and the significance of sclerite-covered taxa for early trochozoan evolution

Zhao

Smith

Yin

et al. 2017

Sci Rep

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Orthrozanclus is a shell-bearing, sclerite covered Cambrian organism of uncertain taxonomic affinity, seemingly representing an intermediate between its fellow problematica Wiwaxia and Halkieria. Attempts to group these slug-like taxa into a single ‘halwaxiid’ clade nevertheless present structural and evolutionary difficulties. Here we report a new species of Orthrozanclus from the early Cambrian Chengjiang Lagerstätte. The scleritome arrangement and constitution in this material corroborates the link between Orthrozanclus and Halkieria, but not with Wiwaxia — and calls into question its purported relationship with molluscs. Instead, the tripartite construction of the halkieriid scleritome finds a more compelling parallel in the camenellan tommotiids, relatives of the brachiopods and phoronids. Such a phylogenetic position would indicate the presence of a scleritome in the common ancestor of the three major trochozoan lineages, Mollusca, Annelida and Brachiozoa. On this view, the absence of fossil Ediacaran sclerites is evidence against any ‘Precambrian prelude’ to the explosive diversification of these phyla in the Cambrian, c. 540–530 million years ago.

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Brachiopods: origin and early history

Cited by 58 publications

References 116 publications

Spermatogenesis in the deep‐sea brachiopod Pelagodiscus atlanticus and the phylogenetic significance of spermatozoon structure

Spermatogenesis in the deep‐sea brachiopod Pelagodiscus atlanticus and the phylogenetic significance of spermatozoon structure

Hyoliths with pedicles illuminate the origin of the brachiopod body plan

Orthrozanclus elongata n. sp. and the significance of sclerite-covered taxa for early trochozoan evolution

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