The Biology of Phoronida

Emig, Christian C.

doi:10.1016/s0065-2881(08)60086-3

Cited by 89 publications

(125 citation statements)

References 68 publications

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“…Thereby, the phoronid would have been guided (as also proposed above for a sipunculan trace maker) by the probing vane in combination with the concentric architecture of the belemnite's microstructure. A preferred orientation of phoronid borings along shell layers has also been noted by Emig (1982). The tube was lined with a chitinous wall, except for the site of bioerosion progress, and the phoronid worm could freely move in this tunnel (Emig, 1982).…”

Section: Lapispecus Cuniculusmentioning

confidence: 75%

“…Unlike sipunculans, phoronids move freely within a chitinous tube and they possess a lophophore (for filter-feeding) at the anterior end of their body, with a mouth opening within and the anus next to the lophophore (see Emig, 1982, for a review). Phoronids reproduce by sexual means, lay eggs, and release larvae, but the majority of extant phoronid species can also divide asexually by transverse fission, occasionally leading to clusters with high numbers of individuals (Emig, 1979(Emig, , 1985.…”

Section: Lapispecus Cuniculusmentioning

confidence: 99%

“…Voigt, 1972Voigt, , 1975Plewes, 1996). Among other modern phoronid species, at least three are known to bioerode solitary tubes into hard substrates (Emig, 1982(Emig, , 1985, but the link between certain extant phoronid species and the morphology of their traces has only been explored cursorily, and the interpretation of fossil phoronid bioerosion traces remains speculative on account of a lack of body fossils (Emig, 2010 and personal communication).…”

Section: Lapispecus Cuniculusmentioning

confidence: 99%

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Classical and new bioerosion trace fossils in Cretaceous belemnite guards characterised via micro-CT

et al. 2017

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Section: Lapispecus Cuniculusmentioning

confidence: 75%

Section: Lapispecus Cuniculusmentioning

confidence: 99%

Section: Lapispecus Cuniculusmentioning

confidence: 99%

See 1 more Smart Citation

Classical and new bioerosion trace fossils in Cretaceous belemnite guards characterised via micro-CT

et al. 2017

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“…Typically, these inhabit a chitinous tube, which may be reinforced with mineral particles, packed into a dense lawn, or embedded in a substrate. About 12 extant species in two genera are recognised (Emig 1977a(Emig , 1979(Emig , 1982, and no ancient phoronid fossils are certainly known (Fenton and Fenton 1934;MacKinnon and Biernat 1970). Although the Lower Cambrian fossil Iotuba was originally described as a phoronid (Chen and Zhou 1997), this is now considered doubtful (Zhifei Zhang, pers.…”

Section: Biological Backgroundmentioning

confidence: 99%

“…Subphylum Linguliformea Williams et al, 1996 Diagnosis as in Williams et al (1996), with emendation ''or in a cylindrical tube of their own secretion'' (after Emig 1982). Class Craniata Williams et al, 1996 Diagnosis as for subphylum Craniiformea and Class Craniata in Williams et al (1996).…”

Section: Phylum Brachiopoda Dume´ril 1806mentioning

confidence: 99%

Molecular evidence that phoronids are a subtaxon of brachiopods (Brachiopoda: Phoronata) and that genetic divergence of metazoan phyla began long before the early Cambrian

Cohen

Weydmann

2005

Organisms Diversity & Evolution

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Concatenated SSU (18S) and partial LSU (28S) sequences ($2 kb) from 12 ingroup taxa, comprising 2 phoronids, 2 members of each of the craniid, discinid, and lingulid inarticulate brachiopod lineages, and 4 rhynchonellate, articulate brachiopods (2 rhynchonellides, 1 terebratulide and 1 terebratellide) were aligned with homologous sequences from 6 protostome, deuterostome and sponge outgroups (3964 sites). Regions of potentially ambiguous alignment were removed, and the resulting data (3275 sites, of which 377 were parsimony-informative and 635 variable) were analysed by parsimony, and by maximum and Bayesian likelihood using objectively selected models. There was no base composition heterogeneity. Relative rate tests led to the exclusion (from most analyses) of the more distant outgroups, with retention of the closer pectinid and polyplacophoran (chiton). Parsimony and likelihood bootstrap and Bayesian clade support values were generally high, but only likelihood analyses recovered all brachiopod indicator clades designated a priori. All analyses confirmed the monophyly of (brachiopods+phoronids) and identified phoronids as the sister-group of the three inarticulate brachiopod lineages. Consequently, a revised Linnean classification is proposed in which the subphylum Linguliformea comprises three classes: Lingulata, 'Phoronata' (the phoronids), and 'Craniata' (the current subphylum Craniiformea). Divergence times of all nodes were estimated by regression from node depths in non-parametrically rate-smoothed and other chronograms, calibrated against palaeontological data, with probable errors not less than 50 My. Only three predicted brachiopod divergence times disagree with palaeontological ages by more than the probable error, and a reasonable explanation exists for at least two. Pruning long-branched ingroups made scant difference to predicted divergence time estimates. The palaeontological age calibration and the existence of Lower Cambrian fossils of both main brachiopod clades together indicate that initial genetic divergence between brachiopod and molluscan (chiton) lineages occurred well before the Lower Cambrian, suggesting that much divergence between metazoan phyla took place in the Proterozoic.

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Larval development of Phoronis pallida (Phoronida): Implications for morphological convergence and divergence among larval body plans

Santagata

2004

Journal of Morphology

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Morphological variation among larval body plans must be placed into a phylogenetic and ecological context to assess whether similar morphologies are the result of phylogenetic constraints or convergent selective pressures. Investigations are needed of the diverse larval forms within the Lophotrochozoa, especially the larvae of phoronids and brachiopods. The actinotroch larva of Phoronis pallida (Phoronida) was reared in the laboratory to metamorphic competence. Larval development and growth were followed with video microscopy, SEM, and confocal microscopy. Early developmental features were similar to other phoronid species. Gastrulation was accomplished by embolic invagination of the vegetal hemisphere. Mesenchymal cells were found in the remaining blastocoelic space after invagination began. Mesenchymal cells formed the body wall musculature during the differentiation of larval features. Body wall musculature served as the framework from which all other larval muscles proliferated. Larval growth correlated best with developmental stage rather than age. Consistent with other phoronid species, differentiation of juvenile tissues occurred most rapidly at the latest stages of larval development. The minimum precompetency period of P. pallida was estimated to be approximately 4-6 weeks. Previously published studies have documented that the planktonic embryos of P. pallida develop faster than the brooded embryos of P. vancouverensis. However, these data showed that the difference in developmental rate between the two species decreased in succeeding larval stages. There may be convergent selective pressures that result in similar timing to metamorphic competence among phoronid and brachiopod planktotrophic larval types. Morphological differences between these larval types result from heterochronic developmental shifts in the differentiation of juvenile tissue. Similarities in the larval morphology of phoronids and basal deuterostomes are likely the result of functional and developmental constraints rather than a shared (recent) evolutionary origin. These constraints are imposed by the functional design of embryological stages, feeding structures, and swimming structures.

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The Biology of Phoronida

Cited by 89 publications

References 68 publications

Classical and new bioerosion trace fossils in Cretaceous belemnite guards characterised via micro-CT

Classical and new bioerosion trace fossils in Cretaceous belemnite guards characterised via micro-CT

Molecular evidence that phoronids are a subtaxon of brachiopods (Brachiopoda: Phoronata) and that genetic divergence of metazoan phyla began long before the early Cambrian

Larval development of Phoronis pallida (Phoronida): Implications for morphological convergence and divergence among larval body plans

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