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Bernard L. Cohen - One of the best experts on this subject based on the ideXlab platform.
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rerooting the rdna gene tree reveals phoronids to be brachiopods without shells dangers of wide taxon samples in metazoan phylogenetics phoronida Brachiopoda
Zoological Journal of the Linnean Society, 2013Co-Authors: Bernard L. CohenAbstract:Molecular phylogenetics has resulted in conflicting accounts of the relationship between phoronids and brachiopods. Taxonomically comprehensive analyses of brachiopod and phoronid ribosomal DNA sequences (rDNAs) rooted with short-branched mollusc sequences uniformly find that phoronids nest within brachiopods as the sister of the three extant inarticulate lineages. Here, this is called the ‘alternate’ topology because it does not match traditional, morphology-based ideas. Many other analyses of protein-coding genes and/or rDNAs place phoronids elsewhere, often as the sister group of all brachiopods, better matching ‘traditional’ ideas. However, these analyses generally are based on data from small selections of brachiopods and phoronids, include data from a wide range of other metazoan taxa, and are rooted with distant outgroups. Here, I show that outgroup rooting of brachiopods and phoronid rDNAs is unreliable, and instead find the root position with procedures that are free from all distortions caused by distantly related taxa, i.e. by Bayesian and maximum likelihood relaxed-clock analyses of a purely ingroup alignment. All such analyses confirm the ‘alternate’ topology: phoronids belong within the Brachiopoda as the sister group of the inarticulates. In addition, nine factors are identified that (singly or in combination) can cause misreporting of the phylogenetic signal in wide taxon-range analyses of both rDNA and amino acid sequence data. © 2012 The Linnean Society of London, Zoological Journal of the Linnean Society, 2012.
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phoronid phylogenetics Brachiopoda phoronata evidence from morphological cladistics small and large subunit rdna sequences and mitochondrial cox1
Zoological Journal of the Linnean Society, 2009Co-Authors: Scott Santagata, Bernard L. CohenAbstract:A matrix of 24 morphodevelopmental characters and an alignment of small subunit (SSU) and large subunit (LSU) rDNA nuclear and cox1 mitochondrial gene sequences (∼4500 sites) were compiled from up to 12 phoronids including most named taxa, but probably constituting only a portion of worldwide diversity. Morphological data were analysed by weighted parsimony; sequence data by maximum and Bayesian likelihood, both with Phoronis ovalis as the local outgroup. Morphological and sequence-based phylogenies were similar, but not fully congruent. Phoronid rDNAs were almost free from mutational saturation, but cox1 showed strong saturation unless distant outgroups and P. ovalis were omitted, suggesting that many phoronid divergences are old (≥100 Myr). rDNA divergence between named phoronid taxa is generally substantial, but Phoronopsis harmeri (from Vladivostock) and Phoronopsis viridis (from California) are genetically close enough to be conspecific. In another alignment, of 24 taxa, phoronid rDNAs were combined with data from brachiopods and distant (molluscan) outgroups. The relative ages of divergence between phoronids and their brachiopod sister-groups, of the split between the P. ovalis and non-ovalis lineages, and of other phoronid splits, were estimated from this alignment with a Bayesian lognormal uncorrelated molecular clock model. Although confidence limits (95% highest probability density) are wide, the results are compatible with an Early Cambrian split between phoronids and brachiopods and with the Upper Devonian latest age suggested for the P. ovalis/non-ovalis split by the putative phoronid ichnofossil, Talpina. Most other ingroup splits appear to be ∼50–200 Myr old. Inclusion of phoronids with brachiopods in the crown clade pan-Brachiopoda suggests that a distinctive metamorphosis and absence of mineralization are ancestral phoronid apomorphies. Worldwide diversity and possible associations between character-states and life-history attributes deserve comprehensive further study.
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The brachiopod fold : a neglected body plan hypothesis
Palaeontology, 2003Co-Authors: Bernard L. Cohen, Lars E Holmer, Carsten LüterAbstract:Attention is drawn to Nielsen's radical body plan concept, here named the 'brachiopod fold hypothesis', under which brachiopods and phoronids are recognized to be transversely folded across the ontogenetic anterior–posterior axis so that, to make useful comparisons with other phyla, these organisms must be conceptually unfolded. Under the hypothesis brachiopod brachial and pedicle shell valves are respectively 'anterior' and 'posterior' rather than 'dorsal' and 'ventral' as traditionally described. The hypothesis makes sense of the symmetry axes of the brachiopod shell, is consistent with various indications from fossil and Recent brachiopods, and gives rise to predicted patterns of axis–determining gene expression that differ from those obtaining under the traditional view of the body plan, whilst the variety of folding movements in different lineages implies that superficially dissimilar morphogenetic folds may be fundamentally homologous. Convergent folding patterns are noted in some other organisms. A previous conjecture that inarticulate linguloid brachiopods were derived from halkieriid–like ancestors is elaborated with proposals that recognize possible functional continuities of coelomic and marginal sclerite functions, and it is noted that an ancestrally facultative fold could have become incorporated by genetic assimilation into the brachiopod developmental program. An experimental approach is outlined to test the possibility that some members of the 'small shelly fauna' may have been members of the halkieriid–like brachiopod stem lineage and it is also suggested that buoyancy modification may have been an important function of mineralization amongst Lower Cambrian floaters and swimmers, since negative buoyancy would facilitate access to the benthic niche.
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eLS - Brachiopoda (Lamp Shells)
Encyclopedia of Life Sciences, 2001Co-Authors: Bernard L. CohenAbstract:Members of the phylum Brachiopoda are predominantly sessile, filter-feeding marine invertebrates with a bivalved shell that, in adult life, is functionally divided into inhalant and exhalant chambers by a ciliated, tentaculate curtain-like feeding organ or lophophore. One subphylum is commonly known as ‘lamp-shells’. Keywords: Brachiopoda; lophophore; inarticulate brachiopod; articulate brachiopod; phoronida
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monophyly of brachiopods and phoronids reconciliation of molecular evidence with linnaean classification the subphylum phoroniformea nov
Proceedings of The Royal Society B: Biological Sciences, 2000Co-Authors: Bernard L. CohenAbstract:Molecular phylogenetic analyses of aligned 18S rDNA gene sequences from articulate and inarticulate brachiopods representing all major extant lineages, an enhanced set of phoronids and several unrelated protostome taxa, confirm previous indications that in such data, brachiopod and phoronids form a well-supported clade that (on previous evidence) is unambiguously affiliated with protostomes rather than deuterostomes. Within the brachiopod-phoronid clade, an association between phoronids and inarticulate brachiopods is moderately well supported, whilst a close relationship between phoronids and craniid inarticulates is weakly indicated. Brachiopod-phoronid monophyly is reconciled with the most recent Linnaean classification of brachiopods by abolition of the phylum Phoronida and rediagnosis of the phylum Brachiopoda to include tubiculous, shell-less forms. Recognition that brachiopods and phoronids are close genealogical allies of protostome phyla such as molluscs and annelids, but are much more distantly related to deuterostome phyla such as echinoderms and chordates, implies either (or both) that the morphology and ontogeny of blastopore, mesoderm and coelom formation have been widely misreported or misinterpreted, or that these characters have been subject to extensive homoplasy. This inference, if true, undermines virtually all morphology-based reconstructions of phylogeny made during the past century or more.
G R Shi - One of the best experts on this subject based on the ideXlab platform.
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patterns of brachiopod faunal and body size changes across the permian triassic boundary evidence from the daoduishan section in meishan area south china
Palaeogeography Palaeoclimatology Palaeoecology, 2016Co-Authors: G R Shi, Yifan Xiao, Tinglu Yang, Kexin Zhang, Mingliang Yue, Bing ChenAbstract:Abstract New analysis of Permian–Triassic brachiopod assemblages and body-size changes in South China provides insights into the process of the environmental crisis in the lead up to the end-Permian mass extinction. The recently discovered Daoduishan section of South China can be considered as an important auxiliary section for the study of brachiopods at the Meishan Section D of South China, the GSSP of the Permian–Triassic Boundary (PTB). This paper studied changes of the brachiopod assemblages and body sizes through the upper part of the Changxing Formation and basal Yinkeng Formation of Daoduishan. The results show that significant changes of brachiopod assemblages took place between Beds 24e and 26. Brachiopods?Prelissorhynchia sp. and Paracruirithyris pygmaea are the dominators in Beds 14–24e, while Tethyochonetes pigmaea and Paryphella spp. are the dominators in Beds 26–29. Body sizes of brachiopods significantly decreased between Beds 24e and 26 and then maintained smaller means in Beds 27–29. Studies of brachiopod morphological features indicate both Tethyochonetes and Paryphella had advantageous adaptations enabling them to copy with living in an anoxic/dysoxic and/or low-productivity environment during the Permian–Triassic crisis.
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late permian marine ecosystem collapse began in deeper waters evidence from brachiopod diversity and body size changes
Geobiology, 2015Co-Authors: G R Shi, Haijun Song, Richard J Twitchett, Y Zhang, K X Zhang, M L Yue, T L Yang, Yifan XiaoAbstract:Analysis of Permian-Triassic brachiopod diversity and body size changes from different water depths spanning the continental shelf to basinal facies in South China provides insights into the process of environmental deterioration. Comparison of the temporal changes of brachiopod diversity between deepwater and shallow-water facies demonstrates that deepwater brachiopods disappeared earlier than shallow-water brachiopods. This indicates that high environmental stress commenced first in deepwater settings and later extended to shallow waters. This environmental stress is attributed to major volcanic eruptions, which first led to formation of a stratified ocean and a chemocline in the outer shelf and deeper water environments, causing the disappearance of deep marine benthos including brachiopods. The chemocline then rapidly migrated upward and extended to shallow waters, causing widespread mass extinction of shallow marine benthos. We predict that the spatial and temporal patterns of earlier onset of disappearance/extinction and ecological crisis in deeper water ecosystems will be recorded during other episodes of rapid global warming.
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paleobiogeographical extinction patterns of permian brachiopods in the asian western pacific region
Paleobiology, 2002Co-Authors: Shen Shuzhong, G R ShiAbstract:Spatial and temporal variations in biological diversity are critical in understanding the role of biogeographical regulation (if any) on mass extinctions. An analysis based on a latest da- tabase of the stratigraphic ranges of 89 Permian brachiopod families, 422 genera, and 2059 species within the Boreal, Paleoequatorial, and Gondwanan Realms in the Asian-western Pacific region suggests two discrete mass extinctions, each possibly with different causes. Using species/family rarefaction analysis, we constructed diversity curves for late Artinskian-Kungurian, Roadian-Wor- dian, Capitanian, and Wuchiapingian intervals for filtering out uneven sampling intensities. The end-Changhsingian (latest Permian) extinction eliminated 87-90% of genera and 94-96% of species of Brachiopoda. The timing of the end-Changhsingian extinction of brachiopods in the carbonate settings of South China and southern Tibet indicates that brachiopods suffered a rapid extinction within a short interval just below the Permian/Triassic boundary. In comparison, the end-Guadalupian/late Guadalupian extinction is less profound and varies temporally in different realms. Brachiopods in the western Pacific sector of the Boreal Realm nearly disappeared by the end-Guadalupian but experienced a relatively long-term press extinction span- ning the entire Guadalupian in the Gondwanan Realm. The end-Guadalupian brachiopod diversity fall is not well reflected at the timescale used here in the Paleoequatorial Realm because the life- depleted early Wuchiapingian was overlapped by a rapid radiation phase in the late Wuchiapin- gian. The Guadalupian fall appears to be related to the dramatic reduction of habitat area for the brachiopods, which itself is associated with the withdrawal of seawater from continental Pangea and the closure of the Sino-Mongolian seaway by the end-Guadalupian.
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a new genus of rhynchonellid brachiopod from the lower triassic of south china and implications for timing the recovery of Brachiopoda after the end permian mass extinction
Palaeontology, 2002Co-Authors: Zhong-qiang Chen, G R Shi, Kunio KaihoAbstract:A new genus, Meishanorhynchia, is proposed based on new material from the Lower Triassic of the Meishan section, South China. It is of a late Griesbachian age based on both associated biozones (ammonoids and bivalves) and radiometric dates of the intercalated volcanic ash beds. Comparison with both Palaeozoic and Mesozoic–Cenozoic-related genera suggests that it may represent the first radiation of progenitor brachiopods in the aftermath of the end-Permian extinction. The lowest brachiopod horizon that contains the genus is estimated to be about 250.1 ± 0.3 Ma. This implies that the initial stage of recovery of Brachiopoda in the Early Triassic was probably about 1.3 ± 0.3 myr after the major pulse of the end-Permian mass extinction (dated as 251.4 ± 0.3 Ma). This is in agreement with Hallam’s expectancy that biotic recovery typically begins within one million years or so of major mass extinctions, in contrast to current views on the end-Permian extinction event which propose that the recovery of most if not all biotic groups in the Early Triassic was severely delayed and only began about five million years after the end-Permian extinction.
Lars E Holmer - One of the best experts on this subject based on the ideXlab platform.
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The oldest Cambrian trilobite – brachiopod association in South China
Gondwana Research, 2021Co-Authors: Zhiliang Zhang, Lars E Holmer, Glenn A. Brock, Mansoureh Ghobadi Pour, Leonid E. Popov, Feiyang Chen, Yanlong Chen, Zhifei ZhangAbstract:Abstract Limestones of the Xihaoping Member of the Dengying Formation in the Xiaoyangba section, South China, yield the oldest known Cambrian brachiopod–trilobite association. In this member, the trilobite Parabadiella cf. huoi co-occurs with the new brachiopod species Eoobolus incipiens sp. nov. The association provides potential for correlation of lower Cambrian successions and gives novel insights into the origin, palaeobiogeographic distribution and early evolution of linguliform brachiopods. Parabadiella occurs in shallow marine clastic and carbonate rocks in South China, demonstrating a broad distribution for this taxon. The new discovery indicates an early Chiungchussuan age (Parabadiella trilobite Zone, Cambrian Age 3) for the longstanding problematic Xihaoping Member. Furthermore, this earliest Parabadiella–Eoobolus association helps to establish close links with the oldest known trilobite–brachiopod assemblage from the upper Micrina etheridgei Zone (Parabadiella huoi trilobite Zone) in Australia. Eoobolus incipiens represents one of the earliest known linguliform brachiopods, with a distinctive mixture of characters shared with both problematic tommotiids, as well as paterinide, lingulide and acrotretide brachiopods, indicating that these features may be plesiomorphic for the Linguliformea. An age-constrained dispersal mode for early lingulate brachiopods is proposed, indicating that the Subphylum Linguliformea may have originated in East Gondwana and South China during Cambrian Age 3, and only subsequently dispersed to other major Cambrian palaeocontinents (e.g. Siberia, Laurentia, Antarctica, Baltica, Avalonia, West Gondwana, North China) during the late stage of the Cambrian evolutionary radiation of animals.
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early cambrian organophosphatic brachiopods from the xinji formation at shuiyu section shanxi province north china
Palaeoworld, 2020Co-Authors: Lars E Holmer, Timothy P Topper, Glenn A. Brock, Bing Pan, Christian B. SkovstedAbstract:Abstract Abundant and diverse small shelly fossils have been reported from Cambrian Series 2 in North China, but the co-occurring brachiopods are still poorly known. Herein, we describe seven genera, five species and two undetermined species of organophosphatic brachiopods including one new genus and new species from the lower Cambrian Xinji Formation at Shuiyu section, located on the southern margin of North China Platform. The brachiopod assemblage comprises one mickwitziid (stem group Brachiopoda), Paramickwitzia boreussinaensis n. gen. n. sp., a paterinide, Askepasma toddense Laurie, 1986 , an acrotretoid, Eohadrotreta cf. zhenbaensis Li and Holmer, 2004 , a botsfordiid, Schizopholis yorkensis (Holmer and Ushatinskaya in Gravestock et al., 2001 ) and three linguloids, Spinobolus sp., Eodicellomus cf. elkaniiformis Holmer and Ushatinskaya in Gravestock et al., 2001 and Eoobolus sp. This brachiopod assemblage suggests a late Age 3 to early Age 4 for the Xinji Formation and reveals a remarkably strong connection with coeval faunas from East Gondwana, particularly the Hawker Group in South Australia. The high degree of similarity (even at species level) further supports a close palaeogeographic position between the North China Platform and Australian East Gondwana during the early Cambrian as indicated by small shelly fossil data.
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Survival on a soft seafloor: life strategies of brachiopods from the Cambrian Burgess Shale
Earth-Science Reviews, 2015Co-Authors: Timothy P Topper, Lars E Holmer, Luke C. Strotz, Jeanbernard CaronAbstract:Abstract Understanding the structure of benthic communities in the Cambrian remains a major challenge. Direct evidence for species interrelationships is rare and therefore past ecological interactions typically cannot be reconstructed with great accuracy. Here we reveal the community patterns and modes of life of brachiopods – one of the most important filter-feeding groups of Cambrian ecosystems – from the Cambrian Burgess Shale Lagerstatte. Burgess Shale brachiopods attached to a range of hard substrates, including skeletal debris, conspecific brachiopods and enigmatic tubes, with an overwhelming preference for attachment on the demosponge Pirania muricata . The dominance of P . muricata as a substrate choice – even in bedding assemblages where P . muricata individuals are rare – and similarities to the gregarious attachment strategies of extant brachiopod species suggests that brachiopods larvae in the Burgess Shale community selected their attachment substrates. The distribution of brachiopod taxa is also intricately linked with the presence of suitable hard substrates, with species declining in bedding assemblages where their preferred hard substrates are absent. In addition, brachiopods in the Burgess Shale community are predominantly low epifaunal tierers and do not exploit niches high in the water column, despite the presence of suitable attachment sites. Our analysis of tiering height versus host height indicates that there is no selection by brachiopod larvae in regard to the height of attachment and individuals attached at the first point of contact with the selected substrate. Through comparisons with the ‘early’ Cambrian Chengjiang Biota, we confirm that by the ‘middle’ Cambrian (Series 3, Stage 5) brachiopods had already developed a range of attachment strategies similar to some modern brachiopod populations. Our results provide significant insight into the ecological constraints and adaptability of brachiopods in the earliest animal communities of the Cambrian.
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Metamorphosis in Craniiformea revisited: Novocrania anomala shows delayed development of the ventral valve
Zoomorphology, 2013Co-Authors: Andreas Altenburger, Andreas Wanninger, Lars E HolmerAbstract:We revisited the brachiopod fold hypothesis and investigated metamorphosis in the craniiform brachiopod Novocrania anomala . Larval development is lecithotrophic and the dorsal (brachial) valve is secreted by dorsal epithelia. We found that the juvenile ventral valve, which consists only of a thin layer that was previously described as periostracal, is not a valve and is not secreted by the same epithelia as the dorsal valve. It is secreted by the attachment area of the larva at the posterior-most tip of the posterior larval lobe. The same attachment area is used by larvae of rhynchonelliform brachiopods during metamorphosis to cement their pedicle to the substrate. N. anomala is therefore not initially attached by a valve but by material corresponding to pedicle cuticle. This is different to previous descriptions, which had led to speculations about a folding event in the evolution of Brachiopoda. We show that the “brachiopod fold hypothesis,” which argues that brachiopods are transversely “folded” across the ontogenetic anterior–posterior axis, should be rejected at least with respect to the craniiforms. The data now suggest that the Craniiformea may be a derived group within the Rhynchonelliformea. This interpretation suggests that the last common ancestor of the Craniiformea has lost the pedicle and the ventral valve in early juvenile development. Characters that have previously been considered to be shared between the Craniiformea and the Linguliformea (clade Inarticulata), such as a through-gut and missing hinge articulation, may thus be secondarily derived characters of the Craniiformea within the Rhynchonelliformea.
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Homologous skeletal secretion in tommotiids and brachiopods
Geology, 2009Co-Authors: Uwe Balthasar, Lars E Holmer, Christian B. Skovsted, Glenn A. BrockAbstract:Tommotiids are distinctive components of the early Cambrian small shelly fauna, almost invariably represented by isolated phosphatic sclerites derived from a multielement protective cover (scleritome). The unusual range of tommotiid sclerite morphologies and unknown construction of the scleritome have severely hampered our understanding of their phylogenetic affinities. However, recent description of rare, articulated scleritome material belonging to the tommotiid genera Eccentrotheca and Paterimitra support the hypothesis that some tommotiids fall within the stem group of the lophophorate phyla Phoronida and Brachiopoda and that at least some tommotiid sclerites are homologous precursors of the shells of organophosphatic brachiopods. Here we show that the shell microstructure of Eccentrotheca and Paterimitra share substantial similarities with paterinid brachiopods. While paterinids possess an overall brachiopod morphology, their microstructure appears more similar to Eccentrotheca and Paterimitra than to nonpaterinate lingulids. These findings strongly support the existence of a brachiopod total group that is solidly rooted within tommotiids, and identify the organophosphatic skeletal composition as plesiomorphic with calcareous shells as derived. The microstructural changes of the proposed tommotiid-brachiopod transition probably reflect an adaptation to fluctuating food and phosphorous intake that came with the switch to a sessile life style at the base of the tommotiid clade.
Glenn A. Brock - One of the best experts on this subject based on the ideXlab platform.
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The oldest Cambrian trilobite – brachiopod association in South China
Gondwana Research, 2021Co-Authors: Zhiliang Zhang, Lars E Holmer, Glenn A. Brock, Mansoureh Ghobadi Pour, Leonid E. Popov, Feiyang Chen, Yanlong Chen, Zhifei ZhangAbstract:Abstract Limestones of the Xihaoping Member of the Dengying Formation in the Xiaoyangba section, South China, yield the oldest known Cambrian brachiopod–trilobite association. In this member, the trilobite Parabadiella cf. huoi co-occurs with the new brachiopod species Eoobolus incipiens sp. nov. The association provides potential for correlation of lower Cambrian successions and gives novel insights into the origin, palaeobiogeographic distribution and early evolution of linguliform brachiopods. Parabadiella occurs in shallow marine clastic and carbonate rocks in South China, demonstrating a broad distribution for this taxon. The new discovery indicates an early Chiungchussuan age (Parabadiella trilobite Zone, Cambrian Age 3) for the longstanding problematic Xihaoping Member. Furthermore, this earliest Parabadiella–Eoobolus association helps to establish close links with the oldest known trilobite–brachiopod assemblage from the upper Micrina etheridgei Zone (Parabadiella huoi trilobite Zone) in Australia. Eoobolus incipiens represents one of the earliest known linguliform brachiopods, with a distinctive mixture of characters shared with both problematic tommotiids, as well as paterinide, lingulide and acrotretide brachiopods, indicating that these features may be plesiomorphic for the Linguliformea. An age-constrained dispersal mode for early lingulate brachiopods is proposed, indicating that the Subphylum Linguliformea may have originated in East Gondwana and South China during Cambrian Age 3, and only subsequently dispersed to other major Cambrian palaeocontinents (e.g. Siberia, Laurentia, Antarctica, Baltica, Avalonia, West Gondwana, North China) during the late stage of the Cambrian evolutionary radiation of animals.
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early cambrian organophosphatic brachiopods from the xinji formation at shuiyu section shanxi province north china
Palaeoworld, 2020Co-Authors: Lars E Holmer, Timothy P Topper, Glenn A. Brock, Bing Pan, Christian B. SkovstedAbstract:Abstract Abundant and diverse small shelly fossils have been reported from Cambrian Series 2 in North China, but the co-occurring brachiopods are still poorly known. Herein, we describe seven genera, five species and two undetermined species of organophosphatic brachiopods including one new genus and new species from the lower Cambrian Xinji Formation at Shuiyu section, located on the southern margin of North China Platform. The brachiopod assemblage comprises one mickwitziid (stem group Brachiopoda), Paramickwitzia boreussinaensis n. gen. n. sp., a paterinide, Askepasma toddense Laurie, 1986 , an acrotretoid, Eohadrotreta cf. zhenbaensis Li and Holmer, 2004 , a botsfordiid, Schizopholis yorkensis (Holmer and Ushatinskaya in Gravestock et al., 2001 ) and three linguloids, Spinobolus sp., Eodicellomus cf. elkaniiformis Holmer and Ushatinskaya in Gravestock et al., 2001 and Eoobolus sp. This brachiopod assemblage suggests a late Age 3 to early Age 4 for the Xinji Formation and reveals a remarkably strong connection with coeval faunas from East Gondwana, particularly the Hawker Group in South Australia. The high degree of similarity (even at species level) further supports a close palaeogeographic position between the North China Platform and Australian East Gondwana during the early Cambrian as indicated by small shelly fossil data.
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Ancestral billingsellides and the evolution and phylogenetic relationships of early rhynchonelliform brachiopods
Journal of Systematic Palaeontology, 2013Co-Authors: Timothy P Topper, David A. T. Harper, Glenn A. BrockAbstract:The relationship of many Cambrian rhynchonelliform brachiopods is poorly understood, with many genera displaying a combination of morphological features that are taxonomically confusing. The study of middle Cambrian–early Tremadocian brachiopods is critical because this interval is sandwiched directly between the two largest radiation phases in the early Palaeozoic and provides raw data for deciphering the events leading up to the explosion of brachiopod genera in the Ordovician. Here we present a parsimony analysis of a wide selection of Cambrian and Ordovician brachiopod genera with a particular focus on the evolution and phylogeny of Billingsellida. The billingselloids were widespread by the late Cambrian and the group was originally thought to represent the ancestral stock of many Ordovician brachiopod lineages. The phylogenetic analyses portray the polytoechioids as derived billingselloids separate from the clitambonitoids that form a sister group. The Gondwanan brachiopod Roanella is interpreted as ...
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Homologous skeletal secretion in tommotiids and brachiopods
Geology, 2009Co-Authors: Uwe Balthasar, Lars E Holmer, Christian B. Skovsted, Glenn A. BrockAbstract:Tommotiids are distinctive components of the early Cambrian small shelly fauna, almost invariably represented by isolated phosphatic sclerites derived from a multielement protective cover (scleritome). The unusual range of tommotiid sclerite morphologies and unknown construction of the scleritome have severely hampered our understanding of their phylogenetic affinities. However, recent description of rare, articulated scleritome material belonging to the tommotiid genera Eccentrotheca and Paterimitra support the hypothesis that some tommotiids fall within the stem group of the lophophorate phyla Phoronida and Brachiopoda and that at least some tommotiid sclerites are homologous precursors of the shells of organophosphatic brachiopods. Here we show that the shell microstructure of Eccentrotheca and Paterimitra share substantial similarities with paterinid brachiopods. While paterinids possess an overall brachiopod morphology, their microstructure appears more similar to Eccentrotheca and Paterimitra than to nonpaterinate lingulids. These findings strongly support the existence of a brachiopod total group that is solidly rooted within tommotiids, and identify the organophosphatic skeletal composition as plesiomorphic with calcareous shells as derived. The microstructural changes of the proposed tommotiid-brachiopod transition probably reflect an adaptation to fluctuating food and phosphorous intake that came with the switch to a sessile life style at the base of the tommotiid clade.
Zhong-qiang Chen - One of the best experts on this subject based on the ideXlab platform.
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The Anisian (Middle Triassic) brachiopod fauna from Qingyan, Guizhou, south-western China
Journal of Systematic Palaeontology, 2019Co-Authors: Zhen Guo, Zhong-qiang Chen, David A. T. HarperAbstract:Like most of the benthos, brachiopods suffered huge losses in biodiversity during the end-Permian extinction and did not fully recover until the Anisian (Middle Triassic). Anisian brachiopod faunas...
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survival strategies of brachiopod faunas from the end permian mass extinction
Palaeogeography Palaeoclimatology Palaeoecology, 2005Co-Authors: Zhong-qiang Chen, Kunio Kaiho, Annette D. GeorgeAbstract:Abstract Global reviews reveal that 102 brachiopod species (including 40 indeterminate species) belonging to 43 genera within 27 families survived the end-Permian mass extinction in South China, the Himalayan regions (southern Tibet, Nepal, Salt Range and Kashmir), southern Alps (Italy), Arctic Canada, western USA and Western Australia. Of these, the surviving brachiopods are most abundant and widespread in South China where they occur in 32 of the 42 Permian–Triassic (P/T) boundary sections around the world. Brachiopod faunas are the most abundant and diverse post-extinction survivors, and their appearance above the end-Permian mass extinction horizon somewhat masks recognition of the end-Permian extinction. These surviving brachiopods occur in three stratal intervals corresponding to the “Mixed Fauna Beds” (MFB hereafter) 1–3 of the P/T boundary beds. A sharp drop in diversity of the brachiopod faunas coincides with the widely accepted end-Permian mass extinction horizon. The post-extinction brachiopods were also affected by a subsequent crisis corresponding to the boundary between MFB 2 and MFB 3 so that most survivors were extinct approximately 0.7 Ma after the end-Permian mass extinction. The surviving brachiopods were mainly Productida, followed by Spiriferida. In particular, small chonetids, chonetid-like productellids and smooth, thin-shelled ambocollid spiriferids are most abundant. Lingula is extraordinarily abundant and widespread approximately 0.7 Ma after the greatest extinction when many regions became devoid of articulate brachiopods. Widespread, broadly adapted and small-sized taxa preferentially survived. Frequent intrageneric speciation of widespread, widely adapted generalist genera enabled survival brachiopods to occupy rapidly and efficiently vacant ecospace in the aftermath of the end-Permian extinction. The ecological habitats of the post-extinction brachiopods are subdivided into nearshore, epeiric sea, restricted carbonate platform, open carbonate platform, ramp and outer shelf environments. Of these, the survival brachiopods are most diverse in the open platform environments. The nearshore zone provided ideal habitats for the nonarticulated brachiopods to occupy; whereas the survivors in the outer shelf are predominantly chonetids and chonetid-like productellids. The most successful survivors, the productid brachiopods, are widely distributed in six types of ecological habitats and thus have no apparent preference for specific environments. The end-Permian extinction resulted in the movement of biogeographical provinces towards the palaeo-equator. The brachiopods survived mostly in the palaeo-equatorial provinces and along the southern margins of the Palaeo-Tethys Ocean.
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Early Triassic recovery of the brachiopod faunas from the end-Permian mass extinction: A global review
Palaeogeography Palaeoclimatology Palaeoecology, 2005Co-Authors: Zhong-qiang Chen, Kunio Kaiho, Annette D. GeorgeAbstract:Abstract Brachiopod faunas in Lower Triassic deposits from Spitzbergen, Primorye of Russia, Japan, Mangyslak of Kazakhstan, Alpine Europe, the Caucasus, the Middle East, the Himalaya, South China, New Zealand, and western USA are taxonomically and stratigraphically reviewed. They comprise survivors of the end-Permian extinction and taxa originating in the Early Triassic. Origination of the Mesozoic-type taxa represents the recovery of Early Triassic brachiopods. The initial recovery of brachiopod faunas began in the late Griesbachian, and the time interval between the end of extinction and the onset of the recovery of brachiopods is much shorter than previously suspected. The Early Triassic recovery of brachiopod faunas is characterized by widespread brachiopod dispersal, multiprovincialism, and the presence of rare Lazarus genera at that time. Taxonomic selectivity of the recovery brachiopod faunas favors the rhynchonellids. The re-population of post-extinction brachiopods varies geographically: there is a preference for regions either previously barren of latest Permian taxa or regions where the pre-extinction Changhsingian and surviving brachiopods are very rare. This unique biogeographic selectivity is probably partly responsible for the impoverished nature of brachiopod faunas in the Triassic (even Mesozoic) oceans. Five intervals of extinction, survival, survival–recovery, recovery–dispersal, and radiation are recognized based on variations in brachiopod faunas from the latest Permian to the Early Triassic. A dramatic reduction in brachiopod diversity at the end-Permian mass extinction is followed by several stepwise declines in diversity in the survival interval, the time during which the surviving brachiopods are dominated by geographically widespread generalist faunas that adapted to a wide variety of environments. The survival interval was followed by a slow re-population of new lineages dominated by progenitor taxa.
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a new genus of rhynchonellid brachiopod from the lower triassic of south china and implications for timing the recovery of Brachiopoda after the end permian mass extinction
Palaeontology, 2002Co-Authors: Zhong-qiang Chen, G R Shi, Kunio KaihoAbstract:A new genus, Meishanorhynchia, is proposed based on new material from the Lower Triassic of the Meishan section, South China. It is of a late Griesbachian age based on both associated biozones (ammonoids and bivalves) and radiometric dates of the intercalated volcanic ash beds. Comparison with both Palaeozoic and Mesozoic–Cenozoic-related genera suggests that it may represent the first radiation of progenitor brachiopods in the aftermath of the end-Permian extinction. The lowest brachiopod horizon that contains the genus is estimated to be about 250.1 ± 0.3 Ma. This implies that the initial stage of recovery of Brachiopoda in the Early Triassic was probably about 1.3 ± 0.3 myr after the major pulse of the end-Permian mass extinction (dated as 251.4 ± 0.3 Ma). This is in agreement with Hallam’s expectancy that biotic recovery typically begins within one million years or so of major mass extinctions, in contrast to current views on the end-Permian extinction event which propose that the recovery of most if not all biotic groups in the Early Triassic was severely delayed and only began about five million years after the end-Permian extinction.