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Jeanbernard Caron - One of the best experts on this subject based on the ideXlab platform.
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Brachiopods hitching a ride an early case of commensalism in the middle cambrian burgess shale
Scientific Reports, 2015Co-Authors: Timothy P Topper, Lars E Holmer, Jeanbernard CaronAbstract:Ecological interactions, including symbiotic associations such as mutualism, parasitism and commensalism are crucial factors in generating evolutionary novelties and strategies. Direct examples of species interactions in the fossil record generally involve organisms attached to sessile organisms in an epibiont or macroboring relationship. Here we provide support for an intimate ecological association between a calcareous Brachiopod (Nisusia) and the stem group mollusc Wiwaxia from the Burgess Shale. Brachiopod specimens are fixed to Wiwaxia scleritomes, the latter showing no signs of decay and disarticulation, suggesting a live association. We interpret this association as the oldest unambiguous example of a facultative ectosymbiosis between a sessile organism and a mobile benthic animal in the fossil record. The potential evolutionary advantage of this association is discussed, Brachiopods benefiting from ease of attachment, increased food supply, avoidance of turbid benthic conditions, biofoul and possible protection from predators, suggesting commensalism (benefiting the symbiont with no impact for the host). While Cambrian Brachiopods are relatively common epibionts, in particular on sponges, the association of Nisusia with the motile Wiwaxia is rare for a Brachiopod species, fossil or living, and suggests that symbiotic associations were already well established and diversified by the “middle” (Series 3, Stage 5) Cambrian.
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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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a spinose stem group Brachiopod with pedicle from the middle cambrian burgess shale
Acta Zoologica, 2006Co-Authors: Lars E Holmer, Jeanbernard CaronAbstract:Holmer, L.E. and Caron, J-B. 2006. A soft-shelled spinose stem group Brachiopod with pedicle from the Middle Cambrian Burgess Shale. — Acta Zoologica (Stockholm) 87 : 273-290 A new genus and species of a Middle Cambrian stem group Brachiopod, Acanthotretella spinosa n. gen. and n. sp., is described from the Burgess Shale Formation. Most of the 42 specimens studied came from the Greater Phyllopod bed (Walcott Quarry) and were collected from five bed assemblages, each representing a single obrution event. Specimens are probably preserved within their original habitat. In contrast to all Brachiopods known from the Burgess Shale, the shells of the new stem group Brachiopod are often deformed and do not show signs of brittle breakage, which suggests that the valves were originally either entirely organic in composition or, more likely, had just a minor mineral component. Acanthotretella spinosa differs from all the other described Cambrian Brachiopods in that it is covered by long, slender and possibly partly mineralized spines that are posteriorly inclined at an oblique angle away from the anterior margin. The spines penetrate the shell and are mainly comparable with the thorn-like organic objects that have been inferred from early siphonotretoid Brachiopods. The pedicle was slender and was composed of a central coelomic region and emerged from an apical foramen at the end of an internal pedicle tube. The finding of a pedicle attached to the macrobenthic algae Dictyophycus and other epibenthos implies that A. spinosa did not have an infaunal mode of life. The visceral region and interior characters are poorly preserved.
Lars E Holmer - One of the best experts on this subject based on the ideXlab platform.
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Himalayan Cambrian Brachiopods
Papers in Palaeontology, 2015Co-Authors: Leonid E. Popov, Lars E Holmer, Nigel C. Hughes, Mansoureh Ghobadi Pour, Paul M. MyrowAbstract:A synoptic analysis of previously published material and new finds reveals that Himalayan Cambrian Brachiopods can be referred to 18 genera, of which 17 are considered herein. These contain 20 taxa assigned to species, of which five are new: Eohadrotreta haydeni, Aphelotreta khemangarensis, Hadrotreta timchristiorum, Prototreta? sumnaensis and Amictocracens? brocki. Well-preserved topotype material from the classic Parahio Valley section is described for three species that have not previously been illustrated photographically. A biostratigraphical scheme based on Cambrian Brachiopod occurrence is integrated with that recently proposed for trilobites. Regional correlations based on shared taxa within and across Himalayan lithotectonic belts demonstrate that erosion of Cambrian rocks in the Kurgiakh orogeny in the Parahio Valley removed little of the Parahio Formation and that all of the fossil-bearing lithotectonic zones share similar late early Cambrian Brachiopods, suggesting regional faunal continuity at the time. Palaeobiogeographical analysis of the Cambrian Brachiopod faunas from the Himalaya shows that they occupied a marginal position of the Australasian segment of Gondwana.
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Brachiopods hitching a ride an early case of commensalism in the middle cambrian burgess shale
Scientific Reports, 2015Co-Authors: Timothy P Topper, Lars E Holmer, Jeanbernard CaronAbstract:Ecological interactions, including symbiotic associations such as mutualism, parasitism and commensalism are crucial factors in generating evolutionary novelties and strategies. Direct examples of species interactions in the fossil record generally involve organisms attached to sessile organisms in an epibiont or macroboring relationship. Here we provide support for an intimate ecological association between a calcareous Brachiopod (Nisusia) and the stem group mollusc Wiwaxia from the Burgess Shale. Brachiopod specimens are fixed to Wiwaxia scleritomes, the latter showing no signs of decay and disarticulation, suggesting a live association. We interpret this association as the oldest unambiguous example of a facultative ectosymbiosis between a sessile organism and a mobile benthic animal in the fossil record. The potential evolutionary advantage of this association is discussed, Brachiopods benefiting from ease of attachment, increased food supply, avoidance of turbid benthic conditions, biofoul and possible protection from predators, suggesting commensalism (benefiting the symbiont with no impact for the host). While Cambrian Brachiopods are relatively common epibionts, in particular on sponges, the association of Nisusia with the motile Wiwaxia is rare for a Brachiopod species, fossil or living, and suggests that symbiotic associations were already well established and diversified by the “middle” (Series 3, Stage 5) Cambrian.
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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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Exceptionally-preserved Mickwitzia from the Indian Springs Lagerstätte.
2014Co-Authors: Aodhán D. Butler, Michael Streng, Lars E Holmer, Loren E. BabcockAbstract:The origin and evolution of Lophotrochozoa can be traced to the plethora of lower Cambrian scleritome taxa. We aim to determine the character suites linking these stem-Lophotrochozoa to their extant crown relatives, in particular the small shelly tommotiids and the stem-group Brachiopods. Tracing the origin of morphological characters from these fossils informs the evolution and construction of lophotrochozoan body plans associated with the Cambrian Explosion. This is achieved by comparing records of exceptional preservation, most conspicuously Burgess Shale type Lagerstatten with more widespread Cambrian stem-Brachiopods and small shelly fossils with their purported extant relatives, for example. Determining morphological character homologies is crucial to reconstructing the Brachiopod stem-group and in polarising character changes associated with the putative transition from scleritome organisms to crown-group Brachiopods. In this thesis arguments for a common origin of specific shell structures and exceptionally preserved soft-tissues are investigated. New records of enigmatic stem-group lophotrochozoans are described from two localities, the Indian Springs and Chengjiang Lagerstatte. Comprising the stem-Brachiopod Mickwitzia cf. occidens, a putative stem-group entoproct Cotyledion tylodes and an enigmatic agglutinated tubular lophophorate possessing an unusual combination of phoronid, Brachiopod and tommotiid characters, Yuganotheca elegans gen. et sp. nov. The interplay of bauplan, microbial activity and environmental factors resulting in such incidences of exceptional soft tissue preservation is also examined critically. Consequently, the evolution of through-gut bearing bilaterians is suggested as the reason for why the Cambrian hosts such a plethora of Lagerstatten. The closure of this taphonomic window is then associated with increased bioturbation following the Cambrian substrate revolution.
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the early cambrian tommotiid micrina a sessile bivalved stem group Brachiopod
Biology Letters, 2008Co-Authors: Lars E Holmer, Glenn A. Brock, Christian B Skovsted, James Valentine, John R. PatersonAbstract:The tannuolinid Micrina belongs to the tommotiids—a common and widely distributed, but poorly understood, group of Early Cambrian fossil metazoans with multiple external organophosphatic sclerites. Recent findings of sessile articulated tommotiid scleritomes indicate that previous reconstructions of tommotiids as slug-like bilaterians with a dorsal cover of sclerites require detailed re-evaluation. Comparative ultrastructural work has already indicated that the tommotiids might be a sister group to the Brachiopoda, with Micrina representing the most derived and Brachiopod-like bimembrate tommotiid. Here we further develop and strengthen this controversial phylogenetic model with a new reconstruction of Micrina, where the two types of sclerites—mitral and sellate—belong to a near bilaterally symmetrical bivalved sessile organism. This new scleritome configuration was tested by recreating an articulated bivalved Micrina from isolated mitral and sellate sclerites; both sclerites have muscles that would have enabled movement of the sclerites. The mitral and sellate sclerites of Micrina are considered to be homologous with the ventral and dorsal valves, respectively, of organophosphatic linguliform Brachiopods, indicating that a simple type of filter-feeding within an enclosed bivalved shell had started to evolve in derived tannuolinids. The new reconstruction also indicates that the phylogenetic range of ‘bivalved’, sessile lophophorates is larger than previously suspected.
Timothy P Topper - One of the best experts on this subject based on the ideXlab platform.
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The dawn of a dynasty : life strategies of Cambrian and Ordovician Brachiopods.
Lethaia, 2017Co-Authors: Timothy P Topper, Zhifei Zhang, Juan Carlos Gutiérrez-marco, David A. T. HarperAbstract:Brachiopods are among the first animal phyla to emerge from the Cambrian Explosion, rapidly diversifying to all major palaeocontinental blocks within 20 million years. The group underwent another steep rise in diversity during the Ordovician, and their relative abundance and diversity made them one of the most successful invertebrate groups during the entire Palaeozoic. During this time, Brachiopods lived in a range of environments and represented a significant component of marine ecosystems, yet information regarding their modes of life and ecology is somewhat limited. Recent studies, primarily from the Chengjiang and Burgess Shale Lagerstätten, have revealed that by the Middle Cambrian (Series 3, Stage 5) Brachiopods from across the phylum had already developed a range of ecological strategies and life modes. Cambrian Brachiopods occupied distinct trophic niches on soft and hard substrates and exhibited at least five types of lifestyles: pedicle attachment, pedicle anchoring, cemented, free-lying and semi-infaunal. Comparisons with Ordovician benthic assemblages show that despite the explosion of Brachiopod taxa witnessed in the Ordovician, with the exception of the appearance of burrowing Brachiopods, life strategies of Brachiopods remained largely the same. Indicating that the majority of life modes observed in Brachiopods had rapidly evolved and was already in place prior to the Great Ordovician Biodiversity Event
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Brachiopods hitching a ride an early case of commensalism in the middle cambrian burgess shale
Scientific Reports, 2015Co-Authors: Timothy P Topper, Lars E Holmer, Jeanbernard CaronAbstract:Ecological interactions, including symbiotic associations such as mutualism, parasitism and commensalism are crucial factors in generating evolutionary novelties and strategies. Direct examples of species interactions in the fossil record generally involve organisms attached to sessile organisms in an epibiont or macroboring relationship. Here we provide support for an intimate ecological association between a calcareous Brachiopod (Nisusia) and the stem group mollusc Wiwaxia from the Burgess Shale. Brachiopod specimens are fixed to Wiwaxia scleritomes, the latter showing no signs of decay and disarticulation, suggesting a live association. We interpret this association as the oldest unambiguous example of a facultative ectosymbiosis between a sessile organism and a mobile benthic animal in the fossil record. The potential evolutionary advantage of this association is discussed, Brachiopods benefiting from ease of attachment, increased food supply, avoidance of turbid benthic conditions, biofoul and possible protection from predators, suggesting commensalism (benefiting the symbiont with no impact for the host). While Cambrian Brachiopods are relatively common epibionts, in particular on sponges, the association of Nisusia with the motile Wiwaxia is rare for a Brachiopod species, fossil or living, and suggests that symbiotic associations were already well established and diversified by the “middle” (Series 3, Stage 5) Cambrian.
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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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Middle Ordovician Brachiopods from the Stairway Sandstone, Amadeus Basin, central Australia
Alcheringa: An Australasian Journal of Palaeontology, 2013Co-Authors: Kristian G. Jakobsen, Timothy P Topper, Glenn A. Brock, Arne Thorshøj Nielsen, David A. T. HarperAbstract:Jakobsen, K.G., Brock, G.A, Nielsen, A.T., Topper, T.P. & Harper, D.A.T., 2013. Middle Ordovician Brachiopods from the Stairway Sandstone, Amadeus Basin, central Australia. Alcheringa. ISSN 0311–5518.Middle Ordovician Brachiopod faunas from the Amadeus Basin, central Australia are poorly known. The Darriwilian Stairway Sandstone was sampled stratigraphically for macrofossils in order to provide new information on marine benthic diversity in this clastic-dominated, shallow-water palaeoenvironment along the margin of northeastern Gondwana. The Brachiopods from the Stairway Sandstone are of low diversity and represent ca 9% of the entire shelly fauna. Five Brachiopod taxa are described from the Stairway Sandstone; all are endemic to the Amadeus Basin at species level. Two new species, Amadeuphyla joanae gen. et sp. nov. and Paralenorthis luritjaorum sp. nov., are described. Unweighted cladistic analysis based on 20 characters places the new genus Amadeuphyla within the Taffinae.Kristian G. Jakobsen [kgjakobs...
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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 ancestral to the clitambonitoids within the Billingsellida and is reassigned to Clitambonitoidea within a new monogeneric family, Roanellidae nov. Antigonambonites displays no obvious relationship with the clitambonitoids and should be formally transferred to the polytoechioids. The monogeneric family Chaniellidae exhibits characters reminiscent of members of the polytoechioids and is transferred to the superfamily Polytoechioidea. The recently reappraised clitambonitoid Arctohedra is interpreted as a basal member of the entire order Billingsellida.13 page(s
Annette D. George - One of the best experts on this subject based on the ideXlab platform.
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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.
Zhong-qiang Chen - One of the best experts on this subject based on the ideXlab platform.
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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.