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Tomasz K. Baumiller - One of the best experts on this subject based on the ideXlab platform.
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Reconstructing predation intensity on Crinoids using longitudinal and cross-sectional approaches
Swiss Journal of Palaeontology, 2018Co-Authors: Tomasz K. Baumiller, Angela StevensonAbstract:Predation has been hypothesized as important to Crinoid ecology, and numerous Crinoid traits have been linked to predation. However, testing such hypotheses requires some assessment of predation intensity, or pressure. Although direct observations of predatory activity on Crinoids are exceedingly rare in the Recent, and unobservable in the fossil record, evidence of predation exists in the form of sublethal damage, especially to their arms. Substantial data exist on the relative frequency, or prevalence, of such injuries, but estimating predation intensity in taxa with ephemeral injuries, such as Crinoids, requires combining the prevalence of injuries with rates at which they heal (regenerate). An alternate, independent estimate of predation intensity involves gathering longitudinal data on the number of injuries incurred by particular individuals over a given time span. In this study, predation intensity on Crinoids is explored experimentally using these two approaches. We demonstrate that for the two feather star species examined, Capillaster multiradiatus and Clarkcomanthus mirabilis , both methods produce reasonably consistent results and that predation intensity is slightly lower on the latter perhaps because it responds to tactile stimulation by crawling deeper into its perch, whereas the former shows no response.
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Spinosity, regeneration, and targeting among Paleozoic Crinoids and their predators
Paleobiology, 2018Co-Authors: V.j.p. Syverson, Forest J. Gahn, Carlton E. Brett, Tomasz K. BaumillerAbstract:Evolving interactions between predators and prey constitute one of the major adaptive influences on marine animals during the Paleozoic. Crinoids and fish constitute a predator—prey system that may date back to at least the Silurian, as suggested by patterns of Crinoid regeneration and spinosity in concert with changes in the predatory fauna. Here we present data on the frequency of breakage and regeneration in the spines of the Middle Devonian camerate Gennaeocrinus and late Paleozoic cladids, as well as an expanded survey of the prevalence of spinosity and infestation by platyceratid gastropods on Crinoid genera during the Paleozoic. Spine regeneration frequency in the measured populations is comparable to arm regeneration frequencies from Mississippian Rhodocrinites and from modern deepwater Crinoid populations. The prevalence of spinosity varies by taxon, time, and anatomy among Paleozoic Crinoids; notably, spinosity in camerates increased from the Silurian through the Mississippian and decreased sharply during the Pennsylvanian, whereas spines were uncommon in cladids until their Late Mississippian diversification. Among camerates, tegmen spinosity is positively correlated with the presence of infesting platyceratid gastropods. These results allow us to evaluate several hypotheses for the effects of predation on morphological differences between early, middle, and late Paleozoic Crinoid faunas. Our data corroborate the hypothesis that predators targeted epibionts on camerate Crinoids and anal sacs on advanced cladids and suggest that the replacement of shearing predators by crushing predators after the Hangenberg extinction affected the locations of spines in Mississippian camerates.
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diversity dynamics of post palaeozoic Crinoids in quest of the factors affecting Crinoid macroevolution
Lethaia, 2016Co-Authors: Przemyslaw Gorzelak, Mariusz A. Salamon, Dawid Trzesiok, Rafal Lach, Tomasz K. BaumillerAbstract:Following the end-Permian biotic crisis which led to the near extinction of Crinoids, this echinoderm class rebounded rapidly during the Mesozoic, resulting in forms with important morphological and behavioural novelties. However, quantitative patterns of Crinoid diversity during the Mesozoic remain largely unexplored. Here, we report results of analyses of the evolutionary dynamics of post-Palaeozoic Crinoid genera spanning a time interval between 250 and 70 Myr. We show that Crinoids reached their Mesozoic peak of genus-level richness during the Late Jurassic. We also document a major reorganization of different ecological Crinoid groups in the Mesozoic. More specifically, the diversity of sessile forms generally increased towards the mid-Mesozoic but decreased significantly starting in the Cretaceous, whereas the number of motile Crinoid genera increased linearly during the Mesozoic. The possible role of biotic and abiotic factors in Crinoid evolution is discussed.
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Diversity dynamics of post-Palaeozoic Crinoids – in quest of the factors affecting Crinoid macroevolution
Lethaia, 2015Co-Authors: Przemysław Gorzelak, Mariusz A. Salamon, Dawid Trzęsiok, Rafał Lach, Tomasz K. BaumillerAbstract:Following the end-Permian biotic crisis which led to the near extinction of Crinoids, this echinoderm class rebounded rapidly during the Mesozoic, resulting in forms with important morphological and behavioural novelties. However, quantitative patterns of Crinoid diversity during the Mesozoic remain largely unexplored. Here, we report results of analyses of the evolutionary dynamics of post-Palaeozoic Crinoid genera spanning a time interval between 250 and 70 Myr. We show that Crinoids reached their Mesozoic peak of genus-level richness during the Late Jurassic. We also document a major reorganization of different ecological Crinoid groups in the Mesozoic. More specifically, the diversity of sessile forms generally increased towards the mid-Mesozoic but decreased significantly starting in the Cretaceous, whereas the number of motile Crinoid genera increased linearly during the Mesozoic. The possible role of biotic and abiotic factors in Crinoid evolution is discussed.
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Predator-induced macroevolutionary trends in Mesozoic Crinoids
Proceedings of the National Academy of Sciences of the United States of America, 2012Co-Authors: Przemysław Gorzelak, Mariusz A. Salamon, Tomasz K. BaumillerAbstract:Sea urchins are a major component of recent marine communities where they exert a key role as grazers and benthic predators. However, their impact on past marine organisms, such as Crinoids, is hard to infer in the fossil record. Analysis of bite mark frequencies on Crinoid columnals and comprehensive genus-level diversity data provide unique insights into the importance of sea urchin predation through geologic time. These data show that over the Mesozoic, predation intensity on Crinoids, as measured by bite mark frequencies on columnals, changed in step with diversity of sea urchins. Moreover, Mesozoic diversity changes in the predatory sea urchins show a positive correlation with diversity of motile Crinoids and a negative correlation with diversity of sessile Crinoids, consistent with a Crinoid motility representing an effective escape strategy. We contend that the Mesozoic diversity history of Crinoids likely represents a macroevolutionary response to changes in sea urchin predation pressure and that it may have set the stage for the recent pattern of Crinoid diversity in which motile forms greatly predominate and sessile forms are restricted to deep-water refugia.
William I. Ausich - One of the best experts on this subject based on the ideXlab platform.
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uncovering the hidden diversity of mississippian Crinoids Crinoidea echinodermata from poland
PeerJ, 2020Co-Authors: Mariusz A. Salamon, William I. Ausich, Tomasz Brachaniec, Bartosz J Plachno, Przemyslaw GorzelakAbstract:Partial Crinoid crowns and aboral cups are reported from the Mississippian of Poland for the first time. Most specimens are partially disarticulated or isolated plates, which prevent identification to genus and species, but regardless these remains indicate a rich diversity of Mississippian Crinoids in Poland during the Mississippian, especially during the late Visean. Lanecrinus? sp. is described from the late Tournaisian of the Debnik Anticline region. A high Crinoid biodiversity occurred during late Visean of the Holy Cross Mountains, including the camerate Crinoids Gilbertsocrinus? sp., Platycrinitidae Indeterminate; one flexible Crinoid; and numerous eucladid Crinoids, including Cyathocrinites mammillaris (Phillips), three taxa represented by partial cups left in open nomenclature, and numerous additional taxa known only from isolated radial plates, brachial plates, and columnals. To date, the youngest occurrence of Gilbertsocrinus was the early Visean of the United States, thus the present finding in upper Visean extends this genus range. Furthermore, the occurrence of Lanecrinus? sp. expands the Western European range of this genus into the Tournaisian. A single partially disarticulated crown, Crinoidea Indeterminate B, is described from the Serpukhovian of the Upper Silesian Coal Basin. In addition, several echinoid test plates and spines are also reported.
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Carboniferous Crinoids
Geological Society London Special Publications, 2020Co-Authors: William I. Ausich, Thomas W. Kammer, Georgy V. MirantsevAbstract:AbstractDuring the Carboniferous, Crinoids were commonly so abundant that their skeletal ossicles formed limestones termed encrinites. Major evolutionary changes occurred within the Camerata and Articuliformes, as the former were displaced by the latter as the dominant clade. Both the Mississippian and the Pennsylvanian subperiods started with high evolutionary rates and ended with low evolutionary rates associated with glaciation. Although not typically used for biostratigraphy, crown-based Crinoid genera can be used as biostratigraphic indicators for Carboniferous stages. Paleozoic Crinoid biodiversity reached its maximum during the Carboniferous, from which there are numerous well-documented localities with high biodiversity. Faunas from the palaeobiogeographical regions of Laurussia, Palaeo-Tethys and Gondwana are reviewed. For Mississippian Crinoids, 37 genera are designated as biostratigraphically useful; and, for the Pennsylvanian, 44 genera are identified. Recognition of the utility of these genera for biostratigraphy is important for dating Crinoid deposits, which may be devoid of other biostratigraphically useful fossils, and add to our overall ability to delineate the temporal resolution of life on Earth.
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juvenile eucladid Crinoid from the middle devonian of turkey
Geodiversitas, 2020Co-Authors: William I. AusichAbstract:A microCrinoid-sized eucladid Crinoid (Eucladida Wright, 2017) is described from the Yiginli Formation (Devonian, Famennian) in the Buyuk Zap Anticline in the Hakkari region of SE Turkey. Compared to other eucladids of similar size, the Yiginli Formation specimen is at a quite advanced morphological stage with arms present through at least the secundibrachials. Early post-larval development is a key for understanding homologies among Crinoid clades; however Paleozoic Crinoids in the microCrinoid range (≤ 2.0 mm) are very rare. This specimen is either at a very advanced developmental stage for its size, or typical microCrinoids are neotenic.
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paleoenvironmental and biostratigraphic implications of echinoderm ossicles trapped within burmese amber
PALAIOS, 2019Co-Authors: Mariusz A. Salamon, William I. Ausich, Przemyslaw Gorzelak, Jihpai Lin, Piotr Duda, Tatsuo OjiAbstract:Marine organisms are uncommonly preserved in amber. Recently, they were reported to be associated with Burmese amber. However, most of specimens from previous reports were preserved on the amber surface or within the sediment surrounding the amber. Based on X-ray tomography and thin-section optical microscopy of Burmese amber, we report here the first genuine and unambiguous evidence of inclusion of Crinoid ossicles preserved in the fossil resin. Preservation of this exclusively marine group in amber gives insights into the paleoenvironment of the Crinoid-amber association and provides additional evidence to support previous observations of shallow-water stalked Crinoids from the mid-Cretaceous, when many stalked Crinoids started to shift offshore due to increased predation pressure during the Mesozoic Marine Revolution. Crinoid remains, represented by disarticulated stem and arm ossicles assignable to Isocrinus cf. legeri (Repelin), point to a mid-Cretaceous age for the Burmese amber and support some previous hypotheses suggesting a close proximity between the resin-producing trees and seawater.
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Ecological and Taphonomic Fidelity in Fossil Crinoid Accumulations
PALAIOS, 2019Co-Authors: David L. Meyer, William I. AusichAbstract:ABSTRACT Among fossiliferous marine facies, deposits rich in stalked echinoderms, particularly encrinites, have long been suspected to be susceptible to taphonomic biases because intact calyxes are under-represented or masked by disarticulated skeletal debris. In the middle Mississippian Fort Payne Formation of south-central Kentucky, penecontemporaneous Crinoid-rich facies are exposed in close proximity along the shores of Lake Cumberland. Crinoidal packstone buildups preserve a broad preservational spectrum, with articulated Crinoid calyxes with arms and columns attached, intact calyxes, holdfasts, and long articulated columns, in a matrix of entirely disarticulated Crinoidal fragments. Along a 250 m transect across the flanks and crest of this buildup, identification of 563 specimens of Crinoids and blastoids revealed a symmetrical distribution of taxa in which the crest was dominated by disparid and camerate Crinoids and the flanks were dominated by camerates. Taphonomic analysis of the same transect showed that intact Crinoid calyxes with or without attached arms and column occurred across the entire buildup, but nearly complete specimens with attached arms and column were most common on the western flank and less common on the crest and eastern flank. Taxonomic and taphonomic distributions demonstrate a primary ecologic zonation across the buildup with only localized post-mortem dispersal of Crinoids. This is the first demonstration of primary ecologic zonation of a Crinoid community preserved within a single lithofacies. Depending on depositional and taphonomic circumstances, Crinoids are preserved intact close to their living site; understanding these physical and biological processes provides a significant feedback in reconstructing these ancient depositional environments.
Aaron W Hunter - One of the best experts on this subject based on the ideXlab platform.
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lakotacrinus brezinai n gen n sp a new stalked Crinoid from cold methane seeps in the upper cretaceous campanian pierre shale south dakota united states
Journal of Paleontology, 2016Co-Authors: Aaron W Hunter, Neal L Larson, Neil H Landman, Tatsuo OjiAbstract:Despite a rich and varied record, Mesozoic stalked Crinoids are relatively rare in the Western Interior Seaway of North America compared to those found in Northern Europe. A unique example of Mesozoic stalked Crinoid is described from cold methane seeps (hydrocarbon seep mounds also called “tepee buttes”) from the Upper Cretaceous (upper Campanian) of the Northern Great Plains of the United States; the first Crinoids to be described from such an environment. The Late Cretaceous Western Interior Seaway has never before yielded any identifiable stalked Crinoid remains. Nevertheless, there have been significant studies on both free living and stalked Crinoids from other locations in the Upper Cretaceous of North America that provide a good basis for comparison. Lakotacrinus brezinai n. gen. n. sp. is characterized by a tapering homeomorphic column with through-going tubuli, lacking any attachment disc. The arms are unbranched and pinnulate, with muscular and syzygial articulations. The unique morphology of the column justifies the establishment of Lakotacrinidae new family. A new suborder Lakotacrinina n. subord., is also proposed as there exists no corresponding taxon within the Articulata that can accommodate all the characteristics of this new genus. This new Crinoid shares many features with other members of the articulates, including bathycrinids, bourgueticrinids and guillecrinids within the Order Comatulida, as currently defined in the revised Treatise of Invertebrate Paleontology. Reconstructing the entire Crinoid using hundreds of semi-articulated and disarticulated (well preserved) fossils, reveals a unique paleoecology and functional morphology specifically adapted to living within this hydrocarbon seep environment.
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Echinoderm palaeoecology from fragments: a tool for facies recognition in mesozoic carbonate sequences
2011Co-Authors: Aaron W HunterAbstract:Echinoderms such as Crinoids (sea lilies), are a major component of the marine benthos from the late Palaeozoic onwards, where they occurred in such high number so as to be rock forming. On death echinoderms will typically disarticulate into many thousands of ossicles which are considered by many palaeontologists to be indeterminate (Benton and Simms 1995). Research into Mesozoic fossil Crinoids has demonstrated that there is currently a lack of understanding of their environmental palaeoecology. This is in part due to taxonomy based soley on exceptionally preserved whole specimens. Thus it has become necessary to consider fragmentary ossicles in defining a more representative palaeoecology. Bulk sampling (10 to 40 kg) of Middle Jurassic (Bathonian) carbonate and muddy sediments of England, where marine environments ranging from open shelf to lagoon are represented, has yielded numerous Crinoid ossicles. Extensive work on exceptionally preserved Middle Jurassic Crinoids from northern Switzerland and British Lower Jurassic has enabled identification of Crinoid ossicles from the English Bathonian to generic level (Hess 1975). Results indicate that the colonisation patterns of Crinoids are strongly influenced by facies type, allowing the community structure of the Crinoids to be clearly defined in ecosystems delineated by substrate type and degree of marine connection. Thus distinct Crinoid communities, based on the presence and absence of generic indicators, can be deduced (Hunter & Underwood 2009). After being successfully developed, the ‘Crinoid model’ was taken a stage further, with its application to three more echinoderm groups: echinoids (sea urchins), asteroids (starfish) and ophiuroids (brittlestars). Previously it was noted that lack of homology in the ossicles made identification beyond family level problematic within these groups. As with the Crinoids, examination of complete specimens in museum collections has allowed the recognition of diagnostic ossicles that can identify tests, spines and marginal plates to generic level. These new data has allowed the construction of a model for echinoderm palaeoecology across marginal marine environments. The application of this model to marine environments outside the British Jurassic, such as the Middle Jurassic of France and the Western Interior, USA, has demonstrated that factors such as substrate and marine connection (salinity) have a greater bias than palaeogeographical and stratigraphic controls. I propose that the small size of these echinoderm micro-fragments and the large number found preserved, means that they can be used as tool for facies recognition alongside other more traditional fossil groups, such as foraminifera and ostracods and are far more informative than many other macrofossils currently used.
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Discovery of dense aggregations of stalked Crinoids in Izu-Ogasawara trench, Japan.
Zoological science, 2009Co-Authors: Tatsuo Oji, Aaron W Hunter, Yujiro Ogawa, Kota KitazawaAbstract:Stalked Crinoids are recognized as living fossils that typically inhabit modern deep-water environments exceeding 100 m. Previous records of stalked Crinoids from hadal depths (exceeding 6000 m) are extremely rare, and no in-situ information has been available. We show here that stalked Crinoids live densely on rocky substrates at depths over 9000 m in the Izu-Ogasawara Trench off the eastern coast of Japan, evidenced by underwater photos and videos taken by a remotely operated vehicle. This is the deepest in-situ observation of stalked Crinoids and demonstrates that Crinoid meadows can exist at hadal depths close to the deepest ocean floor, in a fashion quite similar to populations observed in shallower depths.
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palaeoecology of jurassic encrinites reconstructing Crinoid communities from the western interior seaway of north america
Palaeogeography Palaeoclimatology Palaeoecology, 2008Co-Authors: Aaron W Hunter, Johnpaul ZonneveldAbstract:Jurassic Crinoid communities in North America are poorly known. However, encrinites (rocks chiefly composed of Crinoid debris) are surprisingly common in North America, and represent some of the best examples of post-Palaeozoic Crinoid accumulations. These rocks are highly significant for understanding the ecology of early isocrinid Crinoids, and provide an insight into the wider Crinoid communities of North America. Within this reanalysis of Jurassic Crinoids of the Western Interior Seaway, a number of non-endemic forms are reported, together with some highly specialized Crinoids. Encrinites are varied, with distinct marine and lagoonal communities recognized. These ecological associations are comparable to those seen in the European Jurassic, with many of the classic European genera being present. This new data, and existing data from the Jurassic shallow seas of Europe, demonstrates that Crinoid distribution patterns are largely facies influenced while geographical factors are of limited importance. Even within the same region, taxa in lower energy offshore facies contrast strongly with those found in more restricted facies. However, very similar Crinoid communities characterize comparable facies in North America and Europe.
Tatsuo Oji - One of the best experts on this subject based on the ideXlab platform.
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paleoenvironmental and biostratigraphic implications of echinoderm ossicles trapped within burmese amber
PALAIOS, 2019Co-Authors: Mariusz A. Salamon, William I. Ausich, Przemyslaw Gorzelak, Jihpai Lin, Piotr Duda, Tatsuo OjiAbstract:Marine organisms are uncommonly preserved in amber. Recently, they were reported to be associated with Burmese amber. However, most of specimens from previous reports were preserved on the amber surface or within the sediment surrounding the amber. Based on X-ray tomography and thin-section optical microscopy of Burmese amber, we report here the first genuine and unambiguous evidence of inclusion of Crinoid ossicles preserved in the fossil resin. Preservation of this exclusively marine group in amber gives insights into the paleoenvironment of the Crinoid-amber association and provides additional evidence to support previous observations of shallow-water stalked Crinoids from the mid-Cretaceous, when many stalked Crinoids started to shift offshore due to increased predation pressure during the Mesozoic Marine Revolution. Crinoid remains, represented by disarticulated stem and arm ossicles assignable to Isocrinus cf. legeri (Repelin), point to a mid-Cretaceous age for the Burmese amber and support some previous hypotheses suggesting a close proximity between the resin-producing trees and seawater.
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lakotacrinus brezinai n gen n sp a new stalked Crinoid from cold methane seeps in the upper cretaceous campanian pierre shale south dakota united states
Journal of Paleontology, 2016Co-Authors: Aaron W Hunter, Neal L Larson, Neil H Landman, Tatsuo OjiAbstract:Despite a rich and varied record, Mesozoic stalked Crinoids are relatively rare in the Western Interior Seaway of North America compared to those found in Northern Europe. A unique example of Mesozoic stalked Crinoid is described from cold methane seeps (hydrocarbon seep mounds also called “tepee buttes”) from the Upper Cretaceous (upper Campanian) of the Northern Great Plains of the United States; the first Crinoids to be described from such an environment. The Late Cretaceous Western Interior Seaway has never before yielded any identifiable stalked Crinoid remains. Nevertheless, there have been significant studies on both free living and stalked Crinoids from other locations in the Upper Cretaceous of North America that provide a good basis for comparison. Lakotacrinus brezinai n. gen. n. sp. is characterized by a tapering homeomorphic column with through-going tubuli, lacking any attachment disc. The arms are unbranched and pinnulate, with muscular and syzygial articulations. The unique morphology of the column justifies the establishment of Lakotacrinidae new family. A new suborder Lakotacrinina n. subord., is also proposed as there exists no corresponding taxon within the Articulata that can accommodate all the characteristics of this new genus. This new Crinoid shares many features with other members of the articulates, including bathycrinids, bourgueticrinids and guillecrinids within the Order Comatulida, as currently defined in the revised Treatise of Invertebrate Paleontology. Reconstructing the entire Crinoid using hundreds of semi-articulated and disarticulated (well preserved) fossils, reveals a unique paleoecology and functional morphology specifically adapted to living within this hydrocarbon seep environment.
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The Oldest Post-Palaeozoic Crinoid and Permian-Triassic Origins of the Articulata (Echinodermata)
Zoological science, 2015Co-Authors: Tatsuo Oji, Richard J. TwitchettAbstract:The Crinoidea are the most primitive class of living echinoderms, and suffered a severe crisis during the Late Permian mass extinction event. All post-Palaeozoic Crinoids, including living species, belong to the Articulata, and morphological and recent molecular studies demonstrate that they form a monophyletic clade. The Articulata originated from Palaeozoic cladid Crinoids, but the nature and timing of their origination remains obscure. Problems with understanding the origin and early evolution of the Articulata have arisen because the Permian—Triassic Crinoid fossil record is particularly poor. We report on a new genus and species from the earliest Triassic, which is the oldest known post-Palaeozoic articulate Crinoid and fundamentally alters our understanding of the early evolution of the Articulata. Prior to this study, the most primitive post-Palaeozoic articulate was thought to be Holocrinus of the order Isocrinida. Unexpectedly, the new taxon belongs to the order Encrinida, which reveals a previously hidden diversity of Crinoids in the earliest Triassic. Its discovery implies either a dramatic radiation of Crinoids in the immediate post-extinction aftermath, when environmental conditions were at their most severe, or a pre-extinction origin of the crown group articulates and survival of multiple lineages.
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Discovery of dense aggregations of stalked Crinoids in Izu-Ogasawara trench, Japan.
Zoological science, 2009Co-Authors: Tatsuo Oji, Aaron W Hunter, Yujiro Ogawa, Kota KitazawaAbstract:Stalked Crinoids are recognized as living fossils that typically inhabit modern deep-water environments exceeding 100 m. Previous records of stalked Crinoids from hadal depths (exceeding 6000 m) are extremely rare, and no in-situ information has been available. We show here that stalked Crinoids live densely on rocky substrates at depths over 9000 m in the Izu-Ogasawara Trench off the eastern coast of Japan, evidenced by underwater photos and videos taken by a remotely operated vehicle. This is the deepest in-situ observation of stalked Crinoids and demonstrates that Crinoid meadows can exist at hadal depths close to the deepest ocean floor, in a fashion quite similar to populations observed in shallower depths.
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Food composition of Crinoids (Crinoidea: Echinodermata) in relation to stalk length and fan density: their paleoecological implications
Marine Biology, 2007Co-Authors: Kota Kitazawa, Tatsuo Oji, Michinari SunamuraAbstract:Crinoids have been diverse organisms in marine epifaunal filter feeding communities at any level of tiering above the substrate since they appeared in the Ordovician. Feeding is regarded as the most important factor in producing the Crinoid tiering, which is primarily defined by stalk length. The gut contents of five sympatric Crinoid species (three isocrines and two comatulids) were observed, and these were compared with the stalk length and the fan density. We have classified these Crinoid species into four groups based on the stalk length and fan density, e.g., long stalk with low fan density, long stalk with high fan density, short stalk with low fan density, and short stalk with high fan density. In the gut contents, diatom crusts were found mainly from species with longer stalks, and chlorophyll-like fluorescent material were only detected from the groups with a shorter or no stalk. The group with lower fan density contained more inorganic particles than the group with higher fan density. Therefore, the gut contents and their amounts depend on their stalk lengths and their fan densities. The results imply that diversified morphologies in the Crinoids have evolved through adaptations to different ecological factors such as difference in their diets.
Stephen K. Donovan - One of the best experts on this subject based on the ideXlab platform.
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Neogene Crinoids of southeast Asia: preservation, systematics and significance
Alcheringa: An Australasian Journal of Palaeontology, 2016Co-Authors: Stephen K. Donovan, Renate A. HelwerdaAbstract:Donovan, S.K. & Helwerda, R.A., August 2016. Neogene Crinoids of southeast Asia: preservation, systematics and significance. Alcheringa 41, xxx–xxx. ISSN 0311-5518.The Cenozoic record of fossil Crinoids is poor. In part, this is because the stalked taxa have moved into deep water (>100–150 m water depth) since the Cretaceous, but also results from the propensity for the Crinoid endoskeleton to disarticulate soon after death. Despite this, we report two new, small Crinoid faunas of moderate diversity from the Pliocene of East Kalimantan and the Philippines. Included taxa are columnals of the isocrinid Metacrinus? sp.; a bourgueticrinid cup and columnal, Democrinus? sp.; and cirral and brachial ossicles (isocrinids and comatulids). The preservation of these Pliocene Crinoids is not conducive to classification to the level of species, although some taxa are easier to determine than others, but the precise reason for this dearth of complete specimens remains uncertain. Because of our knowledge of extant crino...
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where are all the Crinoids an enigma of the lower carboniferous mississippian white peak of midland england
Geology Today, 2013Co-Authors: Stephen K. DonovanAbstract:A glut of fossil Crinoids does not lead to a succession being recognised as rich in Crinoids. Crinoid palaeontology relies on cups, crowns and complete specimens, not fragments. The Carboniferous Limestone of the White Peak is rich in Crinoid fragments, but depauperate in named Crinoids. Something needs to be done.
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Was autotomy a pervasive adaptation of the Crinoid stalk during the Paleozoic
Geology, 2012Co-Authors: Stephen K. DonovanAbstract:The Crinoids were the most diverse and numerically most common echinoderms in the Paleozoic, as well as being one of the most important groups of sessile invertebrates. Autotomy (self-mutilation) in the stem, that is, the casting off of the more distal part, is only known to occur in one extant group of Crinoids, the post-Paleozoic isocrinine sea lilies. These Crinoids have a long distal stalk with regularly spaced articulations (i.e., cryptosymplexies) adapted for autotomy. They are connected together by short, mutable collagenous tissues that undergo irreversible destabilization during autotomy; the distal opening of the axial canal is then sealed by new growth of calcite. Paleozoic Crinoids lacked cryptosymplectial articulations, but have other adaptations that may have singly or collectively facilitated autotomy. These include the linking of adjacent short lengths of stalk (i.e., noditaxes) by short ligaments; the evolutionary trend to narrow the axial canal; occlusion of the axial canal in some species; and the ability to seal the axial canal. Other morphological features of relevance to autotomy include the common division of the stem into morphologically distinct regions and attachment by a distal, recumbent radicular runner. The ability to autotomize the distal stem in many Paleozoic Crinoid clades was, at the very least, latent; if overt, it would have facilitated escape from environmental disturbance. It may, in part, explain the great abundance of disarticulated Crinoid stem fragments in many Ordovician to Permian sedimentary deposits.
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The poorly illustrated Crinoid
Lethaia, 2011Co-Authors: Stephen K. DonovanAbstract:Donovan, S.K. 2011: The poorly illustrated Crinoid. Lethaia, Vol. 44, pp. 125–135. Artistic licence is kept under firm control when restoring fossil tetrapods and their natural environments, but the same care is not always applied to reconstructions of ancient invertebrates. Selected renderings of fossil Crinoids illustrate grossly inaccurate skeletal geometry and outmoded ideas of palaeoautecology. Together, these combine to give the public an incorrect impression of what a fossil Crinoid looked like and how it lived, in some instances inferior to what was possible in the 19th century. The reason why Crinoids receive such poor service from artists is, in part, probably due to their being exotic; humans and other tetrapods are a common part of our experience, whereas stalked Crinoids, although extant, can only be seen in life with the aid of a research submersible in deep water (>100 m). Crinoids also have a complex endoskeleton that requires care in illustration. They are unusual creatures in an alien environment even at the present day. But echinoderm palaeontologists need to be more energetic in promoting the correct depiction of ancient species. □Crinoidea, illustration, morphology, palaeoenvironments, reconstruction.
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The cladid Crinoid Gissocrinus Angelin from Wenlock Edge, Shropshire (Silurian)
Proceedings of the Yorkshire Geological Society, 2008Co-Authors: Stephen K. Donovan, D. N. Lewis, C. J. VeltkampAbstract:Summary Complete fossil Crinoids are well known from the Much Wenlock Limestone Formation (Silurian, Wenlock, Homerian), but are only common in the Dudley area of the West Midlands. Elsewhere, Wenlock Crinoids are preserved as disarticulated ossicles. For example, only about six nominal Crinoids are known from the type area of the Much Wenlock Limestone Formation on Wenlock Edge. Herein, we document abundant remains of the cladid Crinoid Gissocrinus spp. from near Much Wenlock, Shropshire, based on common brachial and rare radial ossicles. Brachials are mainly thin and quadrate with a U-shaped adoral groove. There are six nominal species of Gissorcrinus in the Wenlock of the British Isles; probability suggests that this sample contains elements of more than one species.