Relevant bibliographies by topics / Tommotiids

Academic literature on the topic 'Tommotiids'

Author: Grafiati
Published: 10 December 2022
Last updated: 28 January 2023

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Journal articles on the topic "Tommotiids"

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Holmer, Lars E., Christian B. Skovsted, Glenn A. Brock, James L. Valentine, and John R. Paterson. "The Early Cambrian tommotiid Micrina , a sessile bivalved stem group brachiopod." Biology Letters 4, no. 6 (June 24, 2008): 724–28. http://dx.doi.org/10.1098/rsbl.2008.0277.

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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.
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Skovsted, Christian B., Lars E. Holmer, Cecilia M. Larsson, Anette E. S. Högström, Glenn A. Brock, Timothy P. Topper, Uwe Balthasar, Sandra Petterson Stolk, and John R. Paterson. "The scleritome of Paterimitra : an Early Cambrian stem group brachiopod from South Australia." Proceedings of the Royal Society B: Biological Sciences 276, no. 1662 (January 20, 2009): 1651–56. http://dx.doi.org/10.1098/rspb.2008.1655.

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Early Cambrian tommotiids are problematic fossil metazoans with external organophosphatic sclerites that have been considered to be basal members of the lophophorate stem group. Tommotiids are almost exclusively known from isolated or rarely fused individual sclerites, which made previous reconstructions of the actual organism highly conjectural. However, the recent discovery of the first articulated specimens of the tommotiid Eccentrotheca revealed a tubular sclerite arrangement (scleritome) that limited the possible life habit to sessile filter feeding and thus further supported a lophophorate affinity. Here, we report the first articulated specimens of a second tommotiid taxon, Paterimitra from the Early Cambrian of the Arrowie Basin, South Australia. Articulated specimens of Paterimitra are composed of two bilaterally symmetrical sclerite types and an unresolved number of small, asymmetrical and irregular crescent-shaped sclerites that attached to the anterior margin of the symmetrical sclerites. Together, the sclerites form an open cone in which the symmetrical sclerites are joined together and form a small posterior opening near the base of the scleritome, while the irregular crescent-shaped sclerites defined a broad anterior opening. The coniform scleritome of Paterimitra is interpreted to have attached to hard substrates via a pedicle that emerged through the small posterior opening (sometimes forming a tube) and was probably a sessile filter feeder. The scleritome of Paterimitra can be derived from the tubular scleritome of Eccentrotheca by modification of basal sclerites and reduction in tube height, and probably represents a more derived member of the brachiopod stem group with the paired symmetrical sclerites possibly homologous to brachiopod valves.
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Morris, S. Conway, and Chen Menge. "Tommotiids from the Lower Cambrian of South China." Journal of Paleontology 64, no. 2 (March 1990): 169–84. http://dx.doi.org/10.1017/s0022336000018345.

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Tommotiids are a geologically short-lived group of early skeletal fossils, most abundant in the Lower Cambrian. Redescriptions of a lapworthellid (Lapworthella rete Yue, 1987) and a tannuolinid (Tannuolina zhangwentangi Qian and Bengtson, 1989) from the Jiulaodong Formation, Maidiping, Sichuan, augment previous accounts. Lapworthella rete approaches the L. dentata–L. schodackensis complex, but has a prominent external pattern of polygons that probably represent imprints of epithelial cells. Description of Tannuolina zhangwentangi emphasises ultrastructural features, including the mode of growth, development of canals, and possible epithelial imprints on the interior surfaces. Data on size variation of epithelial imprints in tommotiids are reviewed to try to infer possible variations in genome content of the cells. In addition, poorly preserved lapworthellids (Lapworthella sp.) are described from the Qiongzhusi Formation, Meishucun, Yunnan.
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Balthasar, U., C. B. Skovsted, L. E. Holmer, and G. A. Brock. "Homologous skeletal secretion in tommotiids and brachiopods." Geology 37, no. 12 (December 1, 2009): 1143–46. http://dx.doi.org/10.1130/g30323a.1.

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Novozhilova, N. V., M. Steiner, I. V. Korovnikov, and D. A. Tokarev. "Early Cambrian Tommotiids of Khairkhan Section (Central Tyva)." Paleontological Journal 53, no. 6 (November 2019): 575–82. http://dx.doi.org/10.1134/s0031030119060091.

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Teece, Bronwyn L., Glenn A. Brock, John R. Paterson, Christian B. Skovsted, Lars E. Holmer, and Simon C. George. "Using laser micropyrolysis to assess potential relationships between Cambrian tommotiids and organophosphatic brachiopods." Journal of Analytical and Applied Pyrolysis 158 (September 2021): 105277. http://dx.doi.org/10.1016/j.jaap.2021.105277.

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HOLMER, LARS E., CHRISTIAN B. SKOVSTED, CECILIA LARSSON, GLENN A. BROCK, and ZHIFEI ZHANG. "First record of a bivalved larval shell in Early Cambrian tommotiids and its phylogenetic significance." Palaeontology 54, no. 2 (January 12, 2011): 235–39. http://dx.doi.org/10.1111/j.1475-4983.2010.01030.x.

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Butler, Aodhán D., Michael Streng, Lars E. Holmer, and Loren E. Babcock. "Exceptionally preserved Mickwitzia from the Indian Springs Lagerstätte (Cambrian Stage 3), Nevada." Journal of Paleontology 89, no. 6 (November 2015): 933–55. http://dx.doi.org/10.1017/jpa.2016.8.

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AbstractExceptionally preserved specimens of the Cambrian stem-group brachiopod Mickwitzia occidens Walcott, 1908 are described in detail from the Indian Springs Lagerstätte in Nevada, USA. Shell structure and preserved mantle setae from these specimens reveal a variable diagenetic (taphonomic) history and provide insight into the phylogenetic position of mickwitziids. Morphologic and morphometric comparison to M. monilifera (Linnarsson, 1869) from Sweden and M. muralensis Walcott, 1913 from British Columbia, Canada reveals clear species-level distinctions. Scanning electron microscopic analysis allows revision of the generic diagnosis. The Mickwitzia shell is characterized by the presence of inwardly pointing phosphatic cones and tangential setae-bearing tubes. The inwardly pointing cone structures are not consistent with setal bearing structures as previously thought, but rather represent endopunctae-like structures. Acrotretid-like shell structures and shell-penetrating setae in M. occidens strengthen the previously proposed close relationship between stem-group brachiopods and tommotiids, a group of small shelly fossils.
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Parry, Luke A., Gregory D. Edgecombe, Dan Sykes, and Jakob Vinther. "Jaw elements in Plumulites bengtsoni confirm that machaeridians are extinct armoured scaleworms." Proceedings of the Royal Society B: Biological Sciences 286, no. 1907 (July 24, 2019): 20191247. http://dx.doi.org/10.1098/rspb.2019.1247.

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Machaeridians are Palaeozoic animals that are dorsally armoured with serialized, imbricating shell plates that cover or enclose the body. Prior to the discovery of an articulated plumulitid machaeridian from the Early Ordovician of Morocco that preserved unambiguous annelid characters (segmental parapodia with chaetae), machaeridians were a palaeontological mystery, having been previously linked to echinoderms, barnacles, tommotiids (putative stem-group brachiopods) or molluscs. Although the annelid affinities of machaeridians are now firmly established, their position within the phylum and relevance for understanding the early evolution of Annelida is less secure, with competing hypotheses placing Machaeridia in the stem or deeply nested within the crown group of annelids. We describe a scleritome of Plumulites bengtsoni from the Fezouata Formation of Morocco that preserves an anterior jaw apparatus consisting of at least two discrete elements that exhibit growth lines. Although jaws have multiple independent origins within the annelid crown group, comparable jaws are present only within Phyllodocida, the clade that contains modern aphroditiforms (scaleworms and relatives). Phylogenetic analysis places a monophyletic Machaeridia within the crown group of Phyllodocida in total-group Aphroditiformia, consistent with a common origin of machaeridian shell plates and scaleworm elytrae. The inclusion of machaeridians in Aphroditiformia truncates the ghost lineage of Phyllodocida by almost a hundred million years.
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Skovsted, Christian B., Sébastien Clausen, Javier J. Álvaro, and Deborah Ponlevé. "Tommotiids from the early Cambrian (Series 2, Stage 3) of Morocco and the evolution of the tannuolinid scleritome and setigerous shell structures in stem group brachiopods." Palaeontology 57, no. 1 (January 2014): 171–92. http://dx.doi.org/10.1111/pala.12060.

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Dissertations / Theses on the topic "Tommotiids"

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Larsson, Cecilia M. "Early Cambrian Problematic Lophotrochozoans and Dilemmas of Scleritome Reconstructions." Doctoral thesis, Uppsala universitet, Paleobiologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-180195.

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The emergence and radiation of metazoan body plans around the Precambrian/Cambrian boundary, some 500-600 million years ago, seems to be concordant with the appearance and diversification of preservable hard parts. Several Precambrian soft-bodied, multicellular organisms most likely represent stem-group bilaterians, but their fossil record is rather sparse.  In contrast, the Cambrian fossil record is comparably rich – comprising hard part, trace fossil and delicate soft tissue preservation – and most animal phyla that we know of today had evolved by the end of the Cambrian. Consequently, this time represents an important period in the early evolution of metazoan life forms. Most skeletal remnants of invertebrate organisms from this period are preserved in incomplete, disarticulated sclerite assemblages, and the true architecture of the original skeletal structure, the scleritome, may therefore be hard to discern. Many scleritomous taxa have been suggested to be members of the lophotrochozoan clade, while their exact position within this group remains unclear. Such taxa are often referred to as Problematica. This thesis deals with some problematic scleritomous early Cambrian lophotrochozoans, and as such also addresses the dilemmas of scleritome reconstructions. In the first part, completely disarticulated calcareous sclerites from the lower Cambrian of North Greenland are described as Trachyplax arctica. Hypothetical scleritome reconstruction alternatives and comparisons to other scleritome-bearing taxa are discussed, but the lack of articulated material obscures any satisfactory conclusions regarding phylogenetic affinities and the original morphology of the organism. The other part of the thesis focuses on some minute, organophosphatic scleritomous metazoans, tommotiids, found in lower Cambrian limestone successions in South Australia – Paterimitra pyramidalis and Kulparina rostrata – their scleritome architecture and their phylogenetic relationship with paterinid brachiopods. The oldest brachiopod from South Australia, Askepasma saproconcha, and the slightly younger Askepasma toddense are also described and discussed. Based on articulated specimens, recently described partial scleritomes of the tommotiid Eccentrotheca helenia and similarities in shell ultrastructure with both Eccentrotheca and Askepasma, Paterimitra is interpreted as a stem-group brachiopod and reconstructed as a bilaterally symmetrical, sessile, filter feeder with a tubular/conical scleritome. The morphological similarities with Paterimitra point in the same direction for the slightly older Kulparina.
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Butler, Aodhán D. "Decoding the fossil record of early lophophorates : Systematics and phylogeny of problematic Cambrian Lophotrochozoa." Doctoral thesis, Uppsala universitet, Paleobiologi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-261907.

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The evolutionary origins of animal phyla are intimately linked with the Cambrian explosion, a period of radical ecological and evolutionary innovation that begins approximately 540 Mya and continues for some 20 million years, during which most major animal groups appear. Lophotrochozoa, a major group of protostome animals that includes molluscs, annelids and brachiopods, represent a significant component of the oldest known fossil records of biomineralised animals, as disclosed by the enigmatic ‘small shelly fossil’ faunas of the early Cambrian. Determining the affinities of these scleritome taxa is highly informative for examining Cambrian evolutionary patterns, since many are supposed stem-group Lophotrochozoa. The main focus of this thesis pertained to the stem-group of the Brachiopoda, a highly diverse and important clade of suspension feeding animals in the Palaeozoic era, which are still extant but with only with a fraction of past diversity. Major findings include adding support for tommotiid affinity as stem-group lophophorates. Determining morphological character homologies vital to reconstructing the brachiopod stem-group was achieved by comparing Cambrian Lagerstätten with the widespread biomineralised record of Cambrian stem-brachiopods and small shelly fossils. Polarising character changes associated with the putative transition from scleritome organisms to crown-group brachiopods was furthered by the description of an enigmatic agglutinated tubular lophophorate Yuganotheca elegans from the Chengjiang Lagerstätte, China, which possesses an unusual combination of phoronid, brachiopod and tommotiid characters. These efforts were furthered by the use of X-ray tomographic techniques that revealed novel anatomical features, including exceptionally preserved setae in the tommotiid Micrina. The evidence for a common origin of columnar brachiopod shell structures in the tommotiids is suggested and critically examined. Enigmatic and problematic early and middle Cambrian lophotrochozoans are newly described or re-described in light of new evidence, namely: the stem-brachiopod Mickwitzia occidens Walcott from the Indian Springs Lagerstätte, Nevada; a putative stem-group entoproct Cotyledion tylodes Luo and Hu from Chengjiang, China; a new enigmatic family of rhynchonelliform brachiopods exemplified by the newly described Tomteluva perturbata from the Stephen Formation, Canada; and the tommotiid Micrina etheridgei (Tate) from the Flinders Ranges, South Australia. Cladistic analyses of fossil morphological data supports a monophyletic Brachiopoda.
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Bassett-Butt, Lewis. "The Cambrian lophotrochozoans of the Transantarctic Mountains, Antarctica." Licentiate thesis, Uppsala universitet, Paleobiologi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-252137.

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The origin of many lophotrochozoan groups can be traced to “small shelly fossil” (SSF) faunas of the Early Cambrian. Antarctica is a key region of study, due to the continent’s known close geographical proximity to well-studied Australian and Indian basins in in the Cambrian. Few studies have focused on this region however, due to a paucity of data. Re-examination of camenellan sclerites from the Early Cambrian Shackleton Limestone of the Churchill Mountains of Antarctica has revealed a previously unidentified species of Dailyatia in the formation, co-occurring alongside previously described Dailyatia odyssei Evans and Rowell, 1990, as in the Arrowie Basin of Australia. Re-examination of material previously described as Kennardia sp. A and Kennardia sp. B has indicated that these taxa can likely be synonymized as a second species of Dailyatia. Dailyatia sclerites were also found in the temporally equivalent “Schneider Hills Limestone” formation, which cropsout in the Argentina Range of Antarctica. These specimens appear to belongto a third species of Dailyatia, suggesting that the spatial distribution of tommotiids in the Early Cambrian was more complex than previously recognized, and that the group may be useful in future biostratigraphic studies. A study ofthe Middle Cambrian (Drumian Stage) Nelson Limestone Formation of the Neptune Range, Antarctica has revealed a moderately diverse brachiopod and trilobite fauna. The brachiopods have strong faunal links to taxa from South Australia and India, as well as other parts of the Antarctic province, fitting independent strong evidence for a united East Gondwanan region in the Middle Cambrian. An unidentified camenellan tommotiid sclerite is also described from the Nelson Limestone. This extends the worldwide temporal range of the tommotiid clade into the Drumian Stage, and suggests that more basal members of the brachiopod stem-group survived to form part of a more diverse Middle Cambrian fauna.
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Devaere, Léa. "Microfossiles à paroi squelettique du Cambrien inférieur de Montagne Noire (Sud de la France) : apports chronostratigraphiques, paléogéographiques, paléobiologiques et phylogénétiques." Thesis, Lille 1, 2013. http://www.theses.fr/2013LIL10109.

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L’explosion cambrienne est un événement majeur dans l’évolution des métazoaires et des écosystèmes. Cependant, nos connaissances sur ses patrons et sa chronologie sont encore variables selon les taxons et les zones considérés. Les successions de communautés du Cambrien inférieur de Montagne Noire (France, marge perigondwanienne ouest au Cambrien) sont ainsi mal connues et problématiques pour la subdivision chronostratigraphique internationale de ce système. Les microfossiles biominéralisés des carbonates du Cambrien inférieur de cette zone font ici l’objet d’une analyse (chronobio)stratigraphique et paléobiologique. La révision de la faune des Calcaires à Heraultia (unité d’Avène-Mendic) a permis de corriger leur âge (Terreneuvien au lieu d’Étages 3-4) et supporte l’utilisation de Watsonella crosbyi pour définir la base de l’Étage 2 du Cambrien. Des microfaunes des Étages 3 et 3-4 ont été identifiées dans des niveaux carbonatés supérieurs des formations de Marcory (écaille de Mélagues) et Pardailhan (nappe du Minervois) respectivement. Le schéma stratigraphique régional est ainsi révisé. L’une des plus anciennes plateformes carbonatées de l’ouest du Gondwana est identifiée ; des affinités paléobiogéographiques avec la Chine sont reconnues jusqu’à l’Étage 3 tandis que les faunes de l’Étage 4 sont cosmopolites. La découverte de fossiles exceptionnellement préservés d’orthothécidés avec leur système digestif, de sclérites de tommotiidés et de mickwitziidés ont permis de réévaluer les relations phylogénétiques et les processus évolutifs au sein du clade des hyolithes et du groupe total des tommotiidés-phoronidiens-brachiopodes respectivement
The ‘Cambrian explosion’ is a key event in the evolution of metazoans and ecosystems. However, its patterns, processes and timing are still heterogeneously known depending of the considered taxa and area. For example, the lower Cambrian community succession from the Montagne Noire (France, formerly part of western Gondwana margin) is poorly known but problematic for the international chronostratigraphic subdivision of this period. The herein analysis of lower Cambrian, skeletonised microfossils from carbonates of this area is aimed at improving the regional and international chronostratigraphy and illustrating the early evolution of selected taxa. The Heraultia Limestone fauna (Marcou Formation, Avène-Mendic unit) is revised and redated from Stages 3-4 to Terreneuvian, supporting the use of the included Watsonella crosbyi for the definition of the base of the international Cambrian Stage 2. Cambrian Stages 3 and 3-4 microfaunas are identified in carbonate beds and lenses from the uppermost Marcory Formation (Mélagues slice) and the upper Pardailhan Formation (Minervois nappe) respectively. This study allows the redefinition of the regional stratigraphic scheme of the Montagne Noire. It identifies one of the earliest carbonate platforms (Terreneuvian) from western Gondwana with Chinese palaeobiogeographic affinities which maintains till Stage 3 while Stage 4 contains a cosmopolitan fauna. In parallel, the discovery of exceptionally preserved orthothecids with digestive tract, tommotiid sclerites and mickwitziids allowed a reappraisal of phylogenetic relationships and evolutionary processes among hyolith clade and tommotiids-phoronids-brachiopods total group respectively
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Conference papers on the topic "Tommotiids"

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Fjeld, Alyssa, Glenn A. Brock, and Zhiliang Zhang. "DECIPHERING EARLY CAMBRIAN LOPHOTROCHOZOAN RELATIONSHIPS USING TOMMOTIID SCLERITE MICROORNAMENT AND ULTRASTRUCTURE." In GSA Connects 2021 in Portland, Oregon. Geological Society of America, 2021. http://dx.doi.org/10.1130/abs/2021am-369015.

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