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Journal articles on the topic 'Tommotiids'

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Published: 10 December 2022

Last updated: 28 January 2023

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1

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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2

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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3

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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4

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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5

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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6

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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7

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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8

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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9

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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10

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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11

MURDOCK, DUNCAN J. E., PHILIP C. J. DONOGHUE, STEFAN BENGTSON, and FEDERICA MARONE. "Ontogeny and microstructure of the enigmatic Cambrian tommotiid Sunnaginia Missarzhevsky, 1969." Palaeontology 55, no. 3 (February 10, 2012): 661–76. http://dx.doi.org/10.1111/j.1475-4983.2012.01131.x.

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12

Pan, Bing, Glenn A. Brock, Christian B. Skovsted, Marissa J. Betts, Timothy P. Topper, and Guoxiang Li. "Paterimitra pyramidalis Laurie, 1986, the first tommotiid discovered from the early Cambrian of North China." Gondwana Research 63 (November 2018): 179–85. http://dx.doi.org/10.1016/j.gr.2018.05.014.

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13

Sun, Haijing, Martin R. Smith, Han Zeng, Fangchen Zhao, Guoxiang Li, and Maoyan Zhu. "Hyoliths with pedicles illuminate the origin of the brachiopod body plan." Proceedings of the Royal Society B: Biological Sciences 285, no. 1887 (September 26, 2018): 20181780. http://dx.doi.org/10.1098/rspb.2018.1780.

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Hyoliths are a taxonomically problematic group of Palaeozoic lophotrochozoans that are among the first shelly fossils to appear in the Cambrian period. On the basis of their distinctive exoskeleton, hyoliths have historically been classified as a separate phylum with possible affinities to the molluscs, sipunculans or lophophorates—but their precise phylogenetic position remains uncertain. Here, we describe a new orthothecide hyolith from the Chengjiang Lagerstätte (Cambrian Series 2 Stage 3), Pedunculotheca diania Sun, Zhao et Zhu gen. et sp. nov., which exhibits a non-mineralized attachment structure that strikingly resembles the brachiopod pedicle—the first report of a peduncular organ in hyoliths. This organ establishes a sessile, suspension feeding ecology for these orthothecides and—together with other characteristics (e.g. bilaterally symmetrical bivalve shell enclosing a filtration chamber and the differentiation of cardinal areas)—identifies hyoliths as stem-group brachiopods. Our phylogenetic analysis indicates that both hyoliths and crown brachiopods derived from a tommotiid grade, and that the pedicle has a single origin within the brachiopod total group.

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14

Morris, Simon Conway, and Stefan Bengtson. "Cambrian predators: possible evidence from boreholes." Journal of Paleontology 68, no. 1 (January 1994): 1–23. http://dx.doi.org/10.1017/s0022336000025567.

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Boreholes in Cambrian shells are rarely reported but are a potentially significant source of information on levels of predation in early metazoan communities. This paper documents boreholes in a wide variety of Cambrian organisms. Particular attention is devoted to two species of the inarticulate brachiopod Linnarssonia (informally L. sp. A and L. sp. B) from the Middle Cambrian of southern Sweden (Brantevik, Forsemölla) and Bornholm (Læså, ⊘leå). Both successful and abortive holes occur, and both brachial and pedicle valves were attacked. Almost 20 percent of the valves of Linnarssonia sp. B from ⊘leå have successful boreholes, whereas in L. sp. A from Brantevik only 1.4 percent of the valves are bored. The proportion of successful bores in brachial and pedicle valves also varies widely, from 0.8:1 in L. sp. A (Forsemölla) to 5.8:1 in L. sp. B (Læså), although taphonomic bias caused by preferential removal of pedicle valves of L. sp. B may have distorted this ratio. The abundance and distribution of abortive holes also shows variation, with a maximum of 16.3 percent of L. sp. B from Forsemölla and a minimum of 1 percent in L. sp. B from Læså. Preference for brachial or pedicle valves among abortive holes is variable, ranging from 0.3:1 in L. sp. B (Læså) to 6.9:1 in the same species from ⊘leå. With one exception (L. sp. B from Forsemölla) successful bores always outnumber abortives, but the ratio in brachial and pedicle valves varies widely with a maximum in favor of successful bores being reached in brachial valves of L. sp. A from Læså (6:1). Boreholes are nonrandomly distributed. In L. sp. A and L sp. B successful attacks on brachial valves were concentrated in a central zone. Attacks were more scattered in the pedicle valves, although in L. sp. A boreholes tended to occur on the left-hand side. Abortive and successful bores in the enigmatic fossil Mobergella holsti, from the Lower Cambrian of Skäggenäs, southern Sweden, show a conspicuous concentration in the apical region. In addition, boreholes in Lower Cambrian material from Australia (the pseudobrachiopod Aroonia, the tommotiid Micrina) and eastern Siberia (brachiopods, and possibly echinoderms and the tommotiid Lapworthella) are reported. All these bores are attributed to the activity of predators, whose systematic affinities remain uncertain. Holes in tubicolous torellellids from northern Tamdytau, however, may alternatively represent attachment scars of other torellellids.

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15

Skovsted, Christian B., Glenn A. Brock, John R. Paterson, Lars E. Holmer, and Graham E. Budd. "The scleritome of Eccentrotheca from the Lower Cambrian of South Australia: Lophophorate affinities and implications for tommotiid phylogeny." Geology 36, no. 2 (2008): 171. http://dx.doi.org/10.1130/g24385a.1.

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16

DEVAERE, L., and C. B. SKOVSTED. "New early Cambrian sclerites ofLapworthella schodakensisfrom NE Greenland: advancements in knowledge of lapworthellid taxonomy, sclerite growth and scleritome organization." Geological Magazine 154, no. 5 (August 2, 2016): 1061–72. http://dx.doi.org/10.1017/s0016756816000698.

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AbstractThe Cambrian Stage 4 upper Bastion Formation of Albert Heim Bjerge and CH Ostenfeld Nunatak, NE Greenland, yielded 34 excellently preserved sclerites ofLapworthella schodackensisamong other small shelly fossils. Lapworthellids have been interpreted as members of the camenellans, a basal tommotiid group. Little is known about this group although the morphological and ultrastructural features of their sclerites allow a potential reconstruction of a lophophorate body plan. The exquisite material from Greenland provides significant new data for the revision of the species taxonomy, but also for the comprehension of the scleritome structure of lapworthellids and the mode of formation of their sclerites. Two morphotypes ofL. schodackensissclerites are identified: one with a simple apex, occurring in sinistral and dextral forms; and one bilaterally symmetrical sclerite with two apices. All bear a similar ornamentation constructed of repeated growth sets consisting of a reticulate inter-rib groove with tubercles, a densely denticulate rib and a striated sub-rib area. The new data on the ornamentation and observations of the laminar shell microstructure ofL. schodackensisenable us to improve the reconstruction of growth in lapworthellids. Finally, the morphological features of the two types of sclerites provide new information for the reconstruction of the bilaterally symmetrical multi-component lapworthellid scleritome with evidence of the fusion of adjacent sclerites during early ontogeny.

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17

SKOVSTED, CHRISTIAN B., GLENN A. BROCK, TIMOTHY P. TOPPER, JOHN R. PATERSON, and LARS E. HOLMER. "Scleritome construction, biofacies, biostratigraphy and systematics of the tommotiid Eccentrotheca helenia sp. nov. from the Early Cambrian of South Australia." Palaeontology 54, no. 2 (March 2011): 253–86. http://dx.doi.org/10.1111/j.1475-4983.2010.01031.x.

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18

Landing, Ed. "Upper Placentian—Branchian series of mainland Nova Scotia (middle-upper Lower Cambrian): Faunas, paleoenvironments, and stratigraphic revision." Journal of Paleontology 69, no. 3 (May 1995): 475–95. http://dx.doi.org/10.1017/s0022336000034879.

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Lithostratigraphy and depositional and epeirogenic history of the upper Placentian Series (Cuslett-Fosters Point Formations of the Bonavista Group) and Branchian Series (Brigus Formation) are identical in the northern Antigonish Highlands; Cape Breton Island; and eastern Placentia Bay, southeastern Newfoundland. Preliminary evidence suggests that the lower Middle Cambrian is present in the field area. A unified, uppermost Precambrian–Lower Cambrian, formation- and member-level nomenclature is appropriate to Avalonian North America, and the stratigraphic nomenclature of southeastern Newfoundland is applied in northern mainland Nova Scotia.Latest Placentian shoaling and deposition of a peritidal carbonate lithosome and unconformable onlap of the trilobite-bearing Branchian Series occurred in shallow Avalonian shale basins from eastern Massachusetts to central England.Uppermost Placentian Series faunas are very diverse in the Fosters Point Formation. Limited similarities with the South Australian Lower Cambrian are indicated by the presence of Camenella sp. cf. C. reticulosa, Conotheca australiensis, and Hyptiotheca sp., but these forms do not contribute to highly resolved correlation.Twenty-eight taxa are illustrated from the upper Placentian and Branchian Series. Caveacus rectus n. gen. and sp., a phosphatic problematicum, is limited to the upper Placentian Series. The oldest, skeletalized, macrophagous predators are the Pseudoconodontida and the later appearing Protoconodontida (n. orders). The Pseudoconodontida includes the Protohertzinacea n. superfamily and Strictocorniculacea n. superfamily (with the Rhombocorniculidae and Strictocorniculidae n. families). Strictocorniculum vanallerum n. gen. and sp. is described. The tommotiid family Sunnaginiidae emend. includes Eccentrotheca, Sunnaginia, Kulparina, and Jayceia deltiformis n. gen. and sp.

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19

Bengtson, Stefan. "A new mongolian species of the lower cambrian genus camenella and the problems of scleritome-based taxonomy of the tommotiidae." Paläontologische Zeitschrift 60, no. 1-2 (June 1986): 45–55. http://dx.doi.org/10.1007/bf02989421.

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20

Claybourn, Thomas, Christian Skovsted, Marissa Betts, Lars Holmer, Lucy Bassett-Butt, and Glenn Brock. "Camenellan tommotiids from the Cambrian Series 2 of East Antarctica: biostratigraphy, palaeobiogeography, and systematics." Acta Palaeontologica Polonica 66 (2021). http://dx.doi.org/10.4202/app.00758.2020.

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21

Wallet, Elise, Maxime Padel, Léa Devaere, Sébastien Clausen, J. Javier Álvaro, and Bernard Laumonier. "Cambrian Age 3 small shelly fossils from the Terrades inlier, southern Pyrenees, Spain: Biostratigraphic and paleobiogeographic implications." Journal of Paleontology, February 28, 2022, 1–31. http://dx.doi.org/10.1017/jpa.2021.123.

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Abstract The Cambrian stratigraphic succession of the Pyrenees (SW Europe) has undergone a complex Variscan and Alpine tectonothermal history leading to marked metamorphism and development of cleavage networks, which might partly explain the lack of Cambrian fossiliferous beds. This gap has traditionally precluded its paleobiogeographic and biostratigraphic relationships with other neighboring peri-Gondwanan units. Correlations are only based on lithostratigraphic comparisons and radiometric constraints. In this general scheme, the Terrades inlier (Gerona Province, Spain) provides the only significant and indisputable ‘early Cambrian’ fossil record of the Pyrenees. This predominantly siliciclastic outcrop consists of multiple patch reefs and bioherms having yielded archeocyaths dated at Cambrian Epoch 2, Age 3. This paper describes, for the first time, the microfossil assemblage included in the archeocyathan-microbial reefal complex that crops out in the Terrades inlier to clarify its age and affinities with surrounding tectonostratigraphic units. Reefal flanks of patch reefs have yielded bradoriids, brachiopods, molluscs, tommotiids, chancelloriids, hyoliths, and the problematic fossil (and chronostratigraphically significant) Rhombocorniculum cancellatum Cobbold, 1921. In addition to confirming the previously assigned age of the succession, the recovered fauna emphasizes strong affinities with the surrounding Occitan Domain (Montagne Noire, southern Massif Central, France) and Sardinia (Italy). Along with lithostratigraphic comparison and tectonic considerations, this further supports the recent reconstructions positioning the Pyrenean domain between the Montagne Noire (to the southwest) and Sardinia (further to the northeast) on the Gondwana margin during Cambrian times.

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22

Skovsted, C. B. "A silicified tommotiid from the lower Cambrian of Greenland." Bulletin of Geosciences, November 25, 2016, 553–59. http://dx.doi.org/10.3140/bull.geosci.1609.

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23

Guo, Jin, Luke A. Parry, Jakob Vinther, Gregory D. Edgecombe, Fan Wei, Jun Zhao, Yang Zhao, et al. "A Cambrian tommotiid preserving soft tissues reveals the metameric ancestry of lophophorates." Current Biology, September 2022. http://dx.doi.org/10.1016/j.cub.2022.09.011.

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24

Devaere, Léa, and Christian B. Skovsted. "The youngest known tommotiid: Lapworthella bornholmiensis (Poulsen, 1942) from Cambrian Stage 4 to Guzhangian (Miaolingian) strata of Bornholm and southern Sweden." GFF, July 22, 2021, 1–17. http://dx.doi.org/10.1080/11035897.2021.1913761.

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