| 1. |
- Hairapetian, Vachik, et al.
(författare)
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Ordovician of the Anarak Region : implications in understanding Early Palaeozoic history of Central Iran
- 2015
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Ingår i: Stratigraphy. - 1547-139X .- 2331-656X. ; 12:2, s. 22-30
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Tidskriftsartikel (refereegranskat)abstract
- The Pol-e Khavand area south-east of the town of Anarak preserves important clues for understanding geological evolution of Central Iran during the Palaeozoic. New observations confirm the non-conformable relationship between Doshakh metamorphites and overlying unmetamorphosed Lower Palaeozoic sediments, suggesting accretion of the volcanic arc in front of the Yazd block sometime in the late Cambrian to early Ordovician. The newly introduced volcano-sedimentary Polekhavand Formation preserves evidence of a ?Late Cambrian to Early Ordovician post-collisional bimodal volcanism and related extensional regime in the Pol-e Khavand area during that time. The Middle to Upper Ordovician interval of the studied succession is assigned to the newly introduced Chahgonbad Formation. The Darriwilian age of the base of this lithostratigraphical unit is demonstrated by the brachiopods Tritoechia and Yangtzeella which co-occur with a diverse a cephalopod assemblage. The low diversity fauna including brachiopods Hibernodonta sp., Hindella sp., Rostricellula cf. ambigena and trilobites Vietnamia cf. teichmulleri suggest a Katian age for the upper part of the unit. There is insufficient evidence for the existence of the hypothetical Palaeo Tethys suture zone south of the Pol-e Khavand area.
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| 2. |
- Harper, David A.T., et al.
(författare)
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Brachiopods : origin and early history
- 2017
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Ingår i: Palaeontology. - : Wiley. - 0031-0239 .- 1475-4983. ; 60:5, s. 609-631
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Tidskriftsartikel (refereegranskat)abstract
- Despite many major advances in recent years, three key challenges remain in bringing clarity to the early history of the phylum: (1) identifying the origin, morphology and life modes of the first brachiopods; (2) understanding the relationships of the major groups to each other and higher sister taxa; and (3) unravelling the roles of the Cambrian and Ordovician radiations that set the agenda for much of subsequent brachiopod evolution. Since some 95% of all brachiopod taxa are extinct, the fossil record is the primary source of data to frame and test models for the evolution of the phylum. The acquisition of new, and the redescription of existing faunas, in precise spatial and temporal frameworks, using new and well-established analytical and investigative techniques, are as important as ever.
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| 3. |
- Holmer, Lars E., 1960-, et al.
(författare)
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Cambrian rhynchonelliform nisusioid brachiopods : phylogeny and distribution
- 2019
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Ingår i: Papers in Palaeontology. - : John Wiley & Sons. - 2056-2799 .- 2056-2802. ; 5:3, s. 559-575
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Tidskriftsartikel (refereegranskat)abstract
- A comprehensive review and phylogenetic analysis of genera and species presently assigned to the rhynchonelliform superfamily Nisusioidea and family Nisusiidae suggests that this short-lived but important group of brachiopods first appeared in peri-Gondwana during the second half of the Cambrian Series 2, before going extinct by the end of Drumian times. Nisusiides achieved their maximum morphological disparity and geographical distribution during the Wuliuan Age, and Laurentia was probably the major centre of their dispersal. A new phylogenetic analysis suggests an early separation of the lineages of spinose and non-spinose nisusiids. The non-spinose nisusiids probably evolved in Laurentia by the end of Cambrian Series 4. The new nisusiid genus Bellistrophia is described. The new species Nisusia multicostata represents the first documented rhynchonelliform (kutorginide) brachiopod from the Miaolingian (Drumian) of the Alborz Mountains, Iran.
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| 4. |
- Holmer, Lars E., et al.
(författare)
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Ecology, biofacies, biogeography and systematics of micromorphic lingulate brachiopods from the Ordovician (Darriwilian–Sandbian) of south-central China
- 2017
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Ingår i: Papers in Palaeontology. - : Wiley. - 2056-2799 .- 2056-2802. ; 3:3, s. 317-361
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Tidskriftsartikel (refereegranskat)abstract
- Ordovician (Darriwilian to Sandbian) micromorphic linguliform lingulate brachiopods are described from the Guniutan Formation at the Fenxiang section in Hubei province, and the Maocaopu and Cili sections in Hunan province of south-central China, situated on the Yangtze Platform. A total of 7560 specimens from 155 limestone samples (within the interval of Lenodus variabilis – Pygodus anserinus biozones) are assigned to 22 species, representing a low taxonomic diversity and low abundance fauna. The fauna is dominated by the Acrotretoidea, mainly species of the Torynelasmatidae, with Torynelasma the most abundant (more than 40% of total number of specimens), along with the Eoconulidae and Eoconulus (18% of total) representing the second most common forms. Species of the Ephippelasmatidae are also common (16% of total) diverse, and include representatives of Myotreta and Numericoma, as well as Ephippelasma, whereas species of the Scaphelasmatidae are somewhat less common (13% of total). All three investigated sections represent outer shelf environments, but the Maocaopu section is situated in a relatively deeper position, in proximity of the south-eastern outer margin of the Upper Yangtze Platform, close to its boundary with the Jiangnan Slope. A quantitative analysis of the relative abundance data was carried out in order to investigate the biofacies distribution of the micromorphic brachiopod communities across the Yangtze Platform, something that has not been attempted before with Palaeozoic linguliforms. Six lingulate microbrachiopod communities could be recognized in the sections. The major biofacies shift, which occurred in the Cili section in the upper part of the Microzarkodina ozarkodella Zone, at the time of the onset and initial rise of the Mid Darriwilian Carbon Isotope Excursion (MDICE) suggests that these biofacies may have been depth controlled.
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| 5. |
- Holmer, Lars E., 1960-, et al.
(författare)
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Evolutionary significance of a middle Cambrian (Series 3) in situ occurrence of the pedunculate rhynchonelliform brachiopod Nisusia sulcata
- 2018
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Ingår i: Lethaia. - : Scandinavian University Press / Universitetsforlaget AS. - 0024-1164 .- 1502-3931. ; 51:3, s. 424-432
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Tidskriftsartikel (refereegranskat)abstract
- Exceptionally preserved, silicified and articulated complete shells of the rhynchonelliform kutorginate brachiopod Nisusia sulcata are redescribed from the middle Cambrian (Series 3) Marjum Limestone, Utah. Cylindroid sausage-like protrusions, emerging posteriorly between the valves, were originally interpreted as faecal in origin, but restudy under the SEM shows that these features represent silicified pedicles as they are attached in situ to other Nisusia. The Nisusia host most likely was alive at the time of attachment. Restudy of the pedicles of Nisusia provides new phylogenetic information on the anatomy of the earliest rhynchonelliforms. The silicified pedicles differ considerably from the pedicles of living crown group rhynchonelliforms in being strongly annulated, distally tapering, and were likely to have been rather more flexible. The Nisusia pedicles are more similar to the exceptionally preserved pedicles from other Cambrian rhynchonelliform brachiopods, including Kutorgina, Longtancunella and Alisina, but these emerge from the ventral apical foramen rather than from between the valves as in Nisusia. Although generally similar, these two types of pedicles are unlikely to represent homologous structures as Nisusia is provided with both an apical foramen (possibly larval attachment) and a posterior adult pedicle. The similarities may be explained by similar type of accretionary growth from two different types of epithelia. The Nisusia-like pedicle appeared early within the kutorginates and rhynchonellates. The discovery of hollow spines in Nisusia sulcata further supports the generic assignation of the species.
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| 6. |
- Holmer, Lars E., et al.
(författare)
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Reassessment of the early Triassic lingulid brachiopod ‘Lingula’ borealis Bittner, 1899 and related problems of lingulid taxonomy
- 2016
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Ingår i: GFF. - : Informa UK Limited. - 1103-5897 .- 2000-0863. ; 138:4, s. 519-525
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Tidskriftsartikel (refereegranskat)abstract
- The Early Triassic (late Induan to early Olenekian) Lingula borealis Bittner, from the Russkii Island on the Pacific cost of south-eastern Russia is revised, based on re-examination of the type material. Although this species, like most described Triassic lingulids, has remained very poorly understood due to the lack of information on important characters, such as musculature and mantle canals, it has been commonly recorded in subsequent studies and included in attempts at understanding the patterns of extinction and recovery at around the Permian-Triassic boundary. Linguliform brachiopods are some of the notable survivors of this significant mass extinction event. Lingula borealis has previously been referred to Lingularia and provisionally synonymised with Lingularia similis Biernat & Emig. Here, it is shown that it differs from Lingularia similis mainly in characters of mantle canals, musculature and most importantly in details of the pedicle nerve impression. In Lingularia borealis, the impression of the pedicle nerve is symmetrical and goes almost straight between the individual ventral umbonal muscle scars, whereas in Lingularia similis it is asymmetrically positioned towards the smaller left component of the ventral umbonal muscle scar. Shell structures and details of preserved ontogenies have also proven to be important for the discrimination of lingulid taxa, but cannot be provided from the types of Lingularia borealis.
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| 7. |
- Holmer, Lars E., 1960-, et al.
(författare)
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Unusual pitted Ordovician brachiopods from the East Baltic : the significance of coarsely pitted ornamentations in linguliforms
- 2017
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Ingår i: Papers in Palaeontology. - : Wiley. - 2056-2799 .- 2056-2802. ; 3:3, s. 387-399
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Tidskriftsartikel (refereegranskat)abstract
- A characteristic coarsely pitted ornamentation (with pits larger than 0.015 mm across) can be found on some very enigmatic and rare Lower Ordovician phosphatic-shelled linguliform brachiopods, including the paterinid Lacunites balaschovae Gorjansky and the obolid Foveola maarduensis Gorjansky. Both of these species are poorly understood and known from only a few specimens from the Floian of the East Baltic. Here we describe the Ordovician species Lacunites ivantsovi sp. nov. from the lower Darriwilian of the St Petersburg region and Foveola ivari sp. nov. from the Sandbian of Estonia, representing the last known survivors of these genera in the area. The new Darriwilian species of Lacunites is also one of the last members of the Class Paterinata, which most importantly includes some of the earliest known brachiopods from the early Cambrian. The coarsely pitted ornamentation of Foveola ivari is associated with the formation of asymmetrical so-called terrace lines in the umbonal area. The latter may indicate a burrowing life style. The pits in Lacunites and Foveola are directly comparable to the more or less identical coarse pits in the discinoid Trematis. Unlike the microscopic pits found in many fossil linguliforms, it is most likely that the coarse pits were empty in life; the minute surface ornamentation of irregular wrinkles in the outer primary layer continues across the bottom of the depressions in Foveola and Trematis; in the latter the cementing attachment discs of an attached phosphatic tubular Byronia-like organism also extend down into the pits.
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| 8. |
- Jahangir, Hadi, et al.
(författare)
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Biostratigraphy of the Cambrian–Ordovician boundary beds at Kopet-Dagh, Iran
- 2015
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Ingår i: Stratigraphy. - 1547-139X .- 2331-656X. ; 2:12, s. 40-47
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Tidskriftsartikel (refereegranskat)abstract
- A continuous succession comprising upper Cambrian (Furongian) to Lower Ordovician (Tremadocian) conodont biozones is reported for the first time from the Kopet-Dagh Region of northeastern Iran. Seven biostratigraphical units are recognized, including the Proconodontus tenuiserratus and Proconodontus posterocostatus zones; these two lowermost biostratigraphical units are defined by euconodont species which have not been previously reported from Iran and temperate latitude peri-Gondwana. The conodont diversity and abundance decreased significantly above the Eoconodontus notchpeakensis Zone; the conodont faunas of the succeeding Cordylodus proavus, Cordylodus lindstromi (sensu lato) and Cordylodus angulatus zones are characterised by oligotaxic to monotaxic associations dominated by species of Cordylodus. In the absence of diagnostic conodont species, the position of the lower boundary of the Ordovician System in the Kalat Valley Section can be placed somewhat below the first occurrence of the early planktonic graptolite Rhabdinopora flabelliformis, which approximately coincides with the onset of black shale deposition.
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| 9. |
- Popov, Leonid E, et al.
(författare)
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Glendonite occurrences in the Tremadocian of Baltica : first Early Palaeozoic evidence of massive ikaite precipitation at temperate latitude
- 2019
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- The Tremadocian (Early Ordovician) is currently considered a time span of greenhouse conditions with tropical water surface temperature estimates, interpolated from oxygen isotopes, approaching 40 °C. In the mid-latitude Baltoscandian Basin, conodonts displaying low δ18O values, which suggest high temperatures (>40 °C) in the water column, are in contrast with the discovery of contemporaneous glendonite clusters, a pseudomorph of ikaite (CaCO3·6H2O) traditionally considered as indicator of near-freezing bottom-water conditions. The massive precipitation of this temperature sensitive mineral is associated with transgressive conditions and high organic productivity. As a result, the lower Tremadocian sediments of Baltoscandia apparently contain both "greenhouse" pelagic signals and near-freezing substrate indicators. This paradox points to other primary controlling mechanisms for ikaite precipitation in kerogenous substrates, such as carbonate alkalinity, pH and Mg/Ca ratios, as recently constrained by laboratory experiments. Preservation of "hot" conodonts embedded in kerogenous shales rich in δ18O-depleted glendonites suggests both the onset of sharp thermal stratification patterns in a semi-closed basin and the assumed influence of isotopically depleted freshwater yielded by fluvial systems.
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| 10. |
- Popov, Leonid E., et al.
(författare)
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Himalayan Cambrian brachiopods
- 2015
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Ingår i: Papers in Palaeontology. - : Wiley. - 2056-2799 .- 2056-2802. ; 1:4, s. 345-399
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Tidskriftsartikel (refereegranskat)abstract
- 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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| 11. |
- Skovsted, Christian, 1974-, et al.
(författare)
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Taxonomy, morphology, shell structure and early ontogeny of Pelmanotreta nom. nov. from the lower Cambrian of Siberia
- 2015
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Ingår i: GFF. - : Informa UK Limited. - 1103-5897 .- 2000-0863. ; 137:1, s. 1-8
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Tidskriftsartikel (refereegranskat)abstract
- The new generic name Pelmanotreta is proposed under the provisions of the International Code of Zoological Nomenclature (ICZN) to replace Cryptotreta Pelman, 1977 (Brachiopoda), a junior homonym of Cryptotreta Blanc & Foote, 1961 (Arthropoda). This poorly known brachiopod genus and its type and only species, Pelmanotreta neguertchenensis (Pelman, 1977), from the early Cambrian of Siberia is redescribed. The family-level taxonomy of Pelmanotreta and other “cryptotretid” brachiopods is uncertain. In Pelmanotreta, dorsal valves vastly outnumber ventral valves in all collections but new specimens of the poorly known ventral valve reveal a possibly septate and poorly mineralized apical region. A prismatic hexagonal shell structure comparable to that of Salanygolina is described. P. neguertchenensis preserves the earliest known record of a larval shell in brachiopods.
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| 12. |
- Zhang, Zhiliang, et al.
(författare)
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Earliest ontogeny of early Cambrian acrotretoid brachiopods : first evidence for metamorphosis and its implications
- 2018
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Ingår i: BMC Evolutionary Biology. - : Springer Science and Business Media LLC. - 1471-2148. ; 18
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Tidskriftsartikel (refereegranskat)abstract
- Our understanding of the ontogeny of Palaeozoic brachiopods has changed significantly during the last two decades. However, the micromorphic acrotretoids have received relatively little attention, resulting in a poor knowledge of their ontogeny, origin and earliest evolution. The uniquely well preserved early Cambrian fossil records in South China provide a great new opportunity to investigate the phylogenetically important ontogeny of the earliest acrotretoid brachiopods, and give new details of the dramatic changes in anatomy of acrotretoid brachiopods during the transition from planktotrophic larvae to filter feeding sedentary juveniles.
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| 13. |
- Ebbestad, Jan Ove R., et al.
(författare)
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First occurrence of Lesueurilla prima (Gastropoda) from the Middle Ordovician (Darriwilian) of Iran
- 2016
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Ingår i: GFF. - : Informa UK Limited. - 1103-5897 .- 2000-0863. ; 138:4, s. 510-518
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Tidskriftsartikel (refereegranskat)abstract
- The near planispiral euomphaloid gastropod Lesueurilla prima (Barrande in Perner) is a typical part of the cold water Mediterranean fauna in the Lower and Middle Ordovician. It is a signature species in strata of this age in the Prague Basin in the Czech Republic, Montagne Noire in France, and Central Morocco. The species is reported for the first time from the Darriwilian of Iran where it occurs in the upper part of the Shirgesht Formation of the Derenjal Mountains north of Tabas in east Central Iran. It occurs with a small species of the bellerophontoid gastropod Sinuites sp., as well as the calymenid trilobite Neseuretinus birmanicus (Reed) and the pliomerid trilobite Ovalocephalus kanlingensis (Zhang). The biogeographic distribution of Lesueurilla suggests that the genus had its origin in cold water, high-latitude peri-Gondwana areas during the Lower Ordovician, spreading to other peri-Gondwana areas and low-latitude areas of North China, Tarim, and finally Baltica, Laurentia and Australia in the late Middle and Upper Ordovician.
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| 14. |
- Holmer, Lars E., 1960-, et al.
(författare)
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Brachiopod Phylogeny in the Cambrian
- 2018
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Ingår i: 8th INTERNATIONAL BRACHIOPOD CONGRESS. ; , s. 56-57
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Konferensbidrag (refereegranskat)
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| 15. |
- Holmer, Lars E., 1960-, et al.
(författare)
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The attachment strategies of Cambrian kutorginate brachiopods : the curious case of two pedicle openings and their phylogenetic significance
- 2018
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Ingår i: Journal of Paleontology. - : Cambridge University Press (CUP). - 0022-3360 .- 1937-2337. ; 92:1, s. 33-39
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Tidskriftsartikel (refereegranskat)abstract
- The kutorginates are commonly the most abundant rhynchonelliform brachiopod found in the early Cambrian; they are also some of the oldest known rhynchonelliforms, first appearing in the Unnamed Series 2 (Atdabanian equivalent) and becoming extinct sometime in Cambrian Series 3 (Amgaian equivalent). Moreover, kutorginates are the first known member of the rhynchonelliforms for which we have a detailed knowledge of their soft-part anatomy, including the lophophore, digestive tract, and pedicle—all exceptionally preserved in Kutorgina chengjiangensis Zhang et al., 2007 from the early Cambrian Chengjiang Lagerstätte of southern China. The stout and annulated pedicle in the original report was described as protruding between the valves; however, newly collected better-preserved material now clearly shows that the pedicle actually protrudes from the apical perforation of Kutorgina chengjiangensis. This type of apical pedicle has also been described from other early Cambrian rhynchonelliforms, including the problematic chileate Longtancunella chengjiangensis (Zhang et al., 2011a). Exceptionally preserved similar pedicles are also known to emerge apically from the Silurian chileate dictyonellid Eichwaldia subtrigonalis Billings, 1858, as well as from the recently described Silurian chileate Trifissura rigida Holmer, Popov, and Bassett, 2014. However, it is clear that the only other exceptionally preserved kutorginate—a silicified Nisusia—was provided with an adult pedicle emerging between the valves from a posterior gap; thus, Nisusia has two pedicle openings. However, the apical foramen may represent the earliest attachment of the larvae, which subsequently became nonfunctional through ontogeny. It is suggested that both types of attachment strategies may have appeared early in the stem lineage of the Rhynchonelliformea.
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| 16. |
- Popov, Leonid E, et al.
(författare)
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Review of the Ordovician stratigraphy and fauna of the Anarak Region in Central Iran
- 2015
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Ingår i: Acta geologica Polonica. - : Walter de Gruyter GmbH. - 0001-5709 .- 2300-1887. ; 65:4, s. 403-435
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Forskningsöversikt (refereegranskat)abstract
- The Ordovician sedimentary succession of the Pol-e Khavand area, situated on the northern margin of the Yazd block, has important differences from those in other parts of Central Iran. It has been established that the presumably terminal Cambrian to Lower Ordovician volcano-sedimentary Polekhavand Formation, exposed in the Pol-e Khavand area, has non-conformable contact with greenschists of the Doshakh Metamorphic Complex. The succeeding, mainly siliciclastic Chahgonbad Formation contains low to moderately diverse faunal assemblages, including brachiopods, cephalopods, trilobites and tentaculitids. The Darriwilian age of the lower part of the formation is well established by the co-occurrence of brachiopod genera Camerella, Phragmorthis, Tritoechia and Yangtzeella. The associated rich cephalopod fauna is different from the Darriwilian cephalopod associations of the Alborz terrane and may show some affinity with warm water faunas of North China and South Korea. It is likely that the Mid Ordovician fauna recovered from the lower part of the Chahgonbad Formation settled in the area sometime during a warming episode in the late Darriwilian. By contrast the low diversity mid Katian brachiopod association includes only three taxa, which occur together with the trilobite Vietnamia cf. teichmulleri and abundant, but poorly preserved tentaculitids questionably assigned to the genus Costatulites. This faunal association bears clear signatures linking it to the contemporaneous cold water faunas of the Arabian, Mediterranean and North African segments of Gondwana. Four brachiopod species recovered from the Chahgonbad Formation, including Hibernodonta lakhensis, Hindella prima, Lomatorthis? multilamellosa and Yangtzeella chupananica are new to science.
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