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| 2. |
- Álvaro, J. Javier, et al.
(författare)
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Submarine metalliferous carbonate mounds in the Cambrian of the Baltoscandian Basin induced by vent networks and water column stratification
- 2022
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Ingår i: Scientific Reports. - : Springer Nature. - 2045-2322. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- Two massive precipitation events of polymetallic ore deposits, encrusted by a mixture of authigenic carbonates, are documented from the Cambrian of the semi-enclosed Baltoscandian Basin. δ34S (‒9.33 to ‒2.08‰) and δ33S (‒4.75 to ‒1.06‰) values from the basal sulphide breccias, sourced from contemporaneous Pb–Zn–Fe-bearing vein stockworks, reflect sulphide derived from both microbial and abiotic sulphate reduction. Submarine metalliferous deposits were triggered by non-buoyant hydrothermal plumes: plumes of buoyant fluid were trapped by water column stratification because their buoyancy with respect to the environment reversed, fluids became heavier than their surroundings and gravitational forces brought them to a halt, spreading out laterally from originating vents and resulting in the lateral dispersion of effluents and sulphide particle settling. Subsequently, polymetallic exhalites were sealed by carbonate crusts displaying three generations of ikaite-to-aragonite palisade crystals, now recrystallized to calcite and subsidiary vaterite. Th of fluid inclusions in early calcite crystals, ranging from 65 to 78 ºC, provide minimum entrapment temperatures for carbonate precipitation and early recrystallization. δ13Ccarb (‒1.1 to + 1.6‰) and δ18Ocarb (‒7.6 to ‒6.5‰) values are higher than those preserved in contemporaneous glendonite concretions (‒8.5 to ‒4.7‰ and ‒12.4 to ‒9.1‰, respectively) embedded in kerogenous shales, the latter related to thermal degradation of organic matter. Hydrothermal discharges graded from highly reduced, acidic, metalliferous, and hot (~ 150 ºC) to slightly alkaline, calcium-rich and warm (< 100 ºC), controlling the precipitation of authigenic carbonates.
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| 3. |
- 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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| 4. |
- 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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| 5. |
- Holmer, Lars E., 1960-, et al.
(författare)
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Cambrian (Stage 4 to Wuliuan) brachiopods from Sonora, Mexico
- 2022
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Ingår i: Journal of Paleontology. - : Cambridge University Press. - 0022-3360 .- 1937-2337. ; , s. 1-21
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Tidskriftsartikel (refereegranskat)abstract
- The Cambrian successions at the Chihuarruita Hill outcrop, Sonora, Mexico, have yielded two successive linguliform brachiopod assemblages that are transitional between Cambrian Stage 4 and the newly recognized global Wuliuan Stage. The lowermost assemblage includes Dictyonina sp., Paterina sp., Eothele sp., Hadrotreta rara? (Cooper), and Linnarssonia arellanoi? (Cooper), coming from the upper part of the Buelna Formation. The younger, recently named El Gavilán Formation contains a more diverse linguliform brachiopod assemblage, including Acrothele concava Cooper, Batenevotreta? mexicana n. sp., Dictyonina minutipuncta Cooper, Eothele sp., Eoobolus sp., Hadrotreta rara? (Cooper), Linnarssonia arellanoi? (Cooper), Micromitra sp., Paterina sp., and Prototreta sp. The El Gavilán Formation contains a diverse trilobite fauna suggesting Delamaran age in terms of the Laurentian regional stratigraphical scheme. The base of the global Wuliuan Stage and Miaolingian Series is defined by the first occurrence of Oryctocephalus indicus; in the absence of the index species, the base should be provisionally placed at the base of the El Gavilán Formation. The Wuliuan age of the brachiopod assemblage recovered from the El Gavilán Formation is supported by the occurrence of Acrothele in the Cambrian biostratigraphical succession of Himalaya, where the genus makes its first appearance in the Kaotaia prachina Zone. In addition, the co-occurrences of Acrothele and Eothele can be taken as an indication of the Wuliuan age of the fauna. A new biogeographic analysis confirms that the Eothele Fauna first appeared at the end of Cambrian Stage 4, as a result of increased faunal migration within the southern tropical latitudes directed from Australasian Gondwana to Laurentia.
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| 6. |
- 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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| 7. |
- Holmer, Lars E., 1960-, et al.
(författare)
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Linguliform brachiopods from the Cambrian (Guzhangian) Karpinsk Formation of Novaya Zemlya
- 2020
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Ingår i: Papers in Palaeontology. - : John Wiley & Sons. - 2056-2799 .- 2056-2802. ; 6:4, s. 571-592
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Tidskriftsartikel (refereegranskat)abstract
- Abstract A moderately diverse assemblage of micromorphic linguliform brachiopods, including Tapuritreta gribovensis sp. nov., Wahwahlingula? pankovensis sp. nov., Acrothele sp., Anabolotreta? sp., Orbithele? sp. and Stilpnotreta sp., is for the first time described from the Cambrian Karpinsk Formation (Miaolingian, Guzhangian) of the South Island of Novaya Zemlya. The morphology of the metamorphic shell in Acrothele and Wahwahlingula? suggest that both taxa had a single pair of larval setal sacs, similar to the recent discinids, but their metamorphosis was completed only at the end of the pelagic stage and shows that they did have direct development, which is characteristic of all recent lingulides. The biogeographical signature of the new Cambrian brachiopod fauna from Novaya Zemlya is discussed, and the new fauna gives new information on the poorly known Cambrian margins of the Baltica palaeocontinent.
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| 8. |
- 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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| 9. |
- Jahangir, Hadi, et al.
(författare)
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The siphonotretide brachiopod Schizambon from the Early Ordovician of South China : ontogeny and affinity
- 2023
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Ingår i: Papers in Palaeontology. - : John Wiley & Sons. - 2056-2799 .- 2056-2802. ; 9:4
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Tidskriftsartikel (refereegranskat)abstract
- Schizambon is one of the earliest and most distinctive genera in the Order Siphonotretida. However, current knowledge of siphonotretide phylogeny and early evolution requires understanding of their earliest ontogeny. In this study, the new species Schizambon tongziensis from the Tungtzu Formation at Honghuayuan section in Guizhou Province, South China is described; it is also the first record of Schizambon in South China. The new well-preserved specimens shed light on the ontogeny, palaeobiogeographical distribution, phylogeny and early evolution of siphonotretide brachiopods. Characters of metamorphic shells on both valves, outlined by distinct halos, show that Schizambon had a planktotrophic ‘paterinide-type’ larva, typical of many early Palaeozoic brachiopods. Based on the newly obtained data it is inferred that the free-swimming larva of Schizambon settled directly on the ventral side of the body, and this type of ontogeny is probably true for other siphonotretides. The divergence of Schizambon from the main siphonotretide lineage probably happened prior to the Guzhangian Age, well before the occurrence of major biodiversification within the order.
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| 10. |
- Liang, Yue, et al.
(författare)
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Evolutionary contingency in lingulid brachiopods across mass extinctions
- 2023
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Ingår i: Current Biology. - : Elsevier BV. - 0960-9822 .- 1879-0445. ; 33:8, s. 1565-1572.e3
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Tidskriftsartikel (refereegranskat)abstract
- Morphology usually serves as an effective proxy for functional ecology,1,2,3,4,5 and evaluating morphological, anatomical, and ecological changes permits a deeper understanding of the nature of diversification and macroevolution.5,6,7,8,9,10,11,12 Lingulid (order Lingulida) brachiopods are both diverse and abundant during the early Palaeozoic but decrease in diversity over time, with only a few genera of linguloids and discinoids present in modern marine ecosystems, resulting in them frequently being referred to as “living fossils.”13,14,15 The dynamics that drove this decline remain uncertain, and it has not been determined if there is an associated decline in morphological and ecological diversity. Here, we apply geometric morphometrics to reconstruct global morphospace occupation for lingulid brachiopods through the Phanerozoic, with results showing that maximum morphospace occupation was reached by the Early Ordovician. At this time of peak diversity, linguloids with a sub-rectangular shell shape already possessed several evolutionary features, such as the rearrangement of mantle canals and reduction of the pseudointerarea, common to all modern infaunal forms. The end Ordovician mass extinction has a differential effect on linguloids, disproportionally wiping out those forms with a rounded shell shape, while forms with sub-rectangular shells survived both the end Ordovician and the Permian-Triassic mass extinctions, leaving a fauna predominantly composed of infaunal forms. For discinoids, both morphospace occupation and epibenthic life strategies remain consistent through the Phanerozoic. Morphospace occupation over time, when considered using anatomical and ecological analyses, suggests that the limited morphological and ecological diversity of modern lingulid brachiopods reflects evolutionary contingency rather than deterministic processes.
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