| 1. |
- Harper, David A.T., et al.
(författare)
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The Furongian (late Cambrian) Biodiversity Gap : Real or apparent?
- 2019
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Ingår i: Palaeoworld. - Amsterdam : Elsevier BV. - 1871-174X .- 1875-5887. ; 28:1-2, s. 4-12
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Tidskriftsartikel (refereegranskat)abstract
- Two major, extended diversifications punctuated the evolution of marine life during the Early Palaeozoic. The interregnum, however, between the Cambrian Explosion and the Great Ordovician Biodiversification Event, is exemplified by the Furongian Gap when there was a marked drop in biodiversity. It is unclear whether the gap is apparent, due to sampling failure or lack of rock, or real — associated with unique and fluctuating environments, a distinctive palaeogeography and extreme climates during the late Cambrian. Indications suggest that there has been little attention paid to this interval compared with those below and above, while some of the classical areas for Cambrian research, such as Bohemia, have poor coverage through the Furongian. Moreover, based on information available in databases and the literature, together with the ghost ranges of many higher taxa through the Furongian, data suggest that biodiversity in this stage has been significantly underestimated. Emphasis, to date, has been placed on widespread, deeper-water dark shale facies of the interval, with generally low diversity faunas, whereas shallow-water communities have often been neglected.
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| 2. |
- Topper, Timothy P., et al.
(författare)
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A Bradoriid and Brachiopod Dominated Shelly Fauna from the Furongian (Cambrian) of Västergötland, Sweden
- 2013
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Ingår i: Journal of Paleontology. - 0022-3360 .- 1937-2337. ; 87:1, s. 69-83
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Tidskriftsartikel (refereegranskat)abstract
- A small assemblage of shelly fossils, dominated by the brachiopod Treptotreta jucunda and the bradoriid arthropod Mongolitubulus aspermachaera new species is described from a Furongian limestone of Västergötland, south-central Sweden. Mongolitubulus aspermachaera is represented in the assemblage by individual valves and numerous, ornamented spines. Valves and spines share identical ornament and microstructure leaving no doubt that the isolated spines were once attached to the bradoriid valves. Mongolitubulus aspermachaera adds to the increasing list of spinose Cambrian bradoriid arthropods, and Mongolitubulidae new family is erected here to incorporate the genera Mongolitubulus, Tubuterium and Spinospitella. Mongolitubulus aspermachaera represents the youngest member of the new family and supplements the biodiversity of bradoriids in the Furongian, an interval when bradoriid diversity is considered to be very much on the decline. The brachiopod Treptotreta jucunda described predominantly from the ‘middle' to ‘late' Cambrian of Australia is here documented for the first time from outside Gondwana, dramatically extending the biogeographical range of the species. Other elements of the faunal assemblage include typical Baltic Furongian representatives, such as the trilobite Parabolina, the agnostoid Agnostus and the phosphatocopids Hesslandona and Vestrogothia.
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| 3. |
- Topper, Timothy P.
(författare)
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Moulting in the lobopodian Onychodictyon from the lower Cambrian of Greenland
- 2013
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Ingår i: Lethaia. - : Scandinavian University Press / Universitetsforlaget AS. - 0024-1164 .- 1502-3931. ; 46:4, s. 490-495
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Tidskriftsartikel (refereegranskat)abstract
- A number of lobopodian taxa from the Cambrian display pairs of sclerotized plates symmetrically positioned along the dorsum of the animal, predominantly above the walking appendages. Most genera were described from complete body fossils exquisitely preserved in the famous Cambrian Lagerstätten, but lobopodian phosphatized plates are found worldwide as typical components of Cambrian small shelly fossil assemblages (SSF). Details regarding intraspecific and ontogenetic variation in lobopod plates are elusive, and the lack of details of ornamentation in Lagerstätte specimens does not minimize the problem. We document here an assemblage of well-preserved isolated plates of Onychodictyon sp. from the Lower Cambrian (Cambrian Series 2, Stage 4) of North Greenland. Two specimens exhibit perfectly conjoined plates from successive moults. Details of ornamentation and the outline and profile of the fixed plates are identical, but width and length of the underlying plate are 24% larger. These specimens boost the body of evidence that lobopodians moulted but also show that plate outline and ornamentation did not vary during ontogeny.
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| 4. |
- Topper, Timothy P, et al.
(författare)
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The oldest brachiopods from the lower Cambrian of South Australia
- 2013
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Ingår i: Acta Palaeontologica Polonica. - : Polska Akademia Nauk Instytut Paleobiologii (Institute of Paleobiology, Polish Academy of Sciences). - 0567-7920 .- 1732-2421. ; 58:1, s. 93-109
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Tidskriftsartikel (refereegranskat)abstract
- The morphology and organophosphatic shell structure of the paterinate brachiopod Askepasma is documented using new and previously collected specimens from the lower Cambrian of South Australia. Lack of adequately preserved material has seen the majority of paterinate specimens previously reported from South Australia referred to the genus Askepasma and treated under open nomenclature. Large collections of paterinates from the lower Cambrian Wilkawillina, Ajax, and Wirrapowie limestones in the Arrowie Basin, South Australia have prompted redescription of the type species Askepasma toddense and the erection of a new species, Askepasma saproconcha sp. nov. Askepasma saproconcha sp. nov. currently represents the oldest known brachiopod from the lower Cambrian successions in South Australia with a FAD in pre−trilobitic (Terreneuvian, Cambrian Stage 2, lower Atdabanian) strata in the basal part of the Wilkawillina and Wirrapowie limestones. Askepasma toddense predominantly occurs in Abadiella huoi Zone equivalent strata (Unnamed Cambrian Series 2, Stage 3, middle–upper Atdabanian) in the upper part of the lower Wilkawillina, Wirrapowie, and Ajax limestones. The shell microstructure of Askepasma suggests a proximal stem group position within the Brachiopoda and similarities with tommotiid taxa provides further evidence that the ancestry of crown group brachiopods is firmly entrenched within the Tommotiida.
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