Topic
Symphysops
About: Symphysops is a research topic. Over the lifetime, 3 publications have been published within this topic receiving 15 citations.
Papers
TL;DR: A diverse, previously undescribed trilobite fauna from northwest Iran sheds new light on the Early Palaeozoic geography of the Alborz terrane.
Abstract: A diverse, previously undescribed trilobite fauna from northwest Iran sheds new light on the Early Palaeozoic geography of the Alborz terrane. The structural history of the Alborz region is well known, though faunal data for the area are sparse, especially for the Ordovician. Trilobites, brachiopods, conodonts, bryozoans and echinoderms occur in a red grainstone/packstone near the village of Tatavrud, 35 km southwest of Bandar-e-Anzali. The fossils indicate a Late Ordovician age, although lithologically similar outcrops in northern Iran have previously been considered Silurian. Trilobite genera occurring include Trinodus, Geragnostus, Illaenus, Panderia, Phorocephala, Ovalocephalus, Dicranopeltis, Symphysops, Cyclopyge, and Sphaerexochus. Similar assemblages have been reported from the Late Ordovician of Ireland, Spain, Poland, Norway, northwest China, Kazakhstan and the Turkistan–Alai Ridge (Uzbekistan–Kyrgyzstan border). Reconstructions of Late Ordovician geography place the Alborz terrane near the eastern margin of Gondwana, but there is doubt as to its precise location. Some workers have considered it part of the margin while others have considered it a separate terrane. Several species present, including Mezzaluna tatavrudensis n. sp. and Phorocephala cf. ulugtana (Petrunina, 1975) are very similar to taxa described from the Turkistan–Alai Ridge. In addition, the isocolid genus Paratiresias has only been reported from Iran, the Turkistan–Alai Ridge and northwest China. The presence of these taxa indicates that the Alborz terrane was in close proximity to the eastern margin of Gondwana at this time.
14 citations
TL;DR: The trilobite fauna of the upper Ordovician (middle Katian) Pyle Mountain Argillite comprises a mixture of abundant mesopelagic cyclopygids and other pelagic taxa as mentioned in this paper.
Abstract: The trilobite fauna of the upper Ordovician (middle Katian) Pyle Mountain Argillite comprises a mixture of abundant mesopelagic cyclopygids and other pelagic taxa and a benthic fauna dominated by trilobites lacking eyes. Such faunas were widespread in deep water environments around Gondwana and terranes derived from that continent throughout Ordovician time but this is the only known record of such a fauna from North America and thus from Laurentia. It probably reflects a major sea level rise (the ‘Linearis drowning events’) as does the development of coeval cyclopygid-dominated deep water trilobite faunas in terranes that were marginal to Laurentia and are now preserved in Ireland and Scotland. The Pyle Mountain Argillite trilobite fauna occurs with a deep water Foliomena brachiopod fauna and comprises 22 species. Pelagic trilobites (mostly cyclopygids) constitute 36% of the preserved sclerites, and 45% of the fauna is the remains of trilobites lacking eyes, including one new species, Dindymene whittingtoni sp. nov. Three species of cyclopygid are present, belonging in Cyclopyge, Symphysops and Microparia (Heterocyclopyge). Cyclopygids are widely thought to have been stratified in the water column in life and thus their taxonomic diversity reflects the relative depths of the sea-beds on which their remains accumulated. A tabulation of middle and upper Katian cyclopygid-bearing faunas from several palaeoplates and terranes arranged on the basis of increasing numbers of cyclopygid genera allows an assessment of the relative depth ranges of the associated benthic taxa. The Pyle Mountain Argillite fauna lies towards the deeper end of this depth spectrum.
9 citations
TL;DR: The trilobite fauna of the upper Katian (mid-Ashgill in terms of Anglo-Welsh chronostratigraphy) Oriel Brook Formation in the Grangegeeth Terrane, eastern Ireland comprises 16 species as mentioned in this paper.
Abstract: The trilobite fauna of the upper Katian (mid-Ashgill in terms of Anglo-Welsh chronostratigraphy) Oriel Brook Formation in the Grangegeeth Terrane, eastern Ireland comprises 16 species. It is dominated numerically by mesopelagic cyclopygids (Cyclopyge cf. marginata Hawle and Corda and much rarer Symphysops sp.), which comprise 63% of the 156 identifiable sclerites known unequivocally from the formation. Other elements of the trilobite fauna include species of Staurocephalus, Phillipsinella, Nankinolithus and the agnostids Trinodus and Sphaeragnostus. The abundance of cyclopygids in a terrane interpreted as lying within the Iapetus Ocean closer to Laurentia than the Anglo-Welsh sector of Avalonia is consistent with the Late Katian spread of cyclopygids onto low latitude shelves seen in Quebec and Maine in eastern North America, Girvan in SE Scotland and Co. Clare in the Irish Central Terrane. With the exception of the agnostid trilobites, whose mode of life is strongly debated, associated benthic trilobites lacking eyes are fairly rare and the bottom-dwelling fauna does not conform to the atheloptic assemblages that typified many mid- to high latitude Ordovician outer shelf and upper slope settings. The benthic assemblage can be considered in terms of a bathymetrically arranged spectrum of faunas and is closest to that of the deep shelf Phillipsinella parabola—Staurocephalus clavifrons fauna, known from the Upper Ordovician of Avalonia and Baltica and to some extent marginal Gondwana and South China. This is the first record of such a fauna from Laurentia or its marginal terranes and reflects the Late Ordovician breakdown of provincialism in the Iapetus Ocean. The deep-water setting is compatible with that of the associated Foliomena brachiopod fauna.
6 citations
Performance Metrics
| Year | Papers |
|---|---|
| 2012 | 1 |
| 2010 | 1 |
| 2008 | 1 |