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Anisian
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Hugo Bucher – One of the best experts on this subject based on the ideXlab platform.
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A highly diverse bivalve fauna from a Bithynian (Anisian, Middle Triassic) Tubiphytes‐microbial buildup in North Dobrogea (Romania)
Papers in Palaeontology, 2019Co-Authors: Evelyn Friesenbichler, Eugen Grădinaru, Michael Hautmann, Hugo BucherAbstract:This paper describes a rich bivalve fauna from the Tubiphytes‐Limestone Member (Bithynian, early middle Anisian) of the Caerace Formation in North Dobrogea (Romania). We report 51 bivalve species, including 7 new species and 2 new genera: Atrina multicostata sp. nov., Pinna simionescui sp. nov., Chlamys (Praechlamys) prima sp. nov., Entolium reticulatum sp. nov., Scythentolium anisicum sp. nov., Romaniamya mahmudiaensis gen. et sp. nov. and Praedicerocardium vetulus gen. et sp. nov. The latter taxon represents the oldest Triassic megalodontoid. We provide detailed descriptions of the bivalve fauna, discuss the ecology and compare species richness in the Early and Middle Triassic, showing that the bivalve assemblage of North Dobrogea is much more diverse than all previously described Early Triassic bivalve faunas, but not as rich as several faunas from the late Anisian and Ladinian. The relative richness of the Dobrogea fauna with respect to geologically older and younger faunas suggests that it represents an early stage of the main rediversification of bivalves after the end‐Permian mass extinction.
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Anisian (Middle Triassic) ammonoids from British Columbia (Canada): biochronological and palaeobiogeographical implications
Papers in Palaeontology, 2018Co-Authors: Hugo BucherAbstract:New Anisian (Middle Triassic) ammonoids are reported from British Columbia (BC), Canada. Eight species are reported, including one new genus and two new species: Eofrechites roopnarini gen. et sp. nov. and Parafrechites cordeyi sp. nov. New ammonoid subzones are recognized, leading to improved correlation between BC and Nevada: the Hollandites minor Zone is correlated with the interval intercalated between the Unionvillites hadleyi Subzone and the Pseudodanubites nicholsi Subzone; an Eogymnotoceras thompsoni – Anagymnotoceras spivaki Zone is recognized in BC and correlated with the interval intercalated between the Augustaceras escheri and Anagymnotoceras spivaki subzones; Gymnotoceras weitschati is found in BC for the first time and co‐occurs with Eogymnotoceras deleeni, suggesting either a rough correlation with the sum of G. weitschati, G. mimetus and G. rotelliformis zones of Nevada or a strong diachronism of G. weitschati and G. rotelliformis along the Palaeopacific margin of North America. The rare occurrences of low‐palaeolatitude restricted species in the mid‐palaeolatitude record indicate that exchanges were more frequent than previously documented during the Anisian. Despite a preservation bias in north‐eastern BC due to the lower carbonate content, it clearly emerges that the enhanced sampling effort leads to maximal association zones with duration of the same order of magnitude as those of Nevada, indicating that evolutionary turnover rates of ammonoids did not decrease toward higher latitude. Therefore, the common view that geographically differentiated evolutionary rates originates from the latitudinal gradient of taxonomic richness does not hold for Anisian ammonoid faunas along the Palaeopacific margin of North America.
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Early Triassic Marine Biotic Recovery: The Predators’ Perspective
PLoS ONE, 2014Co-Authors: Torsten M Scheyer, Carlo Romano, James F. Jenks, Hugo BucherAbstract:Examining the geological past of our planet allows us to study periods of severe climatic and biological crises and recoveries, biotic and abiotic ecosystem fluctuations, and faunal and floral turnovers through time. Furthermore, the recovery dynamics of large predators provide a key for evaluation of the pattern and tempo of ecosystem recovery because predators are interpreted to react most sensitively to environmental turbulences. The end-Permian mass extinction was the most severe crisis experienced by life on Earth, and the common paradigm persists that the biotic recovery from the extinction event was unusually slow and occurred in a step-wise manner, lasting up to eight to nine million years well into the early Middle Triassic (Anisian) in the oceans, and even longer in the terrestrial realm. Here we survey the global distribution and size spectra of Early Triassic and Anisian marine predatory vertebrates (fishes, amphibians and reptiles) to elucidate the height of trophic pyramids in the aftermath of the end-Permian event. The survey of body size was done by compiling maximum standard lengths for the bony fishes and some cartilaginous fishes, and total size (estimates) for the tetrapods. The distribution and size spectra of the latter are difficult to assess because of preservation artifacts and are thus mostly discussed qualitatively. The data nevertheless demonstrate that no significant size increase of predators is observable from the Early Triassic to the Anisian, as would be expected from the prolonged and stepwise trophic recovery model. The data further indicate that marine ecosystems characterized by multiple trophic levels existed from the earliest Early Triassic onwards. However, a major change in the taxonomic composition of predatory guilds occurred less than two million years after the end-Permian extinction event, in which a transition from fish/amphibian to fish/reptile-dominated higher trophic levels within ecosystems became apparent.
Zuo-yu Sun – One of the best experts on this subject based on the ideXlab platform.
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A new Anisian (Middle Triassic) eosauropterygian (Reptilia, Sauropterygia) from Panzhou, Guizhou Province, China
, 2019Co-Authors: Da-yong Jiang, Wen-bin Lin, Olivier Rieppel, Ryosuke Motani, Zuo-yu SunAbstract:ABSTRACT—Eosauropterygians rapidly diversified in the Anisian (Middle Triassic), a period by which the invertebrates had already completely recovered from the end-Permian mass extinction. The Pelsonian (Anisian) deposits of the small Panxian and Luoping intraplatform basins in southwestern China alone yielded seven or more eosauropterygian taxa. A new Middle Triassic sauropterygian, Panzhousaurus rotundirostris, gen. et sp. nov., is here described based on an almost complete skeleton from the middle Anisian (Middle Triassic) of Panzhou (Guizhou Province, southwestern China). The upper temporal fenestra smaller than the orbit, the broad and flat parietal table, the cervical ribs with two proximal articular heads, the pachyostotic proximal ends of the dorsal ribs, and the unexpanded sacral ribs indicate that the specimen is a pachypleurosaur-like eosauropterygian. The new species also shows some differences from all other eosauropterygians, such as a rounded and shortened snout, 24 cervical and 20 dorsal vertebrae, a straight ulna with a concave posterior margin, and four distal carpals. Phylogenetic analysis also reveals that Panzhousaurus is an eosauropterygian, closely related to pachypleurosaur-like forms. The discovery of Panzhousaurus enriches our knowledge of the diversity of the Panxian fauna and provides new information to test phylogenetic relationships among known eosauropterygians. http://zoobank.org/urn:lsid:zoobank.org:pub:682A4FDD-C048-469F-867A-9F1D5847BD5A Supplemental Data—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP Citation for this article: Jiang, D.-Y., W.-B. Lin, O. Rieppel, R. Motani, and Z.-Y. Sun. 2019. A new Anisian (Middle Triassic) eosauropterygian (Reptilia, Sauropterygia) from Panzhou, Guizhou Province, China. Journal of Vertebrate Paleontology. DOI:10.1080/02724634.2018.1480113.
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A new Anisian (Middle Triassic) eosauropterygian (Reptilia, Sauropterygia) from Panzhou, Guizhou Province, China
Journal of Vertebrate Paleontology, 2018Co-Authors: Da-yong Jiang, Wen-bin Lin, Olivier Rieppel, Ryosuke Motani, Zuo-yu SunAbstract:ABSTRACT—Eosauropterygians rapidly diversified in the Anisian (Middle Triassic), a period by which the invertebrates had already completely recovered from the end-Permian mass extinction. The Pelso…
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New species of Sangiorgioichthys Tintori and Lombardo, 2007 (Neopterygii, Semionotiformes) from the Anisian of Luoping (Yunnan Province, South China)
Zootaxa, 2011Co-Authors: Adriana LÓpez-arbarello, Zuo-yu Sun, Emilia Sferco, Andrea Tintori, Yuan-lin Sun, Da-yong JiangAbstract:We report on a new species of the neopterygian genus Sangiorgioichthys Tintori and Lombardo, 2007, from middle Anisian (Pelsonian) deposits in South China (Luoping County, Yunnan Province). Sangiorgioichthys was previously known from a single species, S. aldae, from the late Ladinian of the Monte San Giorgio (Italy and Switzerland). The recognition of the new species helped to improve the diagnosis of the genus, which is mainly characterized by the presence of broad posttemporal and supracleithral bones, one or two suborbital bones occupying a triangular area ventral to the infraorbital bones and lateral to the quadrate, and elongate supramaxilla fitting in a an excavation of the dorsal border of the maxilla. Sangiorgioichthys sui n. sp. differs from the type species in having two pairs of extrascapular bones, the medial pair usually fused to the parietals, maxilla with a complete row of small conical teeth, long supramaxilla, more than half of the length of the maxilla, only two large suborbital bones posterior to the orbit, and flank scales with finely serrated posterior borders. With the discovery of S. sui n. sp., the number of fish genera shared by the Anisian/Ladinian deposits in the Alps and the Anisian deposits in South China increases, including not only the cosmopolitan Birgeria and Saurichthys, but also, among others, the subholosteans Colobodus (so far only in Panxian), Luopingichthys (so far only in Luoping), Peltopleurus, Habroichthys, and the very specialized neopterygians Placopleurus and Marcopoloichthys (only in Luoping). Therefore, although several fish taxa remain to be studied in the Chinese faunas, the so far available evidence indicates close biogeographic relationship between the Middle Triassic marine faunas of the Western Tethys region.
Zhong-qiang Chen – One of the best experts on this subject based on the ideXlab platform.
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The Anisian (Middle Triassic) brachiopod fauna from Qingyan, Guizhou, south-western China
Journal of Systematic Palaeontology, 2019Co-Authors: Zhen Guo, Zhong-qiang Chen, David A. T. HarperAbstract:Like most of the benthos, brachiopods suffered huge losses in biodiversity during the end-Permian extinction and did not fully recover until the Anisian (Middle Triassic). Anisian brachiopod faunas…
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Anisian (Middle Triassic) marine ichnocoenoses from the eastern and western margins of the Kamdian Continent, Yunnan Province, SW China: Implications for the Triassic biotic recovery
Global and Planetary Change, 2017Co-Authors: Xueqian Feng, Zhong-qiang Chen, Adam D. Woods, Yu Pei, Yuheng Fang, Mao LuoAbstract:Abstract Two Anisian (Middle Triassic) marine ichnocoenoses are reported from the Boyun and Junmachang (JMC) sections located along the eastern and western margins of the Kamdian Continent, Yunnan Province, Southwest China, respectively. The Boyun ichnoassemblage is middle Anisian in age and is dominated by robust Rhizocorallium , while the JMC ichnoassemblage is of an early Anisian age and is characterized by the presence of Zoophycos . The ichnoassemblage horizons of the Boyun section represent an inner ramp environment, while the JMC section was likely situated in a mid-ramp setting near storm wave base as indicated by the presence of tempestites. The ichnofossil-bearing successions are usually highly bioturbated in both the Boyun (BI 3–5, BPBI 5) and JMC (BI 3–4, BPBI 3–4) sections. Three large, morphologically complicated ichnogenera: 1) Rhizocorallium ; 2) Thalassinoides ; and, 3) Zoophycos characterize the Anisian ichnocoenoses. Of these, Rhizocorallium has mean and maximum tube diameters up to 20.4 mm and 28 mm, respectively, while Thalassinoides mean and maximum tube diameters are 14.2 mm and 22 mm, respectively. Zoophycos is present in the early Anisian strata of the JMC section, and represents the oldest known occurrence of this ichnogenus following the latest Permian mass extinction. Similar to coeval ichnoassemblages elsewhere in the world, the Yunnan ichnocoenoses embrace a relatively low ichnodiversity, but their burrows usually penetrate deeply into the sediment, and include large and complex Rhizocorallium and Thalassinoides . All of these ichnologic features are indicative of recovery stage 4 after the latest Permian crisis. Anisian ichnoassemblages occur globally in six different habitat settings, and all show similar ecologic characteristics except for slightly different degrees of ichnotaxonomic richness, indicating that depositional environment is not a crucial factor shaping the recovery of the trace-makers, but may have an impact on their ichnodiversity. When compared with some important Early Triassic (mainly Spathian) ichnoassemblages worldwide, the Anisian ichnocoenoses examined for this study are slightly less diversified, and possess more or less the same maximum burrow sizes, but the penetration depth of burrows and the distribution of burrow sizes are much larger than those from the Early Triassic. It is worthy of note that the lower ichnodiversity of the Anisian ichnocoenoses may have resulted from intense bioturbation by deeper tiers, representing a taphonomic product that is totally unrelated to environmental stress. In addition, Anisian Rhizocorallium and Thalassinoides have much larger burrow sizes than the same ichnotaxa from the Lower Triassic, implying that ichnocoenoses may have recovered in Spathian, but did not stabilize until the Anisian.
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Palaeoecology and taphonomy of two brachiopod shell beds from the Anisian (Middle Triassic) of Guizhou, Southwest China: Recovery of benthic communities from the end-Permian mass extinction
Global and Planetary Change, 2010Co-Authors: Jing Chen, Zhong-qiang Chen, Jinnan TongAbstract:Abstract Two brachiopod shell beds are documented from the Anisian Qingyan Formation at Qingyan, Guizhou province, southwest China. Taphonomic evidence indicates that the shell bed from the Yingshangpo Member of the Qingyan Formation, namely the Madoia sp. ( M ) assemblage, represents an autochthonous assemblage. This assemblage may have inhabited a low-energy, calm environment and the shells have been transported very little but undergone a long-term off burial after death. Another shell bed preserved in the Leidapo Member of the Qingyan Formation is termed the Rhaetina angustaeformis ( R ) assemblage, which represents either a parautochthonous assemblage or a residual and sorted but in situ assemblage living in a high-energy habitat. The M assemblage might be one of the recovery benthic communities following the end-Permian mass extinction because it not only has a much greater diversity, lower dominance, and higher evenness than the Early Triassic brachiopod assemblages, but it also shares similarities with the Changhsingian communities in terms of diversity indices. The Anisian brachiopod assemblage is also similar to the early Wuchiapingian recovery fauna in all diversity indices, but lacks distinctive Lazarus, surviving and generalist taxa, which are characteristic of the recovery shelly faunas following the end-Guadalupian mass extinction. This is probably responsible for the different faunal radiations after the biotic recovery following the end-Permian and end-Guadalupian mass extinctions, respectively. Brachiopod faunas rapidly diversified and proliferated in the middle-late Wuchiapingian, but patchily diversified in the Anisian in South China.