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William G. Parker - One of the best experts on this subject based on the ideXlab platform.
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bite marks on an aetosaur archosauria suchia osteoderm assessing Late Triassic predator prey ecology through ichnology and tooth morphology
PALAIOS, 2021Co-Authors: Susan M Drymala, Kenneth Bader, William G. ParkerAbstract:Trace fossils such as bite marks provide rare, direct evidence of animal behavior, including predator-prey interactions. We present an osteoderm of the aetosaur Typothorax coccinarum from the Late Triassic Chinle Formation of Arizona with several punctures and scores, interpreted here as bite marks, preserved as evidence of predation/scavenging by a large carnivore. The marks include a single bite producing four subparallel fusiform pits on the ventral surface and several additional marks, including striated scores, on the dorsal surface. These traces are described and compared with known contemporaneous carnivorous taxa to determine the source of the bite marks. Some Triassic carnivores, including theropod dinosaurs can be ruled out because of tooth shape and serration densities. Phytosaurs and large paracrocodylomorphs remain as likely candidates based on tooth morphology. Although some phytosaur teeth are too rounded to produce the marks seen in this specimen, we demonstrate that the more lingually flattened teeth typically found in the posterior section of the snout are sufficiently medioLaterally compressed to produce a fusiform pit. A protective function for aetosaur osteoderms cannot be confirmed presently, but the extensive carapace these bones formed would have been a major barrier to both scavengers and active predators and may preserve more feeding/predation traces than previously thought. The bite marks described herein support the hypothesis that aetosaurs were prey items of large archosauromorphs, expanding our understanding of the complex, and seemingly carnivore dominated Late Triassic terrestrial ecosystems of North America.
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redescription of anaschisma temnospondyli metoposauridae from the Late Triassic of wyoming and the phylogeny of the metoposauridae
Journal of Systematic Palaeontology, 2020Co-Authors: Bryan M Gee, William G. Parker, Adam D MarshAbstract:Metoposaurids are non-marine temnospondyls that are among the most common constituents of Late Triassic deposits, but despite their abundance, the evolutionary relationships of the group are poorly...
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the Late Triassic norian adamanian revueltian tetrapod faunal transition in the chinle formation of petrified forest national park arizona
Earth and Environmental Science Transactions of The Royal Society of Edinburgh, 2010Co-Authors: William G. Parker, Jeffrey W MartzAbstract:Recent stratigraphic revisions of the Upper Triassic Chinle Formation of Petrified Forest National Park, in conjunction with precise and accurate documentation of fossil tetrapod occurrences, clarified the local biostratigraphy, with regional and global implications. A significant overlap between Adamanian and Revueltian faunas is rejected, as is the validity of the Lamyan sub-land vertebrate faunachron. The Adamanian–Revueltian boundary can be precisely placed within the lower Jim Camp Wash beds of the Sonsela Member and thus does not occur at the hypothesised Tr-4 unconformity. This mid-Norian faunal turnover, may coincide with a floral turnover, based on palynology studies and also on sedimentological evidence of increasing aridity. Available age constraints bracketing the turnover horizon are consistent with the age of the Manicouagan impact event. The rise of dinosaurs in western North America did not correspond to the Adamanian–Revueltian transition, and overall dinosauromorph diversity seems to have remained at a constant level across it. The paucity of detailed Late Triassic vertebrate biostratigraphic data and radioisotopic dates makes it currently impossible to either support or reject the existence of globally synchronous Late Triassic extinctions for tetrapods.
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a critical re evaluation of the Late Triassic dinosaur taxa of north america
Journal of Systematic Palaeontology, 2007Co-Authors: Sterling J. Nesbitt, Randall B Irmis, William G. ParkerAbstract:Synopsis The North American Triassic dinosaur record has been repeatedly cited as one of the most complete early dinosaur assemblages. The discovery of Silesaurus from Poland and the recognition that Herrerasaurus and Eoraptor may not be theropods have forced a re‐evaluation of saurischian and theropod synapomorphies. Here, we re‐evaluate each purported Triassic dinosaur from North America on a specimen by specimen basis using an apomorphy‐based approach. We attempt to assign specimens to the most exclusive taxon possible. Our revision of purported Late Triassic dinosaur material from North America indicates that dinosaurs were rarer and less diverse in these strata than previously thought. This analysis concludes that non‐dinosaurian dinosauriforms were present in North America in the Late Triassic. Most of the proposed theropod specimens are fragmentary and/or indistinguishable from corresponding elements in the only well‐known Triassic theropod of North America, Coelophysis bauri. No Triassic material ...
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the Late Triassic pseudosuchian revueltosaurus callenderi and its implications for the diversity of early ornithischian dinosaurs
Proceedings of The Royal Society B: Biological Sciences, 2005Co-Authors: William G. Parker, Sterling J. Nesbitt, Randall B Irmis, Jeffrey W Martz, Lori S BrowneAbstract:A new discovery of skeletons of Revueltosaurus callenderi from the Upper Triassic Chinle Formation of Petrified Forest National Park, Arizona clearly shows that Revueltosaurus is not an ornithischian dinosaur as previously supposed. Features such as the presence of a postfrontal, crocodile-normal ankle and paramedian osteoderms with anterior bars place R. callenderi within the Pseudosuchia, closer to crocodylomorphs than to dinosaurs. Therefore, dental characters previously used to place Revueltosaurus within the Ornithischia evolved convergently among other archosaur taxa, and cannot be used to diagnose ornithischian dinosaur teeth. As a result, all other putative North American Late Triassic ornithischians, which are all based exclusively on teeth, are cast into doubt. The only reasonably well-confirmed Late Triassic ornithischians worldwide are Pisanosaurus mertii and an unnamed heterodontosaurid from Argentina. This considerably changes the understanding of early dinosaur diversity, distribution and evolution in the Late Triassic.
Zhaokun Yan - One of the best experts on this subject based on the ideXlab platform.
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Late Triassic tectonic inversion in the upper yangtze block insights from detrital zircon u pb geochronology from south western sichuan basin
Basin Research, 2019Co-Authors: Zhaokun Yan, Yuntao Tian, Pieter Vermeesch, Xilin Sun, Martin Rittner, Andrew Carter, Chongjian Shao, Hu HuangAbstract:The Sichuan Basin and the Songpan‐Ganze terrane, separated by the Longmen Shan fold‐and‐thrust belt (the eastern margin of the Tibetan PLateau), are two main Triassic depositional centres, south of the Qinling‐Dabie orogen. During the Middle–Late Triassic closure of the Paleo‐Tethys Ocean, the Sichuan Basin region, located at the western margin of the Yangtze Block, transitioned from a passive continental margin into a foreland basin. In the meantime, the Songpan‐ Granze terrane evolved from a marine turbidite basin into a fold‐and‐thrust belt. To understand if and how the regional sediment routing system adjusted to these tectonic changes, we monitored sediment provenance primarily by using detrital zircon U‐Pb analyses of representative stratigraphic samples from the south‐western edge of the Sichuan Basin. Integration of the results with paleocurrent, sandstone petrology and published detrital zircon data from other parts of the basin identified a marked change in provenance. Early–Middle Triassic samples were dominated by Neoproterozoic (~700–900 Ma) zircons sourced mainly from the northern Kangdian basement, whereas Late Triassic sandstones that contain a more diverse range of zircon ages sourced from the Qinling, Longmen Shan and Songpan‐Ganze terrane. This change reflects a major drainage adjustment in response to the Late Triassic closure of the Paleo‐Tethys Ocean and significant shortening in the Longmen Shan thrust belt and the eastern Songpan‐Ganze terrane. Furthermore, by Late Triassic time, the uplifted northern Kangdian basement had subsided. Considering the eastward paleocurrent and depocenter geometry of the Upper Triassic deposits, subsidence of the northern Kangdian basement probably resulted from eastward shortening and loading of the Songpan‐Ganze terrane over the western margin of the Yangtze Block in response to the Late Triassic collision among Yangtze Block, Yidun arc and Qiangtang terrane along the Ganze‐Litang and Jinshajiang sutures.
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Late Triassic tectonic inversion in the upper yangtze block insights from detrital zircon u pb geochronology from south western sichuan basin
Basin Research (2018) (In press)., 2018Co-Authors: Zhaokun Yan, Yuntao Tian, Pieter Vermeesch, Xilin Sun, Martin Rittner, Andrew Carter, Chongjian Shao, Hu HuangAbstract:The Sichuan Basin and the Songpan‐Ganze terrane, separated by the Longmen Shan fold‐and‐thrust belt (the eastern margin of the Tibetan PLateau), are two main Triassic depositional centres, south of the Qinling‐Dabie orogen. During the Middle–Late Triassic closure of the Paleo‐Tethys Ocean, the Sichuan Basin region, located at the western margin of the Yangtze Block, transitioned from a passive continental margin into a foreland basin. In the meantime, the Songpan‐Granze terrane evolved from a marine turbidite basin into a fold‐and‐thrust belt. To understand if and how the regional sediment routing system adjusted to these tectonic changes, we monitored sediment provenance primarily by using detrital zircon U‐Pb analyses of representative stratigraphic samples from the south‐western edge of the Sichuan Basin. Integration of the results with paleocurrent, sandstone petrology and published detrital zircon data from other parts of the basin identified a marked change in provenance. Early–Middle Triassic samples were dominated by Neoproterozoic (~700–900 Ma) zircons sourced mainly from the northern Kangdian basement, whereas Late Triassic sandstones that contain a more diverse range of zircon ages sourced from the Qinling, Longmen Shan and Songpan‐Ganze terrane. This change reflects a major drainage adjustment in response to the Late Triassic closure of the Paleo‐Tethys Ocean and significant shortening in the Longmen Shan thrust belt and the eastern Songpan‐Ganze terrane. Furthermore, by Late Triassic time, the uplifted northern Kangdian basement had subsided. Considering the eastward paleocurrent and depocenter geometry of the Upper Triassic deposits, subsidence of the northern Kangdian basement probably resulted from eastward shortening and loading of the Songpan‐Ganze terrane over the western margin of the Yangtze Block in response to the Late Triassic collision among Yangtze Block, Yidun arc and Qiangtang terrane along the Ganze‐Litang and Jinshajiang
Randall B Irmis - One of the best experts on this subject based on the ideXlab platform.
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a complete skeleton of a Late Triassic saurischian and the early evolution of dinosaurs
Science, 2009Co-Authors: Sterling J. Nesbitt, Randall B Irmis, Nathan D Smith, Alan H Turner, Alex Downs, Mark A NorellAbstract:Characterizing the evolutionary history of early dinosaurs is central to understanding their rise and diversification in the Late Triassic. However, fossils from basal lineages are rare. A new theropod dinosaur from New Mexico is a representative of the early North American diversification. Known from several nearly complete skeletons, it reveals a mosaic of plesiomorphic and derived features that clarify early saurischian dinosaur evolution and provide evidence for the antiquity of novel avian character systems including skeletal pneumaticity. The taxon further reveals latitudinal differences among saurischian assemblages during the Late Triassic, demonstrates that the theropod fauna from the Late Triassic of North America was not endemic, and suggests that intercontinental dispersal was prevalent during this time.
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a Late Triassic dinosauromorph assemblage from new mexico and the rise of dinosaurs
Science, 2007Co-Authors: Randall B Irmis, Sterling J. Nesbitt, Kevin Padian, Nathan D Smith, Alan H Turner, Daniel T Woody, Alex DownsAbstract:It has generally been thought that the first dinosaurs quickly replaced more archaic Late Triassic faunas, either by outcompeting them or when the more archaic faunas suddenly became extinct. Fossils from the Hayden Quarry, in the Upper Triassic Chinle Formation of New Mexico, and an analysis of other regional Upper Triassic assemblages instead imply that the transition was gradual. Some dinosaur relatives preserved in this Chinle assemblage belong to groups previously known only from the Middle and lowermost Upper Triassic outside North America. Thus, the transition may have extended for 15 to 20 million years and was probably diachronous at different paleolatitudes.
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a critical re evaluation of the Late Triassic dinosaur taxa of north america
Journal of Systematic Palaeontology, 2007Co-Authors: Sterling J. Nesbitt, Randall B Irmis, William G. ParkerAbstract:Synopsis The North American Triassic dinosaur record has been repeatedly cited as one of the most complete early dinosaur assemblages. The discovery of Silesaurus from Poland and the recognition that Herrerasaurus and Eoraptor may not be theropods have forced a re‐evaluation of saurischian and theropod synapomorphies. Here, we re‐evaluate each purported Triassic dinosaur from North America on a specimen by specimen basis using an apomorphy‐based approach. We attempt to assign specimens to the most exclusive taxon possible. Our revision of purported Late Triassic dinosaur material from North America indicates that dinosaurs were rarer and less diverse in these strata than previously thought. This analysis concludes that non‐dinosaurian dinosauriforms were present in North America in the Late Triassic. Most of the proposed theropod specimens are fragmentary and/or indistinguishable from corresponding elements in the only well‐known Triassic theropod of North America, Coelophysis bauri. No Triassic material ...
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the Late Triassic pseudosuchian revueltosaurus callenderi and its implications for the diversity of early ornithischian dinosaurs
Proceedings of The Royal Society B: Biological Sciences, 2005Co-Authors: William G. Parker, Sterling J. Nesbitt, Randall B Irmis, Jeffrey W Martz, Lori S BrowneAbstract:A new discovery of skeletons of Revueltosaurus callenderi from the Upper Triassic Chinle Formation of Petrified Forest National Park, Arizona clearly shows that Revueltosaurus is not an ornithischian dinosaur as previously supposed. Features such as the presence of a postfrontal, crocodile-normal ankle and paramedian osteoderms with anterior bars place R. callenderi within the Pseudosuchia, closer to crocodylomorphs than to dinosaurs. Therefore, dental characters previously used to place Revueltosaurus within the Ornithischia evolved convergently among other archosaur taxa, and cannot be used to diagnose ornithischian dinosaur teeth. As a result, all other putative North American Late Triassic ornithischians, which are all based exclusively on teeth, are cast into doubt. The only reasonably well-confirmed Late Triassic ornithischians worldwide are Pisanosaurus mertii and an unnamed heterodontosaurid from Argentina. This considerably changes the understanding of early dinosaur diversity, distribution and evolution in the Late Triassic.
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advances in Late Triassic vertebrate paleontology based on new material from petrified forest national park arizona
2005Co-Authors: William G. Parker, Randall B IrmisAbstract:Recent collecting of vertebrate fossils in Petrifi ed Forest National Park as the result of an ongoing inventory of fossil localities has produced numerous important new specimens. These include phytosaur skulls and partial skeletons, aetosaur partial skeletons and isoLated, but complete, osteoderms, as well as new dinosaur material that contributes new information to a currently poor dinosaur record from the Late Triassic of Arizona. Stratigraphic placement of phytosaur and aetosaur fossils from the park shows that several index taxa used for Late Triassic land vertebrate faunachrons overlap and that revision of these faunachrons is needed.
Clemmensen, lars B. - One of the best experts on this subject based on the ideXlab platform.
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A possible phytosaurian (Archosauria, pseudosuchia) coprolite from the Late Triassic fleming fjord group of jameson land, central east Greenland
'Geological Society of Denmark', 2021Co-Authors: Clemmensen, lars B.Abstract:Funding Information: This project is part of a combined sedimentological, palaeontological and magnetostratigraphical investigation of the Late Triassic vertebrate-bearing continental deposits in central East Greenland supported by the Independent Research Fund Denmark. We thank Dennis V. Kent for productive discussions on Late Triassic stratigraphy. We are grateful to Karen Dybkjær, GEUS, for help with palynological examination of the coprolite. We thank Bo Markussen, Department of Mathematical Sciences at the University of Copenhagen, for guidance about statistical analyses. We gratefully acknowledge support from Dronning Margrethes og Prins Henriks Fond, Arbejdsmarkedets Feriefond, Oticon Fonden, Knud Højgaards Fond, Louis Petersens Legat, Det Obelske Familiefond, Ernst og Vibeke Husmans Fond, the Carlsberg Foundation and Geocenter Møns Klint. GEUS provided valuable logistical support. We thank Adrian Hunt and an anonymous referee for constructive reviews.A large, well-preserved vertebrate coprolite was found in a lacustrine sediment in the Malmros Klint Formation of the Late Triassic Fleming Fjord Group in the Jameson Land Basin, central East Greenland. The size and internal and external morphology of the coprolite is consistent with that of crocodilian coprolites and one end of the coprolite exhibits evidence of post-egestion trampling. As the associated vertebrate fauna of the Fleming Fjord Group contains abundant remains of pseudosuchian phytosaurs, the coprolite is interpreted as being from a large phytosaur.publishersversionpublishe
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Issi saaneq gen. Et sp. nov.—A new sauropodomorph dinosaur from the Late Triassic (norian) of jameson land, central east greenland
'MDPI AG', 2021Co-Authors: Clemmensen, lars B.Abstract:UIDB/04035/2020The Late Triassic (Norian) outcrops of the Malmros Klint Formation, Jameson Land (Green-land) have yielded numerous specimens of non-sauropod sauropodomorphs. Relevant fossils were briefly reported in 1994 and were assigned to PLateosaurus trossingensis. However, continuous new findings of early non-sauropod sauropodomorphs around the globe facilitate comparisons and allow us to now revise this material. Here, the non-sauropod sauropodomorph Issi saaneq gen. et sp. nov. is described based on two almost complete and articuLated skulls. The two skulls represent a middle-stage juvenile and a Late-stage juvenile or subadult. Issi saaneq differs from all other sauropodomorphs by several unique traits: (1) a small foramen at the medial surface of the premaxilla; (2) an anteropos-teriorly elongated dorsoposterior process of the squamosal; (3) a relatively high quadrate relative to rostrum height; (4) a well-developed posterodorsal process of the articular. These features cannot be explained by taphonomy, ontogeny, or intraspecific variation. Issi saaneq shows affinities to Brazilian pLateosaurids and the European PLateosaurus, being recovered as the sister clade of the latter in our phylogenetic analysis. It is the northernmost record of a Late Triassic sauropodomorph, and a new dinosaur species erected for Greenland. Issi saaneq broadens our knowledge about the evolution of pLateosaurid sauropodomorphs.publishersversionpublishe
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Cyclotosaurus naraserluki, sp. nov., a new Late Triassic cyclotosaurid (Amphibia, Temnospondyli) from the Fleming Fjord Formation of the Jameson Land Basin (East Greenland)
'Informa UK Limited', 2017Co-Authors: Shubin, neil H., Clemmensen, lars B.Abstract:Sem PDF. Fundacao para a Ciencia e a Tecnologia (SFRH/BD/99580/2014) European Association of Vertebrate Palaeontologists Research Grant (EAVP-ERG) Stan Wood Award of The Palaeontological Association (PA-SW201502) Carlsberg FoundationCyclotosaurus naraserluki, sp. nov., is a new Late Triassic capitosaurid amphibian from lacustrine deposits in the Fleming Fjord Formation of the Jameson Land Basin in Greenland. It is based on a fairly complete and well-preserved skull associated with two vertebral intercentra. Previously reported as Cyclotosaurus cf. posthumus, C. naraserluki is unique among cyclotosaurs for having the postorbitals embaying the supratemporals posteromedially. The anterior palatal vacuity presents an autapomorphic complete subdivision by a wide medial premaxillary-vomerine bony connection. The parasphenoid projects between the pterygoids and the exoccipitals, preventing a suture between the two, a primitive condition shared with Rhinesuchidae, Eryosuchus, and Kupferzellia. Within Cyclotosaurus, the Greenlandic skull has a distinctive combination of circular choanae (shared with C. ebrachensis, C. posthumus, and C. robustus) and a convex posteromedial margin of the tabulars (also present in C. ebrachensis and C. intermedius). A phylogenetic analysis indicates that C. naraserluki is the sister taxon of the middle Norian C. mordax from southern Germany, with which it shares a pair of premaxillary foramina. Cyclotosaurus is one of the most successful and diverse genera of Late Triassic temnospondyls, with at least eight species reported from middle Carnian to Late Norian. Cyclotosaurus naraserluki is the largest amphibian ever reported from Greenland and one of the Late Triassic vertebrates with the highest northern paleolatitude currently known.publishe
Yin Wang - One of the best experts on this subject based on the ideXlab platform.
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Late Triassic extensional tectonics in the northern north china craton insights from a multidisciplinary study of the wangtufang pluton
Journal of Asian Earth Sciences, 2020Co-Authors: Michel Faure, Yan Chen, Lingtong Meng, Jipei Zeng, Yin Wang, Qiuli LiAbstract:Abstract To better understand Late Triassic tectonic setting in the northern North China Craton (NCC), the emplacement mechanism of the Wangtufang pluton, which recorded the synmagmatic regional tectonic signature, has been investigated. Zircon U-Pb ages, and Hf isotopic data, and whole-rock geochemical analyses suggest that the Late Triassic Wangtufang pluton composed of syenogranite and diorite is derived from partial melting of lower crust with some depleted mantle components. Both the syenogranite and diorite appear isotropic. Anisotropy of magnetic susceptibility and gravity studies have been carried out to characterize internal fabrics and shape of the pluton. The diorite forms just thin remnants above the syenogranite. The syenogranite with a series of NW-SE trending dykes intruded into the diorite and its country rocks. In the syenogranite, the gently dipping magnetic foliations strike nearly parallel to the pluton border. The shallow plunging magnetic lineations mainly strike NE–SW. Combining NE-SW trending elongated subsurface shape with central root, unflat bottom, and moderate- to high- inward dipping sidewalls, the syenogranite could be considered as a lopolith-like intrusion. The syenogranite was likely emplaced by inflation of magma pulses from its central conduit and built up by floor depression. Emplacement of the syenogranite was in an extensional setting, considering: (1) the NE–SW striking magnetic lineation, (2) the NE–SW trending elongated subsurface pluton shape, and (3) the orthogonal NW–SE striking syenogranitic dykes considered as tension gashes during the NE–SW trending extension. The Wangtufang pluton provides reliable arguments to the Late Triassic intracontinental extensional setting already suggested in the northern NCC.
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Late Triassic extensional tectonics in the northern north china craton insights from a multidisciplinary study of the wangtufang pluton
Journal of Asian Earth Sciences, 2020Co-Authors: Michel Faure, Yan Chen, Lingtong Meng, Jipei Zeng, Huabiao Qiu, Wei Lin, Zhiheng Ren, Yin WangAbstract:Abstract To better understand Late Triassic tectonic setting in the northern North China Craton (NCC), the emplacement mechanism of the Wangtufang pluton, which recorded the synmagmatic regional tectonic signature, has been investigated. Zircon U-Pb ages, and Hf isotopic data, and whole-rock geochemical analyses suggest that the Late Triassic Wangtufang pluton composed of syenogranite and diorite is derived from partial melting of lower crust with some depleted mantle components. Both the syenogranite and diorite appear isotropic. Anisotropy of magnetic susceptibility and gravity studies have been carried out to characterize internal fabrics and shape of the pluton. The diorite forms just thin remnants above the syenogranite. The syenogranite with a series of NW-SE trending dykes intruded into the diorite and its country rocks. In the syenogranite, the gently dipping magnetic foliations strike nearly parallel to the pluton border. The shallow plunging magnetic lineations mainly strike NE–SW. Combining NE-SW trending elongated subsurface shape with central root, unflat bottom, and moderate- to high- inward dipping sidewalls, the syenogranite could be considered as a lopolith-like intrusion. The syenogranite was likely emplaced by inflation of magma pulses from its central conduit and built up by floor depression. Emplacement of the syenogranite was in an extensional setting, considering: (1) the NE–SW striking magnetic lineation, (2) the NE–SW trending elongated subsurface pluton shape, and (3) the orthogonal NW–SE striking syenogranitic dykes considered as tension gashes during the NE–SW trending extension. The Wangtufang pluton provides reliable arguments to the Late Triassic intracontinental extensional setting already suggested in the northern NCC.
