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Ammonoids from the Zhuganpo Member of the Falang Formation at Nimaigu and their relevance for dating the Xingyi Fossil-Lagerstaette (Late Ladinian, Guizhou, China).

Authors:
Zou Xiaodong
Zou Xiaodong
Zou Xiaodong
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Marco Balini at University of Milan
Marco Balini
Dayong Jiang at Peking University
Dayong Jiang
Andrea Tintori at University of Milan
Andrea Tintori
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Abstract

In this contribution we provide the sistematic description, the biostratigraphic classification and the correlation of the ammonoid faunas collected between 2010 and 2013 at Nimaigu (Wusha) near Xingyi (Guizhou, South China) from the Falang Formation. The sampled interval includes the Zhuganpo Member, which provided the worldwide known Xingyi Fossilagerstätte, and the lowermost part of the overlying Wayao Member. Ammonoid resulted quite aboundant but their preservation is not always very good. The new genera Yangites, Sinomeginoceras and Haoceras are described on the basis of four new species. Xenoprotrachyceras, Detoniceras, Ptychites, Trachycearas and Clionitites are also recognized, together with a specimen attributed with doubt to Parasturia. Most of the faunas are endemic and the typical representatives of the Upper Ladinian ammonoid zones have not been recognized. A new local biostratigraphic scale is proposed, consisting of Haoceras xingyiense zone, Trachyceras beds and Trachyceras multituberculatum zone, in stratigraphic order. The Trachyceras beds and the Trachyceras multituberculatum zone are attributed to the Lower Carnian, but most of the bio-chronostratigraphic analysis is focused on the Haoceras xingyiense zone because this biozone is directly overlying the vertebrate bearing interval. The correlation of the new biozone is discussed and its stratigraphic position is comprised between the upper Meginae to lower Sutherlandi Zones of the North American scale. This correlation leads to solve the problem of the age of the Xingyi Fossilagerstätte, that for more than 30 years was matter of discussion. This age is now early to middle Late Ladinian.
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Specimen D H U h W U/D H/W SGR
ws2012-59-1 58.2 23 22 13.2 11.4 0.37 2.01 74.24
holotype
ws2012-57-2 60.5 24 20.4 16.10 - 0.33 - 49.06
ws2012-57-1 50.1 18.6 17.5 14 11.7 0.34 1.58 32.85
ws2012-59-5 52 20.1 17.1 14.8 11.2 0.32 1.79 35.81
ws2012-68-4 31.2 14.2 9.5 7.5 7.6 0.30 1.86 89.33
ws2012-59-8 30 11 12 7.0 8-0 0.4 1.37 57.14
ws2012-88-1 30 10.3 11 8.7 6.8 0.36 1.51 18.39
Specimen D H U W U/D H/W H/U
ws2012-70-1
holotype
37.0 17.0 10.0 4.8 0.27 3.54 1.7
ws2012-68-2 36.2 14.9 9.8 5.0 0.27 2.98 1.52
Specimen D H U W U/D H/W H/U
ws2012-71-1
holotype
36.3 16.8 10.1 6.0 0.27 2.8 1.66
Specimen D H U h W U/D
ws2012-238-3 25.0 - 7.1 - - 0.28
Specimen D H U W U/D H/W
ws2012-162-1 12.1 4.9 4.0 3.1 0.33 1.58
... The age of Xingyi Fauna was confirmed to be late Ladinian (Middle Triassic) by the ammonoid biostratigraphic correlation and isotope dating ( Zou et al., 2015a; Z.G. Li et al., 2016b;Sun et al., 2016), which proposed that the Xingyi Fauna is the only known late Ladinian (Middle Triassic) Fossil Lagerst?tte characterized by exceptionally well-preserved marine reptiles and fishes in the world ( Ji et al., 2012). ...
... The fossiliferous level of the Xingyi Fauna at the Nimaigu section lies in the middle part of the Zhuganpo Member of the Falang Formation; its top is about 48 m below the base of the Wayao Member of the Falang Formation (Sun et al., 2016; Fig. 1B). Zou et al. (2015a) recognized three ammonoid biozones at this section, including Haoceras xingyiensis Zone, Trachyceras beds and T. multituberculatum Zone in ascending order. The H. xingyiensis Zone, whose base is about 0.6 m above the fossiliferous level of the Xingyi Fauna (from Layer 57 to Layer 88), can be partly correlated to the North American lower Sutherlandi Zone, which indicates that the age of the Xingyi Fauna is middle Late Ladinian ( Zou et al., 2015a). ...
... Zou et al. (2015a) recognized three ammonoid biozones at this section, including Haoceras xingyiensis Zone, Trachyceras beds and T. multituberculatum Zone in ascending order. The H. xingyiensis Zone, whose base is about 0.6 m above the fossiliferous level of the Xingyi Fauna (from Layer 57 to Layer 88), can be partly correlated to the North American lower Sutherlandi Zone, which indicates that the age of the Xingyi Fauna is middle Late Ladinian ( Zou et al., 2015a). This is also supported by the U-Pb dating on the Zircon samples from tuff at the bottom of Layer 47, 240.8 ? ...
Middle Triassic Xingyi Fauna: Showing turnover of marine reptiles from coastal to oceanic environments
Article
  • May 2017
  • Palaeoworld
The late Ladinian (Middle Triassic) Xingyi Fauna from the Zhuganpo Member of the Falang Formation yields abundant and well-preserved marine reptiles. Bed-by-bed excavation at Wusha in Xingyi of Guizhou Province reveals two marine vertebrate assemblages in a fossiliferous horizons that span 5.1 m in total thickness. The lower assemblage is marked by the near-shore sauropterygians, including the pachypleurosaur Keichousaurus, the nothosaurians Nothosaurus and Lariosaurus, with a strong paleobiogeographic affinity to western Tethys. The upper assemblage consists of oceanic ichthyosaurs and pistosaurs, including the large shastasaurid ichthyosaur Guizhouichthyosaurus, the euichthyosaur Qianichthyosaurus, pistosaurs Yunguisaurus and Wangosaurus, and the thalattosaur Xinpusaurus, with a closer paleobiogeographic affinity to North America. The coastal pachypleurosaur and nothosaurid sauropterygians disappeared in the upper assemblage, suggesting that they were replaced by an oceanic marine reptile community that emerged. The reptilian composition of the upper assemblage is similar to that of the Guanling Biota, which is of the Early Carnian (Late Triassic) in age and thus somewhat younger than the Xingyi Fauna. The ecological turnover of marine reptiles from near-shore to the open ocean community corresponds to the paleoenvironmental changes indicated by lithofacies analysis, δ¹³C and the global sea level changes.
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... Enos et al. (2006) reported that the Zhuganpo Formation yielded a typical Ladinian ammonoid association, including age diagnostic Anolcites (=Trachyceras). Based on a large ammonoid collection, Zou et al. (2015) also suggested that most of the Zhuganpo Formation in the Xingyi area was of Ladinian age except for the upper part which was assigned to the Carnian. ...
... The hiatus in the Ladinian is thus interpreted to be a regional phenomenon and likely represents the manifestation of the GLR (Yin, 1982). The difference in stratigraphic scheme between the Xingyi (Zou et al., 2015) and Zhenfeng areas (this study) probably reflects a large, intra-regional variation and the diachronous nature of the Zhuganpo Formation. Complete Ladinian successions are probably only developed in deep-water settings as found in Luodian and possibly in the Xingyi Basin (Wang et al., 2005;Zou et al., 2015). ...
... The difference in stratigraphic scheme between the Xingyi (Zou et al., 2015) and Zhenfeng areas (this study) probably reflects a large, intra-regional variation and the diachronous nature of the Zhuganpo Formation. Complete Ladinian successions are probably only developed in deep-water settings as found in Luodian and possibly in the Xingyi Basin (Wang et al., 2005;Zou et al., 2015). ...
Early Carnian conodont fauna at Yongyue, Zhenfeng area and its implication for Ladinian-Carnian subdivision in Guizhou, South China
Article
  • Feb 2017
  • PALAEOGEOGR PALAEOCL
The subdivision of Ladinian and Carnian strata in Guizhou, South China has been a matter of intense debate because of the paucity of age-diagnostic faunas. Here we have carried out a detailed conodont biostratigraphic investigation on the Yangliujing, Zhuganpo and Wayao formations in the Yongyue section of western Guizhou Province. Conodonts are only prolific in the Zhuganpo and Wayao formations. Three genera and twenty species are identified, including two new species Quadralella wanlanensis n. sp. and Quadralella yongyueensis n. sp. They represent a rather endemic fauna of latest Ladinian to early Carnian age. Four conodont zones are established. They are, in the ascending order, the Paragondolella foliata, Quadralella polygnathiformis, Quadralella tadpole, and Quadralella aff. praelindae zones. Thus in the study area, the Zhuganpo Formation is generally of early Carnian (Julian 1) age whilst the Wayao Formation probably extends from the Julian 2 into the late Carnian (Tuvalian substage). The Ladinian–Carnian boundary (LCB) cannot be precisely defined due to the absence of the ammonoid Daxatina Canadensis and the paucity of conodonts. However, the LCB is unlikely lower than the Yangliujing–Zhuganpo formation contact. The Julian 1–Julian 2 (early Carnian) substages boundary is defined in the uppermost Zhuganpo Formation by the occurrence of basal Julian 2 ammonoid Austrotrachyceras ex gr. A. austriacum and is also evidenced by the disappearance of most short-range Julian 1 conodonts in the overlying Wayao Formation.
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... Biostratigraphical studies of marine reptiles and ammonites suggest a late Middle Triassic (late Ladinian) age for the lower part of the Zhuganpo Member of the Falang Formation (Young, 1958;Chen, 1985;Li & Jin, 2003, 2009Zou et al., 2015;Li C et al., 2016). This age determination has recently been supported by a zircon U-Pb age dating (240.8 ± 1.8 Mya) for the fossil beds (Li et al., 2016). ...
... This age determination has recently been supported by a zircon U-Pb age dating (240.8 ± 1.8 Mya) for the fossil beds (Li et al., 2016). Although a younger Late Triassic (Carnian) age was proposed by Wang et al. (1998) on the basis of conodont biostratigraphy, this was rejected by Zou et al. (2015), who commented that the conodont identification by Wang et al. (1998) is inaccurate. ...
Redescription and phylogenetic reassessment of Asialepidotus shingyiensis (Holostei: Halecomorphi) from the Middle Triassic (Ladinian) of China
Article
Full-text available
  • Jan 2018
The previously alleged 'semionotid' fish Asialepidotus shingyiensis from the Middle Triassic (Ladinian) marine deposits of Guizhou and Yunnan, China has recently been identified as a halecomorph, but its phylogenetic relationships with other halecomorphs remain controversial. This taxon was successively placed in different halecomorph orders: Amiiformes, Parasemionotiformes and 'Panxianichthyiformes'. Here, a detailed redescription of Asialepidotus is presented based upon a comparative study of the original material with 50 new specimens. Newly recognized anatomical information includes a V-shaped rostral, paired vomers, a toothed parasphenoid, a dermosphenotic with a canal-bearing innerorbital flange, a splint-like quadratojugal, a branch of the infraorbital sensory canal in the maxilla, and many elements in the hyoid and branchial apparatuses and the lower jaw. Results of a cladistic analysis incorporating these new data indicate that the 'Panxianichthyiformes' is a poorly defined, paraphylectic grade; Asialepidotus is not sister to Panxianichthys as previously suggested; instead, it is more derived than Panxianichthys and consists of the sister taxon of the clade Robustichthys plus Jurassic-Cretaceous ionoscopiforms. This phylogen-etic reassessment of Asialepidotus extends the stratigraphic range of the Ionoscopiformes in China by ~4 Myr and supports the hypothesis that the early ionoscopiform diversification was already established by the Middle Triassic.
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... The whole fossil assemblage was named the Xingyi Fauna, or Xingyi Biota (Benton, 2013;Lu et al., 2017). Biostratigraphical studies of invertebrates and marine reptiles (Young, 1958;Chen, 1985;Li and Jin, 2003, 2009;Zou et al., 2015;Li C et al., 2016) generally suggest a late Middle Triassic (Ladinian) age for this biota, as supported by the recent zircon U-Pb dating (240.8±1.8 ...
A large peltopleurid fish (Actinopterygii: Peltopleuriformes) from the Middle Triassic of Yunnan and Guizhou, China
Article
Full-text available
  • Apr 2018
Peltopleuriformes are a stem group of neopterygian fishes from the Middle-Late Triassic marine ecosystems in Europe and South China, including the Peltopleuridae and Thoracopteridae. Among them, peltopleurids are commonly small-sized fishes with a standard length (SL) rarely exceeding 55 mm. Here, a new peltopleurid, Peltopleurus tyrannos sp. nov., is described based on three well-preserved specimens from the Middle Triassic (Ladinian) of Fuyuan, Yunnan and Xingyi, Guizhou, China. The discovery documents the largest species (SL = 72 mm) of this genus in the Middle Triassic and provides new insights into the morphologic and trophic diversifications of peltopleurids. In addition to large conical teeth on the oral margins of the jaws, the new peltopleurid bears many blunt teeth of various sizes on the oral margin of the palatopterygoid, which may be used for crushing some hard-shelled invertebrates (e.g., crustaceans) or small armored fishes. By contrast, the more commonly founded relative, P. orientalis, from the same ecosystem (Xingyi Biota) is toothless and has a much smaller body size (SL = 26 mm), and probably represents a schooling fish that fed on small planktonic invertebrates. The new finding shows that Peltopleurus from the late Middle Triassic Xingyi Biota of South China had evolved into two different ecomorphotypes. Citation Xu G H, Ma X Y, Zhao L J, 2018. A large peltopleurid fish (Actinopterygii: Peltopleuriformes) from the Middle Triassic of Yunnan and Guizhou, China. Vertebrata PalAsiatica, 56(2): 106-120 Peltopleuriformes are an order of stem-neopterygian fishes from the Middle-Late
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... This finding has also a really high stratigraphic significance, allowing the sites to be correlated on the basis of fossil fishes (Thoracopterus wushaensis may not be the only one, but that needs confirmation). The associated ammonoids indeed are problematic because, while the alpine faunas contain the typical taxa making up the basis of Middle Triassic stratigraphy, the Chinese ammonites are mostly endemic ( Zou et al., 2015) (Fig. 2). Strange to say, in this case ammonoids are more endemic than fishes! ...
Triassic actinopterygians across Tethys: state of the art
Conference Paper
Full-text available
  • Aug 2017
During the 5 th International Meeting on Mesozoic Fishes held at Santillo, Mexico, we first presented the great novelty of the marine Triassic findings in southern China. The discovery and following first studies had already shown their important implications not only for paleontology but also for paleogeography. One advantage of fishes over marine reptiles is their size when we want to recognize an assemblage and compare it to others. Fishes indeed are far smaller and more numerous than reptiles, so that the chances to have a 'complete' fish assemblage are much higher. We believe that very fast migrations were possible, but not all the fishes were either interested or able to travel such a long distance. Oceanic currents in the Tethys had clockwise direction in the northern hemisphere, making westwards migration easier in the tropical region where our fishes lived.
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... The exact locality and horizon of the holotype is unknown. The new specimen was found about 0.6 m below the base of ammonite Haoceras xingyiensis Zone (middle late Ladinian, Middle Triassic) at the main excavation quarry in Nimaigu Village, Wusha Town, Xingyi City, Guizhou Province, China, as reported byZou et al. (2015). The specimen was found in layer 30 of the lower faunal assemblage, together with Keichousaurus and Nothosaurus youngi, as well as the actinopterygian fishes Asialepidotus and Habroichthys (Tintori et al., 2015). ...
A new specimen of Lariosaurus xingyiensis (Reptilia, Sauropterygia) from the Ladinian (Middle Triassic) Zhuganpo Member, Falang Formation, Guizhou, China
Article
Full-text available
  • Apr 2017
A new specimen of Lariosaurus xingyiensis is described and provides new information on the dermal palate of the skull and the postcranial skeleton. Based on a comprehensive comparison with the holotype specimen, an amended diagnosis of L. xingyiensis is given on the basis of the following features: a medium-sized species of Lariosaurus with jugal absent, longitudinal diameter of upper temporal fenestra about 1.7 times longitudinal diameter of orbit, retroarticular process elongate, clavicles without anterolaterally expanded corners, posterior scapular process (blade) slender and elongate, humerus distinctly shorter than femur, and dorsal process of ilium with distinct tubercular ornamentation. Two phylogenetic analyses of Nothosauridae demonstrate that Nothosaurus as previously conceived is not monophyletic whereas Lariosaurus is a monophylum. Three species previously referred to Nothosaurus are more closely related to Lariosaurus and are hereby reassigned to Lariosaurus, namely, L. juvenilis, L. youngi, and L. winkelhorsti. SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP Citation for this article: Lin, W.-B., D.-Y. Jiang, O. Rieppel, R. Motani, C. Ji, A. Tintori, Z.-Y. Sun, and M. Zhou. 2017. A new specimen of Lariosaurus xingyiensis (Reptilia, Sauropterygia) from the Ladinian (Middle Triassic) Zhuganpo Member, Falang Formation, Guizhou, China. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2017.1278703.
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... Horizon and Locality?Middle part of Zhuganpo Member ( D 'Zhuganpo Formation' of Wang et al. [2002] ), Falang Formation ; about 0.6 m below the base of the ammonite Haoceras xingyiensis Zone, which is in part equivalent to the lower part of the North American Frankites sutherlandi Zone, of the middle Late Ladinian, Middle Triassic (Zou et al., 2015). Nimaigu Village, Wusha Town, Xingyi City, Guizhou Province, People's Republic of China. ...
A new species of Xinpusaurus (Reptilia, Thalattosauria) from the Ladinian (Middle Triassic) of Xingyi, Guizhou, southwestern China
Article
Full-text available
SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP Citation for this article: Li, Z.-G., D.-Y. Jiang, O. Rieppel, R. Motani, A. Tintori, Z.-Y. Sun, and C. Ji. 2016. A new species of Xinpusaurus (Reptilia, Thalattosauria) from the Ladinian (Middle Triassic) of Xingyi, Guizhou, southwestern China. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2016.1218340. 2016
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... Our approach combines conodont interval and assemblage zones (based on a combination of conodont species) with ammonoid/bivalve ranges to define the biostratigraphic scheme, therefore excluding problems caused by regional differences in the first and last occurrences of individual conodont species. Our biostratigraphy supports conclusions of a recent ammonoid study (Zou et al., 2015 ) that assigned the upper part of Zhuganpo Fm. (studied in this paper) and the overlying Wayao Fm. to the Carnian. However, our biostratigraphic age assignment for the Long Chang sequence differs from that inferred by magnetostratigraphy and cyclostratigraphy performed on similar lithological units (Zhang et al., 2015). ...
Climate warming, euxinia and carbon isotope perturbations during the Carnian (Triassic) Crisis in South China
Article
  • Jun 2016
  • EARTH PLANET SC LETT
The Carnian Humid Episode (CHE), also known as the Carnian Pluvial Event, and associated biotic changes are major enigmas of the Mesozoic record in western Tethys. We show that the CHE also occurred in eastern Tethys (South China), suggestive of a much more widespread and probably global climate perturbation. Oxygen isotope records from conodont apatite indicate a double-pulse warming event. The CHE coincided with an initial warming of 4 °C. This was followed by a transient cooling period and then a prolonged ∼7 °C warming in the later Carnian (Tuvalian 2). Carbon isotope perturbations associated with the CHE of western Tethys occurred contemporaneously in South China, and mark the start of a prolonged period of carbon cycle instability that persisted until the late Carnian. The dry-wet transition during the CHE coincides with the negative carbon isotope excursion and the temperature rise, pointing to an intensification of hydrologic cycle activities due to climatic warming. While carbonate platform shutdown in western Tethys is associated with an influx of siliciclastic sediment, the eastern Tethyan carbonate platforms are overlain by deep-water anoxic facies. The transition from oxygenated to euxinic facies was via a condensed, manganiferous carbonate (MnO content up to 15.1 wt%), that records an intense Mn shuttle operating in the basin. Significant siliciclastic influx in South China only occurred after the CHE climatic changes and was probably due to foreland basin development at the onset of the Indosinian Orogeny. The mid-Carnian biotic crisis thus coincided with several phenomena associated with major extinction events: a carbonate production crisis, climate warming, oscillations, marine anoxia, biotic turnover and flood basalt eruptions (of the Wrangellia Large Igneous Province).
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The Ladinian–Carnian conodont fauna at Yize, Yunnan, southwestern China, with implications for conodont palaeoecology and palaeogeography
Article
Full-text available
  • Feb 2023
Subdivisions of Ladinian–Carnian boundary beds and the lower Carnian strata in South China are challenging owing to a paucity of west Tethyan ammonoids. We investigated a conodont fauna in a continuous section at Yize in eastern Yunnan Province to provide a biostratigraphic solution. Five genera and 24 conodont species are recognized, and five conodont zones are established. The zones are, in ascending order, the Paragondolella inclinata Zone, the Quadralella polygnathiformis Zone, the Quadralella praelindae Zone, the Quadralella auriformis Zone and the Quadralella robusta Zone. The Ladinian–Carnian boundary is provisionally defined by the first occurrences of Quadralella polygnathiformis and Quadralella intermedia in the cherty limestone member of the Zhuganpo Formation. Regional correlations via conodont biostratigraphy indicate that the Zhuganpo Formation is probably diachronous, with a maximal range spanning the upper Ladinian to the lower Carnian. Amongst all common late Ladinian – early Carnian conodont genera, Paragondolella , Quadralella and Mazzaella are probably cosmopolitan. Budurovignathus was restricted to a few basins and probably preferred offshore or deep-water environments.
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A large peltopleurid fish (Actinopterygii: Peltopleuriformes) from the Middle Triassic of Yunnan and Guizhou, China
Article
Full-text available
  • Dec 2017
Peltopleuriformes are a stem group of neopterygian fishes from the Middle-Late Triassic marine ecosystems in Europe and South China, including the Peltopleuridae and Thoracopteridae. Among them, peltopleurids are commonly small-sized fishes with a standard length (SL) rarely exceeding 55 mm. Here, a new peltopleurid, Peltopleurus tyrannos sp. nov., is described based on three well-preserved specimens from the Middle Triassic (Ladinian) of Fuyuan, Yunnan and Xingyi, Guizhou, China. The discovery documents the largest species (SL = 72 mm) of this genus in the Middle Triassic and provides new insights into the morphologic and trophic diversifications of peltopleurids. In addition to large conical teeth on the oral margins of the jaws, the new peltopleurid bears many blunt teeth of various sizes on the oral margin of the palatopterygoid, which may be used for crushing some hard-shelled invertebrates (e.g., crustaceans) or small armored fishes. By contrast, the more commonly founded relative, P. orientalis, from the same ecosystem (Xingyi Biota) is toothless and has a much smaller body size (SL = 26 mm), and probably represents a schooling fish that fed on small planktonic invertebrates. The new finding shows that Peltopleurus from the late Middle Triassic Xingyi Biota of South China had evolved into two different ecomorphotypes.
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A revision of the Early Carnian Trachyceratidae (Ammonoidea) of Northeastern Asia
Article
Full-text available
  • Sep 2012
Major morphological features of the shell are studied, and new trachyceratid genera, Boreotrachyceras gen. nov. with the type species B. omkutchanicum (Bytschkov) and Okhototrachyceras gen. nov. with the type species O. seimkanense (Bytschkov), are established based on material from the Lower Carnian of the Omolon Massif and Northern Okhotsk Region. The first record of the genus Trachyceras in the Boreal Realm allows the correlation of the omkutchanicum Zone of Northeastern Asia with the standard aon Zone.
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A new species of Xinpusaurus (Thalattosauria) from Upper Triassic of China
Article
Full-text available
  • Jan 2004
A new species of Xinpusaurus Yin in Yin et al., 2000 (Thalattosauria, Thalattosauridae), is described from the Wayao Member of the Falang Formation (Tuvalian, Carnian, Upper Triassic) of Guanling County in Guizhou, southwestern China. It is the third thalattosaur species known from the Guanling faunal assemblage of marine reptiles. The type and only specimen consists of an entire skeleton, including a complete skull. It differs from the type species, X. suni, by its smaller adult size, the larger nasal, the more slender angular and low retroarticular process, the shape of the cervical neural spines, the number of presacral vertebrae, the large size of the scapula, the shape of the radius, the presence of a well ossified carpus, the more slender femur, the smaller hindfin, the presence of a complete row of distal tarsal ossifications, and the proportions of the metatarsals. It is consequently referred to a new species, Xinpusaurus kohi. A new analysis of thalattosaur interrelationships based on 30 cranial and postcranial characters corroborates a sister-group relationship between Xinpusaurus and Nectosaurus from the Carnian of California.
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Discovery of Upper Ladinian Ammonoids at the Type Locality of the Lower Carnian Desatoyense Zone (South Canyon, New Pass Range, Nevada)
Article
Full-text available
  • Jan 2008
S outh Canyon, located in the New Pass Range in central Nevada (Fig. 1), is one of the most important localities for Upper Triassic marine invertebrates in North America. This site yields very rich ammonoid faunas, as well as cnidarians (Muller, 1936; Stanley, 1979; Roniewicz and Stanley, 1998), foraminifers (Gazdzicki and Stanley, 1983), bivalves (Waller and Stanley, 1998, 2005; Hopkin and McRoberts, 2003), and brachiopods.
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Taxonomy and stratigraphic significance of Trachyceras silberlingi n. sp., from the Lower Carnian of South Canyon (New Pass Range, central Nevada, USA)
Article
  • Sep 2012
New intensive bed-by-bed ammonoid collecting efforts conducted in 2010 and 2011 at South Canyon, the type locality of the lowest Carnian Desatoyense Zone of the North American chronostratigraphic scale, have lead to the recognition of a new species of Trachyceras that is herein described The new species is dedicated to Norman J. Silberling (1928-2011), who was widely recognized as the leading authority on marine Triassic stratigraphy in western US for over 50 years. T. silberlingi n. sp. is characterized by a peculiar ornamentation consisting of two spiral rows of bullae on the flank (first row on umbilical shoulder and second row at about 70% of whorl height) and by ribs frequently looped in pairs at the lateral bulla. The new species, from South Canyon site F, the stratigraphically highest level of the fossiliferous succession of the middle member of the Augusta Mountain Formation, represents the first definite occurrence of the genus Trachyceras Laube, 1869 in this succession. For this reason T. silberlingi n. sp. is of great importance for the revision of the Desatoyense Zone, a unit defined on the basis of a large collection of ammonoids described in 1941 from the lower part of the middle member of the Augusta Mountain Formation, without regard for the number and position of fossil bearing levels. We herein propose the subdivision and replacement of the former Desatoyense Zone with two biostratigraphic units: the lower unit referred to as the Daxatina beds, is an informal biozone characterized by the occurrence of Daxatina and Frankites sutherlandi, and the overlying Trachyceras silberlingi biozone is a range zone characterized by the occurrence of Trachyceras, based on the new species. The chronostratigraphic potential of this proposed subdivision is briefly outlined, but it will be more accurately defined upon completion of the taxonomic revision of the South Canyon ammonoid faunas.
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The Late Triassic Black Shales of the Guanling Area, Guizhou Province, South-West China: a unique marine Reptile and pelagic Crinoid fossil Lagerstätte
Article
  • Jan 2008
  • Palaeontology
: Black shales of the lower member of the Carnian Xiaowa Formation (previously known as the Wayao Member of the Falang Formation or as the Wayao Formation) in the Guanling area, Guizhou Province, south-west China, are yielding a rich marine reptile fauna and exceptional remains of pelagic crinoids. The black shales represent deposition on the drowned southern margin of the Yangtze Platform during a Maximum Flooding Interval. The relatively reduced sedimentation rates led to the formation of the Lagerstätte through the accumulation of fossils in the anoxic bottom sediments over a prolonged period of time. Invertebrate fossils represent almost exclusively pelagic forms, such as a diverse ammonite fauna and halobiid bivalves. The spectacular finds of colonies of large (stem lengths > 11 m) crinoids of the genus Traumatocrinus attached to driftwood prove that this crinoid was the first to evolve a pseudoplanktonic life style. The other crinoid is the planktonic roveacrinid Osteocrinus. The marine reptile fauna, represented by probably hundreds of skeletons, is numerically dominated by three species of ichthyosaurs and four species of thalattosaurs. The thalattosaurs fill a palaeobiogeographic gap between the Alpine thalattosaur faunas and those from western North America. Two species of placodonts are rare finds. As for the thalattosaurs, the placodont occurrences greatly expand the geographic range of the group because placodonts have been known previously only from the Mediterranean region, the Alps and the Muschelkalk Basin. The unique abundance of thalattosaurs contrasts with a scarcity of fishes. Although we suggest that the fauna is authochthonous and inhabited surface waters, it must have represented an unusual ecosystem. However, the possibility remains that both the marine reptiles and the Traumatocrinus colonies were concentrated in the region by currents and do not reflect the biocoenosis.
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Triassic ammonoid biostratigraphy: An overview
Article
  • Jun 2010
The Triassic chronostratigraphic scale was built on two centuries of research on ammonoid biostratigraphy and biochronology. Two Triassic stage bases and all of the Triassic substages are currently defined by ammonoid bioevents. The study of Triassic ammonoids began during the late 1700s, and in 1895, Edmund von Mojsisovics, Wilhelm Waagen and Carl Diener published an essentially complete Triassic chronostratigraphic scale based on ammonoid biostratigraphy. This scale introduced many of the Triassic stage and substage names still used today, and all terminology of stages and substages subsequently introduced has been based on ammonoid biostratigraphy. Early Triassic ammonoids show a trend from cosmopolitanism (Induan) to latitudinal differentiation (Olenekian), and the four Lower Triassic substage (Griesbachian, Dinerian, Smithian and Spathian) boundaries are globally correlated by widespread ammonoid biotic events. Middle Triassic ammonoids have provinciality similar to that of the Olenekian and provide a basis for recognizing six Middle Triassic substages. Late Triassic ammonoids provide a basis for recognizing three stages divided into five substages. The main uncertainty for the future of Triassic ammonoid biostratigraphy is not the decline of the ammonoids as a tool for dating and correlation of Triassic strata but, rather, the dramatic decrease in the number of specialists, due to the lack of replacement of experienced palaeontologists who started their activity in the 1950s and 1960s.
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Ammonoid biostratigraphy of the Middle Triassic Latemar platform (Dolomites, Italy) and its correlation with Nevada and Canada
Article
  • Jul 2005
  • Geobios
An extensive study of the ammonoid fauna occurring in the lagoonal facies of a Middle Triassic isolated carbonate platform (Latemar platform, Dolomites, Italy) has been undertaken, and ammonoids from selected coeval successions (Punta Zonia, Marmolada, Rio Sacuz) have been illustrated. Ammonoids from Latemar have been collected in 20 distinct horizons (storm deposits) within the ca. 500 m thick lagoonal succession of the platform, thus providing a biostratigraphy of a series which is unusually expanded for this time interval, close to the Anisian–Ladinian boundary. Contrary to general opinion, some ammonoids of the Latemar and other coeval carbonate platforms of the Dolomites (Marmolada, Cernera), in particular Aplococeras avisianum, Lecanites misanii, Celtites spp., and Paranevadites sp., are also present in nearby basinal series. The same taxa have been found in North American localities deposited at the opposite margin of Panthalassa. The homotaxis of these ammonoids in North America and Latemar allow to establish a global scale correlation between the Southern Alps and North America with the highest resolution to date possible. In the context of this study, Aplococeras transiens n. sp. and Esinoceras nerinae n. sp are established.
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New Information on the Protorosaurian Reptile Macrocnemus fuyuanensis Li et al., 2007, from the Middle/Upper Triassic of Yunnan, China
Article
A new specimen of the protorosaur Macrocnemus fuyuanensis, from the Zhuganpo Member of the Falang Formation at Fuyuan (Yunnan Province, southwestern China), is described and compared with Macrocnemus bassanii. The new specimen is the first in the genus Macrocnemus that clearly shows details of the preorbital region of the skull. A large, plate-like lacrimal is located in front of the tall, columnar prefrontal that defines the anterior margin of the orbit. A longitudinally oriented nasal groove extends along the anterior two-thirds of the snout, accommodating the external naris at its anterior part. A similar preorbital depression has previously been described for Dinocephalosaurus and it is also reported here for the first time in Tanystropheus. The new specimen confirms the status of Macrocnemus fuyuanensis as a species distinct from Macrocnemus bassanii on the basis of a humerus that significantly exceeds the radius in length. The occurrence of both Macrocnemus and Tanystropheus in southwestern China further underscores the close faunal affinities of the eastern and western Tethyan realms during the Middle and early Late Triassic.
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Sauropterygian from Triassic of Guizhou, China
Article
  • Jul 1999
A new sauropterygian,Anshunsaurus huangguoshuensis, is described on the basis of a well-preserved skull from the Late Triassic Wayao Member of Falang Formation, Guizhou Province, southwestern China. It is ascribed to Eusauroptetrygia because it possesses the following characters: the rostrum is mainly composed by the premaxillae; the nasals are small, paired and separated from one another by the premaxillae; the external nares are close to the orbits; and the frontals are fused.Anshunsaurus differs from other Triassic sauropterygians in its large size, long rostrum and the supratemporal fenestrae slightly smaller than orbits. It is further considered to be closely related toPistosaurus on the basis of the nasals contact with the prefrontals; large pineal foramen, lain in the anterior part of the parietal table; the squamosals not in contact posterior to the supratemporal fenestra. The discovery ofAnshunsaurus with the ichthyosaurs in the same locality indicates a new assemblage of Triassic marine tetrapods in China.
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