Fossil middle triassic “sea cows” – placodont reptiles as macroalgae feeders along the north-western Tethys coastline with Pangaea and in the Germanic basin

The descriptions of fossil Triassic marine pla- codonts as durophagous reptiles are revised through comparisons with the sirenia and basal proboscidean mammal and palaeoenvironment analyses. The jaws of placodonts are conver- gent with those of Halitherium/Dugong or Mo- eritherium in their general function. Whereas Halitherium possessed a horny oral pad and counterpart and a special rasp-like tongue to grind seagrass, as does the modern Dugong, placodonts had large teeth that covered their jaws to form a similar grinding pad. The sirenia also lost their anterior teeth during many Millions of years and built a horny pad instead and specialized tongue to fed mainly on seagrass, whereas placodonts had only macroalgae availa- ble. Indirect evidence for Triassic macroalgae is provided by benthic palaeocommunities from different layers and extended European regions in the Germanic Basin. Studies of tooth wear stages for Placodus indicate that anterior teeth may have been used in a similar manner to the procumbent front teeth of modern Dugong. Paraplacodus and Placodus seem to have used these teeth as spatulas to dig out seaplants. Cyamodus and other placodonts such as Placochelys had smaller or reduced anterior teeth. The scarcity of highly worn palatine or maxillary and lower jaw dentary Placodus or Cyamodus teeth (less then 0.5%) suggests that they had a relatively soft diet. The seaplants would only have been squeezed in a similar feeding strategy to that of modern Dugong feeding on seagrass without jaw rotation and grinding. The phylogenetic trend in tooth reduction within the placodonts Paraplacodus, Placodus, especially in Cyamodus but also Placochelys, and Henodus within 11 My appears to have been a result of this plant-feeding adaptation and may even explain the origin or at least close relationship of the earliest Upper Triassic turtles as toothless algae and jellyfish feeders, in terms of the long-term convergent development with the sirens.

Biodiversity and Sequence of the Middle Triassic Panxian Marine Reptile Fauna,Guizhou Province,China

The Middle Triassic Panxian fauna is a physical marker and representative record of the rapid recovery of the Triassic marine ecosystem following the Early Triassic stagnant stage after the end-Permian mass extinction. Ten marine reptile taxa have been found from the 1.82-2.10 m-thick fossiliferous level in the Upper Member of the Guanling Formation, which can be subdivided into three marine reptile beds through the analysis on the stratigraphic distributions of fossil reptiles. The Lower Reptile Bed yields the sauropterygians Placodus inexpectatus Jiang et al., 2008 and Lariosaurus hongguoensis Jiang et al., 2006, the ichthyopterygians Xinminosaurus catactes Jiang et al., 2008 and Phalarodon cf. Phalarodon fraasi Merriam, 1910, associated with Mixosaurus panxianensis Jiang et al., 2006, representing a stage of predominance of durophagous taxa. In this bed, the large complete skeletons may reach up to 2.3 m in length, and lithofacies and chemostratigraphic analyses indicate a relatively deep carbonate platform with an oxic water environment near the bottom, as well as a rising sea level The Middle Reptile Bed yields the sauropterygian Nothosaurus yangjuanensis Jiang et al., 2006 and the archosaur Qianosuchus mixtus Li et al., 2006, associated with Mixosaurus panxianensis Jiang et al., 2006. The fossils in this bed are characterized by its pincering dentition and large overall body size, with the largest possibly exceeding 3 m in length. This bed might represent a time of deepest basin with relatively anoxic condition near the bottom. The Upper Reptile Bed yields the sauropterygians Wumengosaurus delicatomandibularis Jiang et al., 2008, Keichousaurus sp., the protorosaur Dinocephalosaurus orientalis Li, 2003, and the ichthyopterygian Mixosaurus panxianensis Jiang et al., 2006. In this bed, reptilian taxa characterized by suction feeding appeared, and most are less than 1 m long. This bed corresponds to a period of decreasing water depth.

Biostratigraphy of Triassic Marine Reptiles in Southwest Guizhou and Its Adjacent Area

This paper briefly reviews the Triassic marine reptile fossils in Guizhou Province, especially the fossils that have been recently found in the Guanling area. Based on three sections at Guanling and Xingyi, Guizhou Province and Luoping, Yunnan Province, four horizons with vertebrate fossils are recognized in the Middle and Upper Triassic of this area; They are from bottom to top: Member I and Member II of the Guanling Formation, and the Zhuganpo Member and the Wayao Member of the Falang Formation.

Guanling Biota: A Marker of Triassic Biotic Recovery from the end-Permian Extinction in the Ancient Guizhou Sea

After a slow recovery from the end-Permian extinction during the Early Triassic and rapid radiation in the Middle Triassic, evolution of organisms reached a new peak phase in the Late Triassic. The Guanling Biota from the Wayao Member （conodont Paragondolella polygnathiformis Zone）, Falang Formation, Xinpu, Guanling County, Guizhou Province, southwestern China corresponds to this peak that marks the full recovery from the end-Permian extinction of marine ecosystems. The biota is of high diversity, containing well preserved and completely articulated skeletons of vertebrates comprising marine reptiles, fishes, and invertebrates including crinoids, ammonites, bivalves, and other fossils, and is one of the best examples of marine ecosystem records in life history. The fossil marine reptiles and crinoids are most significant in this biota, especially the marine reptiles, which provide an important link between the Triassic Pacific and Tethys, and between Triassic basal forms and the Jurassic-Cretaceous marine top predators. The most remarkable fossils are the large completely articulated ichthyosaur skeletons up to and more than 10 m, and the first recorded thalattosaurs and placodonts in China. Following our review, of the 17 named reptilian taxa the eight listed here are considered to be valid： three ichthyosaurs （Qianichthyosaurus zhoui Li, 1999; Guizhouichthyosaurus tangae Cao and Luo in Yin et al., 2000, Guanlingsaurus liangae Yin in Yin et al., 2000）, three thalattosaurs （Anshunsaurus huangguoshuensis Liu, 1999, Xinpusaurus suni Yin in Yin et al., 2000, Xinpusaurus kohi Jiang et al., 2004）, and two placodonts （Sinocyamodus xinpuensis Li, 2000, Psephochelys polyosteoderma Li and Rieppel, 2002）. Mixosaurus guanlingensis Cao in Yin et al., 2000 might be a junior synonym of Qianichthyosaurus zhoui Li, 1999, and Cymbospondylus asiaticus Li and You, 2002 and Panjiangsaurus epicharis Chen and Cheng, 2003 might be junior synonyms of Guizhouichthyosaurus tangae Cao and Luo in Yin et al., 2000. It needs to re-describe the holotypes after a complete preparation for clarifying the taxonomic status of Typicusichthyosaurus tsaihuae Yu in Yin et al., 2000, Xinpusaurus bamaolinensis Cheng, 2003, Neosinosaurus hoangi （Zhou in Yin et al., 2000）, Wayaosaurus geei Zhou in Yin et al., 2000, Wayaosaurus bellus Zhou in Yin et al., 2000 and Placochelys ？ minutus Yin and Luo in Yin et al., 2000.

A new cyamodontoid placodont from Triassic of Guizhou, China

A new cyamodontoid placodont is named (Pse-phochelys polyosteoderma gen. et. sp. nov.) and described based on a three-dimensionally preserved specimen. The material comes from the Wayao Member of the Falang Formation (Carnian, Late Triassic) in Guizhou Province, southwestern China. The skull of Psephochelys shows a unique combination of characteristics observed in Psepho-derma and Placochelys, and the carapace is diagnostic of a new taxon as well. The ventral dermal armor of Psephochelys differs from all other known cyamodontoids in that it comprises irregular marginal osteoderms in loose contact with each other, and gastralia between them. The cranial suture pattern is in part difficult to analyze due to apparent co-ossification of elements, or poor delimitation of sutures. This affects primarily the demarcation of the nasal from the prefrontal, and the relation between the anterior part of the parietal, posterior ends of the frontals, and postfrontals. However, the postfrontal appears to enter the

Discovery of the Middle-Late Triassic elasmobranch ichthyoliths from the Guanling area,Guizhou,SW China

应用Johns等(1997)的形态分类系统,对首次报道出现于贵州关岭地区中上三叠统的软骨鱼类的微体化石进行了初步研究,描述了其中的1个牙齿化石(可能属于弓鲛鲨科的)和7个鳞片类化石的形态属种,其中包括两个鳞片类化石的新属种,即Lobaticoronacf.floriditurris,Sacrisubcoronacf.circabasis,Glabrisubcoronacf.arduidevexa,Parvi-coronadacrysulcan.gen.et.n.sp.s.f.,Annulicoronapyramidalisn.gen.et.n.sp.s.f.,new(?)parageneraA和new(?)parageneraB。还初步探讨了软骨鱼类微体化石在三叠纪地层划分中的应用,以及中国西南部三叠纪软骨鱼类与北美相当地层中软骨鱼类的洲际对比。

Sedimentary-volcanic tuffs formed during the early Middle Triassic volcanic event in Guizhou Province and their stratigraphic significance

The sedimentary-volcanic tuff (locally called “green-bean rock”) formed during the early Middle Triassic volcanic event in Guizhou Province is characterized as being thin, stable, widespread, short in forming time and predominantly green in color. The green-bean rock is a perfect indicator for stratigraphic division. Its petrographic and geochemical features are unique, and it is composed mainly of glassy fragments and subordinately of crystal fragments and volcanic ash balls. Analysis of the major and trace elements and rare-earth elements (REE), as well as the related diagrams, permits us to believe that the green-bean rock is acidic volcanic material of the calc-alkaline series formed in the Indosinian orogenic belt on the Sino-Vietnam border, which was atmospherically transported to the tectonically stable areas and then deposited as sedimentary-volcanic rocks there. According to the age of green-bean rock, it is deduced that the boundary age of the Middle-Lower Triassic overlain by the sedimentary-volcanic tuff is about 247 Ma.

A New Discovery of Colobodus Agassiz, 1844(Colobodontidae) from the Carnian(Upper Triassic) of Guizhou, South China

Objective Critical review of the Colobodontidae reveals that this family has important research value.Colobodontidae was universally accepted as a significant taxon among all Triassic ichthyolite in 2002.However,most colobodontids are probably confined to the Anisian and Ladinian in the western Tethys(Mutter,2004).This work describes a well-preserved colobodontid discovered in Guizhou,South China.

First Record of Protorosaurid Reptile (Order Protorosauria) from the Middle Triassic of China

A new genus and species of the family Tanystropheidae, Dinocephalosaurus orientalis gen. et sp. nov., is described based on a nearly complete skull. This is the first record of the order Protorosauria from China. It also represents the only known occurrence of Tanystropheidae outside Europe, the Middle East and North America. Dinocephalosaurus is quite similar to Tanystropheus from Monte San Giorgio, Switzerland. Primarily it is distinguished from Tanystropheus in the shape of the premaxilla, maxilla, jugal and parietal. Although the family Tanystropheidae is now referred to the order Protorosauria, the new material from China indicates that the archosauromorph affinities of tanystropheids need further investigation. The discovery of Dinocephalosaurus provides new clues for the study of the evolution and radiation of Protorosauria and Tanystropheidae. It is also important for the study of the eastern Tethyan Fauna and the paleobiogeographical relationship between Europe and southern China in the Triassic.

Stratigraphic Correlation of Middle TriassicSequences among Different Paleogeographic Sedimentary Facies in South China

Affected by the Indosinian movement, the sediments in the main part of South China, Yangtze platform, started to transform from marine to continental during the Middle Triassic. In the meantime, a noticeable paleogeographic and sedimentary facies differentiation occurred in the marginal regions of the platforms and produced completely different lithologic and paleontologic sequences in various paleogeographic gradients and sedimentary facies areas, which brought about the difficulties for the stratigraphic correlation based on the traditional stratigraphies. This paper proposes to use some characteristic environmental events as the markers of the stratigraphic correlation across various paleogeographic sedimentary facies, considering that some distinctive regional environmental events should have affected at the same time on the entire basin or the connected sedimentary regions and produced some closely related sedimentary records in the stratigraphic sequences though the affected intensity and recorded pattern might be different among the regions. The change of violent relative sea level (generally water depth) and the alteration of tectonic activity summarized from the dynamic mechanism of sedimentation are the best markers of environmental events for stratigraphic correlation. Based on the analysis and recognition of some significant environmental events at the typical stratigraphic sequences from various paleogeographic sedimentary facies and combined with the consideration of the variations in expressed form and strength of the events among different paleogeographic gradients and sedimentary facies, the stratigraphic sequences from different sedimentary facies can be easily correlated directly. Furthermore, the evolutionary history of the whole sedimentary basin can be clearly established.

Guanling Biota: A Rare Biota in Sea Early Late Triassic

Guanling biota has been found at the bottom of Wayao Formation of UpperTriassic (Carn-ic stage) near Xinpu town, Guanling County, Guizhou Province, China. There are a lotof crinoids and marine reptiles, which is a characteristic of Guanling biota, including ammonites,bivalve, brachiopod, fish, conodont and plant. These fossils are featured not only with the largequantity, but also with their extraordinary perfect forms. This paper explores the meaning,geological background, present situation of study and scientific significance of Guanling biota.

The Discovery of a Crinoid Community in the LateTriassic Zhuganpo Formation of Guizhou Provinceand Its Geological Significance

: Recently a rich and well—preserved crinoid community including Traumatocrinus and Encrinus has been found in the Late Triassic Zhuganpo Formation in Guanling and Xingyi, Guizhou province, China. Among the fossils Traumatocrinus is the richest, and most of it occurs as clusters, with each cluster containing 3–42 crinoid branches. Study of the stem and calyx of Traumatocrinus shows that the number of stem-joints (columnals) is equal to the total stem length × K (5.85 per cm × stem—diameter). There are about 376 first- and second—order columnals on the whole stem. This number seems to coincide with the number of days in a year at that time. According to the present study of the palaeoecological environment of the crinoid community, it is considered that the reproduction and preservation of the crinoid community were controlled by the Late Triassic regression and the restricted bay of an interior sea behind the S—shaped shoal zone.

Sauropterygian from Triassic of Guizhou,China

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 Eusauropterygia 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 to Pistosaurus 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 of Anshunsaurus with the ichthyosaurs in the same locality indicates a new assemblage of Triassic marine

Cephalopods of the “Falang Formation” (Triassic) from Guanling and Zhenfeng Counties, Guizhou Province, China

The 'Falang Formation' of western Guizhou was previously called the 'Halobia Bed' and considered to be I .adinian in age. It was subdivided upward into the Zhuganpo, Laishike and Longchang members based on ammonites and the Trachyceras multitubertulatum Zone of the Longchang Member was put in the Lower Carnian. Here in the present paper, 4 genera and 9 species of ammonites and 1 nautiloid genus and species collected from the upper part of the 'Falang Formation' (i.e. the Wayao Formation used in this paper, equivalent to the Laishike Member from Guanling and Zhenfeng counties are described. The geological and geographical distribution of these cephalopods, as well as the co-existing conodonts, put the Wayao Formation to the late early Carnmian.

Triassic Transgressive-Regressive Sequences in Guizhou-Guangxi Region, South China

Seven third-order transgressive-regressive sequences are recognized in the Early Triassic -Early Carnian stratigraghc succession of Guizhou-Guangxi region, South China. Based on currently available ages by the correlation of conodont ammonites and bivalve faunas, these sequences range approximately from 1.0 Ma to 5.6 Ma, with the average of 3 Ma. They occur largely in the Griesbachian-Dienerian, Smithian,uppermost Smithian-lowermost Anisian, Lower Anisian, Middle Anisian, Upper Anisian-Upper Ladinian and the uppermost Ladinian-Lower Carnian respectively, and can be grouped into three second-order transgressive-regressive supersequences. A relative sea level curve is established from the sequence stratigraghic analysis. Transgressive-regressive sequences,bounded by transgressive surfaces and the correlatable unconformities, are real unconformity-bounded units of lower rank. Each sequence comprises transgressive, highstand and regressive systems tracts, and can be easily correlated with the depositional sequence.

RE-EXAMINATION OF THE MIDDLE TRIASSIC "REEFS" IN CENTRAL GUIZHOU, SOUTH CHINA——THE DISCOVERY OF TRIASSIC CALICHE DEPOSITS

The Middle Triassic 'reefs' went through from NE to SW the whole region of Guizhou Province and rimmed a carbonate platform during the Middle Triassic Ladinian time, and represent a barrier 'reef' belt of Triassic carbonate platform-margin. The barrier 'reef'

REE Geochemical Study of the Permian-Triassic Marine Sedimentary Environment in Guizhou Province

This paper deals with the REE geochemical characteristics of Permian\|Triassic marine carbonate rocks in Guizhou Province. It is found that there are two broad categories of stratigraphic units in the region studied in accordance with their ∑REE contents and REE distribution patterns: one is characterized by LREE enrichment and slight Ce depletion, with the REE distribution patterns similar to those of North American shales, and the other features relative HREE enrichment and relatively remarkable Ce depletion, with the REE distribution patterns close to those of pelagic sediments. In terms of their different ∑REE contents, five types of stratigraphic units can be distinguished. Incorporation of detrital minerals, REE complexing capability, oxidation\|reduction conditions of the media are the main factors affecting the REE composition and REE distribution patterns of marine carbonate rocks in the region studied. In the light of REE geochemical characteristics of carbonate rocks, coupled with sedimentary facies analysis , this paper discusses the characteristics of the Permian\|Triassic marine sedimentary environment in Guizhou Province and its evolutional rules.

Conodont Evidence for the Age of the Panxian Fauna,Guizhou,China

Detailed conodont analysis on the Yangjuan-Chupiwa section, Xinmin, Panxian County, Guizhou Province, revealed a conodont sequence including four Anisian conodont zones, viz. Nicoraella germanica Zone, Nc. kockeli Zone, Paragondolella bifurcata Zone and Neogondolella constricta Zone. These zones indicate that the upper Guanling Formation consists of strata from the Bithynian to the lllyrian of the Anisian. Appearance of Neogondolella constricta suggests that the Anisian/Ladinian boundary might be in the overlying Yangliujing Formation. The Panxian Fauna with well-preserved marine reptile and fish fossils is proved to belong to the lower part of the conodont Nc. kockeli Zone in the studied area. Thus, the age of the Panxian Fauna could be the early Pelsonian of the Anisian.

贵州关岭地区法郎组瓦窑段菊石类新材料

本文对采自于贵州关岭地区上三叠统卡尼阶法郎组瓦窑段上部的齿菊石目化石进行了研究,共识别出3属3种,其中包含一新种Arctosirenites mingqingensissp.nov.。Arctosirenites mingqingensis sp.nov.以具有细密横肋及粗壮腹缘瘤为特征,属Klipsteinia在华南为首次发现。根据Klipsteinia和Arctosirenites组合特征判断贵州关岭地区上三叠统法郎组瓦窑段底部时代为晚三叠世早卡尼期早期(Julian 1),上部时代归属于晚卡尼期早期(Tuvalian 1),并且认为造成法郎组瓦窑段底部的岩性变化是由于构造因素导致,而并非受到卡尼期湿润幕事件(CPE,Carnian Pluvial Episode)的影响。