The palaeoecology of the dinosaurs of the Wessex Formation (Wealden Group, Early Cretaceous), Isle of Wight, Southern England

The Wessex Formation on the Isle of Wight yields an Early Cretaceous dinosaur fauna. Sedimentological evidence shows that this represents a mosaic of fluvial, floodplain and lacustrine environments within a relatively narrow east-west oriented valley. The vegetational cover on the alluvial plain had a savannah-or chaparral-like aspect, probably of low productivity. The relative scarcity of small aquatic vertebrates, absence of coals, abundance of oxidixed sediments and the presence of immature calcretes indicate seasonal water supply. The dinosaur taxa compising the Wessex Formation faunal assemblage represent a single palaeocommunity which inhabited the local alluvial plain, although some species may have been transient. The fauna had a relatively low diversity and this is attributed to the low productivity of the local vegetation. Iguanodontids and Hypsilophodon were the dominant elements in the fauna. In contrast to Late Jurassic dinosaur faunas, sauropods are less abundant in the Wessex Formation, although they remain taxonomically diverse. It is concluded that climatic changes which took place in the Late Jurassic or Early Cretaceous resulted in the appearance of low productivity vegetation and that this was incapable of supporting large sauropod populations.     

The Triassic fish faunas of the Cuyana Basin,Western Argentina

Abstract: The continental deposits of the Cuyana Basin, western Argentina, have yielded the most diverse, but so far almost unstudied, Triassic ichthyofaunas of South America. Here, we review these faunas and show that only eight of the 29 named taxa can be considered valid, including the chondrostean Neochallaia, the acrolepid Challaia, Guaymayenia, a taxon of uncertain affinities, and five species of the perleidiform family Pseudobeaconiidae. The first three taxa most probably come from Middle Triassic sediments, while the pseudobeaconiids are of Late Triassic age. Other material, although not diagnostic, probably represents other species, and thus, the diversity of actinopterygians in the Cuyana basin is certainly higher than currently recognized. For the Late Triassic fish fauna, the absence of crown‐group neopterygians and a single record of a sarcopterygian is noteworthy and probably indicates some degree of endemism in this fauna, also supported by the high abundance of pseudobeaconiids, which are unknown from other areas. Furthermore, on the basis of the age indicated by the fishes and the available geological information, we discuss the age of the local fauna of the Cerro Bayo, close to the city of Mendoza, and the Agua de la Zorra Formation, Uspallata.     

Early Ordovician bivalves from Dali, West Yunnan, China

A bivalve fauna of Early Ordovician (late Arenig) age is described from the Hsiangyang Formation of the eastern part of West Yunnan, China. The fauna contains elements in common with Early Ordovician faunas of southern Gondwanan areas such as the Montagne Noire and Morocco and with those of Avalonia, together with several previously undescribed taxa. The following taxa are new: Biseriodonta simplex gen. et sp. nov.; Glyptarca sinensis sp. nov.; Trigonoglyptarca magna gen. et sp. nov.; Erhaiconcha xiangyangensis gen. et sp. nov.; Fasciculodonta impressa gen. et sp. nov.; Yunnanoredonia laevis gen. et sp. nov.; Daliella gen. nov.; Goniophorina ( Goniophorina ) contracta sp. nov.; Haidongoconcha radialis gen. et sp. nov.; Eopterinea aequiconcha gen. et sp. nov. The bivalve fauna includes the most diverse glyptarcid fauna and the earliest nuculanid and paracyclid known hitherto.   Eastern West Yunnan belonged to the Indochina terrane and it is concluded that the bivalve fauna represents a high-latitude assemblage and that the Indochina terrane should be considered a component part of the Peri-Gondwanan continent in the Ordovician; its bivalve faunas contrast with those of neighbouring terranes which have affinities with those of lower latitudes.     

Dispersal and diversity in the earliest North American sauropodomorph dinosaurs, with a description of a new taxon

Sauropodomorph dinosaurs originated in the Southern Hemisphere in the Middle or Late Triassic and are commonly portrayed as spreading rapidly to all corners of Pangaea as part of a uniform Late Triassic to Early Jurassic cosmopolitan dinosaur fauna. Under this model, dispersal allegedly inhibited dinosaurian diversification, while vicariance and local extinction enhanced it. However, apomorphy-based analyses of the known fossil record indicate that sauropodomorphs were absent in North America until the Early Jurassic, reframing the temporal context of their arrival. We describe a new taxon from the Kayenta Formation of Arizona that comprises the third diagnosable sauropodomorph from the Early Jurassic of North America. We analysed its relationships to test whether sauropodomorphs reached North America in a single sweepstakes event or in separate dispersals. Our finding of separate arrivals by all three taxa suggests dispersal as a chief factor in dinosaurian diversification during at least the early Mesozoic. It questions whether a 'cosmopolitan' dinosaur fauna ever existed, and corroborates that vicariance, extinction and dispersal did not operate uniformly in time or under uniform conditions during the Mesozoic. Their relative importance is best measured in narrow time slices and circumscribed geographical regions.     

Tetrapod association and palaeoenvironment of the Los Colorados Formation (Argentina): a significant sample from Western Gondwana at the end of the Triassic

The Los Colorados Formation constitutes a continuous continental succession deposited in Western Argentina during the Late Triassic, a time period that is crucial to the record of the faunistic turnover at the Triassic-Jurassic boundary. Many authors have pointed out that its rich tetrapod fauna represents a unique transitional assemblage with elements typical of both Late Triassic and Early Jurassic. However, the possibility that the fauna represented a mixture of Triassic and Jurassic horizons was also proposed. Recently, stratigraphic control of the fossiliferous levels was developed in order to correlate the different localities of the extense Los Colorados outcrops, and a revision of the taxonomic status of most tetrapods recovered is currently undergoing. Preliminary results confirm previous assumptions about the transitional nature of the assemblage where typical Triassic taxa are associated with dinosaur groups known from Early Jurassic levels in other Gondwanan areas. The fossiliferous levels of the upper third of the sequence included several basal archosaurs (aetosaurs, rauisuchids, sphenosuchians), protosuchian crocodiles, dinosaurs (sauropodomorphs, tetanuran theropods), derived therapsids and primitive chelonians. New evidence about tetrapod ichnites of chirotheroid affinities is added to the fossiliferous association.     

A Megaraptor-like theropod (Dinosauria: Tetanurae) in Australia: support for faunal exchange across eastern and western Gondwana in the Mid-Cretaceous

The fossil record of Australian dinosaurs in general, and theropods in particular, is extremely sparse. Here we describe an ulna from the Early Cretaceous Eumeralla Formation of Australia that shares unique autapomorphies with the South American theropod Megaraptor. We also present evidence for the spinosauroid affinities of Megaraptor. This ulna represents the first Australian non-avian theropod with unquestionable affinities to taxa from other Gondwanan landmasses, suggesting faunal interchange between eastern and western Gondwana during the Mid-Cretaceous. This evidence counters claims of Laurasian affinities for Early Cretaceous Australian dinosaur faunas, and for the existence of a geographical or climatic barrier isolating Australia from the other Gondwanan continents during this time. The temporal and geographical distribution of Megaraptor and the Eumeralla ulna is also inconsistent with traditional palaeogeographic models for the fragmentation of Gondwana, but compatible with several alternative models positing connections between South America and Antarctica in the Mid-Cretaceous.     

Late Paleozoic faunal, climatic, and geographic changes in the Baoshan block as a Gondwana-derived continental fragment in southwest China

The Carboniferous and Permian of the Baoshan block consist of three major depositional sequences: a Lower Carboniferous carbonate sequence, a Lower Permian siliciclastic sequence, and a Middle Permian carbonate sequence. These three sequences were interrupted by two major regressive events: first, the Namurian Uplift ranging in age from Serpukovian to Gzhelian, and second, the Post-Sakmarian Regression occurring probably at Artinskian time in the Baoshan block, although the precise time interval of the latter event is still unclear. The Baoshan block is characterized by warm-water, highly diverse and abundant faunas during the Early Carboniferous, by cold-water and low diversity faunas during the Early Permian, and by possibly warm-water but low diversity faunas during the Middle Permian. The Sweetognathus bucaramangus conodont fauna constrains the upper boundary of the diamictite-bearing siliciclastic deposits (Dingjiazhai Formation) to the Sakmarian to early Artinskian, as well as the eruption of the rifting basalts (Woniusi Formation) to, at least, the post-early Artinskian. Paleozoogeographically, affiliation of the faunas in the Baoshan block changed from Eurasian in the Early Carboniferous, to Peri-Gondwanan in the Early Permian, and to Marginal Cathaysian/Cimmerian in the Middle Permian. Cimmerian blocks have more or less comparable geohistory to one another in the Carboniferous and Permian. During the Middle Permian, the eastern Cimmerian blocks such as Sibumasu (s.s), Baoshan, and Tengchong are not far from the palaeoequator, but apparently more distant than the western Cimmerian blocks based on the presence or absence of some index taxa such as the fusulinaceans Eopolydiexodina and Neoschwagerina, and the corals Thomasiphyllum and Wentzellophyllum persicum.     

滇西保山地区石炭纪、二叠纪古动物地理演化

探讨滇西保山地块晚古生代Ｔｉｎｇ类、有孔虫、珊瑚、牙形刺、腕足类等动物群的古生物地理属性,根据牙形刺和Ｔｉｎｇ类化石,确定长期争论的丁家寨组的时代为Ａｒｔｉｎｓｋｉａｎ期,小型单体珊瑚Ｃｙａｔｈａｘｏｎｉａ动物群可出现在从早石炭世到二叠纪的多种沉积环境中,不一定指示冷水冈瓦纳型。根据沉积特征及对环境特别敏感的珊瑚和Ｔｉｎｇ类动物群的分布特点,结合全球构造事件,恢复保山地块的古地理演化模式。早石炭世     

内蒙古宁城道虎沟地区中侏罗世非海相双壳类Ferganoconcha

Ferganoconcha是广泛分布于我国北部、中亚、西伯利亚和乌拉尔地区下、中侏罗统的一类非海相双壳类。Ferganoconchasibirica的产出表明道虎沟地区道虎沟层与辽西地区的海房沟组和冀北地区的九龙山组层位相当,时代介于早侏罗世晚期至中侏罗世之间。结合昆虫和叶肢介化石反映的时代,认为道虎沟层的时代可能为中侏罗世早中期。综合近年来在Ferganoconchidae的分类方面取得的进展,对F.sibirica进行了重新厘定。     

Molecular phylogenetic evidence for ancient divergence of lizard taxa on either side of Wallace's Line

Wallace's Line, separating the terrestrial faunas of South East Asia from the Australia-New Guinea region, is the most prominent and well-studied biogeographical division in the world. Phylogenetically distinct subgroups of major animal and plant groups have been documented on either side of Wallace's Line since it was first proposed in 1859. Despite its importance, the temporal history of fragmentation across this line is virtually unknown and the geological foundation has rarely been discussed. Using molecular phylogenetics and dating techniques, we show that the split between taxa in the South East Asian and the Australian-New Guinean geological regions occurred during the Late Jurassic to Early Cretaceous in two independent lizard clades. This estimate is compatible with the hypothesis of rifting Gondwanan continental fragments during the Mesozoic and strongly rejects the hypothetical origin of various members of the Australian-New Guinean herpetofauna as relatively recent invasions from South East Asia. Our finding suggests an ancient fragmentation of lizard taxa on either side of Wallace's Line and provides further evidence that the composition of modern global communities has been significantly affected by rifting and accretion of Gondwanan continental plates during the Middle to Late Mesozoic.     

Fossil coniferous wood from the Middle Jurassic of Liaoning Province, China

Silicified coniferous wood was collected from the Lanqi Formation (late Middle Jurassic in age) at Shebudaigou Village, Liaoning Province, China. Three taxa are identified, namely Pinoxylon dacotense Knowlton, Xenoxylon phyllocladoides Gothan, and Araucariopitys sp. Based on these new data, and those of other fossil plants reported previously from the same formation, we consider the climate during the deposition of the Lanqi Formation was subtropical, humid and seasonal. In this respect the Lanqi flora differs from the coeval Shimengou and Longmen floras from North China. The Longmen flora was deposited during more humid, subtropical conditions, while the Shimengou Formation indicates that the climate was warm temperate and dry. Our data would suggest that the Late Jurassic climatic pattern was initiated as early as the late Middle Jurassic.     

Late Triassic (Late Norian) gastropods from the Wallowa Terrane (Idaho,USA)

A diverse Late Triassic (Late Norian) gastropod fauna is described from the Mission Creek Limestone of the Wallowa terrane (Idaho, USA). Sample standardization by rarefaction analysis indicates that the fauna is even more diverse than the Late Triassic gastropod fauna from the Pucara Formation (Peru) which represents the most diverse gastropod fauna from South America. The gastropod fauna consists of 66 species; several genera are reported for the first time from North America. A high percentage of the species are highly ornamented and several have distinct siphonal canals. This suggests that the appearance of truly Mesozoic elements among the gastropods began before the Mesozoic Marine Revolution in other clades. The fauna is dominated by high-spired strongly ornamented procerithiids, a group more characteristic for the Jurassic. Comparison of the present fauna and the Iranian Nayband Formation gastropod fauna show that the procerithiids underwent a first global radiation in the Late Triassic. The high number of new species in this fauna suggests that sampling of Late Triassic gastropod faunas is still incomplete and hinders palaeobiogeographic considerations. Previous suggesions that gastropod faunas from the Wallowa and Wrangellia terranes resemble each other and are distinct from those of Alexander, Chulitna, and Farewell terranes are basically corroborated. The gastropod fauna of the Mission Creek Limestone differs considerably from that of the western and central Tethys but shares several taxa with the Late Triassic gastropod fauna of the Pucara Formation in Peru. Thus, the Hispanic corridor was probably not present in the Norian but opened only in the Early Jurassic. The subfamily Andangulariinae is introduced and placed in the Zygopleuridae. The generaSpiniomphalus, Nodoconus, Gudrunella, Blodgettella, Idahospira, andSiphonilda and the subgenusCryptaulax (Wallowax) are introduced. 27 species are erected. A lectotype is designated forCryptaulax rhabdocolpoides Haas, 1953.      

First report of Apatosaurus (Diplodocidae: Apatosaurinae) from the Cleveland-Lloyd Quarry in the Upper Jurassic Morrison Formation of Utah: Abundance,distribution, paleoecology,and taphonomy of an endemic North American sauropod clade

A cervical vertebra preserved at the famous and productive Cleveland-Lloyd Dinosaur Quarry in the Upper Jurassic Morrison Formation of Utah is that of an Apatosaurus, a sauropod dinosaur genus not previously recognized at the site and the first new dinosaur taxon identified at the site in years. The presence of Apatosaurus at a mudstone site dominated by other taxa, both theropod and sauropod, suggests a pattern of preservation within the Morrison Formation in which sites in fine-grained sediments yield dramatically uneven relative abundances of dinosaurs, with variable dominant taxa by site, compared with more time-averaged and attritional coarse-grained channel sandstone deposits. In addition, the continued demonstration of the wide-spread occurrence and abundance of Apatosaurus within the Morrison Formation, and the absence of its clade among diplodocid faunas on other continents, suggest that this group may have been endemic to North America during the Late Jurassic and that it may have originated there, though this is far from clear.     

A diverse Upper Jurassic dinosaur ichnofauna from central‐west Portugal

Mateus, O. & Milàn, J. 2009: A diverse Upper Jurassic dinosaur ichnofauna from central‐west Portugal. Lethaia, Vol. 43, pp. 245–257. A newly discovered dinosaur track‐assemblage from the Upper Jurassic Lourinhã Formation (Lusitanian Basin, central‐west Portugal), comprises medium‐ to large‐sized sauropod tracks with well‐preserved impressions of soft tissue anatomy, stegosaur tracks and tracks from medium‐ to large‐sized theropods. The 400‐m‐thick Lourinhã Formation consists of mostly aluvial sediments, deposited during the early rifting of the Atlantic Ocean in the Kimmeridgian and Tithonian. The stratigraphic succession shows several shifts between flood‐plain mud and fluvial sands that favour preservation and fossilization of tracks. The studied track‐assemblage is found preserved as natural casts on the underside of a thin bivalve‐rich carbonate bed near the Tithonian–Kimmeridgian boundary. The diversity of the tracks from the new track assemblage is compared with similar faunas from the Upper Jurassic of Asturias, Spain and the Middle Jurassic Yorkshire Coast of England. The Portuguese record of Upper Jurassic dinosaur body fossils show close similarity to the track fauna from the Lourinhã Formation. □Dinosaur tracks, Lusitanian Basin, Portugal, skin impressions, Upper Jurassic.     

The Permian fusulinoidean faunas of the Sibumasu and Baoshan blocks: their implications for the paleogeographic and paleoclimatologic reconstruction of the Cimmerian Continent

Permian fusulinoidean faunas occur in mainly four stratigraphic levels in the Baoshan Block of West Yunnan and the Sibumasu Block of Southeast Asia, which constituted part of the eastern Cimmerian Continent. The oldest fauna, from the upper part of the Dingjiazhai Formation in the Baoshan Block, consists of Pseudofusulina, Eoparafusulina, and a new boultoniid genus, and is assignable to the Yakhtashian (=Artinskian). The second one, which occurs in the basal part of the Ratburi Limestone and its equivalent strata in the Sibumasu Block, is represented by Monodiexodina, and is probably referable to the Bolorian (=Kungurian). The third fauna, composed of Eopolydiexodina, Rugososchwagerina, Yangchienia, Chusenella, Jinzhangia, and several other genera, is dated to the Murgabian (=Wordian), and occurs in the lower part of the Shazipo and Daaozi formations in the Baoshan Block and the main part of the Ratburi Limestone in the Sibumasu Block. The youngest fauna of probably Dzhulfian (=Wuchiapingian) age is found in the upper part of the Ratburi Limestone, and contains Nanlingella, Reichelina, Codonofusiella?, and a few staffellid genera. A smaller foraminiferal genus, Shanita, found from the upper part of the Ratburi Limestone and the upper part of the Shazipo Formation is also an important element of the foraminiferal assemblage near the Midian-Dzhulfian (=Capitanian-Wuchiapingian) boundary in the Baoshan and Sibumasu blocks.In the eastern Cimmerian Continent, low generic diversity throughout the Permian and the paucity of Tethys-characterizing neoschwagerinid and verbeekinid genera during Middle Permian time are two remarkable features of the Permian fusulinoidean faunas. In the Cimmerian Continent, the generic diversity of Permian fusulinoidean faunas in space and time gradually increases from the Early Permian to late Middle Permian as well as from the eastern Cimmerian areas to western ones. The temporal increase of the generic diversity can be explained by the northward drift of the Cimmerian Continent during Permian time. In contrast, the lower generic diversity of the eastern Cimmerian Permian fusulinoidean faunas against western ones is possibly due to an oblique arrangement of the continent to paleolatitude. Thus, the western Cimmerian Continent was more proximal to the tropical Tethyan domain than its eastern part. In addition, the Middle Permian Cimmerian paleobiogeographic region is likely to be subdivided into two subregions, the western Tethyan Cimmerian and the eastern Gondwanan Cimmerian, based on the distribution pattern of verbeekinid and neoschwagerinid fusulinoideans and overall generic diversity. The scarce occurrence or total absence of these essentially Tethys-indicating fusulinoideans in the Baoshan and Sibumasu blocks suggests that the eastern Cimmerian Continent was still far from the equatoro-tropical Cathaysian domain and was probably in a warm temperate or subtropical zone until the end of the Permian. The eastern Cimmerian areas finally migrated into a tropical zone by the Late Triassic judging from well-developed Carnian sponge-coral buildups in the Chaiburi Formation in the Sibumasu Block.     

Theropod fauna from southern Australia indicates high polar diversity and climate-driven dinosaur provinciality

The Early Cretaceous fauna of Victoria, Australia, provides unique data on the composition of high latitude southern hemisphere dinosaurs. We describe and review theropod dinosaur postcranial remains from the Aptian-Albian Otway and Strzelecki groups, based on at least 37 isolated bones, and more than 90 teeth from the Flat Rocks locality. Several specimens of medium- and large-bodied individuals (estimated up to ~8.5 metres long) represent allosauroids. Tyrannosauroids are represented by elements indicating medium body sizes (~3 metres long), likely including the holotype femur of Timimus hermani, and a single cervical vertebra represents a juvenile spinosaurid. Single specimens representing medium- and small-bodied theropods may be referrable to Ceratosauria, Ornithomimosauria, a basal coelurosaur, and at least three taxa within Maniraptora. Thus, nine theropod taxa may have been present. Alternatively, four distinct dorsal vertebrae indicate a minimum of four taxa. However, because most taxa are known from single bones, it is likely that small-bodied theropod diversity remains underestimated. The high abundance of allosauroids and basal coelurosaurs (including tyrannosauroids and possibly ornithomimosaurs), and the relative rarity of ceratosaurs, is strikingly dissimilar to penecontemporaneous dinosaur faunas of Africa and South America, which represent an arid, lower-latitude biome. Similarities between dinosaur faunas of Victoria and the northern continents concern the proportional representatation of higher clades, and may result from the prevailing temperate-polar climate of Australia, especially at high latitudes in Victoria, which is similar to the predominant warm-temperate climate of Laurasia, but distinct from the arid climate zone that covered extensive areas of Gondwana. Most dinosaur groups probably attained a near-cosmopolitan distribution in the Jurassic, prior to fragmentation of the Pangaean supercontinent, and some aspects of the hallmark 'Gondwanan' fauna of South America and Africa may therefore reflect climate-driven provinciality, not vicariant evolution driven by continental fragmentation. However, vicariance may still be detected at lower phylogenetic levels.     

First palynological data from the Jurassic South Xiangshan Formation (Nanjing area,China)

The outcrops of the Xiangshan Group have been studied since the beginning of the twentieth century, yielding a rich macroflora (the Xiangshan Flora), mainly from the lower part of the Xiangshan Group (South Xiangshan Formation). Nevertheless, no palynological data have been published so far from the South Xiangshan Formation. The present study provides the first palynostratigraphic data of the South Xiangshan Formation. More than 50 fossil taxa from 30 fossil genera have been identified, allowing for a more accurate dating. The most characteristic taxa are Polycingulatisporites triangularis, Quadraeculina anellaeformis, Manumia delcourtii, Ischyosporites variegatus, Callialasporites turbatus, C. trilobatus, C. minus, and Sestrosporites pseudoalveolatus, suggesting a late Toarcian-late Aalenian age for the South Xiangshan Formation. These results are consistent with previous studies suggesting a middle-late Early Jurassic age for this formation; consequently, the most probable age for the South Xiangshan Formation is late Toarcian (late Early Jurassic).     

Conodonts from the Permian Jisu Honguer (Zhesi) Formation of Inner Mongolia, China

The Jisu Honguer Formation (“Zhesi Formation”) is a North China marine carbonate unit of Permian age containing a mixed fauna of Tethyan, Boreal and endemic elements. The age of the Jisu Honguer Formation has been thought to range from Artinskian to Kazanian based on previous studies using mostly benthic macrofossils. A typical Mesogondolella aserrata conodont fauna is reported from the lower part of the upper member of the Jisu Honguer Formation in the Ulanqub District, Zhesi area, of northern China. The fauna indicates a Middle Permian (Guadalupian) age, most likely late Wordian to early Capitanian, for the strata yielding conodonts. The whole Jisu Honguer Formation could be assigned to the Wordian to early Capitanian age. The overlying Yihewusu Formation is probably of Capitanian age. There are no Wuchiapingian marine deposits in the Zhesi area. As characteristic of the open sea Guadalupian conodont faunas of the Tethys, smooth Mesogondolella dominate the fauna. The view that all Tethyan Guadalupian conodont faunas consist exclusively of serrated Mesogondolella cannot be confirmed. Three new species are described: Mesogondolella neoprolongata C. - y. Wang, Mesogondolella mandulaensis C. - y. Wang and Wardlawella jisuensis C. - y. Wang.