First elaphrosaurine theropod dinosaur (Ceratosauria: Noasauridae) from Australia — A cervical vertebra from the Early Cretaceous of Victoria

Elaphrosaurinae is an enigmatic clade of gracile ceratosaurian theropod dinosaurs known from the Late Jurassic of Africa (Elaphrosaurus bambergi) and Asia (e.g., Limusaurus inextricabilis), and the early Late Cretaceous of Argentina (Huinculsaurus montesi). Elaphrosaurinae is often placed within Noasauridae as the sister taxon to Noasaurinae, a clade of small-bodied theropods that lived in South America, Africa, Madagascar and India throughout much of the Cretaceous. Herein, we report the first evidence of Elaphrosaurinae from Australia: a nearly complete middle cervical vertebra from the upper Lower Cretaceous (lower Albian) Eumeralla Formation of Cape Otway, Victoria, Australia. The fact that this site would have been situated at ~76°S towards the end of the Early Cretaceous (~110–107 Ma) implies that elaphrosaurines were capable of tolerating near-polar palaeoenvironments, whereas its age indicates that elaphrosaurines persisted in Australia until at least the late Early Cretaceous. The new Australian elaphrosaurine, in tandem with the recently described Huinculsaurus montesi from the Cenomanian–Turonian of Argentina, implies that the spatiotemporal distribution of Elaphrosaurinae has heretofore been greatly underestimated. Historic confusion of elaphrosaurines with coelurosaurs, especially ornithomimosaurs, coupled with our generally poor understanding of noasaurid evolution, might explain the apparent dearth of fossils of this theropod clade worldwide.     

A large-clawed theropod (Dinosauria: Tetanurae) from the Lower Cretaceous of Australia and the Gondwanan origin of megaraptorid theropods

Megaraptoridae comprises a clade of enigmatic Gondwanan theropods with characteristic hypertrophied claws on the first and second manual digits. The majority of megaraptorids are known from South America, although a single genus (Australovenator) plus additional indeterminate material is also known from Australia. This clade has a controversial placement among theropods, and recently has been interpreted alternatively as a carcharodontosaurian or a tyrannosauroid lineage. We describe new fragmentary but associated postcranial remains from the opal fields of Lightning Ridge (middle-Albian, Griman Creek Formation) in north-central New South Wales. The new unnamed taxon exhibits a number of unusual features that suggest the presence of a hitherto unrecognised Australian megaraptorid. From an Australian perspective, the Lightning Ridge taxon predates Australovenator by ca. 10 Ma and is minimally coeval with megaraptoran material reported from the Eumeralla Formation of Victoria (but potentially 6.1–9.5 Ma younger). It is also notable as the largest predatory dinosaur yet identified from Australia and is only the second theropod known from more than a single element. A Bayesian phylogenetic approach integrating morphological, stratigraphic and palaeogeographic information tested both the carcharodontosaurian and tyrannosauroid placements for Megaraptora. Regardless of the preferred placement among Tetanurae, rigorous palaeobiogeographic analyses support an Asian origin of Megaraptora in the latest Jurassic (about 150–135 Ma), an Early Cretaceous (about 130–121 Ma) divergence of the Gondwanan lineage leading to Megaraptoridae, and an Australian root for megaraptorid radiation. These results indicate that Australia's Cretaceous dinosaur fauna did not comprise simply of immigrant taxa but was a source for complex two-way interchange between Australia–Antarctica–South America leading to the evolution of at least one group of apex predatory dinosaurs in Gondwana.     

Theropod remains from the uppermost Cretaceous of Colombia and their implications for the palaeozoogeography of western Gondwana

Dinosaur remains from Upper Cretaceous outcrops of northern Gondwana are extremely rare, in contrast with the much richer sample of coeval beds from southern Gondwana. Dinosaur remains from the uppermost Cretaceous Ortega locality of the Upper Magdalena Basin (Maastrichtian) of the Department of Tolima, Colombia, provides new information on northern Gondwanan faunas of this time. A revision of dinosaur material from this outcrop, consisting of three theropod shed teeth, reveals the presence of two morphotypes. One of them is referred to Abelisauridae based on the presence of crowns with mesial margin with a strong curvature beginning at about the second-third of the crown height and straight to slightly concave distal margin. The second morphotype exhibits un-serrated mesial and distal margins without carinae and no constriction at the base of the crown, a combination of features only observed in unenlagiine dromaeosaurids within Theropoda. Members of these clades are also present in coeval beds of southern and central South America, Madagascar, northern Africa, and India, indicating a cosmopolitan distribution in western and central Gondwana during the Late Cretaceous. Regarding South America, abelisaurid and probably dromaeosaurid theropods are recorded across a large latitudinal area, from the Palaeo-Equator to considerably high palaeo-latitudes in Patagonia, and probably spanning quite different environmental conditions.     

Diversity of theropod ootaxa and its implications for the latest Cretaceous dinosaur turnover in southwestern Europe

The scarcity of diagnostic skeletal elements in the latest Cretaceous theropod record of the Ibero-Armorican domain (southwestern Europe) prevents to perform accurate phylogenetic, paleobiogeographic, and diversity studies. In contrast, eggs and eggshells of theropod dinosaurs are relatively abundant and well known in this region from which several ootaxa have been described. Here, we describe the first Late Maastrichtian theropod ootaxon (Prismatoolithus trempii oosp. nov.) from SW Europe and demonstrate that oological record can be used as a proxy for assessing diversity of egg-producers and may help to complement their scarce bone record. The performed analyses indicate that the theropod taxa and ootaxa reach their diversity maxima during the Late Campanian and start to decrease near the Campanian–Maastrichtian boundary at both global and regional scales. The oological diversity of theropods in the Ibero-Armorican domain is consistent with the theropod diversity identified at high taxonomic level. Two distinct assemblages of theropod ootaxa can be recognized in the latest Cretaceous of the Ibero-Armorican domain. Their temporal transition can be correlated with other dinosaur faunal changes recorded in the region. This faunal turnover took place around the Early–Late Maastrichtian boundary, involving ornithopods, sauropods, ankylosaurs and, according to the present results, theropods as well.     

Reassessment of coelurosaurian (Dinosauria,Theropoda) remains from the Upper Cretaceous Wangshi Group of Shandong Province,China

Non-avian theropods are well represented in the Cretaceous of Asia. However, the first theropod remains ever reported from China, from the Wangshi Group of Shandong Province, have not been reassessed since they were described by Carl Wiman in 1929, despite the great strides that have been made in theropod phylogenetics in the last eight decades. The remains redescribed herein consist of four vertebrae (two cervicals, one dorsal and one caudal) from one site, and a caudal vertebra and ungual phalanx from another. The vertebrae from the first site are assigned to tyrannosauroids and ornithomimosaurs, as is the caudal vertebra from the second site, whereas the manual ungual also bears resemblances to those of non-maniraptoran coelurosaurs (specifically compsognathids and ornithomimosaurs). Theropods remain relatively rare in the Wangshi Group; nevertheless, the remains redescribed herein highlight the potential for the discovery of more theropod remains in future excavations.     

Distribution of the dentary groove of theropod dinosaurs: Implications for theropod phylogeny and the validity of the genus Nanotyrannus Bakker et al., 1988

This study examines the phylogenetic distribution of a morphologic character, described as a groove containing pores, on the lateral surface of the dentary bone in theropod dinosaurs. The nature of this groove is a feature unique to theropods. Of the 92 theropod taxa examined for the presence and absence of this feature, 48 possessed and 44 lacked this feature. Distribution of this character was compared to published phylogenetic analyses of theropods, in order to evaluate the utility of the dentary groove as a diagnostic feature. 80% of pre-Tyrannoraptoran theropods possessed the dentary groove, with only 6 reversals in basal theropod clades. Theropods with beaks or edentulous jaws all lacked a dentary groove. Tyrannosauroidea is marked by mosaic distribution of this character. Among tyrannosauroids, the dentary groove occurs only in Dryptosaurus and the Albertosaurinae (Albertosaurus + Gorgosaurus). Nanotyrannus lancensis, sometimes described as representing juvenile Tyrannosaurus rex, also possesses this groove, unlike the remainder of the Tyrannosaurinae. Nanotyrannus lancensis was included in a phylogenetic analysis of Tyrannosauroidea and was recovered within Albertosaurinae. We recommend that Nanotyrannus stand as a valid taxon nested within the Albertosaurinae, based on the presence of this groove, as well as other features of the skull.     

http://www.sciencedirect.com/science/article/pii/S1674987115300050

The intense study of coleopteran inclusions from Spanish(Albian in age) and French(Albian-Santonian in age) Cretaceous ambers,both of Laurasian origin,has revealed that the majority of samples belong to the Polyphaga suborder and,in contrast to the case of the compression fossils,only one family of Archostemata,one of Adephaga,and no Myxophaga suborders are represented.A total of 30 families from Spain and 16 families from France have been identified(with almost twice bioinclusions identified in Spain than in France);13 of these families have their most ancient representatives within these ambers.A similar study had previously only been performed on Lebanese ambers(Barremian in age and Gondwanan in origin),recording 36 coleopteran families.Few lists of taxa were available for Myanmar(Burmese) amber(early Cenomanian in age and Laurasian in origin).Coleopteran families found in Cretaceous ambers share with their modern relatives mainly saproxylic and detritivorous habits in the larval or adult stages,rather than wood-boring behavior.Fifteen of the coleopteran families occur in both the Lebanese and Spanish ambers;while only five are present in both Spanish and French.Considering the paleogeographic proximity and similarity of age of the Spanish and French ambers,the small number of taxa found in common at both areas is surprising.The ancient origin for the Lebanese and Spanish ambers,the paleogeography(including some barriers for terrestrial biota) and the local paleohabitats are factors that may explain the dissimilarity with the French specimens.Wildfires are believed to be a more likely cause of resin production during the Cretaceous than infestation by beetles.Current knowledge of the beetle species found in the Cretaceous ambers is introduced.     

The longest theropod trackway from East Asia,and a diverse sauropod-, theropod-, and ornithopod-track assemblage from the Lower Cretaceous Jiaguan Formation,southwest China

Here we report a large dinosaur tracksite from an extensive fluvial sandstone surface in the Lower Cretaceous Jiaguan Formation of Sichuan Province, China. The site contains over 250 individual tracks comprising at least 18 recognizable trackways, including the longest theropod trackway (cf. Eubrontes) known from China. This exceptional theropod trackway consists of 81 successive footprints covering a distance of 69 m. The tracks are well-preserved and are expressed both as true tracks on the main “upper” surface and as transmitted undertracks on a locally exposed “lower” bed. Also recorded are six other theropod trackways, including small Grallator-like ichnites, eight sauropod trackways (cf. Brontopodus), and three small ornithopod (cf. Ornithopodichnus) trackways with a parallel orientation, which may indicate gregarious behavior. Several trackways of a larger theropod trackmaker show pes imprints with elongated traces of the metatarsals, suggesting extramorphological (substrate-controlled) variation and/or plantigrade posture, which is here interpreted as indicating a change in gait assumed in response to deep and soft sediment. The assemblage indicates a diverse dinosaur fauna in the Lower Cretaceous Sichuan Basin with variously sized theropods, sauropods, and ornithopods. The late occurrence of footprints of the Grallator-Eubrontes plexus in Lower Cretaceous strata is further evidence of the extended stratigraphic range of this morphotype and the distinct palaeobiogeographic distribution of these trackmakers in East Asia.     

A reappraisal of a putative record of abelisauroid theropod dinosaur from the Middle Jurassic of England

Abelisauroidea are a recently recognized clade of theropod dinosaurs that have a predominantly Gondwanan distribution. Recently, a distal theropod tibia from the Middle Jurassic of England was identified as an abelisauroid, representing one of the oldest records of the group in general and the only Jurassic occurrence in Europe. On this basis, rapid radiation of abelisauroid and a global distribution of this clade in the Jurassic were suggested. Here, the specimen in question is re-examined and the characters used for referral to the Abelisauroidea are re-evaluated. None of the proposed characters can be demonstrated to represent abelisauroid synapomorphies and all have a wider distribution; especially coelurosaurian theropods, which are known from contemporaneous beds in England, frequently show the same character combination. Thus, there is currently no secure evidence for the occurrence of abelisauroids in the Jurassic of the northern Hemisphere, and the early evolution of this clade remains poorly known. Furthermore, other fragmentarily known taxa previously referred to Abelisauroidea based on putative synapomorphies of the distal tibia, such as Ozraptor and Austrocheirus, should be considered as Theropoda indet.     

A bothremydid from the middle Cenomanian of Portugal identified as one of the oldest pleurodiran turtles in Laurasia

The relatively complete and well preserved shell of a turtle, from the middle Cenomanian of Nazaré (Portugal), is studied here. It is recognized as a member of the crown group Pleurodira and, more specifically, of Bothremydidae. Pleurodira are one of the two lineages of modern turtles, their origin being in Gondwana. Pleurodira are very abundant in the uppermost Cretaceous record of Europe. However, this new finding is one of the few occurrences in the lower Upper Cretaceous of Laurasia. A single member of Bothremydidae had so far been identified in Portugal: the late Campanian-early Maastrichtian Rosasia soutoi. It was the only Cretaceous turtle identified in that country both at specific and at generic levels, being exclusive of Portugal. The taxon from Nazaré is identified as Algorachelus peregrinus, this form is also present in the contemporaneous beds in Spain, and is the oldest member of Bothremydidae in Laurasia. Algorachelus peregrinus is confirmed here to be a coastal form, which facilitated its spread. The two oldest known bothremydids from Laurasia, the European A. peregrinus and the North American Paiutemys tibert, are compared for the first time. They are recognized as closely related taxa. This study provides new data allowing a more precisely characterization of the oldest so far known dispersal event of Pleurodira in Laurasia, which was performed by an African lineage of Bothremydidae that reached the east coast of the Atlantic Ocean at least in the middle Cenomanian, and the west region of that Ocean at least in the late Cenomanian.     

A golden age for ectoparasitoids of Embiodea: Cretaceous Sclerogibbidae (Hymenoptera,Chrysidoidea) from Kachin (Myanmar), Charentes (France) and Choshi (Japan) ambers

Sclerogibbid wasps are obligate parasitoids of webspinners (Embiodea). Both groups have a particularly scarce geological record and are known since the Cretaceous: there are only four species of webspinners known from Burmese amber, and only two sclerogibbids were described from Barremian Lebanese and Cenomanian Burmese ambers. Here we report transferred genus from Aptian Choshi (Japan) amber and new sclerogibbids from Cenomanian Burmese and Charentese (France) ambers. The taxa described from Burmese amber are: Burmasclerogibba aptera gen. et sp. nov., Cretosclerogibba gen. nov. (with C. antennalis sp. nov., C. contractocollis sp. nov., C. neli sp. nov. and C. rasnitsyni sp. nov.) and Edrossia vetusta gen. et sp. nov. The first European fossil sclerogibbid Gallosclerogibba alnensis gen. et sp. nov. is described from Charentese amber. The holotype of Chosia yamadai Fujiyama, from Choshi amber, is re-described; it appears to be the oldest Laurasian sclerogibbid. The significant abundance and variety of Burmese sclerogibbid wasps (60% of fossil species known worldwide), as proxy of their hosts, were probably caused by the protection granted to them by the silk webs and possibly by the limited predation from ornithuromorph birds or crown-group ants. While all three extant sclerogibbid genera have apterous females, genera with winged females (Cretosclerogibba and Edrossia) dominated in Burmese amber. Small silk galleries from hosts may have favored the preservation of wings in females of Cretaceous sclerogibbids. Most new species described in the present paper, in addition to C. yamadai, are characterized by a very slender neck and a very long frontal process concealing the antennal toruli. These characters disappeared in extant species. We suggest that this loss was caused by a change in the fauna of predators, penalizing species with long neck and rostrum.     

Charophyte biostratigraphy of the non-marine Lower Cretaceous in the Central Tunisian Atlas (North Africa): Palaeobiogeographic implications

The chronostratigraphic framework of the non-marine deposits of the Central Tunisian Lower Cretaceous (Kebar Formation) is reviewed from a biostratigraphic viewpoint. The outcrops located in the Jebel Kebar, Jebel Ksaïra and Jebel Koumine localities provided charophyte assemblages belonging to two biochronozones: Ascidiella cruciata-Pseudoglobator paucibracteatus (upper Barremian–lower Aptian) and Clavator grovesii lusitanicus (upper Aptian–lower Albian). Clavatoraceans from the upper Barremian–lower Aptian in the Tunisian Atlas are reported here for the first time. The assemblage consists of Atopochara trivolvis var. triquetra, Ascidiella iberica var. inflata, Globator maillardii var. trochiliscoides, Globator maillardii var. biutricularis, Echinochara peckii var. lazarii, Clavator harrisii var. harrisii and Clavator harrisii var. reyi. In addition, a new characean species, Mesochara magna nov. sp. Trabelsi and Martín-Closas, is described herein. The results show that the Kebar Formation is diachronous in Central Tunisia, with a more complete record to the north (Jebel Koumine) than in the type locality (Jebel Kebar). Barremian–Aptian diapiric activity is proposed as the factor that controls the diachronous nature of this formation.The late Barremian–early Aptian charophyte assemblages from the Kebar Formation display strong affinities with the contemporaneous floras of the European basins, thus suggesting that intense supraregional floristic exchanges occurred between the Tethyan islands scattered throughout what is now Western Europe and North Africa. The biogeographic distribution of these charophytes leads to the hypothesis that the peri-Tethyan Archipelago acted as an effective bridge for the intercontinental exchanges of these plants between Laurasia and Gondwana.     

Small scale scrapes suggest avian display behavior by diminutive Cretaceous theropods

A set of about 25 diminutive sub-parallel scrapes in the Cretaceous Haman Formation of South Korea fit the morphology of the small theropod track Minisauripus which is also known from this formation. The scrapes are interpreted as evidence of display behavior, and suggest that the trace maker was an adult engaged in avian-like courtship behavior. Although avian theropods are also known from this formation, the scrapes are inconsistent with their foot morphology. Although large theropod scrapes have been interpreted as evidence of display behavior they are only known from North America. Thus, the scrapes described here are the first reported from Asia, and the first interpreted as evidence of display behavior in such a diminutive species.     

陕西商洛地区下白垩统大型兽脚类恐龙足迹

记叙了中国陕西省商洛市邵涧村下白垩统东河群2个大型兽脚类恐龙足迹,并将其归于Megalosauripus isp.。 东河群的时代与热河生物群同期,邵涧Megalosauripus isp. 可能可与热河生物群的大型兽脚类恐龙之足部形态做简 单对比。此外,邵涧Megalosauripus isp.造迹者的体长约为7.4m,这意味着早白垩世的陕西中南部亦存在着大型的 兽脚类恐龙。邵涧Megalosauripus isp.的发现,不仅为中国早白垩世恐龙足迹增加了新的成员,而且为将来在该地 区下白垩统中发现大型兽脚类恐龙的骨骼化石提供了确凿的依据。     

Ostracoda during the Early Aptian (Early Cretaceous) greenhouse period on the Isle of Wight, England

The earliest Aptian marine transgression of the Lower Cretaceous across southern England resulted in the collapse of the generally freshwater Barremian environment and the initiation of marine mileux. Salinities passed from fresh-oligohaline to meso- and pliohaline, reaching fully marine conditions during the obsoletum Subzone (P. fissicostus Zone). Newly formed environmental niches were rapidly occupied by ostracod associations. In the Isle of Wight, freshwater Cypridea-rich assemblages in the lower Shepherd's Chine Member (Vectis Formation) were gradually replaced by faunas dominated by Sternbergella cornigera, Mantelliana mantelli and Theriosynoecum fittoni. Marine taxa recorded from the Atherfield Clay Formation migrated predominantly from the Paris Basin and include Asciocythere albae, Schuleridea derooi, Neocythere gottisi, N. bordeti, Cythereis geometrica, Cytheropteron stchepinskyi and Protocythere croutesensis.     

An abelisaurid from the latest Cretaceous (late Maastrichtian) of Morocco,North Africa

During the latest Cretaceous, distinct dinosaur faunas were found in Laurasia and Gondwana. Tyrannosaurids, hadrosaurids, and ceratopsians dominated in North America and Asia, while abelisaurids and titanosaurians dominated in South America, India, and Madagascar. Little is known about dinosaur faunas from the latest Cretaceous of Africa, however. Here, a new abelisaurid theropod, Chenanisaurus barbaricus, is described from the upper Maastrichtian phosphates of the Ouled Abdoun Basin in Morocco, North Africa on the basis of a partial dentary and isolated teeth. Chenanisaurus is both one of the largest abelisaurids, and one of the youngest known African dinosaurs. Along with previously reported titanosaurian remains, Chenanisaurus documents the persistence of a classic Gondwanan abelisaurid-titanosaurian fauna in mainland Africa until just prior to the end-Cretaceous mass extinction. The animal is unusual both in terms of its large size and the unusually short and robust jaw. Although it resembles South American carnotaurines in having a deep, bowed mandible, phylogenetic analysis suggests that Chenanisaurus may represent a lineage of abelisaurids that is distinct from those previously described from the latest Cretaceous of South America, Indo-Madagascar, and Europe, consistent with the hypothesis that the fragmentation of Gondwana led to the evolution of endemic dinosaur faunas during the Late Cretaceous.     

Carbon and oxygen-isotope stratigraphy of the Early Cretaceous carbonate platform of Pădurea Craiului (Apuseni Mountains,Romania): A chemostratigraphic correlation and paleoenvironmental tool

Stable C and O isotope records were obtained from carbonate rocks spanning the Hauterivian to Cenomanian interval collected in several sections from the carbonate platform of Pădurea Craiului (Apuseni Mountains, Romania). In the absence of some key biostratigraphic marker species, stable isotopes were applied as a tool for stratigraphic correlation and dating. The composite δ¹³C and δ¹⁸O curves for the Early Cretaceous shows variable conditions with large positive and negative excursions and provide information on past environmental changes. The Hauterivian and the Barremian limestones (Blid Formation) display lower δ¹³C values (−2.8‰ to +2.9‰) relative to the Aptian–Albian deposits (−2.6‰ to +5.4‰) (Ecleja, Valea Măgurii and Vârciorog Formations). The red detrital formation (Albian–Cenomanian) is characterized by a highly variable distribution of the δ¹³C values (−3.5‰ to +3.9‰). Based on the similarities between the C-isotope curve established in Pădurea Craiului and from other sections in the Tethyan and the Pacific regions, two major oceanic anoxic events characterized by δ¹³C positive excursions were clearly recognized. The first is the OAE1a event (Early Aptian) in the upper part of the Ecleja Formation and the Valea Măgurii Formation. The second is the OAE1b event (Late Aptian–Albian) in the upper part of the Vârciorog Formation and in the Subpiatră Member. The position of the Aptian/Albian boundary is estimated to be at the upper part of the Vârciorog Formation, immediately after the beginning of the δ¹³C positive excursion. The δ¹³C data show major negative excursions during the Barremian (Blid Formation), Early Aptian (Ecleja Formation), and Late Aptian (Vârciorog Formation). The O isotope variation pattern (−10.2‰ to −2.1‰) is consistent with progressively warming temperatures during the Early Barremian followed by a cooling period. A subsequent warming period culminated in the Early Aptian. A significant cooling phase corresponds to the Late Aptian and Early Albian and the climate cooled again during the Late Albian and into the Early Cenomanian stage. The data provide a better understanding of the Early Cretaceous sedimentation cycles in Pădurea Craiului and create a more reliable framework for regional correlations.     

A new ornithischian dinosaur from the Cretaceous Liangtoutang Formation of Tiantai,Zhejiang Province,China

A new ornithischian dinosaur, Yueosaurus tiantaiensis gen. et sp. nov., is erected based on a partial postcranial skeleton from the Liangtoutang Formation (Aptian–Cenomanian) of Zhejiang Province, China. It differs from other ornithischians in possessing the following unique combination of characters: prominent and slightly ventrally directed cervical parapophyses; anteroposteriorly narrow neural spines on caudal vertebrae; scapula with a ventroscapular groove, supraglenoidal buttress, supraglenoid fossa, and a strong anteroventral expansion of the scapular blade. Yueosaurus represents the first basal ornithopod taxon from southeastern China. It expands our understanding of the Cretaceous dinosaurian fauna of Zhejiang Province.     

Jurassic–Cretaceous radiolarian biostratigraphy and sedimentary environments of the Ceno-Tethys: records from the Xialu Chert in the Yarlung-Zangbo Suture Zone,southern Tibet

Radiolarian biostratigraphic research has been carried out along two continuous sections through the Xialu Chert, one of the accreted sheets included in the Yarlung-Zangbo Suture Zone. Six radiolarian zones have been identified as follows: Laxtorum(?) jurassicum Zone (Aalenian), Tricolocapsa plicarum Zone (Bajocian–lower Bathonian), Stylocapsa(?) spiralis Zone (upper Callovian–Oxfordian), Hsuum maxwelli Zone (Kimmeridgian), Pseudodictyomitra carpatica Zone (upper Tithonian–lower Valanginian), and Turbocapsula costata Zone (Aptian).A reconstructed stratigraphy of the Xialu Chert, based on lithological succession and radiolarian dating, indicates that the chert exhibits a long depositional history, at least from early Middle Jurassic (Aalenian) to late Early Cretaceous (Aptian). The separation of the Lhasa Block from the northern Gondwana margin must, therefore, be dated before the Aalenian. The absence of calcareous sediments in the Xialu Chert indicates that the oceanic basin was deeper than the CCD throughout the depositional history. The transition from chert to siliceous mudstone is recorded sometime in Early Cretaceous, most probably around the Barremian/Aptian boundary. This means that the oceanic plate had already started being consumed at a trench by that time. The accretion of the Xialu Chert occurred after the Aptian time.