Upper Maastrichtian ammonite biostratigraphy of the Gulf Coastal Plain (Mississippi Embayment,southern USA)

The Cretaceous outcrop belt of the Mississippi Embayment in the Gulf Coastal Plain (GCP) spans the Cretaceous/Paleogene (K/Pg) boundary. A detailed reconstruction of this time interval is critical for understanding the nature of biotic and environmental changes preceding the end-Cretaceous Mass Extinction event and for deciphering the likely extinction mechanism (i.e., bolide impact versus volcanism). Eight sections encompassing the K/Pg succession across the Mississippi Embayment were analyzed using biostratigraphic sampling of ammonites, dinoflagellates, and nannofossils. An upper Maastrichtian ammonite zonation is proposed as follows, from oldest to youngest: Discoscaphites conradi Zone, D. minardi Zone, and D. iris Zone. Our study documents that the ammonite zonation established in the Atlantic Coastal Plain (ACP) extends to the GCP. This zonation is integrated with nannofossil and dinoflagellate biostratigraphy to provide a framework to more accurately determine the age relationships in this region. We demonstrate that ammonites and dinoflagellates are more reliable stratigraphic indicators in this area than nannofossils because age-diagnostic nannofossils are not consistently present within the upper Maastrichtian in the GCP. This biostratigraphic framework has the potential to become a useful tool for correlation of strata both within the GCP and between the GCP, Western Interior, and ACP. The presence of the uppermost Maastrichtian ammonite D. iris, calcareous nannofossil Micula prinsii, and dinoflagellates Palynodinium grallator and Disphaerogena carposphaeropsis suggests that the K/Pg succession in the GCP is nearly complete. Consequently, the GCP is an excellent setting for investigating fine scale temporal changes across the K/Pg boundary and ultimately elucidating the mechanisms causing extinction.     

Integrated biostratigraphic and sequence stratigraphic framework for Upper Cretaceous strata of the eastern Gulf Coastal Plain, USA

Upper Cretaceous (Santonian-Maastrichtian stages) strata of the eastern US Gulf Coastal Plain represent a relatively complete section of marine to nonmarine mixed siliciclastic and carbonate sediments. This section includes three depositional sequences which display characteristic systems tracts and distinct physical defining surfaces. The marine lithofacies are rich in calcareous nannoplankton and planktonic foraminifera which can be used for biostratigraphic zonation. Integration of this zonation with the lithostratigraphy and sequence stratigraphy of these strata results in a framework that can be used for local and regional intrabasin correlation and potentially for global interbasin correlation. Only the synchronous maximum flooding surfaces of these depositional sequences, however, have chronostratigraphic significance. The sequence boundaries and initial flooding surfaces are diachronous, and their use for correlation can produce conflicting results. The availability of high resolution biostratigraphy is critical for global correlation of depositional sequences.     

Tectonic geomorphology of the Mississippi Valley between Osceola, Arkansas and Friars Point, Mississippi

A geomorphic study of the Mississippi River and its alluvial valley between Osceola, Arkansas and Friars Point, Mississippi has identified anomalous surface features that can be linked to known geological structures. For example, relatively recent deformation along Big Creek fault zone, White River fault zone, Bolivar-Mansfield tectonic zone, Blytheville Arch, Crittenden County fault zone, and Reelfoot Rift margins is suggested by river and topographic anomalies. Faults and plutons appear to affect drainage networks, and the morphology of Crowleys Ridge suggests significant fault control. The many anomalies probably reflect a fractured suballuvial surface. Although movement along these fractures will most likely occur in seismically active areas, the probability of movement elsewhere     

An Upper Cretaceous (middle Campanian) marine chondrichthyan and osteichthyan fauna from the Rattlesnake Mountain sandstone member of the Aguja Formation in West Texas

A thin phosphate-granule conglomerate within the Upper Cretaceous (middle Campanian) Rattlesnake Mountain sandstone member of the Aguja Formation preserves a diverse chondrichthyan and osteichthyan fauna. This highly fossiliferous deposit (the ‘Ten Bits Microsite’) yielded about 5000 teeth, spines, and denticles in a small amount of matrix (c. 150 kg). About 30 identifiable species of sharks, rays, and bony fishes are recognized. Two of the three most abundant chondrichthyan species at Ten Bits (Scapanorhynchus texanus and Ischyrhiza mira) are also the most common species in other middle to late Campanian marine vertebrate faunas along the Gulf and Atlantic Coastal Plain. The myliobatiform rays Brachyrhizodus and Rhombodus that occur at Ten Bits also appear to be characteristic of the Gulf and Atlantic Coast, as are lamniform sharks such as Cretalamna and Serratolamna. These taxa are entirely absent or extremely rare in Western Interior Campanian faunas. In contrast, some small orectolobiform sharks (Cantioscyllium, Chiloscyllium, Columbusia) and small rays (Protoplatyrhina) found at Ten Bits are common in shallow water faunas of the Western Interior and Texas Coastal Plain, but rarely reported from the eastern Gulf or Atlantic Coast. The common Western Interior ray Myledaphus bipartitus does not occur at Ten Bits or in any Gulf or Atlantic Coast fauna. Ptychotrygon agujaensis is abundantly represented in the Ten Bits fauna, but unknown in correlative marine faunas. Although Ptychotrygon occurs in all Western Interior, Gulf and Atlantic Coastal Plain faunas, it is represented elsewhere by apparently endemic species at each collection site. The differences between Western Interior, Gulf, and Atlantic Coastal Plain faunas probably reflect latitudinal variation in water temperature or salinity, or different oceanic water circulation patterns between the Western Interior Seaway and the Gulf or Atlantic Coast that restricted the distributions of some marine fish species. The Ten Bits fauna shares typical species with both Western Interior and Gulf and Atlantic Coast faunas, reflecting its position at the border between these provinces; however, the dominant taxa found at Ten Bits are the same as those found on the Gulf and Atlantic Coast, and indicate that western Texas was more closely allied biogeographically with that province than with the Western Interior of North America. One species tentatively identified in the Ten Bits fauna on the basis of a single tooth, Igdabatis cf. I. indicus, is otherwise known only from southern Europe and Asia, although a similar large myliobatid ray also occurs rarely in Texas Coastal Plain faunas. These occurrences indicate that western Texas may have been near the northern limit of the range for some tropical Tethyan marine vertebrate species.     

A palynological biozonation for the Maastrichtian Stage (Upper Cretaceous) of South Carolina, USA

Three palynological biozones are proposed for the Maastrichtian Stage of South Carolina. In ascending stratigraphic order, the biozones are the Carolinapollis triangularis (Ct) Interval Biozone, the Holkopollenites chemardensis (Hc) Interval Biozone, and the Sparganiaceaepollenites uniformis (Su) Interval Biozone. Integration of the biostratigraphy with lithologic and geophysical log data suggests that within the study area, the upper and lower boundaries of each zone are bounded by regional unconformities, and that a three-fold subdivision of the Maastrichtian Stage is warranted. The biozonation is based on the analysis of 114 samples from 24 subsurface and three outcrop sections from the Coastal Plain of South Carolina; samples from an additional seven subsurface and 18 outcrop sections from North Carolina and Georgia were examined to evaluate the geographic extent of the biozones. One new genus and five new species of pollen are described, and emendations are presented for two genera and one species of pollen.     

Correlation of Upper Cretaceous strata from Lima Peaks area to Madison Range, southwestern Montana and southeastern Idaho, USA

An⁴⁰Ar/³⁹Ar age of 85.81 Ma±0.22 my was obtained on sanidine from a volcanic procellanite bed near the top of the 2135+m-thick Upper Cretaceous Frontier Formation in the Lima Peaks area of southwestern Montana. This early Santonian age, combined with previously determined age data including a palynological age of Cenomanian for the lower Frontier at Lima Peaks, and a U-Pb isotopic date of about 95 Ma for the base of the Frontier Formation in the eastern Pioneer Mountains north of the Lima Peaks area, provides an age range for the nonmarine formation. In the Madison Range, farther east in southweastern Montana, this age range corresponds to marine strata of not only the Frontier Formation, but also the overlying Cody Shale and Telegraph Creek Formation, a sequence that totals less than 760 m thick.The Upper Cretaceous marine formations of the madison Range are closely zoned by molluscan faunas that are well constrained with radiometric dates. The⁴⁰Ar/³⁹Ar age of 85.81 Ma±0.22 my at Lima Peaks is bracketed by radiometric dates for theScaphites depressus—Protexanites bourgeoisianusbiozone and the overlyingClioscaphites saxitonianus—Inoceramus undulatopilcatusbiozone of the Western Interior. Fossils of both of these biozones are present in the Cody Shale and the Telegraph Creek Formation in the Madison Range. The Telegraph Creek contains two units of volcanic ash that are approximate time equivalents of the volcanic procellanite of the Lima Peaks area. Clasts in the conglomerate of the upper part of the Frontier in the Lima Peaks area were shed during the initial stages of uplift of the Blacktail-Snowcrest Highlands which rose to the north. The dated porcellanite lies above the conglomerates and indicates that the uplift was initiated by middle or late Coniacian, 87–88 Ma.     

A tooth of Archaeopterygidae (Aves) from the Lower Cretaceous of France extends the spatial and temporal occurrence of the earliest birds

The Late Jurassic Archaeopterygidae, comprising the iconic genus Archaeopteryx, is altogether among the earliest, basalmost and best-known Mesozoic avian taxa. The geographic distribution of Archaeopteryx is hitherto restricted to a limited region of southern Germany, probably due to preservation biases. Here we describe a tooth sorted among the more than 35,000 isolated teeth found by sieving sediments from the Cherves-de-Cognac locality (western France, Lower Cretaceous). This tooth crown is morphologically similar to teeth of the German specimens of Archaeopteryx (sensu lato), despite minor differences. The Cherves-de-Cognac tooth differs much more importantly from all other known taxa. It shares with different specimens of Archaeopteryx the general tooth size, recurved shape affecting apical third of crown, thin apical-mesial carina, constriction at base of crown giving distinctive S shape of distal edge in profile, absence of other ornamentation or serration, and shape of crown section. Incidentally, former assignments of teeth from the Upper Jurassic of Guimarota (Portugal) to cf. Archaeopteryx are unwarranted, as those teeth markedly differ from the Archaeopterygidae in several crucial features. We assign the new tooth to the family Archaeopterygidae, the earliest European birds, making it the first member of the family in Europe outside Germany, and extending its temporal occurrence to the early Cretaceous.     

Stratigraphy and sedimentation rates of Upper Cretaceous deep-water systems of the Rhenodanubian Group (Eastern Alps, Germany)

In the Bavarian Alps (Germany), west of the Isar River, the abyssal deposits of the Lower Barremian to Upper Campanian Rhenodanubian Group consist of siliciclastic and calcareous turbidites alternating with hemipelagic non-calcareous mudstones. The up to 1500-m-thick succession, deposited in the Penninic Basin to the south of the European Plate, is characterized by a low mean sedimentation rate (c. 25 mm kyr⁻¹) over 60 million years. Palaeocurrents and turbidite facies distribution patterns suggest that sedimentation occurred on a weakly inclined abyssal plain. The highest sedimentation rates (up to 240 mm kyr⁻¹) were associated with the calcareous mud turbidites of the newly defined Röthenbach Subgroup, which includes the Piesenkopf, Kalkgraben and Hällritz formations (Middle Coniacian to Middle Campanian). These calcareous turbidites prograded from the west, and interfinger towards the east with red hemipelagic claystone. A high sea level presumably favoured pelagic carbonate production and accumulation on the shelves and on internal platforms in the western part of the basin, whereas siliciclastic shelves with steep slope angles have bordered the eastern part of the basin, where a dearth of turbidite sedimentation and increased Cretaceous oceanic red beds deposition occurred. In contrast to the eustatically-induced Middle Coniacian to Lower Campanian Cretaceous oceanic red beds (calcareous nannoplankton zones CC14 to CC18), red hemipelagites of Early Cenomanian age (upper part of calcareous nannoplankton zone CC9) and early Late Campanian age (upper part of zone CC21 and zone CC22) are interpreted as the result of regional tectonic activity.     

四川都江堰市、彭州、什邡地区的侏罗系

龙门山中段都江堰市、彭州市、什邡县等地的侏罗系十分发育，呈ＮＥ－ＳＷ向展布。在１９９１～１９９５年１／５万区调期间，从这个地区测制的一些侏罗系剖面中划分出了千佛崖组、沙溪庙组、遂宁组和莲花口组４个岩石地层单位，并与邻区相应地层单位进行了对比，总结了它们的岩石特征和相变；根据ＥＳＲ（电子自旋共振）测年资料讨论了侏罗纪的年代地层划分；并简要叙述了千佛崖期湖相、沙溪庙—遂宁期河流相和莲花口期洪积相（冲积扇相）的划分依据。     

Biostratigraphic and biogeographic implications of a hadrosaurid (Ornithopoda: Dinosauria) from the Upper Cretaceous Almond Formation of Wyoming,USA

The results of Barnum Brown's 1937 expedition to the Almond Formation of Wyoming consisted of two unidentified ceratopsian skulls and a partial hadrosaurid specimen (AMNH 3651). The hadrosaurid is here attributed to the Maastrichtian genus Saurolophus, verifying previous biostratigraphic correlations of this formation using ammonite zones. Fossiliferous lower Maastrichtian formations occurring latitudinally between those of Alberta, Canada, and southwestern Texas, USA, such as the Almond Formation, are essential for testing the effects and duration of apparent hadrosaurid faunal segregation earlier in the Campanian, and indirectly aiding in the placement of faunal boundaries that are currently unknown for the late Campanian. The discovery of Saurolophus in Wyoming, a close relative of the Campanian genus Prosaurolophus, affirms that the segregation of hadrosaurid faunas established in the late Campanian (～75 Ma) continued for at least 3 million years. Combining occurrences of Saurolophus from Mongolia and the Moreno Formation of California with those of Alberta, Canada, this genus appears to have had one of the largest geographic ranges of any equivalent clade of hadrosaurid dinosaur, although species level distributions are still uncertain.     

A snapshot into the terrestrial ecosystem of an exceptionally well-preserved dinosaur (Hadrosauridae) from the Upper Cretaceous of North Dakota,USA

A palynological investigation of sedimentary rocks enclosing an exceptionally well-preserved fossil dinosaur (Hadrosauridae) discovered in the upper part of the Hell Creek Formation in south western North Dakota was conducted in order to document the immediate paleoenvironment of this dinosaur. The specimen, an Edmontosaurus annectens is remarkable in having exceptional three-dimensional preservation of soft tissue around the skeleton, indicating rapid burial. A well-preserved palynological assemblage dominated by fern and bryophyte spores, with lesser gymnosperm and angiosperm pollen was recovered. Sparse fresh-water algae and marine dinoflagellate cysts were also recorded. The palynofacies is dominated by wood fragments, including charcoal, with little amorphous organic matter. The presence of some typical pollen taxa of the Wodehouseia spinata Assemblage Zone including Striatellipollis striatellus, Tricolpites microreticulatus, Leptopecopites pocockii as well as a diverse suite of Aquilapollenites, is fully consistent with a Late Cretaceous (late Maastrichtian) age. The palynoflora indicates a local vegetation composed of a canopy of conifers dominated by Pinaceae and a minor sub-canopy of Taxodium and cycads, as well as an understory of hydrophilous ferns, mosses and herbaceous angiosperms, indicative of a warm and humid climate – an environment where this specific hadrosaur roamed over 66 million years ago.     

The fossil record (calcareous nannofossils and foraminifers) in single intervals of the Upper Cretaceous flysch sequence of the West Carpathians, Czechoslovakia

Studies of calcareous nannofossils and microfossils and their distribution in different intervals of the flysch rhythms in the Kloko ník brook in the Bílé Karpaty Unit of the Magura Group of nappes in the West Carpathians gave the following results. The highest species diversity of calcareous nannofossils was found in the lower parts of the Bouma Te hemipelagic intervals. The Campanian marker species Ceratolithoides aculeus and Aspidolithus parcus were found in practically all layers studied. A stratigraphically important foraminiferal fauna was obtained from the upper parts of the Bouma Te intervals, including the Campanian-Maastrichtian planktic foraminifers Globotruncana arca and Globotruncanita stuartiformis. In the non-calcareous pelagites, agglutinated species with a range from the Late Cretaceous to the Paleogene dominate.     

Ichnology of prodeltaic hyperpycnite–turbidite channel complexes and lobes from the Upper Cretaceous Prairie Canyon Member of the Mancos Shale,Book Cliffs,Utah, USA

The Upper Cretaceous Prairie Canyon Member of the Mancos Shale, Book Cliffs, Utah, contain outstanding examples of prodeltaic turbidity and hyperpycnal flow deposits. Sandstone‐rich, heterolithic and mudstone‐rich channel fills occur near the north‐west entrance to Tusher Canyon, Gunnison Butte and Bootlegger Wash. Mudstone‐rich and heterolithic‐rich hyperpycnal channel deposits are mostly unbioturbated, locally displaying a few specimens of Phycosiphon incertum, Protovirgularia dichotoma, Rosselia socialis, Schaubcylindrichnus coronus and Palaeophycus tubularis. Sandstone‐rich channel deposits consist of wave‐reworked turbidites and hyperpycnites, containing Helminthoidichnites tenuis, Lockeia siliquaria, Phycodes isp., Phycosiphon incertum, Protovirgularia dichotoma, Rosselia socialis, Skolithos linearis and Fugichnia. Scolicia isp. and Chondrites isp. occur locally. Strata along the south‐west entrance of Tusher Canyon record deposition in a prodelta turbidite lobe, but far from its axis. With the exception of a few specimens of Ophiomorpha isp., bioturbation is restricted to the top of the succession, where Curvolithus simplex, Gyrochorte comosa, Lockeia siliquaria, Palaeophycus tubularis and Ptychoplasma excelsum occur. Strata at Hatch Mesa record deposition in a hyperpycnal lobe, near to its axis. Sandstone beds include Curvolithus simplex, Gyrochorte comosa, Ophiomorpha nodosa, Palaeophycus tubularis, Phycosiphon incertum, Protovirgularia dichotoma, Ptychoplasma excelsum, Schaubcylindrichnus freyi, Skolithos linearis, large specimens of Rosselia socialis and indeterminate crustacean burrows. Chondrites isp. is present in the mudstone. High rates of both episodic and sustained sedimentation, degree of substrate consolidation, freshwater discharge and water turbidity are the most important stress factors in both channels and lobes. Taxonomic composition, uneven distribution of bioturbation through the successions, and overall low ichnodiversity help to distinguish these prodeltaic deposits from bathymetrically equivalent offshore strata in the same basin. Hyperpycnal flow deposits are formed in a wide variety of environmental settings, therefore displaying high ichnological variability. Such variability is summarized by characterising ichnofaunas from four different depositional settings: (i) lakes; (ii) shelf deltas; (iii) shelf‐edge deltas; and (iv) deep‐marine systems.     

上黑龙江盆地虎拉林早白垩世岩体锆石U-Pb年代学、Hf同位素及地球化学特征研究

上黑龙江盆地虎拉林金矿床位于兴蒙造山带东段大兴安岭北部额尔古纳微地块北缘,夹持于蒙古鄂霍茨克缝合带与得尔布干断裂之间,其矿体主要赋存于隐爆角砾岩中,与早白垩世岩浆活动形成的花岗斑岩、石英斑岩关系密切。本文采用LA-ICP-MS锆石U-Pb定年方法,获得花岗斑岩岩体结晶年龄为141.7±1.1 Ma(MSWD=0.086)、石英斑岩(2件)岩体结晶年龄为144.9±0.56Ma(MSWD=0.580)和142.6±0.74 Ma(MSWD=0.077),两者均为早白垩世岩浆活动产物。两岩体锆石ε_Hf(t)分别介于-4.14～0.16、-2.25～1.37,且大部分数据位于球粒陨石演化线之下,两阶段模式年龄(t_DM2)分别为987.08～1259.04 Ma、908.38～1138.56 Ma。岩石地球化学特征显示,花岗斑岩w(SiO₂)为66.21%～66.70%,w(Al₂O₃)为15.18%～15.45%,w(Na₂O+K₂O)为7...     

Discovery of Pseudofrenelopsis gansuensis from the Lower Cretaceous of Wangqing, Jilin Province, and Its Significance in Correlation of Cretaceous Red Beds in China

New data from abundant vegetative shoots and cuticular analysis are provided for the Cretaceous cheirolepidiaceous conifer Pseudofrenelopsis gansuensis Deng, Yang et Lu. The material was found from a new locality of the Lower Cretaceous strata in the Luozigou Basin, Wangqing, Jilin Province, northeastern China. Pseudofrenelopsis is a common plant in the Dalazi Formation of the Yanji Basin about 150 km from Wangqing, but there exists different species, Pseudofrenelopsis dalatzensis only. Both P. dalatzensis and P. gansuensis have been recorded from the Lower Cretaceous of Jiuquan, Gansu Province, but they are in different stratigraphic horizons. The Lower Cretaceous plant-bearing strata in Luozigou have used to correlate with the Dalazi Formation of the Yanji Basin. The discovery of P. gansuensis, which is lower in horizon than P. dalatzensis in Jiuquan, may indicate that they are also different in horizon in Jilin. Cheirolepidiaceous conifers are among the few fossils of red beds of the Early Cretaceous in China. The present discovery of Pseudofrenelopsis gansuensis provides important evidence for classification, correlation and determination of geological ages of the Early Cretaceous non-marine red deposits of the two separate basins in remote areas of North China.     

Clay Mineralogical and Geochemical Studies of Detrital Rocks of the Upper Cretaceous Salt-bearing Strata,Simao Basin,SW China:Implication for Provenance and Source Weathering

正1 Introduction Geological studies established on several sections in Lanping-Simao basin have shown that the salt-bearing strata of Mengyejing formation(Yunlong Fm.in Lanping basin)are constituted by an alternation of salt layers and interbedded facies.The latter consists mainly of mudstones,and mudstone-rich conglomerate.The mineralogy and geochemistry of salt-bearing beds and     

Paleoenvironment of the Folsom archaeological site, New Mexico, USA, approximately 10,500 C yr B.P. as inferred from the stable isotope composition of fossil land snail shells

Well-preserved aragonitic land snail shells (Vallonia) from late Pleistocene Eolian sediment in the Folsom archaeological site in New Mexico exhibit an overall decrease of δ¹⁸O_PDB from maximum values of +2.7‰ (more positive than modern) to younger samples with lower average values of about −3.6‰ (within the modern range). The age of the samples (approximately 10,500 ¹⁴C yr B.P.) suggests that the decrease in δ¹⁸O may manifest climatic changes associated with the Younger Dryas. Some combination of increased relative humidity and cooler temperatures with decreased δ¹⁸O of precipitation during the times of snail activity can explain the decrease in shell δ¹⁸O. A well-known Paleoindian bison kill occurred at the Folsom site during this inferred environmental transition.Average δ¹³C values of the aragonite shells of the fossil Vallonia range from −7.3 to −6.0‰ among different archaeological levels and are not as negative as modern values. This suggests that the proportion of C₄ vegetation at the Folsom site approximately 10,500 ¹⁴C yr B.P. was greater than at present; a result which is consistent with other evidence for higher proportions of C₄ plants in the region at that time.     

西藏岗巴地区海相上白垩统碳、氧同位素对比实验结果偏差分析

对西藏南部岗巴地区上白垩统部分全岩样品进行了碳、氧同位素不同实验室、不同时间的对比实验，目的在于了解样品处理过程可能对试验结果的影响程度。结果发现，不同实验室的结果偏差比同一实验室不同时间的结果偏差大，碳同位素比值的偏差比氧同位素比值的偏差大。不同实验室结果偏差的关键原因是样品制备方法和岩性的不同：手工碎样、选样、磨样较难避免徽裂隙中充填的方解石脉和小型生物扰动组构对同位素值的影响，而毫米级直径钻头刮样取样则很大程度上可以避免；钙质页岩和泥灰岩受影响的程度相对较小，生物碎屑灰岩受影响较大。碳同位素比值偏差大干氧同位素。前者基数比后者大4～5倍可能是主要原因。     

A new ornithopod (Dinosauria,Ornithischia) from the Upper Cretaceous of Antarctica and its palaeobiogeographical implications

A new ornithopod dinosaur from the Upper Cretaceous (Maastrichtian) Snow Hill Island Formation, at James Ross Island, Antarctica is here described. This new taxon, named as Morrosaurus antarcticus gen. et sp. nov., is represented by a fragmentary right hind limb belonging to a medium-sized individual. Our phylogenetic analysis nests the new taxon in a monophyletic clade of Southern Hemisphere ornithopods that includes most Patagonian and Antarctic ornithopods. Several members of this group share a slender and bunched foot with narrow metatarsal IV, expanded chevrons, and bowed humerus without deltopectoral crest. Several features indicate that these ornithopods exhibit adaptations for a specialized cursorial mode of life. The recognition of Patagonian and Antarctic Ornithopoda belonging to a monophyletic clade reinforces palaeobiogeographical signals indicating that Patagonia, Antarctica and Australia shared a common Late Cretaceous terrestrial fauna.