Cretaceous Research最新文献

Isolated mosasaur teeth and vertebrae recovered from beds of the Guadalupe Group of central Boyacá, Colombia, are reported. A partial tooth crown identified as Globidens sp., found in the Labor-Tierna Formation (Maastrichtian), represents the first report of this genus from northern South America and its most equatorial occurrence. A tooth crown recovered from the Plaeners Formation (upper Campanian–lower Maastrichtian), represents the youngest record of the subfamily Plioplatecarpinae in Colombia. These occurrences collectively constitute the youngest record of the family Mosasauridae in Colombia and expand both the taxonomic diversity and biogeography of mosasaurids in northern South America.

Upper Cretaceous vertebrate records from Chile are mostly known by historical mentions with unknown repositories and uncertain stratigraphic provenance. This contribution reviews and complements two marine vertebrate assemblages from the Upper Cretaceous of central Chile, which were part of the ancient Arauco Basin. The oldest assemblage (lower Maastrichtian) comprises abundant condrichthyans referred to Carcharias gracilis, Odontaspis cf. winkleri, Scapanorhynchus sp., Centrophoroides appendiculatus, Squatina sp., Cretorectolobus sp., Orectolobidae indet., Paraorthacodus sp., Ischyrhiza chilensis and Biropristis landbecki, which adds to the previously reported occurrences of Echinorhinus sp. and Myledaphus araucanus. In addition, chimeroids referred to as Edaphodon kawai and remains of a leatherback turtle referable to Mesodermochelys sp. are here described, the latter being its first occurrence outside Japan. The younger assemblage (upper Maastrichtian) includes similar chondrichthyans and a higher diversity of marine reptiles, including plesiosaurians (Aristonectes sp., Aristonectinae indet., and Elasmosauridae indet.), sea turtles (Pancheloniidae indet.) and diverse mosasaurs (Halisaurus sp., Tylosaurinae indet., and the first local occurrence of Plioplatecarpinae indet.). Throughout the Maastrichtian, the local marine vertebrates likely suffered a declination in abundance but a rise in diversity, with evidence of a marked alteration in middle levels of the trophic web during the upper Maastrichtian. This fauna shows a main influence from the northern hemisphere (especially from the Western Interior Sea), acquiring a more marked Weddellian influence during the end of the Maastrichtian. The studied material allows a better understanding of the Upper Cretaceous vertebrate marine fauna in lower latitudes of the southeastern Pacific.

A non-hadrosaurid hadrosauroid, Qianjiangsaurus changshengi gen. et sp. nov., is named and described here based on an incomplete, partially articulated skeleton from the top of the Upper Cretaceous Zhengyang Formation in Qianjiang District, Chongqing Municipality, southwest China. The skeleton displays a transitional morphology between non-hadrosaurid hadrosauroids and hadrosaurids. The diagnosis of the taxon is therefore defined as a unique combination of characters, including a series of plesiomorphic features typical of non-hadrosaurid hadrosauroids, some apomorphic features common among hadrosaurids but rarely reported in non-hadrosaurid hadrosauroids, and a probable autopomorphy, namely the fan-shaped prepubic process of the pubis strongly anteroposteriorly constricted and dorsoventrally expanded, with the length/height ratio of ∼0.79. Phylogenetic analysis recovers a sister-taxon relationship between Qianjiangsaurus and Plesiohadros outside of Hadrosauridae, and the clade consisting of the two taxa is positioned higher on the tree than Gobihadros and Gilmoreosaurus, but below the clade of Telmatosaurus + Tethyshadros, Eotrachodon and Zhanghenglong. Combining the morphological data with the phylogenetic topology identifies Q. changshengi as a late-branching non-hadrosaurid hadrosauroid. Given that the age assemblage of the eight hadrosauroids closely related to Qianjiangsaurus in phylogeny spans the Santonian–early Maastrichtian time interval, the top of the Zhengyang Formation, from which Qianjiangsaurus is recovered, is possibly restricted to the late Late Cretaceous in age. Hierarchical clustering of twelve hadrosauroid-bearing dinosaur assemblages from the Late Cretaceous deposits of Asia shows a strong correlation between the Zhengyang Formation and the Djadokhta and Baruungoyot formations in Mongolia that supports coeval interchange of dinosaur faunas across East Asia.

The Early Cretaceous geological record contains evidence of major and abrupt global environmental changes. Understanding the past water-column redox fluctuations and paleoenvironmental evolution of Early Cretaceous environments is, therefore, pivotal for a better comprehension of this period as a whole. In this sense, to investigate the processes that modulated the deposition and preservation of the Romualdo Epicontinental Sea sediments (Aptian–Albian record of the Araripe Basin, Brazil), we present a multi-proxy study using samples from a new borehole drilled in the central area of the Araripe Basin. To unravel the origin, evolution, and demise of this shallow sea, a sedimentological and geochemical characterization was applied. We combine facies association, trace-fossil and petrographic analyses, bulk chemical data (pXRF), TOC and IR quantification (total organic carbon and insoluble residue, respectively), and SEM-EDS images. We identified twelve lithofacies that were grouped into four facies associations. The onset of the deposition of the Romualdo Formation is characterized by the transition from a fluvio-deltaic environment (FA-1) to an epicontinental sea (FA-2) that prevailed and further shifted into a deltaic environment (FA-3). The uppermost facies association (deltaic-fluvial; FA-4) reveals a continentalization process and the demise of the shallow sea. The variations of geochemical proxies were examined to assess terrigenous supply, salinity, redox conditions of bottom water, and primary bioproduction. Based on these proxies, we determined five chemostratigraphic units (U-A to U-E) that revealed a dynamic interplay between organic matter accumulation, paleoenvironmental shifts, and redox conditions. Our results demonstrate that the influx of nutrients from continental sources fostered pulses of biological productivity that, coupled with the low-oxygen environment, resulted in the preservation of organic-rich rocks (high TOC horizons). Notably, the enrichment of redox-sensitive trace elements (RSTEs) suggests that these organic-rich rocks were deposited under euxinic/oxygen-depleted environmental conditions, demonstrating that substantial variations in oxygen levels occurred. Overall, geochemical fluctuations indicate that climatic conditions and siliciclastic input primarily drove the lithofacies variation and organic matter accumulation. Lastly, the results provide constraints on the driving mechanisms that allowed the preservation of organic-rich mudstones of the Romualdo Formation, which is particularly relevant for other studies investigating similar processes in past epicontinental seas.

The earwig family Labiduridae occupies a putatively important position in the phylogeny of Dermaptera and is clearly of significant antiquity, with occurrences from the mid-Cretaceous and perhaps the Early Cretaceous. Nonetheless, palaeontological data on the family remains scant. Here we report a new genus and species of labidurids from mid-Cretaceous Kachin amber. Metaxylabis baii gen. et sp. nov. is described and figured, and its characters are compared with those of all other Mesozoic Labiduridae. The genus can be excluded from all of the current subfamilies of Labiduridae and is placed in its own subfamily, Metaxylabidinae subfam. nov. Remarks are given on the phylogenetic affinities of Mesozoic fossils and the need for more extensive sampling of palaeontological and genomic data.

The Early Cretaceous avian ichnofauna of Laurasia, particularly in East Asia, is remarkably abundant. The northwestern region of China is the most productive area for bird tracks. Recently, four avian-dominated track sites have been discovered in the Cretaceous Lanzhou-Minhe Basin of Gansu, where the shorebird track Koreanaornis, the ankylopollexian track Caririchinium and the turtle track Chelonipus occur. The Kongjiasi site yields a new type of the fluvio-lacustrine Chelonipus ichnocoenosis related to birds, which was previously defined to include only non-avian theropods and turtles. The site is associated with a waterfront foraging site of a Cretaceous shorebird which might be due to the invertebrate-rich substrate. The sole association of both bird and other theropod tracks with Chelonipus ichnocoenosis may indicate a difference in the appetite of avian and non-avian theropods for littoral foraging sites. And a review of the global turtle track-related ichnofauna and ichnocoenosis may offer new insights into the qualitative speculation of palaeobathymetry in riparian environments.

In this study the stable isotopes of belemnites, are presented from the Coniacian–Maastrichtian interval (∼76–66 Ma) derived from the chalks of Yorkshire and Norfolk, UK, deposited on the western North Atlantic shelf. Cathodoluminescence and elemental geochemistry of the belemnites reveals that most of the rostra were well preserved. If interpreted in terms of temperature, our oxygen isotope record reveals that during the Coniacian (at ∼43 °N) the climate was relatively warm, with maximum mean temperatures of ∼26 °C, followed by cooling to <∼21 °C during the Campanian and Maastrichtian. This overall stratigraphic trend is similar to other records, suggesting that the cooling pattern was not a regional trend and, therefore, driven predominantly by global mechanisms. Within our belemnite data, we also observe a decline in δ¹³C at the Campanian- Maastrichtian boundary, again consistent with other records. This trend has been interpreted as a result of an increased ratio of organic to inorganic carbon introduced into the oceans, driven by increased weathering and reworking of organic-rich sediments exposed on continental shelves during a sea-level fall. The latter related to a build-up of polar ice. Although our oxygen isotope data point to a cooling this was not necessarily linked to polar ice formation.

The bony-fishes of the clade Lepisosteidae, commonly called ‘gars’ or ‘gar-fish’, are a lineage of proficient piscivores with evolutionary history spanning about 150 million years, which are today represented by two genera inhabiting the freshwater and brackish areas of southeastern North America, Central America, and Cuba. This was not the case during the Late Cretaceous when lepisosteids were more diverse and had much wider geographical distribution. Gar fossils, albeit very fragmentary, are a common component of the Upper Cretaceous freshwater and brackish vertebrate assemblages in Europe, yet all of the pre-upper Campanian records come from the western and central parts of the Late Cretaceous European Archipelago. Here we describe new lepisosteid material from Bulgaria, comprising nine teeth and three scales found at the uppermost Santonian–lowermost Campanian Vrabchov Dol vertebrate locality. These fossils represent the easternmost record of gars within the European Archipelago to date. Despite being found in a lagoonal to foreshore deposits, the paleontological content of the locality, the incompleteness and preservational state of the material, as well as the predominantly non-marine ecology of modern and fossils gars suggest that these fossils belong to fishes which inhabited more inland, freshwater environments. The Vrabchov Dol lepisosteids remains are the first record of gars in Bulgaria and one of the rare documented occurrences of Mesozoic osteichthyans in the country. This material expands the paleobiogeographic distribution of the Lepisosteidae within the European Archipelago.

The early evolutionary and biogeographical history of Gondwanan iguanodontian dinosaurs is poorly understood due to their scarce Lower Cretaceous fossil record. In South America, the Lower Cretaceous iguanodontian osteological record is very fragmentary and most published reports cannot be used to discard or confirm hadrosauroid affinities. The single exception is Tietasaura from Brazil, whose incomplete femur shows a combination of traits found only in non-hadrosauroid iguandontians. Furthermore, no skeletal remains whatsoever of Lower Cretaceous iguanodontians have been reported from the western margin of South America. Here, we describe an isolated ornithopod caudal centrum (SGO.PV.22900) from the Lower Cretaceous Quebrada Monardes Formation in the Atacama Desert, northern Chile. Although incomplete, SGO.PV.22900 presents iguanodontian traits, such as the sub-hexagonal contour of the articular faces, the rectangular profile in lateral view and the absence of transverse processes below the neurocentral suture. We were also able to use quantitative measurements to explore taxonomic affinities, by carrying out a Linear Discriminant Analysis (LDA) and a Principal Components Analysis (PCA) using measurements of caudal centra of several iguanodontian species. The results of both analyses are consistent with those of our comparisons and suggest that SGO.PV.22900 belongs to a non-hadrosauroid iguanodontian ornithopod. This specimen represents one of the most compelling and best documented pieces of osteological evidence of Lower Cretaceous non-hadrosauroid iguanodontian dinosaurs in South America and provides further support for the presence of iguanodontians in the southwestern margin of Gondwana since at least the Early Cretaceous, as previously suggested based on footprints.

Dyrosauridae, a clade of neosuchian crocodyliforms, was a significant component of terrestrial and aquatic ecosystems across the latest Cretaceous to Paleogene of North Africa. Here, we report a dyrosaurid mandibular symphysis recovered from the middle–upper Campanian Quseir Formation near Kharga Oasis in the southern Western Desert of Egypt.

This is a partial mandible (MUVP 635), including dentaries and splenials, assigned to Dyrosauridae based on its dental pattern, size, and the shape of the splenial in the symphysis. MUVP 635 exhibits alveolar diameters shorter than the interalveolar distances within the same row. Moreover, the seventh dentary alveolus is significantly large, comparable in size to the fourth dentary alveolus, while the sixth dentary alveolus is positioned close to the seventh dentary alveolus and is as small as the eighth dentary alveolus, which is adjacent to the ninth dentary alveolus. Phylogenetic analysis places MUVP 635 as an early-diverging member of Dyrosauridae, consistent with its middle–late Campanian age. It aligns with a polytomy with Chenanisuchus lateroculi and Anthracosuchus balrogus identified as the most basal members of Dyrosauridae. The discovery of new dyrosaurid material in the Quseir Formation extends the range of Dyrosauridae to the middle Campanian, highlighting the taxonomic richness of the dyrosaurid clade across North Africa and supporting hypotheses of the African origin for this family.