Cretaceous Research最新文献

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.

Here we report tetrapod tracks from a stratigraphic level of Maastrichtian age in the Yacoraite Formation (Maimará ichnosite, Jujuy Province, Argentina). The ichnological material consists of convex hyporeliefs whose formation was induced by growth of microbial mats in an upper subtidal-lower intertidal setting. Ichnological features that are recognized in tracks and traces allowed to include them into the categories of ‘punting tracks’ and ‘buoyancy tracks’. These categories suggest swim behaviours of the producers, which are tentatively interpreted as crocodylomorphs. Reconstruction of the filling process leading to tracks preservation and inclusion into the geological record enabled reconstructing at least two different phases of mats development, one dominated by chemical precipitation and the other by trapping and binding of coated grains and other particles. These two phases of mat growth are related to slightly changing energetic conditions of the palaeoenvironment and further support a marine origin for the unit. Finally, it is suggested that biologically induced, in-situ mineral precipitation promotes fast formation of overtracks through early lithification achieving preservation of tetrapod tracks well before their complete filling.

The late Campanian-Maastrichtian in the Ibero-Armorican domain is rich in titanosaurian fossils. The sauropod remains exhibit a high degree of morphological variability, especially in the commonly-found appendicular elements. The phylogenetic relationships of the Ibero-Armorican titanosaurs are still uncertain but we do know that they experienced a Campanian-Maastrichtian herbivorous faunal turnover. It is probable that the small-to-medium-sized Lirainosaurinae-dominated faunas of the Campanian were replaced by late–early Maastrichtian large-bodied lithostrotian dominated faunas. In this context, the Villalba de La Sierra Formation has yielded an abundant sample of medium-to-large sized titanosaurs. In this study we analyze the morphological variability in the appendicular skeleton of the titanosaurs from the Campanian-Maastrichtian Ibero-Armorican domain. We follow previous attempts to classify the commonly-found isolated titanosaurian femora and expand the proposed methodology. The use of combined phenotypic characters and linear morphometrics can be helpful to analyze the morphological variability and diversity of the Ibero-Armorican titanosaurs. Our findings corroborate the presence of at least two exclusive morphotypes in the Lo Hueco fossil site and one exclusive morphotype in the Poyos site, as well as the presence of previously defined Lirainosaurinae across the Pyrenees during the Campanian-Maastrichtian. The Villalba de La Sierra Formation titanosaurs are also clustered with large-bodied late Maastrichtian titanosaurs. It is possible that either the large-bodied late–early Maastrichtian immigrants, with possible Gondwanan affinities, entered the Iberian Peninsula much earlier or that this group was already present at least during the Campanian-Maastrichtian transition, as the small-sized Lirainosaurinae declined.

Here, we report the occurrence of a large number of fossil fruits with distinctive germination pores along with a petrified stem, resembling morphologically and anatomically the extant palm tribe Cocoseae Mart. ex Dumort. of the subfamily Arecoideae. The permineralized fruits and locule casts, assigned to Palmocarpon drypeteoides (Mehrotra, Prakash, and Bande) Manchester et al., and the stem of Palmoxylon sp. were recovered from the Deccan Intertrappean Beds (late Mastrichtian–early Danian sediments; c. 66–65 Ma) of Umariya Ryt. village in Dindori District, Madhya Pradesh, Central India. Using micro–computed tomography (mCT) and standard thin section methods, we observed for the first time that these fossil palm fruits have a persistent basal trimerous perianth. These fossils, along with other reports in the literature, suggest that cocosoid palms were dominant among the arecoid palms of the Deccan Intertrappean beds in Madhya Pradesh. At present, the modern relatives do not grow in the same area but they occur in tropical forests of southeastern and eastern India as well as other regions including parts of South America, Asia, Europe, and Africa. The expansions and retraction of the cocosoid palms likely coincide with climate change. The recovery of cocosoid fossils (present and earlier reported) and previously described tropical elements from the same fossil locality suggest the existence of tropical climatic conditions during the period of depositions. We also revisit the historical phytogeography of the cocosoid palms.

Fossil caddisfly larval cases (CLCs) are of great significance for reflecting the habits of ancient caddisfly and indicating the paleoenvironment. Multiple layers with bioherms formed by fossil CLCs and stromatolites were found to be distributed in the Lower Cretaceous in Liupanshan Basin, Central China. In order to deeply understand the characteristics and formation environment of the CLCs-stromatolite bioherms, a series studies were conducted on the Yaoshan section in the northeastern of the basin. Morphological anatomy, mineralogy, element geochemistry, and isotope geochemistry are included in the studies. It reveals that the CLCs-stromatolite bioherms in Yaoshan are mainly composed of calcite and dolomite mineralogically, and CLCs and stromatolite morphologically.

In the bioherms, a large number of fossil CLCs stacked orderly, with a conical shape perpendicular to the stratum distribution. The bioherms were deposited in a semi-enclosed saline lake in hot and dry paleoclimate, and they were mainly formed during the periods when the evaporation increased, the water body became shallower, and the supply of terrestrial material increased.