Late Cretaceous Research Articles

Comparative analysis of chloroplast genomes on Meliaceae species: insights into the evolution and species identification

IntroductionMeliaceae, a significant group in Sapindales, possesses material and medicinal value due to its applications in timber and bioactive compounds. However, the high morphological diversity of the Meliaceae species and the lack of comparative studies of chloroplast (cp) genomes have led to great challenges in the classification and identification of Meliaceae species.MethodsIn this study, we sequenced the complete cp genomes of three Toona species (Toona fargesii, Toona ciliata, and Toona sinensis), and conducted comparative analyses of these cp genomes along with 29 previously published cp genomes of Meliaceae. Additionally, we performed the phylogenetic analyses and estimated the divergence times of Meliaceae.ResultsThe cp genomes of 32 Meliaceae species ranged from 158,558 bp to 160,978 bp in length. Specifically, the cp genomes of Toona varied from 159,242 bp to 159,617 bp in length. These cp genomes contained a total of 135 unique genes, comprising 90 protein-coding, 8 rRNA, and 37 tRNA genes. Divergence time estimation revealed that the Meliaceae family diverged into two subfamilies (Cedreloideae and Melioideae) approximately 72.92 Ma (95% HPD: 60.62-87.01 Ma) in the Late Cretaceous. The diversification of Cedreloideae (47.86 Ma, 95% HPD: 47.42-48.22 Ma) occurred later than that of Melioideae (66.60 Ma, 95% HPD: 55.41-79.73 Ma). Furthermore, comparative genomic analysis identified 52 to 116 simple sequence repeats (SSRs) and twelve highly variable regions (HVRs) found among the cp genomes of Meliaceae.DiscussionDivergence time estimation indicates that most Meliaceae species have a relatively recent origin, with rapid divergence occurring during the Late Oligocene or Early Miocene epochs. Comparative analysis of cp genomes revealed that Meliaceae exhibits relative conservation in terms of cp genome size, inverted-repeat (IR) boundary, genome structure, HVRs and codon patterns. Although differences exist between the Cedreloideae and Melioideae subfamilies, the overall similarity remains notably high. Furthermore, the ycf1, trnK-rps16, and ndhF-rpl32 regions exhibited the highest nucleotide polymorphism within Meliaceae, while the rpl22 gene displayed significant genetic diversity within both subfamilies. As candidate molecular markers, these regions may effectively distinguish among species. These findings not only provide insights into the evolution and species identification but also establish a scientific foundation for future systematics within Meliaceae.

Formation and Development of Abnormal Low Pressure in the Yanchang Formation of the Central‐Eastern Ordos Basin and its Influencing Factors

AbstractThe present‐day pressure pattern is the ultimate result of the evolution of paleo‐pressure, so understanding the variation of stress throughout geological history is of great significance for oil and gas accumulation. In this study, the fission track method was used to reconstruct the cooling history of sandstone samples from the Yanchang Fm. in the central‐eastern Ordos Basin and the cause of the low‐pressure anomaly in the Yanchang Fm. was analyzed. The max. burial depth pressure was reconstructed and the pressure evolution of the formation in the Futan 1 well was simulated, using Petromod 1D. The fission track data and Petromod 1D simulation results indicate that the Yanchang Fm. reached its max. burial depth and experienced a high paleo‐pressure of 30.92 MPa at around 100 Ma. Since the Late Cretaceous, the formation pressure evolution in the study area can be divided into two stages. From 100 to 20 Ma, the formation slowly uplifted, with the pressure gradually decreasing. Since the Miocene (about 20 Ma), the pressure rapidly decreased to the current pressure of approximately 6.92 MPa. Based on the above research results, the influence of pore rebound and temperature decrease on formation pressure was quantitatively calculated. The results show that during the first stage, the pressure reduction caused by pore rebound and cooling was 3.86 MPa and 3.49 MPa, respectively, with a decrease of about 12.48% and 11.28%. During the second stage, the pressure reduction caused by pore rebound and cooling was 6.32 MPa and 9.60 MPa, respectively, with a decrease of about 20.43% and 31.04%. The formation of low pressure in the Yanchang Fm. in the central and eastern basin is mainly controlled by pore rebound and temperature reduction, caused by erosion after stratigraphic uplift. The decrease in temperature plays a decisive role in determining the formation process of the low‐pressure oil reservoir.

First hadrosauroid record from Petreşti-Arini (Transylvanian Basin, Romania; Upper Cretaceous) and its implications for the evolution of the Hațeg Island vertebrate faunas

First hadrosauroid record from Petreşti-Arini (Transylvanian Basin, Romania; Upper Cretaceous) and its implications for the evolution of the Hațeg Island vertebrate faunas

A Revision of the Maastrichtian Exogyrinae Subfamily from the Kallankurichchi Formation, Ariyalur Sub-basin, India — Taxonomy and Palaeobiogeographic Implications

ABSTRACT Oysters are commonly found in marine Jurassic-Cretaceous deposits worldwide, prompting extensive taxonomic studies that have led to inconsistencies in their identification. The present study re-evaluates the Exogyrinae subfamily with an extensive database from the Maastrichtian Kallankurichchi Formation. We identified four species belonging to three genera of the Exogyrinae subfamily-Rhynchostreon cauveryensis sp. nov., Aetostreon sp. indet., Ceratostreon flabellatum and Ceratostreon pliciferum. While the genus Rhynchostreon has previously been reported from the Cenomanian of India, this study reports a new species of the genus Rhynchostreon, R. cauveryensis sp. nov., from the Maastrichtian Kallnakurichchi Formation. Also, this is the first record of the genus Aetostreon in India as well as the first report of Ceratostreon flabellatum from this region. We also present a morphologic revision of the previously described Ceratostreon pliciferum from the Kallankurichchi Formation. Geometric morphometric analysis was employed to quantify and compare the detailed morphology of R. cauveryensis sp. nov. and Ceratostreon pliciferum. In the present study, the paleobiogeographic distributions of the studied taxa were also investigated to trace their potential migration routes. The findings enhance our understanding of the morphology and migration history of the Exogyrinae subfamily during the Late Cretaceous.

The Role of Reunion Mantle Plume in Resetting the Subductions and Drifts of the Indian Plate During Late Cretaceous

AbstractRe‐examining the paleomagnetic data from the Late Cretaceous Deccan volcanic sequence reveals an anomalous NNW drift and counterclockwise rotation within the NNE trajectory of India‐Eurasia convergence. This drift visible in the segmentation pattern of the Central Indian Ridge between 21°S–17°S is reflected in paleomagnetic signatures. Further, using seismic tomographic and marine magnetic anomaly data, we infer that this anomalous motion of the Indian subcontinent was an artifact of the closure of Xigaze and Baluchistan, as well as the reactivation of Sunda subduction systems. The collision of Greater India with the Xigaze interoceanic arc and subsequent slab breakoff initiated the NW drift. The collision of the Baluchistan arc with the mainland Indian subcontinent and the ensuing slab breakoff led to the cessation of this NW drift. Subduction initiation along the Sunda system to the east reinstated the NNE drift for the Indian plate. These events are coeval with impingement of the Reunion mantle plume during C30n–C29n anomalies. We propose that the Reunion plume had greater synergy of multiple dynamic events to induce; (a) the tilting of the Indian plate, (b) accelerated convergence, (c) slab break‐offs along Baluchistan and Xigaze subduction zones, (d) restoration of the subduction along Sunda system resulting a relatively steady NNE trajectory for the Indian subcontinent until its collision with Lhasa at ∼50 Ma.

Bioluminescence and repeated deep-sea colonization shaped the diversification and body size evolution of squaliform sharks.

Understanding the underlying mechanisms that have generated the striking biodiversity inhabiting deep-sea ecosystems remains a challenge in evolutionary biology. Here, we addressed this topic by studying the macroevolutionary dynamics that have shaped the diversification of squaliform sharks, an iconic clade of deep-sea vertebrates. Using phylogenetic comparative methods and fossil-based Bayesian diversification estimates, both at species level, we combined fossil record data with molecular phylogenies to provide a quantitative framework for understanding the evolutionary history of Squaliformes. We reveal that early squaliform lineages originated in shallow water during the Early Cretaceous and experienced multiple independent shifts toward the deep sea during the Late Cretaceous. Importantly, we show that these shifts were likely facilitated by the acquisition of bioluminescence, which significantly impacted body size evolution among squaliform lineages. Furthermore, deep-sea colonization events coincide with periods of climate warming and marine transgression at the Cenomanian-Turonian and Palaeocene-Eocene transitions. Following these colonizations, deep-sea squaliform lineages have diversified over the last 30 Myr, resulting in one of the richest deep-sea radiations in sharks. These results demonstrate how the complex interplay between key innovation and colonization of new habitats drove major ecological transition, highlighting the importance of an integrative framework when studying deep-time macroevolutionary dynamics.

Palaeoenvironmental and palaeoecological inferences from inclusions in vertebrate omnivore coprolites from the Upper Cretaceous Lameta Formation of central India

Palaeoenvironmental and palaeoecological inferences from inclusions in vertebrate omnivore coprolites from the Upper Cretaceous Lameta Formation of central India

The Tectono‐Thermal Evolution of Western Norway – New Insights From Low‐Temperature Thermochronology

AbstractThe tectono‐thermal evolution of Western Norway's onshore rifted margin is debated. Previous studies suggest it does not exhibit a typical rifted margin cooling pattern. We present 29 new apatite fission track (AFT) ages and 54 new apatite single grain (U‐Th)/He ages from 14 samples, covering the onshore transition from the northern North Sea to the Norwegian Sea margin. AFT ages range from 323 ± 27 Ma to 140 ± 4 Ma, and (U‐Th)/He ages range from 228 ± 12 Ma to 57 ± 3 Ma. The samples show no clear age‐elevation correlation and large age offsets over short distances. Inverse thermal history modeling using HeFTy on 13 samples together with other geological constraints identifies four tectonic domains with distinct thermal and structural histories: (a) The inner Nordfjord subregion is dominated by N‐S striking faults, cooled to upper crustal levels (<8 km) in the Permian, remained stable until the Late Cretaceous, and experienced increased Cenozoic cooling. (b) The Sognefjord subregion cooled to upper crustal levels in the Carboniferous and offsets of AFT ages across fjords indicates Triassic/Jurassic reactivation of various faults. (c) The Hornelen subregion is dominated by prominent E‐W faults inherited from ductile precursors and shows the oldest AFT and (U‐Th)/He ages, reaching surface conditions already in the Jurassic with limited later reheating. (d) The Møre subregion shows rapid cooling in the Jurassic, likely due to footwall uplift accompanied by considerable topography. The new data set indicates a complex fragmentation of the onshore margin influenced by ductile precursor structures.

Ankylosaurian remains from a new Campanian–Maastrichtian locality in Northern Patagonia, Argentina

In South America, the fossil record of thyreophorans is scarce compared with that of Laurasian landmasses. The earliest finds date back to the first half of the twentieth century and consist of an isolated scute and incomplete caudal vertebrae from Upper Cretaceous beds in northern Patagonia. For decades, South American ankylosaurian remains were represented by isolated and poorly informative specimens, but this has recently changed with discovery of the nearly complete skeleton of Stegouros elengassen, from Maastrichtian beds in southern Chile. The aim of the present study is to report on new fossils of armoured dinosaurs from the Upper Cretaceous (Campanian–Maastrichtian) Allen Formation at the Arriagada Farm locality near Salitral Ojo de Agua in Río Negro Province. The new specimens include teeth, scutes and a partial sacrum belonging to at least three individuals. These derive from a different locality than the coeval Patagopelta cristata, which is the only currently named armoured dinosaur from Argentine Patagonia. Some of the remains were found intermingled with bones and eggs belonging to the alvarezsaurid theropod Bonapartenykus ultimus and thus constitute a novel dinosaur life assemblage from South America. Rodrigo Álvarez Nogueira* [ralvareznogueira@gmail.com]; Federico L. Agnolín [fedeagnolin@yahoo.com.ar]; Sebastián Rozadilla [sebastianrozadilla@gmail.com]; Mauro Aranciaga-Rolando [mauro.a_guido@hotmail.com]; Fernando E. Novas [fernovas@yahoo.com.ar], Laboratorio de Anatomía Comparada y Evolución de los Vertebrados, Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”—CONICET, Av. Angel Gallardo 470, C1405DJR, Ciudad Autónoma de Buenos Aires, Argentina

A new species of Elisama Giebel, 1856 (Blattaria: Blattulidae) discovered in mid-Cretaceous Kachin amber of northern Myanmar

Elisama Giebel, 1856 is a cockroach genus of the family Blattulidae Vishniakova, 1982 ranging from the Late Jurassic to the Late Cretaceous. Elisama kacerovae sp. nov. is herein described based on a completely preserved adult, and it is the first representative of the genus in Cenomanian northern Myanmar amber. It differs from other species of Elisama in being smaller in size, having a darkly striated pronotum with translucent nota and in the forewing with stem of M appressing R in the basal half of the wing. Elisama shares a dark macula on the forewings with Vrtula Vršanský, 2008, Huablattula Qiu, Wang et Che, 2019, Svabula Vršanský, 2005, Nogueroblatta Martínez-Delclòs, 1993 and Spono Vršanský, 2024. Some blattulid genera, such as the former four, are likely in need of revision. Except for E. globosa from Mdeyrij-Hammana amber in Lebanon, all species were discovered in sedimentary rocks of former Gondwana and Laurasia. It is possible that representatives of Elisama mainly prospered in less humid environments with milder climate instead of tropical forest ecosystems, where they were apparently rare in the fossil record, although taphonomic bias cannot be ruled out completely.

Revision of Romanian sauropod dinosaurs reveals high titanosaur diversity and body-size disparity on the latest Cretaceous Haţeg Island, with implications for titanosaurian biogeography

The Hațeg Basin and surrounding areas in Transylvania, western Romania, have been a hotspot for research on vertebrate faunas of the Late Cretaceous European Archipelago. One of the historically earliest titanosaurian sauropod dinosaurs to be discovered, the ‘dwarfed’ species Magyarosaurus dacus comes from lower Maastrichtian deposits in this basin; however, this species has been neglected, with no modern treatment of its anatomy, taxonomy or phylogenetic affinities. Via detailed anatomical study of historical and undescribed remains, combined with archival data, we identify shared autapomorphies that link multiple partial skeletons. Our analysis of hundreds of specimens (including >20 monospecific assemblages) enables the stabilization of the type species Magyarosaurus dacus. We propose the presence of three additional, but only partly contemporaneous taxa – Paludititan nalatzensis, Petrustitan (‘Magyarosaurus’) hungaricus n. gen. and Uriash kadici n. gen. n. sp. (the latter being amongst the largest known sauropods of the Late Cretaceous European Archipelago). We present a new phylogenetic analysis (152 taxa scored for 570 characters), with implications for broader titanosaurian evolutionary relationships and biogeography: Magyarosaurus is recovered either as a member or a close relative of Saltasauridae; Paludititan has affinities with Lognkosauria, along with the contemporaneous Lohuecotitan; Petrustitan is most closely related to South American early diverging eutitanosaurian taxa; and Uriash also shares affinities with Gondwanan taxa. Our findings strengthen the hypothesis that latest Cretaceous European titanosaurs belonged to Gondwanan lineages that invaded the former area during the Barremian–Albian. We interpret the presence of body-size disparity as either evidence that large-bodied taxa were ecologically excluded from body-size reduction by competition with small-bodied titanosaurs, or that dwarfing occurred stratigraphically earlier among several lineages and the small-bodied titanosaurs on Hațeg Island are the descendants of existing dwarfed ancestors. Finally, we find no indication of a body size-related titanosaurian turnover in the uppermost Cretaceous of the Transylvanian area.

Magmatic record of Cretaceous marginal basin termination along the western segment of the Central Cordillera of Colombia

ABSTRACT Marginal basins are the result of extensional tectonics along convergent margins. These basins include an early stage of seafloor spreading that, in some cases, is followed by tectonic inversion and deformation of the basin and the formation of a new magmatic arc front. The Early Cretaceous extensional tectonics along the South American Plate caused the development of multiple pre-Andean back-arc and marginal basins along the continental margin. These basins were inverted during the onset of the Andean orogeny in the Late Cretaceous. For instance, in the Northern Andes, the remnants of this Cretaceous history are found in the Central Cordillera, which can be used to understand the magmatic record associated with the birth and death of marginal basins. In this contribution, we integrate U-Pb zircon geochronology, whole-rock geochemistry, Hf and Nd isotopes from Cretaceous volcanic and plutonic rocks at the western margin of Colombia’s Central Cordillera, as well as new zircon U-Pb geochronology and Hf isotopes from the Santa Isabel Stock in the axis of this cordillera. Geochronological results and published data show a magmatic arc record between 78 and 99 Ma that followed the Albian-Aptian MORB-like and less enriched arc signatures associated with the early stages of marginal basin formation. Older pre-Cretaceous detrital and inherited zircons and the observed field relations confirm that this magmatism was built on a thinned continental crust encased by Triassic basement rocks. The documented spatiotemporal and compositional evolution of the Cretaceous arc-related rocks from the western flank of the Central Cordillera documents the transition from a seafloor spreading stage characterized by magmas sourced from an adiabatically melted mantle to the formation of a new arc front that becomes more enriched and influenced by continental crust as the sub-arc mantle is again responsible for magma generation processes.

Late Mesozoic tectonic transition and sedimentary response of Yihezhuang Salient, Luxi area, eastern North China Craton: implication for coal-forming mechanism

The late Mesozoic tectonic and sedimentary evolution characteristics of Yihezhuang Salient help determine the controlling factors for coeval coal-forming mechanisms in the eastern North China Craton. Within the established tectono-stratigraphic framework, the late Mesozoic Yihezhuang Salient was identified using unconformity surfaces, faulting activity, balanced sections and paleogeomorphic characteristics, as a tectonic transition. The late Mesozoic sedimentary characteristics and the sedimentary evolution in response to the tectonic transition were analysed based on field outcrops, drilling data, core samples and seismic profiles. The results demonstrated that the late Mesozoic tectonic transition underwent three evolutionary stages: (1) the early stage, the Lower and Middle Jurassic developed meandering river facies with thin coal seams and an Upper Jurassic braided river with no coal seams; (2) the main stage, i.e. the Late Jurassic and Early Cretaceous, negative tectonic inversion caused transformation into a small, faulted basin with a developing fan delta and lacustrine facies; and (3) the late stage, extrusion and denudation occurred with no deposition in the Upper Cretaceous. Coal seams only developed in the Lower and Middle Jurassic, owing to the sedimentary facies and paleoclimate that were influenced by the tectonic transition of the eastern North China Craton.

Characterization of Polycyclic Aromatic Hydrocarbons in a Shale Strata Profile from the First Member of the Upper Cretaceous Qingshankou Formation in the Sanzhao Sag, Songliao Basin, NE China.

The first member of the Upper Cretaceous Qingshankou Formation (K2 qn 1) stands as the most significant source rock layer in the Songliao Basin, concurrently serving as the principal target for shale oil exploration. Polycyclic aromatic hydrocarbons (PAHs), as one of the main components of soluble organic matter in mudstone and shale, are of significant importance for revealing the hydrocarbon generation mechanisms in source rocks and the formation conditions of shale oil. However, systematic research on PAHs in the K2 qn 1 layer of the Songliao Basin has not yet been conducted. Our study concentrated on a comprehensive set of 34 rock core samples, covering the entire K2 qn 1 layer, retrieved from the SYY3 well in the Sanzhao Sag of the northern Songliao Basin. The geochemical characteristics of a diverse range of PAHs were meticulously assessed through gas chromatography-mass spectrometry (GC-MS). Meanwhile, this study preliminarily discussed possible influential factors on the formation of alkylated PAHs (a-PAHs) and the isomerization of parent PAHs (p-PAHs) in our samples. The results revealed that PAHs predominantly consist of the phenanthrene, naphthalene, and chrysene series, trailed by the pyrene, fluorene, dibenzothiophene, and benzopyrene series. In contrast to the lower unit (>2015.00 m) of the K2 qn 1 layer, the upper unit (<2015.00 m) exhibits generally lower PAH concentrations and reduced levels of dibenzothiophene series, implying lower biological productivity and more oxidized sedimentary waters. The upper unit exhibits a higher content of 1,2,5-trimethylnaphthalene, 1,2,5,6-tetramethylnaphthalene, retene, pyrenes, fluoranthene, benzopyrenes, and benzofluoranthene, suggesting elevated levels of contributions from terrestrial higher plants. Maturity parameters of alkyl naphthalene and methylphenanthrene, along with vitrinite reflectance (R o), indicate a close maturity in both units. Most of the a-PAHs/p-PAH ratios are higher in the lower unit than in the upper unit, indicating more pronounced alkylation. The ratios of p-PAH isomers, including benzo[b]fluorene/benzo[a]fluorene, benzo[a]pyrene/benzo[e]pyrene, and benzo[a]anthracene/chrysene, exhibit a vertical distribution pattern similar to the a-PAHs/p-PAH ratios, indicating that less stable p-PAH isomers are more prevalent in the lower unit. By comparing the a-PAHs/p-PAH ratios and the ratios of p-PAH isomers with conventional geochemical parameters of saturated hydrocarbons, it was preliminarily revealed that the catalytic effects of clay minerals, along with fluctuating biological inputs, can substantially affect PAH alkylation and p-PAH isomerization. Sediment reductivity slightly enhances PAH alkylation without obviously impacting p-PAH isomerization, and salinity shows no significant effect on these processes. The above insights offer molecular geochemical evidence of PAHs, which aids in understanding the heterogeneity of the K2 qn 1 source rock, facilitates oil source correlation, and optimizes the selection of sweet spots within shale oil formations.

Petrogenesis of the alkaline lamprophyre cluster between Molí d’en Ponç and Collet de la Cidereda (eastern Catalonian Coastal Ranges, NE Iberia)

Abstract This work focuses on the cretaceous camptonite cluster between Molí d’en Ponç and Collet de la Cidereda, eastern Montseny massif from the Catalan Coastal Ranges (NE Iberian Peninsula). These post-orogenic lamprophyres (~ 79 Ma) crosscut Palaeozoic and late Variscan granitoids. Their intrusion is related to the opening of the Bay of Biscay. Thus, they belong to the Late Cretaceous Iberian Alkaline Igneous Province. The studied cluster comprises two sills displaying a N110-N140-trending direction and subvertical dikes that intrude the camptonite sills or the granodioritic host rock. DyN/YbN ratios ≥ 2.4 show that the primary melts of the studied camptonites were generated at pressures higher than ~ 2.5 GPa (~ 80 km) on the garnet stability field close to the transition to the spinel stability field. The more evolved melts, corresponding to sodic alkaline basalts, were subjected to within-plate enrichment and fractional crystallization processes. The olivine antecrysts and microlites correspond to forsterite (Fo74 to Fo88). They do not show peridotitic mantle source composition and some are in equilibrium with sulfides. The clinopyroxene antecrysts correspond to diopside (Mg# 75–80) and do not show peridotitic mantle source composition. The forsterite, diopside, and kaersutite antecrysts display compositional oscillatory variations related to mixing processes associated with ascending successive magma pulses. The higher concentrations of Mn in forsterite and diopside microlites from the groundmass, compared to the antecrysts, are consistent with a more evolved composition of the ascending magma. The pressure estimation obtained from diopside antecryst cores (~ 1 GPa) supports the stagnation of ascending magma in the lower crust or the transitional boundary between the lower crust and upper mantle. The pressure obtained from clinopyroxene antecryst rims is ~ 0.28 GPa.

An asymmetric Late Cretaceous back-arc basin south of Tibet?

The Indus-Yarlung suture zone (southern Tibet) between the Indian plate−derived Tibetan Himalaya and the Asian continental crust intruded by the Gangdese magmatic arc of southern Tibet hosts a &amp;lt;20-km-wide band of ophiolites overlain by Asia-derived clastic sedimentary rocks of the Xigaze forearc basin. How wide this basin was prior to India-Asia collision is unknown: it may have been a typical forearc basin width, i.e., ∼150−200 km, but was also proposed to have become separated from Tibet in the Late Cretaceous by a back-arc basin thousands of kilometers wide. To test this, we present the first paleomagnetic study of upper Cretaceous redbeds of the 71.2−69.3 Ma Padana Formation in the Xigaze forearc basin, near Sangsang town, Ngamring county, Tibet, China (∼86°E). High-temperature magnetic components were isolated at 580 °C or 600−680 °C and passed reversal and fold tests demonstrating a primary magnetization that we corrected for inclination shallowing. Our results reveal that the Xigaze forearc basin at ∼86°E was situated at 18.4° ± 3.6°N at ca. 70 Ma, indicating a separation from Lhasa of &amp;lt;500 km. To reconcile our new data with coeval, much lower, paleolatitudes from the Ladakh arc to the west (∼77°E) we reconstruct a Late Cretaceous−Paleogene opening and closure of an asymmetric back-arc basin in the western Neotethys. This suggests that the distribution of India-Asia convergence was laterally unevenly partitioned over the pre-collisional plate boundaries.

Cretaceous Antarctic bird skull elucidates early avian ecological diversity.

Fossils representing Cretaceous lineages of crown clade birds (Aves) are exceptionally rare but are crucial to elucidating major ecological shifts across early avian divergences. Among the earliest known putative crown birds is Vegavis iaai1-5, a foot-propelled diver from the latest Cretaceous (69.2-68.4 million years ago)6 of Antarctica with controversial phylogenetic affinities2,7-10. Initially recovered by phylogenetic analyses as a stem anatid (ducks and closely related species)1,2,11, Vegavis has since been recovered as a stem member of Anseriformes (waterfowl)7-9, or outside Aves altogether10. Here we report a new, nearly complete skull of Vegavis that provides new insight into its feeding ecology and exhibits morphologies thatsupport placement among waterfowl within crown-group birds. Vegavis has an avian beak (absence of teeth andreduced maxilla) and brain shape (hyperinflated cerebrum andventrally shifted optic lobes). The temporal fossa is well excavated and expansive, indicating that this bird had hypertrophied jaw musculature. The beak is narrow and pointed, and the mandible lacks retroarticular processes. Together, these features comprise a feeding apparatus unlike that ofany other known anseriform but like that ofother extant birds that capture prey underwater (for example, grebes and loons). The Cretaceous occurrence of Vegavis, with a feeding ecology unique among known Galloanserae (waterfowl and landfowl), is further indication that the earliest anseriform divergences were marked by evolutionary experiments unrepresented in the extant diversity3,11-13.

Relationship between hydrocarbon genration-expulsion and deformation in exhumated Lower Cretaceous kitchen of the Austral-Magallanes basin, Southern Patagonia

The thermal evolution of the hydrocarbon exhumated kitchen of the Rio Mayer Formation (Lower Cretaceous) in the Austral-Magallanes basin, was characterized in two profiles outcropping in the Southern Patagonian Andes. This study presents an integration of fluid inclusions, organic petrology, geochemistry, and apatite fission-track data incorporated into a one-dimensional (1D) basin and petroleum system modeling, to evaluate the timing of hydrocarbon generation and expulsion processes. In Ea. La Federica (internal fold-thrust belt domain), the lower organic-rich interval of Rio Mayer Formation is at present-day conditions in oil window, with development of natural fractures filled with fibrous calcite crystals. In Ea. Cristina, the unit is in dry gas window (basement domain), with natural fractures filled with granular calcite and quartz. The kitchens began the generation and expulsion processes from the west (Lower Cretaceous) to east (Upper Cretaceous - Eocene), i.e., from basement to internal and external fold-thrust belt domains. The advance of the orogenic wedge deactivated and exhumated those kitchens from west to east as well. The western kitchen was deactivated during the Late Cretaceous, while eastern kitchen, during the Eocene. These successive compressional pulses conditioned the eastward migration of the hydrocarbon generation front and would have favored the charge of reservoirs located in the westward (foreland region). The results of this study emphasize the importance to consider the temporal source kitchens activation related to Andean deformation, in order to a better comprehension of basin-scale controls related to source rock evolution and petroleum system development.

A new species of the cirripede genus Proverruca Withers, 1914 (Crustacea, Thoracica) from the upper Campanian (Upper Cretaceous) of northeastern Belgium

A new species of the cirripede genus Proverruca, P. ornata sp. nov., is described from the lower upper Campanian (Belemnitella woodi belemnite Zone) Zeven Wegen Member (Gulpen Formation) at Haccourt, province of Liège, northeastern Belgium. It displays remarkable variation in external sculpture during ontogeny.

Macrofaunal Paleocommunities and Microfacies Analysis from the Upper Cretaceous in North Eastern Desert of Egypt

AbstractThe Upper Cretaceous successions of Wadi Umm‐Khayshar, southern Galala Plateau, North Eastern Desert, Egypt, are composed of highly diversified faunas and subdivided from base to top into the Galala (Middle–Late Cenomanian), Maghra El Hadida (Latest Cenomanian–Late Turonian), Matulla (Coniacian–Santonian), and Sudr (Campanian–Maastrichtian) formations. Five ammonite biozones are recorded in the studied section: Neolobites vibrayeanus, Vascoceras cauvini (late Cenomanian), Vascoceras proprium, Choffaticeras segne, and Coilopoceras requienianum (Turonian) zones. The paleoenvironments of the Upper Cretaceous succession are interpreted based on detailed study and microfacies analysis that reflect a deposition in a homoclinal ramp platform ranging from intertidal to deep subtidal. The paleoecology of the Cenomanian–Turonian succession in the studied section is explained based on a detailed study of macrofaunal associations and sedimentary facies. Quantitative analysis (Q‐mode cluster analysis, using the Raup–Crick Paired group method) of 1029 macrobenthic specimens, including 45 species of mollusks and echinoids yielded five macrofaunal associations (A–E) that are described and interpreted as remnants of communities. The nektonic elements are represented by 235 cephalopod specimens of 20 species; heatmap cluster analyses show the distribution of these specimens during the Upper Cenomanian–Turonian stages. Environmental parameters (substrate consistency, rate of sedimentation, water energy, surface‐water productivity, and oxygen availability) controlled the distribution of the studied macrofauna. The five associations are divided into two major groups: low‐stress associations (A, B, C, and D), and a high‐stress association (E). The low stress associations are recorded from two different habitats: (1) a high‐energy, firm substrate habitat, dominated by epifaunal bivalves, large epifaunal gastropods and a regular echinoid; (2) a low‐energy, soft substrate habitat dominated by infaunal bivalves and echinoids. The high stress association is dominated by only two species and recorded from a high‐energy shoal environment during a regression phase. A detailed study of macrobenthos and cephalopods provides a good paleoecological understanding of Cenomanian–Turonian succession in the Wadi Umm–Khayshar section.