An actinopterygian-dominated fish fauna from the Upper Cretaceous Williams Fork Formation, northwestern Colorado, and evidence for provinciality across Laramidia at the Campanian/Maastrichtian boundary

Termites became the dominant decomposers of the tropics after two diversification pulses.

High-latitude terrestrial ecosystems are commonly viewed as marginal environments to deep-time evolutionary innovation, yet their role in shaping biotic dispersal, diversification, and survivorship remains poorly understood. The Upper Cretaceous Prince Creek Formation of northern Alaska (paleolatitude ~80-85°N) yields the most northerly known Mesozoic mammals and provides a rare opportunity to examine the ecological and biogeographic roles of polar terrestrial ecosystems. Here, we describe three multituberculate species, Camurodon borealis, Qayaqgruk peregrinus, and Kaniqsiqcosmodon polaris, and integrate comparative morphology with phylogenetic and biogeographic analyses to evaluate patterns and timing of dispersal and diversification across a high-latitude Asian-American terrestrial corridor. Qayaqgruk peregrinus is recovered within the Mongolian Djadochtatherioidea, representing the earliest direct evidence for multituberculate dispersal from Asia into North America. Kaniqsiqcosmodon polaris constitutes the oldest known member of the Microcosmodontidae, suggesting a high-latitude origin for a derived North American lineage that later diversified during the Paleocene following the Cretaceous-Paleogene mass extinction. Camurodon borealis represents the northernmost occurrence of the Cimolomyidae. Pronounced variation in dental morphology among the Prince Creek multituberculates indicates ecological differentiation and niche partitioning within an extreme, highly seasonal polar environment. Our findings indicate that Late Cretaceous Arctic ecosystems supported both sustained intercontinental exchanges as early as 91.82 Ma and endemism. Our results challenge interpretations of polar regions as evolutionary peripheries and instead identify them as important contributors to mammalian evolutionary dynamics prior to the Cretaceous-Paleogene mass extinction.

ABSTRACT Sauropod dinosaurs are one of the most common components of the Cretaceous continental fauna of South America. However, juvenile specimens are poorly documented to date. Here, we describe an incomplete juvenile titanosaur from the Upper Cretaceous of Argentina. The preserved material belongs to a single individual and is sufficiently diagnostic to classify it as a juvenile Neuquensaurus australis. The specimen represents an individual approximately 44–63% of adult individual size. Anatomical comparison with adult specimens reveals that fusion between different structures (neural arches and their centra, scapula and coracoid, and sacral centra) started late during the ontogeny (at least in ontogenetic stages more advanced than inferred for the juvenile individual here studied). Invasion of pneumatic diverticula within the bones also appears to be developed in a more advanced ontogenetic stage. Overlapping elements between the juvenile and adult skeletons indicate allometric changes for Neuquensaurus australis throughout ontogeny, which contrast with previous hypotheses about isometric growth in titanosaurs. Histological data reveals a rapid growth rate in the juvenile individual. However, the presence of at least one cyclical growth mark in the cortex challenges previous hypotheses regarding growth dynamics in sauropod dinosaurs, which postulate that interrupted growth only occurred at advanced ontogenetic stages.

Palynological evidence of postcatastrophe fungal proliferation after global calamities has been found for the Permian-Triassic and Cretaceous-Paleogene (K/Pg) extinction events. However, unlike the globally documented post-Permian fungal bloom, evidence of a post-Cretaceous event has previously been limited to a single site in New Zealand. Our analysis of a K/Pg boundary section from the Denver Basin in Colorado revealed a fungal proliferative spike occurring immediately after the Chicxulub meteorite impact. The discovery of a postimpact fungal bloom in North America corroborates the New Zealand finding and supports the interpretation that this was a global phenomenon. We also identified a prolonged interval of elevated fungal abundance in the Late Cretaceous, dating to approximately 30,000 to 10,000 y before the impact, temporally correlated to a period of climatic cooling at the site and intriguingly coincident with the high-volume Poladpur phase of the Deccan Traps volcanic eruptions. Taken together with reports of fungal expansion following prior global calamities, these findings indicate that fungi can often flourish in the aftermath of ecosystem-level collapse. Given the capacity of fungi to cause disease in both plants and animals, the occurrence of fungal proliferative events has potential implications for the recovery of species surviving global cataclysms.

Paleogene post-collisional forearc evolution of the Northern Andes revealed by U-Th-Pb detrital zircon geochronology and Lu-Hf systematics, in the Cauca Basin, Colombia

Revaluation of the taxonomy and diversity of Lepisosteiformes from the Alcântara Formation (Cenomanian, Upper Cretaceous), Brazil

The impact of transgression on the development model of lacustrine source rocks: Insights from the Upper Cretaceous Qingshankou Formation source rocks in the Songliao Basin

ABSTRACT Multituberculates were one of the most successful mammalian groups during the late Mesozoic. However, due to taxonomic and temporal gaps in the successive fossil record, the origin and early evolutionary history of Cimolodonta in the Late Cretaceous of Asia remain unclear. To address these issues, further discoveries of multituberculates, particularly from regions outside of Mongolia, are essential. We here describe a new cimolodontan multituberculate, Koshikibaatar kashimaensis gen. et sp. nov., from the middle Campanian Himenoura Group in Kagoshima Prefecture, southwestern Japan. This new species is characterized by dentary showing a low difference in height between the mandibular body below p3 and below m1, lower dental formula 1.0.2.2, slender lower incisor completely covered with enamel, single-rooted and peg-like p3, arcuate and triple-rooted p4 with 12 serrations, which has a weak protrusion of the mesial margin and a nearly symmetrical dorsal arch in lateral view and is higher than the occlusal level of molars, and m1 with cusp formula 5:3. These characteristics are obviously different from those of derived cimolodontans from the Upper Cretaceous of Asia, especially Mongolia, and suggest that the new species represents a relatively plesiomorphic cimolodontan multituberculate. The discovery of Koshikibaatar implies that the taxonomic diversity of Asian multituberculates during the Late Cretaceous was likely more diverse than previously recognized.

Studies of Upper Cretaceous deposits in North America have provided invaluable insights into the continental ecosystems of this time. Theropod (Saurischia, Dinosauria) pedal phalanges are commonplace in these deposits but can be difficult to identify at a finer taxonomic resolution. This, in part, results from a lack of data regarding the individual, ontogenetic, and intraspecific variation that exists among theropod pedal phalanges, and potential differences in phalanx shape that distinguish individual families and species. In this study, we use elliptic Fourier analysis to quantify pedal phalanx shape in a sample of individuals of known species from multiple theropod families in multiple views. The resulting variables were analyzed using principal component analysis to identify patterns of (dis)similarity among different theropod taxa and between phalanx positions and, as such, provide insights into the phalanx shape variation that existed among North American theropods during the Late Cretaceous. This study finds that caenagnathids often possess more gracile pedal phalanges relative to other theropod taxa, particularly when viewed dorsally or ventrally (e.g., for digits II, III, and IV). Although tyrannosaurid and ornithomimid pedal phalanges are generally similar to one another, even in similarly sized individualsthe former are found to be more robust in shape than the latter for certain phalanges (e.g., II-1, III-2, and III-3) in dorsal and ventral views. In some instances, the shape of the lateral, medial, and distal margins of tyrannosaurid pedal phalanges differ considerably from those of ornithomimids (e.g., IV-1 in dorsal/ventral view; II-1, III-4, IV-5 in lateral/medial view). The use of elliptic Fourier analysis here provides quantitative data on the variation present among Late Cretaceous theropod pedal phalanges and provides evidence that theropod taxa can be identified down to the family level based on pedal phalanx morphology. This greatly increases the potential utility of isolated theropod phalanges in biodiversity assessments of Cretaceous fossil assemblages, particularly those with a lack of well-preserved skeletal samples.

Apex and meso-predators of the Cretaceous exhibited distinct macroevolutionary trajectories, reflecting differential responses to ecological and environmental pressures. However, the role of evolutionary process in shaping macroevolutionary trends of apex and meso-predatory Cretaceous theropods remains poorly understood. Here, I use the maxillary shape and size, combined with phylogenetic comparative methods, to elucidate distinct macroevolutionary trends among three lineages of larger (apex-pedators) and medium-size (meso-predators) Cretaceous theropods (Carcharodontosauria, Abelisauridae, and Coelurosauria). Abelisaurids primarily explored morphological innovation in skull shape while maintaining relatively stable body sizes through time. Carcharodontosaurids, in contrast, followed a size-driven evolutionary path, achieving gigantism while retaining conservative cranial morphologies. Coelurosaurs, particularly tyrannosauroids, adopted a mixed strategy, displaying early cranial modifications during the Jurassic, followed by an explosive increase in cranialsize in the Late Cretaceous. These divergent strategies reveal an evolutionary decoupling between cranial shape and size, characterized by an initial phase of disruptive selection promoting morphological divergence, followed by stabilizing selection and phenotypic canalization that ultimately shaped specialized adaptive responses in each clade. These results highlight how evolutionary history, ecological interactions, and developmental constraints structured the diversification of apex and meso-predator theropods.

We provide a detailed description of the dental morphology of Gobiconodon zofiae based on the holotype and clarify its diagnostic features in comparison with other species in the genus. We also report a new species, Gobiconodon gong zhulingensis sp. nov., from the lower Upper Cretaceous Quantou Formation in Gongzhuling City, Jilin Province, based on a maxilla with five molariforms. The dental morphologies of both species allow us to reassess tooth assignments in Gobiconodon and support a dental formula of 2.1.3.4/2.1.3.5 for the genus. The molariforms of Gobiconodon exhibit a distinct type of tooth widening that is achieved primarily through cusp inflation, without pronounced cusp rotation or the addition of new cusps. In addition to the differences in occlusal pattern, embrasure shearing dominated by an orthal power stroke, accompanied by a labiolingually directed component of relative displacement of the lower teeth during mastication also distinguishes Gobiconodon from other eutriconodontans, particularly triconodontids, suggesting an in sectivorous and/or omnivorous diet for Gobiconodon. The tooth shapes and wear patterns described here indicate diverse ecomorphological specializations and species diversification within eutriconodontans.

ABSTRACT Late Cretaceous mammals from North America are predominantly known from isolated teeth and fragmentary jaws and from localities representing coastal lowlands along the Western Interior Seaway. Here, we report craniodental and associated postcranial remains of a new species of the cimolodontid multituberculate genus Cimolodon from the Upper Cretaceous (Campanian) El Gallo Formation of Baja California, México. The specimen was deposited along the Pacific Coast between 75.17 ± 0.30 Ma and 74.55 ± 0.18 Ma. It represents the most complete mammal known from the Mesozoic of México and one of the best known cimolodontan multituberculates from North America. Morphologically, the new species, Cimolodon desosai, is most like C. nitidus, but differences include upper anterior premolar shape, molar cusp formulae, and relative length proportions of the cheek teeth. Phylogenetic analysis supports placement of the new species within Cimolodon and Ptilodontoidea, but uncertainties remain regarding relationships among cimolodontan families. Using the craniodental and postcranial data, we quantitatively reconstruct C. desosai as a small-bodied (∼100 g), animal-dominated omnivore with a scansorial locomotor mode. With the new taxonomic occurrence, the El Gallo mammalian local fauna is now known from 16 specimens referred to three multituberculate species (Mesodma cf. M. formosa, ?Stygimys sp., and Cimolodon desosai), one metatherian (Pediomys sp.), and one eutherian (Gallolestes pachymandibularis). Although further sampling is needed, the mammalian local fauna presently shows greatest biogeographic affinities with the Terlingua local fauna of western Texas.

The latest Cretaceous saw the final diversification of dinosaurs before the K/Pg extinction. Discussions of end-Cretaceous dinosaur diversity have focused on well-sampled faunas from Laurasia; far less is known about dinosaurian faunas of the Southern Hemisphere, especially Africa. The late Maastrichtian Phosphates of Morocco provide a rare window into African dinosaur diversity. Abelisaurids, lambeosaurines, and titanosaurian sauropods are known. However, no diagnostic titanosaur remains have been recovered, leaving the affinities of these sauropods unclear. We describe Phosphatotitan khouribgaensis gen. et sp. nov., a new titanosaur from the Maastrichtian of Sidi Chennane, Khouribga Province. Phosphatotitan is represented by dorsal, sacral, and caudal vertebrae, and the pelvis. The new species differs from titanosaurs described from the Cretaceous of Africa and Europe but resembles South American Lognkosauria, and especially Patagotitan, in having short dorsal and caudal centra, expanded dorsal and caudal neural spines, and a broad pubis. Its small size relative to other Lognkosauria (3.5–4 tonnes) suggests a lineage selected for small size. The close relationships of Morocco’s titanosaurs and abelisaurids to South American species may reflect a wide distribution of these clades prior to the opening of the South Atlantic and the separation of Africa and South America ~100 Ma, while a complex pattern of oceanic dispersal may explain the presence of distinct saltasauroid lineages worldwide. The latest Cretaceous Gondwanan dinosaur faunas were highly endemic due to a combination of continental fragmentation, extinction, and dispersal, creating high endemism in southern continents and within Africa, suggesting that Maastrichtian dinosaur diversity is underestimated.

This study fills a knowledge gap in the distribution of the Upper Cretaceous dinosaur tracks in central China by examining two newly discovered tracksites near Xiakou village (Nanzhang County) and Jiuxian town (Yuan’an County), Hubei Province. Eleven Isolated tracks were analyzed to identify the ichnofauna assemblage. Morphometric analysis indicates the presence of tridactyl and rounded morphologies. The tridactyl tracks are consistent with a small-sized theropod and ornithischian ichnofauna, whereas the rounded shape remains ichnotaxonomically indeterminate. These tracks are the first reported dinosaur ichnite from central China at this age. Despite limited preservation, this research highlights how extromorphological factors influence track morphology, a key issue in ichnological studies. Overall, it contributes new data on the presence of dinosaur ichnofauna in China during the late Mesozoic.

Recent advances in molecular phylogenies have revolutionised our understanding of brittle star systematics and evolutionary history. Although genetic data have provided new grounds for age estimates of phylogenetic divergences, direct fossil evidence is currently the only robust means to determine the minimum age of clades. The present study discusses an exceptional opportunity to robustly pinpoint the minimum age of an extant genus of brittle star. The presumed ophiolepidid brittle star species Ophiolepis? falsa Jagt & Kutscher, in Jagt, 2000, from lower upper Campanian (Upper Cretaceous, c. 79 Ma) deposits in north-east Belgium, is here recorded from coeval strata in the Münsterland Basin (northern Germany) and transferred to the previously monospecific extant hemieuryalid genus Actinozonella Stöhr, 2011. An unusually well-preserved specimen, completely free from mineralised matrix, allows both dorsal and ventral sides of the disc and short arm stumps to be examined. In this way, characters not visible in the holotype of Ophiolepis? falsa could be analysed; these revealed its taxonomic affinity with Actinozonella, dating that genus to at least 79 Ma. The close morphological similarity between Actinozonella and Ophiomisidium Koehler, 1914, and to some species currently assigned to Ophiomastus Lyman, 1878, is discussed.

Cranial crests have evolved multiple times in the evolutionary history of vertebrates, serving primarily for visual display. In duck-billed lambeosaurines, one of the most successful dinosaur clades of the Late Cretaceous, the cranial crest became hollow along the paired premaxillae and nasals, and was secondarily selected as a resonating structure atop the skull roof, facilitating acoustic signaling. Here we report the first instance of a hollow supracranial crest in a non-lambeosaurine ornithopod dinosaur, the early-branching hadrosauroid Qianjiangsaurus changshengi, where the paired accessory endonasal cavities just above the nasal cavity proper occur following the dorsoventral thickening of the nasals. This novel nasal cavity configuration is associated with the helmet-like hollow supracranial crest solely formed by the nasals. Comparative resonance modeling suggests that the nasal cavity of Q. changshengi could amplify low-frequency vocalizations similar to those of late-branching lambeosaurines. Seven analogous skull features (including the hollow supracranial crest) and similar low-frequency acoustic capabilities of nasal cavities between Q. changshengi and late-branching lambeosaurines reveal a striking morphological and functional convergence that would likely facilitate safer, more efficient social communication among hadrosauroids. This convergence can be explained by adaptive evolution under similar selection pressures, combined with developmental constraints due to gene pleiotropy.

In this study, 252 bromalite specimens from the paleontological collection of the Benemérita Escuela Normal de Coahuila were examined. These specimens were collected in the Cerro del Pueblo Formation (Upper Campanian) in the state of Coahuila, Mexico, and analyzed to obtain paleoecological and, for the first time, taphonomic data. A total of 18 morphotypes were classified and assigned to various potential producers, including teleosts, basal actinopterygians, elasmobranchs, crocodilians, testudines, amphibians, reptiles, theropod dinosaurs, and possibly other groups of omnivorous vertebrates. A multivariate analysis supported relationship between morphotypes and their associated potential producers. Additionally, some specimens present macroscopic and microscopic inclusions, such as bone remains and plant fragments, suggesting that these could represent predator-prey and herbivore-plant interactions. In contrast, traces of bioerosion in some specimens suggest coprophagy. The oxidized/reduced colorations, fragmentation, and biostratinomic alterations in the specimens indicate that they were likely deposited in floodplain environments. Furthermore, the ichnogenera Alococopros isp., Eucopros isp., and Struocopros isp. were identified within the collection, thus representing the first coprolite ichnotaxonomic records for northern Mexico from the Late Cretaceous. The biotic interactions inferred from the inclusions in the bromalites, their associated potential producers, and their distinct taphonomic histories suggest the presence of a diverse fauna that inhabited the various types of terrestrial and transitional environments within the Cerro del Pueblo Formation at the end of the Cretaceous.

Four new genera with four new species and one new combination of Mantispidae are described from the Upper Cretaceous (Cenomanian) amber of northern Myanmar: Tholomantispa quinata gen. et sp. nov., Tholomantispa zhangzhiqiae comb. nov., Heteromantispa polytricha gen. et sp. nov., Trimantispa poseidoni gen. et sp. nov., and Tribelomantispa yangjiani gen. et sp. nov. These species exhibit unique morphological characteristics, such as scale-like setae on forewings, unique male genitalia structure, and specialized raptorial foreleg, which provide valuable information for the study of character transformation and adaptive evolution within Mantispidae. The scale-like setae on the forewings suggests potential secondary loss in extant taxa. Similarly, the documentation of processes on the forefemur across multiple genera introduces a novel morphological trait within Mantispidae, enriching our knowledge of their structural diversity.

The Bauru Aquifer System (BAS), the hydrostratigraphic equivalent of the Bauru Group (Upper Cretaceous), serves as the primary source of private groundwater supply for the municipality of Bauru (State of São Paulo, Brazil). The BAS is widely contaminated by nitrate, while the Guarani Aquifer System (GAS) is the primary source of public water supply for the city. Usually, basalts from the Serra Geral Formation hydraulically isolate the BAS from the GAS. However, a local stratigraphic peculiarity—the "basalt window"—results in the absence of such basalts, raising concern for possible hydraulic connectivity, especially given the strategic importance of the GAS in the state of São Paulo. This study identified the Araçatuba Formation, a new geological unit in the area, which functions as an aquitard and can confine the GAS even where basalts are absent. The new lithostratigraphy was proposed based on (i) interpretation of geophysical logs from 46 tubular wells, (ii) drilling of a 130 m borehole with geophysical logging (gamma ray, spontaneous potential, resistivity, and sonic) and core description, and (iii) implicit 3D geological modeling using Leapfrog Works®. These combined methods enabled the delineation of the Bauru Group’s geological framework (Marília, Adamantina, and Araçatuba formations from top to base). The Araçatuba aquitard, with thicknesses ranging from 8 to 26 m in the study area, provides confirmed confinement for the GAS, even within the "basalt window" and under downward hydraulic gradients. Distinct geophysical signatures were defined for each mapped stratigraphic unit, providing a guide for future interpretations in other areas.