The Turonian echinoid fauna of northern Cantabria (Spain), exposed within the UNESCO Global Geopark Costa Quebrada and adjacent sections west of Santander, is revised. Eighteen taxa are recognised from lower Turonian to lower upper Turonian strata. Several previously published identifications are revised, and additional taxa are documented for the first time. The fauna comprises cidaroids, phymosomatoids, cassiduloids, holectypoids, and a diverse assemblage of irregular echinoids, with particularly abundant representatives of Conulus, Camerogalerus, Roweaster, Protocardiaster, Plesiocorys, Micraster and Hemiaster.The assemblages provide important insights into the palaeoecology and biogeography of the North Cantabrian Basin during the Turonian. Diversity patterns and faunal composition changed in response to sea-level fluctuations and associated shifts from relatively proximal glauconitic depositional settings to more distal marl–limestone successions. Cassiduloids and holectypoids are most characteristic of proximal settings, whereas cardiasterids, hemiasterids, and later Micraster-dominated assemblages are associated with increasingly distal environments. A major faunal turnover occurred during an early late Turonian flooding event, coinciding with the proliferation of Micraster and Plesiocorys.Biogeographically, the fauna shows strong affinities with Boreal echinoid assemblages known from southern England, northern France, Germany, Poland, and the Czech Republic, despite the study area occupying an intermediate position between the Boreal and Tethyan realms. The results contribute to a better understanding of Turonian echinoid distribution patterns and environmental gradients within the Northern Transitional Subprovince.
The definition of the Jurassic/Cretaceous (J/K) boundary remains a significant global challenge. This study presents a revised biostratigraphic framework for the Tithonian–Berriasian transition in the Vaca Muerta Formation (Neuquén Basin, Argentina), based on ammonite high-resolution data from the Las Loicas and Las Alcantarillas sections. New ammonite identifications enhance the correlation of the J/K boundary beds of the Neuquén Basin with other mid-to-lower latitude regions. Seven ammonite assemblage zones are recorded, spanning the lower Tithonian Virgatosphinctes andesensis to the upper Berriasian Argentiniceras noduliferum zones. The latter is reinterpreted as upper Berriasian (Boissieri Zone, Paramimounum Subzone), at approximately 139.55 +/- 0.18 Ma in the Las Loicas Section. Previously obtained ages of 140.338 +/- 0.083 Ma and 139.956 +/- 0.063 Ma therefore indicate upper lower Berriasian beds of the Substeueroceras koeneni Zone. Integration of the biostratigraphy, numerical U/Pb ages, and high-resolution Gamma Ray Spectrometry data from both sections enables their correlation despite unresolved discrepancies in calcareous nannofossil zonation. Our results provide valuable data for evaluating alternative proposals for the J/K boundary placing, favouring a relocation into the upper Tithonian, between the Windhauseniceras internispinosum/lower "Corongoceras alternans" zones, and close to an age of 143.715 +/- 0.43 Ma.
Cretaceous palms have often been considered indicative of warm or tropical paleoenvironments based on the modern distribution of the clade's extant representatives. In this work, we describe two new taxa of the fossil genus Palmoxylon from the uppermost Cretaceous (upper Maastrichtian) Chorrillo Formation in Southern Patagonia. One of the species, Palmoxylon kospi sp. nov., exhibits anatomical features that allow its referral to the Arecoideae. The second taxon, Palmoxylon anciborae sp. nov., is placed within the tribe Trachycarpeae of the subfamily Coryphoideae. Because both subfamilies contain taxa distributed across both tropical and non-tropical regions, and considering that Trachycarpeae includes some of the most cold-tolerant extant palms, their reliability as climatic proxies was analyzed. Integrating these findings with previous climatic inferences, including palynological and paleopedological proxies, these new palm taxa are interpreted as non-tropical palms that grew under temperate and seasonally humid climatic conditions. Consequently, the traditional use of Cretaceous palms as definitive indicators of tropical or warm conditions is challenged, reinforcing the need to evaluate subfamilial or tribal affinities alongside their specific climatic ranges. Furthermore, because terms like “warm” and “tropical” have often been used without clear reference to a standard climatic classification scheme, making precise comparisons difficult, we encourage future studies to explicitly adopt and state their chosen climatic classification framework.
The Jurassic/Cretaceous (J/K) boundary remains the only Phanerozoic transition without a designated Global Boundary Stratotype Section and Point (GSSP). This study investigates a J–K carbonate succession in eastern Mexico, spanning the Pimienta and Tamaulipas Inferior formations near Mazatepec, Puebla. Integrated petrographic, isotopic, and geochemical data provide new insights into paleoenvironmental evolution and geochemical changes across the J–K transition. The succession comprises organic-rich lime mudstones, radiolarian wackestone, and bioclastic wackestone–packstone, interbedded with volcanic ash layers, and crosscut by igneous intrusions. Petrographic analyses reveal dominant micritic to near-micritic textures, suggesting—alongside geochemical evidence—that although localized diagenetic alteration occurred, most of the carbonate succession shows preservation of at least near-primary signatures. Paleo-redox proxies indicate reducing bottom-water conditions throughout most of the Tithonian and into the base of the Berriasian. Two euxinic intervals are identified: a localized pulse in the lower Tithonian and a developed euxinic phase in the lower part of the middle Tithonian. Outside these intervals, anoxic conditions prevailed during much of the Tithonian, followed by a progressive shift toward suboxic conditions across the J–K transition and into the lower Berriasian. Volcanic proxies indicate enhanced activity during the middle Tithonian and a decline into the Berriasian. The δ13Ccarb record shows a pronounced negative excursion during the Tithonian, followed by a sustained positive shift across the J–K interval that contrasts with the persistently decreasing Tethyan trend. This divergence reflects strong local control by redox conditions, volcanism, and basin restriction, highlighting the importance of regional paleoceanographic processes in shaping carbon-cycle dynamics across the J–K transition.
Gasparinisaura cincosaltensis is a small bipedal ornithopod from the Anacleto Formation (lower to middle Campanian) of the Río Negro Province (Argentina). The holotype MUCPv 208 contains a partial postcranium, as well as the only near-complete cranium from a non-hadrosauriform ornithopod in the entire Southern Hemisphere. G. cincosaltensis was first assigned to a grade of basal iguanodonts, then related to the Elasmaria based on characters from the humerus and femur. However, some originally described cranial characters contradicted such iguanodontian affinities, making this taxon phylogenetically unstable. Here, we review the holotype skull of G. cincosaltensis and clarify its phylogenetic relationships using an updated data matrix. The skull was X-ray tomographed with an odontological CT-scan, and its braincase was virtually extracted. First-hand observations and scanning data are combined, allowing to (1) highlight a pattern of taphonomic deformation and crushing, (2) find a new suite of unique cranial traits, and (3) perform an in-depth revision of character scoring. Our phylogenetic analysis shows that G. cincosaltensis is rooted closer to the Elasmaria within the Dryosauridae. Altogether with D. lettowvorbecki, they form the internal specifiers of a new node-based subfamily of gondwanan dryosaurids: the Dysalotosaurinae. The clade is supported by a set of unique cranial features not observed in Dryosaurus, such as the presence of a bilobate anterodorsal branch of lacrimal, and an advanced midline split of the paired squamosal processes of parietal. Finally, we argue that the large orbit of G. cincosaltensis is probably genuine, and not related to a juvenile state of maturity.
Albian–Cenomanian calcareous claystone sequences drilled in the Mentelle Basin (MB) offshore southwest Australia at International Ocean Discovery Program sites U1513, U1514, and U1516 yield mostly well preserved but highly fluctuating populations of planktic foraminifera and calcareous nannofossils. The sites were deposited at a high paleolatitude (60–61°S) in the southeast Indian Ocean. The chronostratigraphic framework for the recovered sequences is primarily based on biostratigraphically important calcareous nannofossil species with 25 Albian and 15 Cenomanian nannofossil bioevents correlated to Boreal or low to mid-latitude zonations, providing reliable datums for the age-depth curves at each of the sites. The low diversity, high dominance planktic foraminiferal assemblages generally lack age diagnostic species and are assigned to a southern high latitude zonal framework. The planktonic foraminifer species, Planohedbergella antescheri Huber and Petrizzo and Praeglobotruncana praedelrioensis Huber and Petrizzo, are described as new, ranging within the Albian at all three MB sites.Onset of open marine conditions in the Mentelle Basin occurred by ∼112 Ma based on age determination of the oldest Albian sample yielding calcareous microplankton. The composition and structure of the calcareous nannofossil assemblages indicate the Albian and Cenomanian surface waters were generally of low fertility and supported relatively low carbonate productivity, punctuated by four episodes of enhanced fertility correlated directly to Oceanic Anoxic Events. The fertility episodes were coeval with significant increases in the rate of sediment accumulation, suggesting the enhanced nutrient availability promoted increased biogenic carbonate production in an otherwise sediment- and nutrient-starved paleoenvironment. Upper Albian–middle Cenomanian intervals with abundant clinoptilolite pseudomorphs of calcisphere and radiolarian shells formed during periods of low foraminiferal abundance and enhanced biosiliceous productivity.
The present work is an attempt to identify the incomplete, isolated teeth and disarticulated sauropod dinosaur bones recorded from the Upper Cretaceous Mahadek Formation of South West Khasi Hills District of Meghalaya, India. The assemblage comprises two teeth and disarticulated bone fragments including partially preserved humerus, scapula, dorsal rib and vertebrae. Comparative analysis of the dental material with Late Cretaceous titanosaurian sauropods from multiple localities revealed closest affinity to Morphotype I teeth recorded from the Kem Kem beds of Morocco, consistent with titanosauriforms/titanosaur attribution. The postcranial elements show significant morphological affinities with Jainosaurus septentrionalis, Huabeisaurus allocotus, Lirainosaurus astibiae, and other Late Cretaceous titanosaurian sauropods. However, the inadequate morphological evidence for definitive generic identification of the teeth and postcranial elements could not be established owing to the paucity of fossils, poor preservation and fragmentary condition. Therefore, the specimens are assigned to Titanosauria indet. with probable titanosaur affinities. Paleohistological data indicate rapid bone deposition, extensive secondary remodeling, and somatic maturity of the Meghalaya specimens reflecting growth strategies shared by titanosaurian sauropods across Gondwana and Laurasia. Finally, this study focuses on the taphonomic mode of the bones suggesting a medium to high energy, fast sedimentation and rapid burial with evidences of abrasion and fragmentation, and sedimentological analysis indicates deposition in a braided fluvial floodplain with episodic high-energy flooding facilitating burial and preservation. These findings are therefore very significant, enriching our understanding of dinosaur diversity and distribution in the Upper Cretaceous formations of India and opening up a wealth of possibilities for future research.
Tarachoptera represents an extinct basal lineage with Amphiesmenoptera, offering significant insights into the early evolution of wing scales and pheromone-related structures in holometabolous insects. However, the diversity and evolutionary significance of wing-associated androconial structures within Tarachoptera remain poorly understood. Here, this study describes three new species of Tarachocelidae assigned to two genera from mid-Cretaceous Kachin amber of northern Myanmar: Retortocelis ventricosa sp. nov., Retortocelis confluvena sp. nov., and Kinitocelis robustivena sp. nov. Detailed morphological examinations reveal substantial variation among these species in wing venation, costal fold morphology, and wing-associated sensory structures. Notably, Retortocelis ventricosa sp. nov. preserves campaniform sensilla and setae associated with the forewing veins, suggesting that mechanosensory adaptations related to flight control were already present in Tarachoptera early in its evolutionary history. Comparative measurements of forewing area and costal fold area across species of Retortocelis demonstrate notable interspecific differences in the relative development of the costal fold. Furthermore, character mapping of wing androconial scales within Amphiesmenoptera reveals a scattered distribution across the phylogenetic tree, suggesting that wing-associated androconial systems may have evolved convergently in Tarachoptera, Trichoptera, and Lepidoptera. These findings expand the known diversity of Tarachoptera and provide new perspectives on the early diversification of sensory and pheromone-related wing structures with Amphiesmenoptera.
Pliosauridae includes large sauropterygians, which were dominant predators from the middle Jurassic to the Early Cretaceous. The fossil record of Early Cretaceous plesiosaurians has improved in recent years; however, aspects such as their biogeographic patterns and extinction remain understudied due to several gaps in the Cretaceous record. Here, we report the first occurrence of pliosaurids in Cretaceous outcrops of Mexico, collected in two sites in the Coyame region of Chihuahua, northern Mexico. The first specimen is a disarticulated vertebral series, and the second is an isolated tooth. Both specimens belong to the clade Thalassophonea. In the first specimen, a combination of features, such as the proportions of length to height of the pectoral centra and the positions of the foramina on the ventral and dorsal surfaces, is consistent with those observed in Cretaceous thalassophonean pliosaurids. The second specimen is identified as a Thalassophonea based on its robust crown and the conspicuous apicobasal ridges on the enamel. These fossils represent the first known pliosaurids from the Aptian of North America, enhancing our knowledge of the group during the Early Cretaceous in this region.
Carbon (δ13Corganic, δ13Ccarbonate) and oxygen (δ18Ocarbonate) isotope records presented from DSDP Site 534A from the central Atlantic integrated with biostratigraphy, provides insights into the pattern of changes in carbon cycling, climate and ocean circulation. This study builds on the pioneering work of the DSDP, and utilises the extensive datasets published combined with new stable isotope data. We additionally examine the Jurassic/Cretaceous boundary to evaluate whether a distinct carbon isotopic pattern is observable. The dataset from Site 534A is one of the very few where long-term records of both δ13Ccarbonate and δ13Corganic have been developed. These data from DSDP Site 534A record the temporal evolution of the carbon isotopes, together with oxygen isotopes that are interpreted as a temperature proxy. The Δ13C (i.e. the offset between δ13Ccarbonate and δ13Corganic) data are interpreted as a pCO2 proxy. A Bathonian-Callovian δ13Ccarbonate and δ13Corganic rise is followed by a Late Jurassic to earliest Cretaceous decline and the globally recognized isotopically positive event, the Weissert Event in the Valanginian. A distinctive δ13Ccarbonate and δ13Corganic shift to more negative values in the mid-late Tithonian, the Volgian Isotopic Carbon Excursion (VOICE), as recognised elsewhere, is not identified. The δ18O record shows seawater temperature changes closely following the pCO2 proxy record whereby rising pCO2 and temperatures are seen in the Bathonian-Callovian, and occur in the early Valanginian. Temperatures and pCO2 maxima occur the early Valanginian prior to the onset of the Weissert positive event. The inferred pCO2 rise is coincident with the earliest Paraná-Etendeka volcanic phase.
This study provides the first sampling and comprehensive biostratigraphic reassessment of rudist bivalve assemblages from the Urgonian Formation of the Subalpine Platform in southeastern France. Particular attention is given to faunas occurring below, within, and above the Lower Orbitolina Beds (LOB) Member, a distinctive orbitolinid-rich marly interval that separates the Lower and Upper Urgonian Limestone members. The age of the LOB Member remains controversial and has been variably assigned from the upper Barremian to the lowermost Aptian, mainly on the basis of disputed orbitolinid biostratigraphy. New rudist data reveal the occurrence of Agriopleura-bearing assemblages both below and above the LOB Member. This distribution demonstrates that deposition of the LOB Member predates the European-wide disappearance of Agriopleura and therefore cannot be younger than the middle–late Barremian (Gerhardtia sartousiana ammonite Zone), as calibrated in neighbouring Urgonian successions of the Languedoc and Provence domains. Instead, the rudist assemblages support a late early Barremian age for the LOB Member, as corroborated by both the underlying rudist occurrences and the absence of characteristic late Barremian rudist faunas that are otherwise widespread in coeval Urgonian deposits elsewhere in southeastern France. The study also confirms the marked progradational trend within the overlying Upper Urgonian Limestone Member toward the Vocontian Basin. Available data, both rudists and ammonites, indicate that the Upper Urgonian Limestones Member is older (early late Barremian age) and clearly truncated in the northern Vercors, while it becomes younger (latest Barremian age) in the southwestern Vercors, where more distal depositional settings are recorded. Besides the LOB Member, two additional orbitolinid-rich marly horizons are recognized: one in the southeastern Vercors, occurring within the Gerhardtia sartousiana Zone and correlating southward with the Font Froide–La Béguère marly complex; and another at Col de la Chau in the southwestern Vercors, mainly spanning the Imerites giraudi Zone and correlating with the Pas de la Couronne Marls. These occurrences demonstrate the existence of distinct episodes of orbitolinid proliferation during the deposition of the Upper Urgonian Limestone Member.
