Late Cretaceous Research Articles

Abstract The Late Cretaceous (Campanian–Maastrichtian) vertebrate ichnotaxa Patagonichornis venetiorum Casamiquela 1996 and Tridigitichnus inopinatus Casamiquela 1996 were established based on material preserved on a sandstone slab from the Angostura Colorada Formation, Montón Iló quarry, Río Negro Province, Patagonia, Argentina. This slab, along with others from the same locality, was used for constructions near Ingeniero Jacobacci town. The holotype-bearing slab is currently housed at the Museo di Storia Naturale di Venezia Giancarlo Ligabue (Venice, Italy). This study aims to reconstruct the circumstances surrounding these holotypes. Through visits to the Museo Antropológico e Histórico Jorge H. Gerhold (Ingeniero Jacobacci, Argentina), the original sidewalk from which the slab was removed, was identified. Moreover, nine track-bearing slabs with avian footprints and invertebrate traces were identified on the same sidewalk. Due to limited accessibility of the original descriptions, these ichnotaxa have received little scientific attention. Although P . venetiorum and T . inopinatus remain available names under ICZN regulations, their ichnotaxonomical validity requires further assessment. To highlight their importance as movable paleontological heritage, a detailed report —including descriptions, photographs, and 3D model— was prepared for the Ingeniero Jacobacci and Venice museums. The compiled data serve as a crucial reference for future research and conservation initiatives, promoting their patrimonial, educational, and touristic value. This work underscores the importance of interdisciplinary collaboration for the study and preservation of paleontological heritage.

New discoveries of lepidosteoid scales from the Upper Cretaceous in Songliao Basin, China

New materials on the Late Cretaceous (Cenomanian) turtles' assemblages from Bahariya depression, Western Desert, Egypt

Emergent features in northern Western Desert, Egypt: proxies for progressive uplifting of the Tethys platform and the related palaeoclimate shifts since the latest Cretaceous

New sharks in a chondrichthyan fauna from the Upper Cretaceous Aguja Formation (lower Campanian) of West Texas support biogeographic segregation among chondrichthyans in the Western Interior

The Cretaceous marks the peak of magmatic activity in southeastern (SE) China, which is attributed to the subduction of the paleo-Pacific plate beneath the South China Block. This region constitutes a significant igneous belt along the active continental margin of the western Pacific. Despite extensive research, the origin and evolution of Cretaceous felsic volcanic rocks are still debated. This study investigates the characteristics of zircon U-Pb-Hf isotopes and trace elements, and whole-rock geochemistry of Cretaceous volcanic rocks from the Wenzhou–Taizhou region in SE Zhejiang, and discusses their spatio-temporal patterns and petrogenesis. The results indicate that rhyolitic volcanic rocks formed during the period ca. 114 Ma and 95 Ma, representing two distinct magmatic episodes spanning the transition from the late Early to early Late Cretaceous. The late Early Cretaceous and early Late Cretaceous volcanic rocks are of a hybrid crust–mantle origin, as evidenced by their distinct Nb/Ta ratios, zircon εHf(t) values, and variable trace element enrichments (Ti, Hf, U, Nb, and Yb). These compositional signatures suggest partial melting of late Paleoproterozoic to early Mesoproterozoic basement materials, with increasing mantle contributions over time. Both volcanic phases exhibit elevated Nb/Yb, Th/Nb, and U/Yb ratios, indicating a subduction-modified source akin to arc magmas. Together with calculated initial melt temperatures (<800 °C for Early Cretaceous, >800 °C for Late Cretaceous) and whole-rock rare-earth elements (REEs) distribution patterns (U-shaped with δEu = 0.37–0.65, seagull-shaped with δEu = 0.19–0.62, respectively), it is suggested that both phases of the volcanic magmas were generated through water-assisted (hydrous) melting, whereas the later phase formed at relatively higher temperatures and with a diminished water contribution via dehydration melting under extensional conditions. The generation of voluminous high-silica magmas in the SE China coastal region is probably linked to the rollback and retreat of the paleo-Pacific plate.

The Termit Basin, a well-explored hydrocarbon-rich basin in West Africa, provides an excellent case study for investigating oil families, paleoenvironments and organic matter (OM) inputs in the Trans-Saharan epicontinental basins. This study examines nineteen newly discovered southeastern oils using gas chromatography, gas chromatography-mass spectrometry and stable carbon isotopic analysis. While three oil families (I, II and III) were previously identified in the basin based on discoveries made prior to 2020, this study identified, for the first time, family I oils in the far east of the basin, and first recognized two new families (IV and V) by chemometric analysis and correlations of fourteen biomarkers and carbon isotope compositions. Families I and IV show more terrigenous inputs than family V. Our results do not support previous work suggesting that family I was derived from algal-dominated OM. Compared with family I, a contribution of marine sources was defined for family IV, although terrigenous inputs remained significant. Family V originated from source rocks with more inputs of marine OM. Family V is divided into subfamilies V1 and V2, of which subfamily V2 is distinguished by greater algal inputs under more reducing conditions. The identification of family V proved the presence of a new petroleum system related to marine algal-rich source rocks in the Termit Basin. Our results suggest significant terrigenous OM influx and extensive marine algae blooms in the Trans-Saharan epicontinental seas during the Late Cretaceous, coinciding with sea-level changes.

A new crocodylomorph fossil specimen (ML2631) from the Upper Jurassic of Lourinhã (Portugal) is described, based on a partially preserved skull table and braincase. The specimen was recovered from the Zimbral vertebrate microfossil assemblage, located in the lower part of the Praia Azul Member of the Lourinhã Formation (Kimmeridgian–Tithonian transition). The fossil was scanned using high-resolution micro-computed tomography (µCT), enabling the digital reconstruction of internal cranial structures, such as the brain cavity, cranial nerves, inner ear and paratympanic sinus system. These reconstructions represent the first neuroanatomical data ever reported for Atoposauridae, a clade of small-bodied neosuchian crocodylomorphs common in the Late Jurassic and Cretaceous of Europe. Phylogenetic analysis places ML2631 within Atoposauridae and contributes to resolving previously uncertain relationships within the group. Although fragmentary, ML2631 exhibits a unique combination of anatomical features, including a dorsolaterally open cranioquadrate passage, a sagittal crest along the frontal and parietal, a large, posteriorly placed and septate choana, large supratemporal fenestrae with a distinct posterior fossa and a squamosal lobe bearing a discontinuous lateral groove. These traits, amongst others, distinguish ML2631 from all other known atoposaurid species. Additionally, its neuroanatomical proportions suggest a dwarf adult individual with low-frequency auditory sensitivity and moderate visual acuity, consistent with a primarily terrestrial or nearshore lifestyle, coherent with the depositional environment of the fossil site. Taken together, these results highlight the taxonomic and evolutionary relevance of the specimen and underline the importance of future discoveries of more complete material to confirm its systematic and phylogenetic status within Atoposauridae.

It has long been debated whether non-avian dinosaurs went extinct abruptly or gradually at the end-Cretaceous (66 million years ago), because their fossil record at this time is mostly limited to northern North America. We constrain a dinosaur-rich unit to the south, the Naashoibito Member in New Mexico, to the very latest Cretaceous (~66.4 to 66.0 million years), preserving some of the last-known non-avian dinosaurs. Ecological modeling shows that North American terrestrial vertebrates maintained high diversity and endemism in the latest Cretaceous and early Paleogene, with bioprovinces shaped by temperature and geography. This counters the notion of a low-diversity cross-continental fauna and suggests that dinosaurs were diverse and partitioned into regionally distinct assemblages during the final few hundred thousand years before the end-Cretaceous asteroid impact.

New Data on Diatoms and Silicoflagellates of the Late Cretaceous of the Ust’-Manya Section, Severnaya Sos’va River, Subpolar Trans-Urals

Azhdarchidae was a diverse group of toothless pterosaurs and one of the few lineages of flying reptiles to survive to the end of the Cretaceous. Despite including medium-sized forms, the group is notable for their gigantic representatives, which correspond to the largest known flying animals. Azhdarchids had a nearly global distribution during the Late Cretaceous, including the Arabian Plate, with records in Lebanon and Jordan, such as the iconic Arambourgiana philadelphiae. Here, we report the first azhdarchid, and indeed the first pterosaur, from Syria, recovered from early Maastrichtian phosphate deposits of the Palmyrides mountain chain, near Palmyra (Tadmur). It corresponds to a fragmentary left humerus, missing both its proximal and distal ends, with a preserved length of 289mm. The Syrian pterosaur was exceptionally large, with extrapolations suggesting that, if complete, its humerus would be only about 10% smaller than the holotype humerus of Quetzalcoatlus northropi, the largest known pterosaur. The new pterosaur fossil also represents the uncommon record of a giant azhdarchid in marine deposits, confirming that these gigantic animals, though classically considered continental, could also inhabit nearshore environments. The find also underscores the widespread occurrence of gigantic azhdarchids until the latest Cretaceous, just prior to their Cretaceous/Paleogene extinction, and highlights the potential for fossil discoveries in understudied regions such as the Middle East.

This study reports a well-developed columnar joint setin organic-richcarbonate source rocks, exhibiting distinct vertical prismatic columnswith hexagonal to polygonal cross sections. These columnar jointsare found within the Upper Cretaceous Muwaqqar Chalk Marl (MCM) Formation,in central Jordan. While columnar joints are commonly observed inigneous rocks, their occurrence in carbonate mudrocks is unique andhas rarely been documented in stratigraphic records. This study aimsto characterize the geometry and petrographic features of columnarjoints observed in organic-rich carbonate source rocks and investigatethe mineralogical and geochemical alterations associated with theirdevelopment. Thorough petrographic and geochemical investigationswere carried out to better understand the characteristics, paleoenvironmentalcontext, and associated processes that controlled the formation ofthese honeycomb-shaped mudrocks. Our findings suggest that the observedcolumnar joints resulted from subsurface thermal alteration due tothe endogenous combustion of the organic-rich carbonate source rocks.This combustion process has led to the development of joints orientedperpendicular to the bedding planes, extending throughout a 2-m-thickinterval. These joints slightly taper downward while preserving theirpolygonal pattern, with column diameter decreasing from 3 to 1 cm.The development of columnar joints within the study interval is primarilyattributed to volume contraction resulting from the consumption oforganic matter during combustion and textural and pore-structure changesthat occurred during recrystallization. This is corroborated by asignificant reduction of total organic carbon (TOC) content, whichreduced to less than 1 wt % in the combusted interval, compared toan average TOC of 15 wt % in the surrounding relevant strata. Thefindings of this study highlight a unique geological phenomenon thathas not been previously widely documented in stratigraphic records.

ABSTRACT Ophthalmosaurids were a globally distributed clade of ichthyosaurs that thrived from the Middle Jurassic to the early Late Cretaceous. Although their fossil record spans a wide palaeogeographic range, much of what is known about their anatomy and diversity derives from Late Jurassic localities in the Northern Hemisphere. In contrast, Late Jurassic forms from the Southern Hemisphere remain comparatively less known. Here we describe Eternauta patagonica gen. et sp. nov. a new ophthalmosaurid from the Tithonian deposits of the Vaca Muerta Formation. The holotype, previously referred to Caypullisaurus bonapartei Fernández, 1997, comprises a skull, teeth, a forelimb, and rib fragments. Phylogenetic analyses consistently recover Eternauta as a member of Platypterygiinae. Diagnostic features include a unique morphology of the pterygoid, an expanded postorbital contribution to the ventral margin of the orbit, and a retroarticular process that is strongly angled posterodorsally. These traits, together with a low jaw-opening mechanical advantage and relatively large sclerotic aperture, suggest a feeding strategy for capturing small, agile prey. The anatomical and functional features of Eternauta expand the known morphological and ecological disparity of Late Jurassic ophthalmosaurids, reinforcing the significance of the Vaca Muerta Formation as a key unit for understanding ichthyosaur evolution across the Jurassic – Cretaceous transition. URN:lsid:zoobank.org:pub:68200526-150C-41 CD-8655-D250066BF215

Abstract Investigating the evolutionary history and species diversification patterns in hyperdiverse lineages is essential for understanding how species diversity accumulates and how floras assemble historically across diverse regions. A large angiosperm family, Apocynaceae, exhibited remarkable diversity in functional traits including growth form, fruit types, and pollen aggregation, which may have a substantial impact on species diversification rates. However, the lack of a robust and well dated phylogeny has hindered our understanding of Apocynaceae diversification. To address this gap, we reconstructed a robust phylogeny covering 22 of 25 tribes using plastome sequences, then employed this framework to estimate divergence times, analyze diversification patterns, and investigate associations between species diversification and functional traits. The plastome phylogenies received strong nodal support across most branches. Among higher taxonomic groupings, three subfamilies (Asclepiadoideae, Secamonoideae, and Periplocoideae) were monophyletic. At the tribal levels, 19 tribes were strongly supported as monophyletic except Melodineae, Willughbeieae, and Vinceae. Additionally, five genera (Vincetoxicum, Cynanchum, Hoya, Marsdenia, and Aganosma) were identified as nonmonophyletic. Our analyses revealed that Apocynaceae originated in the paleotropics during the middle Late Cretaceous. Integrating binary state speciation and extinction (BiSSE), hidden state speciation and extinction (HiSSE), and fast, intuitive state‐dependent speciation‐extinction (FiSSE) analyses, we found that species with pollinia had a higher speciation rate than those without. Dry‐fruited species had a higher speciation rate than those with fleshy fruits. Furthermore, Bayesian analysis of macro‐evolutionary mixtures (BAMM) detected a diversification rate increase coinciding with the evolution of pollinia with clip‐type attachment mechanisms in the subfamily Asclepiadoideae. Herbs had the highest speciation rate, followed by climbers and self‐supporting species. Our findings contribute to understanding the historical assembly of floras in tropical and subtropical Asia.

After the return of giant sauropod dinosaurs in the form of titanosaurids to North America in the Campanian of the Late Cretaceous, Alamosaurus sanjuanensis is generally considered to have been the sole taxon on the continent over a few million years. The possibility of one species existing that long is very low because sauropods often exhibit taxonomic diversity in the same habitat. The fossils from the southwestern states and northern Mexico are all incomplete, overlapping elements are often scarce, and sometimes differ in ontogenetic development. The fragmentary New Mexican A. sanjuanensis material from the early Maastrichtian lower Ojo Alamo Formation shows significant distinctions from the much later partial skeletons from the late Maastrichtian lower North Horn Formation of Utah. The latter is therefore made the holotype of Utetitan zellaguymondeweyae. Some late Maastrichtian Texas fossils can be assigned to U. zellaguymondeweyae, others cannot. Fossils from the middle Campanian cannot be assigned to either genus. Southwestern North America supported a diversity of titanosaurids, which may have formed a Utetitan miniclade as they evolved in semi-isolation from the global titanosaurid fauna. Past calculations that these titanosaurids were among the most massive in the group are not borne out by scaling of skeletal restorations.

Abstract Tectonically, the southern Lower Yangtze region lies between the Dabie Orogenic Belt and Jiangnan Orogenic Belt. A series of Meso-Cenozoic basins developed in this area serve as a crucial window for revealing the basin structure and tectonic-sedimentary evolution in Eastern China. While geologically significant, the current understanding of these basins’ fundamental geological characteristics remains constrained. In particular, the basin’s structural framework and formation-evolution processes lack constraints from integrated geophysical data. This study conducted a systematic investigation into the structural characteristics, sedimentary filling patterns, and formation-evolution processes of three representative Meso-Cenozoic basins in the southern Yangtze region using deep seismic reflection and magnetotelluric sounding methods. The results indicate that two sets of thrust faults with opposite dips have developed within the crust of the study area, with the convergence center of the opposing thrusts located in the Huaining Basin, which controls the distribution of regional Jurassic strata. The central Huaining volcanic basin is associated with magma upwelling, with its main sedimentary filling occurring in the Early Cretaceous. In contrast, the Qianshan and Wangjiang basins are half-graben faulted basins formed under extensional stress. These faulted basins entered an active phase since the Late Cretaceous, marked by discontinuous sedimentation of the Upper Cretaceous to Paleogene strata. The boundary fault of the Qianshan Basin is considered the eastern branch fault of the Tan-Lu Fault, characterized by an evolutionary history of early strike-slipping followed by late-stage extension. Moreover, the boundary fault of the Wangjiang Basin exhibits a negative inversion structure, undergoing a dynamic transition from an early compressional thrusting phase to a subsequent extensional regime. The southern Lower Yangtze region experienced at least two compressional tectonic events during the Paleogene, which induced differential uplift and erosion of the basins. In light of the above analysis, a structural and sedimentary evolution model for the Meso-Cenozoic basins in the southern Lower Yangtze region has been constructed. The research findings provide important support for regional oil and gas exploration practices and further deepening the understanding of tectonic evolution processes in the Lower Yangtze region.

ABSTRACT The Central Sakarya Basin (CSB) is a back-arc basin in western Türkiye that formed during the Early Jurassic due to the subduction of the Intra-Pontid Ocean. The Late Cretaceous Vezirhan Formation consists of marine pelagic rocks deposited during the basin’s transgressive phase. This study identifies various soft-sediment deformation structures (SSDS) within the Vezirhan Formation for the first time, which are important for understanding palaeoseismicity and deformation mechanisms. The sedimentological and structural features of the succession were analysed along with SSDS identification to better understand the palaeoenvironment and tectonic-sedimentary processes in the Central Sakarya Basin during the Late Cretaceous. The formation consists of two main sedimentary lithofacies (LF): mud-dominated (LF-1) and debris flow sediment-dominated (LF-2), including lime-mudstones, cherty limestones, radiolarite, and volcanic interlayers with SSDS. The most common deformation structures are slump folds, sedimentary breccias, syn-sedimentary faults, sedimentary dykes and sills, load casts, chaotically deformed strata, and boudin-like structures. The upper section of the complexly deformed strata, where SSDS are found, is often sharply intersected by an erosional surface. This suggests that the deformation occurred during or immediately after the deposition of these deformed layers. The types, sizes, and complex nature of the SSDS indicate a high sedimentation rate, liquefaction-fluidisation processes, and an unstable slope environment. Some deformed layers are interpreted as seismic responses to earthquakes that triggered mass flows linked to active tectonism. Overall, the characteristics of the Vezirhan Formation and the SSDS structures indicate a tectonically active deep-water slope palaeoenvironment in the Central Sakarya Basin during the Late Cretaceous.

ABSTRACT In this paper, we complement and extend the list of aphid taxa from Obeshchayushchiy, described from the Late Cretaceous. A new endemic subfamily is established based on new materials: Promissaphidinae subfam. nov. within the Mesozoic family Oviparosiphidae. By examining aphid fossil records in rock imprints in conjunction with amber fossils, we delve into the taxonomic diversity of the Late Cretaceous aphids and the evolution of aphids during this period. http://www.zoobank.org/urn:lsid:zoobank.org:act:54F2CF1C-FA7C-4D9C-9313-CCB31EC0D23B.

Crocodyliforms of the São José do Rio Preto Formation (Bauru Basin, Upper Cretaceous), taxonomic and preservational aspects

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