A nitrogen isotopic shift in fish otolith-bound organic matter during the Late Cretaceous.

The nitrogen isotopes of the organic matter preserved in fossil fish otoliths (ear stones) are a promising tool for reconstructing past environmental changes. We analyzed the 15N/14N ratio (δ15N) of fossil otolith-bound organic matter in Late Cretaceous fish otoliths (of Eutawichthys maastrichtiensis, Eutawichthys zideki and Pterothrissus sp.) from three deposits along the US east coast, with two of Campanian (83.6 to 77.9 Ma) and one Maastrichtian (72.1 to 66 Ma) age. δ15N and N content were insensitive to cleaning protocol and the preservation state of otolith morphological features, and N content differences among taxa were consistent across deposits, pointing to a fossil-native origin for the organic matter. All three species showed an increase in otolith-bound organic matter δ15N of ~4‰ from Campanian to Maastrichtian. As to its cause, the similar change in distinct genera argues against changing trophic level, and modern field data argue against the different locations of the sedimentary deposits. Rather, the lower δ15N in the Campanian is best interpreted as an environmental signal at the regional scale or greater, and it may be a consequence of the warmer global climate. A similar decrease has been observed in foraminifera-bound δ15N during warm periods of the Cenozoic, reflecting decreased water column denitrification and thus contraction of the ocean's oxygen deficient zones (ODZs) under warm conditions. The same δ15N-climate correlation in Cretaceous otoliths raises the prospect of an ODZ-to-climate relationship that has been consistent over the last ~80 My, applying before and after the end-Cretaceous mass extinction and spanning changes in continental configuration.

Exceptionally preserved shark fossils from Mexico elucidate the long-standing enigma of the Cretaceous elasmobranch Ptychodus.

The fossil fish Ptychodus Agassiz, 1834, characterized by a highly distinctive grinding dentition and an estimated gigantic body size (up to around 10 m), has remained one of the most enigmatic extinct elasmobranchs (i.e. sharks, skates and rays) for nearly two centuries. This widespread Cretaceous taxon is common in Albian to Campanian deposits from almost all continents. However, specimens mostly consist of isolated teeth or more or less complete dentitions, whereas cranial and post-cranial skeletal elements are very rare. Here we describe newly discovered material from the early Late Cretaceous of Mexico, including complete articulated specimens with preserved body outline, which reveals crucial information on the anatomy and systematic position of Ptychodus. Our phylogenetic and ecomorphological analyses indicate that ptychodontids were high-speed (tachypelagic) durophagous lamniforms (mackerel sharks), which occupied a specialized predatory niche previously unknown in fossil and extant elasmobranchs. Our results support the view that lamniforms were ecomorphologically highly diverse and represented the dominant group of sharks in Cretaceous marine ecosystems. Ptychodus may have fed predominantly on nektonic hard-shelled prey items such as ammonites and sea turtles rather than on benthic invertebrates, and its extinction during the Campanian, well before the end-Cretaceous crisis, might have been related to competition with emerging blunt-toothed globidensine and prognathodontine mosasaurs.

Cretaceous chloranthoids: early prominence, extinct diversity and missing links.

BACKGROUND: The Chloranthaceae comprise four extant genera (Hedyosmum, Ascarina, Chloranthus and Sarcandra), all with simple flowers. Molecular phylogenetics indicates that the Chloranthaceae diverged very early in angiosperm evolution, although how they are related to eudicots, magnoliids, monocots and Ceratophyllum is uncertain. Fossil pollen similar to that of Ascarina and Hedyosmum has long been recognized in the Early Cretaceous, but over the last four decades evidence of extinct Chloranthaceae based on other types of fossils has expanded dramatically and contributes significantly to understanding the evolution of the family. SCOPE: Studies of fossils from the Cretaceous, especially mesofossils of Early Cretaceous age from Portugal and eastern North America, recognized diverse flowers, fruits, seeds, staminate inflorescences and stamens of extinct chloranthoids. These early chloranthoids include forms related to extant Hedyosmum and also to the Ascarina, Chloranthus and Sarcandra clade. In the Late Cretaceous there are several occurrences of distinctive fossil androecia related to extant Chloranthus. The rich and still expanding Cretaceous record of Chloranthaceae contrasts with a very sparse Cenozoic record, emphasizing that the four extant genera are likely to be relictual, although speciation within the genera might have occurred in relatively recent times. In this study, we describe three new genera of Early Cretaceous chloranthoids and summarize current knowledge on the extinct diversity of the group. CONCLUSIONS: The evolutionary lineage that includes extant Chloranthaceae is diverse and abundantly represented in Early Cretaceous mesofossil floras that provide some of the earliest evidence of angiosperm reproductive structures. Extinct chloranthoids, some of which are clearly in the Chloranthaceae crown group, fill some of the morphological gaps that currently separate the extant genera, help to illuminate how some of the unusual features of extant Chloranthaceae evolved and suggest that Chloranthaceae are of disproportionate importance for a more refined understanding of ecology and phylogeny of early angiosperm diversification.

New Data on Hesperornithids (Aves: Ornithurae) from the Campanian of the Lower Volga Region (Late Cretaceous, Russia).

Taxonomic diversity of Late Cretaceous hesperornithids (Aves: Hesperornithidae) of European Russia and Eastern Europe as a whole remain poorly understood, and the morphology of these large flightless birds is poorly known. New finds of Hesperornithidae in the Karyakino locality (Saratov oblast, Russia) confirm the coexistence of two forms of these flightless seabirds in the Campanian (mid-Late Cretaceous) of the Lower Volga region. A femur is described for the first time for Hesperornis rossicus Nessov et Yarkov, 1993, indicating that this large species is morphologically distinct from North American H. regalis Marsh, 1872.

New application of strontium isotopes reveals evidence of limited migratory behaviour in Late Cretaceous hadrosaurs.

Dinosaur migration patterns are very difficult to determine, often relying solely on the geographical distribution of fossils. Unfortunately, it is generally not possible to determine if a fossil taxon's geographical distribution is the result of migration or simply a wide distribution. Whereas some attempts have been made to use isotopic systems to determine migratory patterns in dinosaurs, these methods have yet to achieve wider usage in the study of dinosaur ecology. Here, we have used strontium isotope ratios from fossil enamel to reconstruct the movements of an individual hadrosaur from Dinosaur Provincial Park in Alberta, Canada. Results from this study are consistent with a range or migratory pattern between Dinosaur Provincial Park and a contemporaneous locality in the South Saskatchewan River area, Alberta, Canada. This represents a minimum distance of approximately 80 km, which is consistent with migrations seen in modern elephants. These results suggest the continent-wide distribution of some hadrosaur species in the Late Cretaceous of North America is not the result of extremely long-range migratory behaviours.

New record of a Mesozoic gondwanatherian mammaliaform from Southern Patagonia.

Gondwanatheria is an enigmatic mammaliaform clade distributed in the Cretaceous and Paleogene of South America, Africa, Madagascar, India and Antarctica. The Mesozoic record in South America is restricted to the Latest Cretaceous of Río Negro and Chubut provinces, Argentina and Magallanes Region of southern Chile. The aim of the present contribution is to describe a new specimen of gondwanatherian mammaliaforms from beds belonging to the Maastrichtian Chorrillo Formation, cropping out 30 km SW of El Calafate, Santa Cruz Province, Argentina. It is represented by a single molariform referable to the species Magallanodon baikashkenke with which it shares a unique combination of characters. Analysis of the unique combination of characters exhibited by Magallanodon shed doubts on the monophyly of Ferugliotheriidae and suggest that South American taxa may be closely related to each other. The wide geographical distribution and occurrence of gondwanatherians on geological units of diverse origins suggest that they were capable of facing disparate environmental conditions.

Evolutionary diversification of taiwanioid conifers: evidence from a new Upper Cretaceous seed cone from Hokkaido, Japan.

A single cylindrical seed cone 2 cm long, 1.1 cm wide has been found preserved in a calcium carbonate marine concretion from the Hakobuchi Formation (late Campanian-early Maastrichtian) of Hobetsu, Hokkaido, Japan. The cone, attached to a bent peduncle lacking leaves, has helically arranged bract/scale complexes that arise at right angles from the cone axis in the middle of the cone. The cone axis, ca. 1 mm wide, has a broad cylinder of secondary vascular tissue, and lacks a continuous resin canal system. Bract-scale complexes are laminar, cordate-orbiculate, and upturned distally, consisting primarily of bract tissue with no visible scale tip. The vascular trace to the bract/scale complex originates as a rod that divides laterally into several traces at the level of seed attachment. A single resin canal originates at the base of the bract-scale complex abaxial to the vascular strand, but more distally there are up to ca. 15 large resin canals that form a single row. Two to three inverted winged seeds are attached adaxially near the cone periphery. Cone structure and vascularization are most similar to those in the Cupressaceae, Subfamily Taiwanioideae, differing from living Taiwania cryptomerioides by having up to three seeds/scale rather than two, an abruptly upturned bract tip, in details of bract/scale vasculature, and a cone peduncle lacking leaves. This cone is described as Mukawastrobus satoi Stockey, Nishida and Rothwell. Together with previously described Early to Late Cretaceous taiwanioid seed cones from Mongolia and Hokkaido the new species demonstrates that the taxonomically diagnostic characters of such conifers are as subtle as those of Cretaceous and Cenozoic sequoioid Cupressaceae. This realization emphasizes that evolutionary diversification and turnover among taiwanioid conifers during the Cretaceous and Paleogene are probably far greater than currently recognized.

Modelling the climatic niche of turtles: a deep-time perspective.

Ectotherms have close physiological ties with the thermal environment; consequently, the impact of future climate change on their biogeographic distributions is of major interest. Here, we use the modern and deep-time fossil record of testudines (turtles, tortoises, and terrapins) to provide the first test of climate on the niche limits of both extant and extinct (Late Cretaceous, Maastrichtian) taxa. Ecological niche models are used to assess niche overlap in model projections for key testudine ecotypes and families. An ordination framework is applied to quantify metrics of niche change (stability, expansion, and unfilling) between the Maastrichtian and present day. Results indicate that niche stability over evolutionary timescales varies between testudine clades. Groups that originated in the Early Cretaceous show climatic niche stability, whereas those diversifying towards the end of the Cretaceous display larger niche expansion towards the modern. Temperature is the dominant driver of modern and past distributions, whereas precipitation is important for freshwater turtle ranges. Our findings demonstrate that testudines were able to occupy warmer climates than present day in the geological record. However, the projected rate and magnitude of future environmental change, in concert with other conservation threats, presents challenges for acclimation or adaptation.

A Late Cretaceous Piper (Piperaceae) from Colombia and diversification patterns for the genus.

PREMISE OF THE STUDY: Documented fossil floras in the neotropics are sparse, yet their records provide evidence on the spatial and temporal occurrence of taxa, allowing for testing of biogeographical and diversification scenarios on individual lineages. A new fossil Piper from the Late Cretaceous of Colombia is described here, and its importance for assessing diversification patterns in the genus is addressed. METHODS: Leaf architecture of 32 fossil leaf compressions from the Guaduas Formation was compared with that of 294 extant angiosperm species. The phylogenetic position of the fossil named Piper margaritae sp. nov. was established based on leaf traits and a molecular scaffold of Piper. The age of the fossil was independently used as a calibration point for divergence time estimations. KEY RESULTS: Natural affinities of P. margaritae to the Schilleria clade of Piper indicate that the genus occurred in tropical America by the Late Cretaceous. Estimates of age divergence and lineage accumulation reveal that most of the extant diversity of the genus accrued during the last ∼30 Myr. CONCLUSIONS: The recent radiation of Piper is coeval with both the Andean uplift and the emergence of Central America, which have been proposed as important drivers of diversity. This pattern could exemplify a recurrent theme among many neotropical plant lineages.

Updated cranial and mandibular description of the Late Cretaceous (Maastrichtian) baenid turtle Saxochelys gilberti based on micro-computed tomography scans and new information on the holotype-shell association.

Saxochelys gilberti is a baenid turtle from the Late Cretaceous Hell Creek Formation of the United States of America known from cranial, shell, and other postcranial material. Baenid turtles are taxonomically diverse and common fossil elements within Late Cretaceous through Eocene faunas. Detailed anatomical knowledge is critical to understanding the systematics and morphological evolution of the group. This is particularly important as baenids represent an important group of continental vertebrates that survived the mass extinction event associated with the Cretaceous/Paleogene boundary. High-resolution micro-computed tomography scanning of the holotype skull reveals additional anatomical details for the already well-known Saxochelys gilberti. This includes the revision of some anatomical statements from the original description, but also detailed knowledge on internal anatomical features of the braincase and the description of a well-preserved axis (cervical vertebra 2). Our new detailed description and previous work on the shell and postcrania make Saxochelys one of the best-described, nearly complete baenid turtles, which are often only known from either isolated shell or cranial material. A revised phylogenetic analysis confirms the position of Saxochelys gilberti as a derived baenid (Eubaeninae) more closely related to Baena arenosa than to Eubaena cephalica. Supplementary Information: The online version contains supplementary material available at 10.1186/s13358-023-00301-6.

Enameloid-bound δ15 N reveals large trophic separation among Late Cretaceous sharks in the northern Gulf of Mexico.

The nitrogen isotopic composition (15 N/14 N ratio, or δ15 N) of enameloid-bound organic matter (δ15 NEB ) in shark teeth was recently developed to investigate the biogeochemistry and trophic structures (i.e., food webs) of the ancient ocean. Using δ15 NEB , we present the first nitrogen isotopic evidence for trophic differences between shark taxa from a single fossil locality. We analyze the teeth of four taxa (Meristodonoides, Ptychodus, Scapanorhynchus, and Squalicorax) from the Late Cretaceous (83-84 Ma) Trussells Creek site in Alabama, USA, and compare the N isotopic findings with predictions from tooth morphology, the traditional method for inferring shark paleo-diets. Our δ15 NEB data indicate two distinct trophic groups, with averages separated by 6.1 ± 2.1‰. The lower group consists of Meristodonoides and Ptychodus, and the higher group consists of Scapanorhynchus and Squalicorax (i.e., lamniforms). This δ15 NEB difference indicates a 1.5 ± 0.5 trophic-level separation between the two groups, a finding that is in line with paleontological predictions of a higher trophic level for these lamniforms over Meristodonoides and Ptychodus. However, the δ15 NEB of Meristodonoides is lower than suggested by tooth morphology, although consistent with mechanical tests suggesting that higher trophic-level bony fishes were not a major component of their diet. Further, δ15 NEB indicates that the two sampled lamniform taxa fed at similar trophic levels despite their different inferred tooth functions. These two findings suggest that tooth morphology alone may not always be a sufficient indicator of dietary niche. The large trophic separation revealed by the δ15 NEB offset leaves open the possibility that higher trophic-level lamniforms, such as those measured here, preyed upon smaller, lower trophic-level sharks like Meristodonoides.

Osteology and reassessment of Dineobellator notohesperus, a southern eudromaeosaur (Theropoda: Dromaeosauridae: Eudromaeosauria) from the latest Cretaceous of New Mexico.

Dromaeosaurids (Theropoda: Dromaeosauridae), a group of dynamic, swift predators, have a sparse fossil record, particularly at the end of the Cretaceous Period. The recently described Dineobellator notohesperus, consisting of a partial skeleton from the Upper Cretaceous (Maastrichtian) of New Mexico, is the only diagnostic dromaeosaurid to be recovered from the latest Cretaceous of the southwestern United States. Reinterpreted and newly described material include several caudal vertebrae, portions of the right radius and pubis, and an additional ungual, tentatively inferred to be from manual digit III. Unique features, particularly those of the humerus, unguals, and caudal vertebrae, distinguish D. notohesperus from other known dromaeosaurids. This material indicates different physical attributes among dromaeosaurids, such as use of the forearms, strength in the hands and feet, and mobility of the tail. Several bones in the holotype exhibit abnormal growth and are inferred to be pathologic features resulting from an injury or disease. Similar lengths of the humerus imply Dineobellator and Deinonychus were of similar size, at least regarding length and/or height, although the more gracile nature of the humerus implies Dineobellator was a more lightly built predator. A new phylogenetic analysis recovers D. notohesperus as a dromaeosaurid outside other previously known and named clades. Theropod composition of the Naashoibito Member theropod fauna is like those found in the more northern Late Cretaceous North American ecosystems. Differences in tooth morphologies among recovered theropod teeth from the Naashoibito Member also implies D. notohesperus was not the only dromaeosaurid present in its environment.

A new chelid turtle, Prochelidella palomoi sp. nov., from campanian Anacleto Formation, Neuquén Basin, North-Western Patagonia, Argentina.

The new turtle remains were found in the Anacleto Formation (Campanian) exposed in the Aguada Grande site. This area is located 10 km from the south of the city of Rincón de Los Sauces, in the north of the province of Neuquén, Patagonia, Argentina. The specimen (MAU-Pv-AG-452) consists of a partially preserved skull, carapace remains, an almost complete plastron, and a left ilium. The skull shows some features (a developed retropterygoid foramen, and a big muscle attachment area over the basisphenoid) that allow us to refer this specimen to the genus Prochelidella. The visceral view of the first costal bone exhibits deeper axillary buttresses that extend 2/3 of the costal width. This condition is also observed in the costal bone of Prochelidella buitreraensis from the Candeleros Formation (Cenomanian). The scute pattern observed in the anterior lobe of the plastron shows a large gular that extends along the entoplastra length, and small extragulars over the epiplastra. In contrast with the scute scheme observed in Prochelidella cerrobarcinae and Prochelidella portezuelae where the gular does not extend beyond the first 1/3 of the entoplastron. The phylogenetic analyses performed recovered this new species as a member of Prochelidella. The material recovered from the Anacleto Formation represents the first undoubtedly finding of Prochelidella in the late Cretaceous (Campanian) and the second skull recognized for the genus.

A new pan-kinosternid, Leiochelys tokaryki, gen. et sp. nov., from the late Maastrichtian Frenchman formation, Saskatchewan Canada.

Previously, only a single member of Pan-Kinosternidae (Yelmochelys rosarioae) had been documented from the Late Cretaceous epoch. In this report we describe a new pan-kinosternid genus and species, herein named Leiochelys tokaryki, based on a nearly complete, articulated skeleton from the Late Cretaceous (Maastrichtian) Frenchman Formation of Saskatchewan, Canada. L. tokaryki differs most notably from the previously described Y. rosarioae in having triangular plastral lobes, and in that the suture between the hyo- and hypoplastron is in line with the suture between the fifth and sixth peripherals. A maximum parsimony analysis suggests that L. tokaryki is intermediate between Y. rosarioae and crown-group kinosternids. Kinosternid features present in L. tokaryki include the presence of a reduced plastral bridge that extends from the posterior tip of peripheral 4 to the anterior tip of peripheral 7, two inframarginals that contact one another, a smooth triturating surface, and participation of the palatine in the triturating surface. An unexpected feature of the skull is the presence of a large stapedial canal, suggesting that the decrease in size of the stapedial canal and increase in the canalis caroticus cerebralis occurred independently in Dermatemydidae and Kinosternidae. The character-states of the skull and skeleton of L. tokaryki indicate that morphological changes occurring during the diversification of Kinosternoidea were more complex than expected based on data from derived members of the group.

Description of the first definitive Corythosaurus (Dinosauria, Hadrosauridae) specimens from the Judith River Formation in Montana, USA and their paleobiogeographical significance.

Despite the long history of research in the late Campanian Judith River Formation in northern Montana, most of the vertebrate fossils are represented by fragmentary remains, making precise taxonomic identifications difficult. Contrary to this, the partially contemporaneous Dinosaur Park Formation, Alberta, Canada is known for its tremendous fossil preservation, permitting rigorous studies of dinosaur diversity, evolution, and biostratigraphy. Hadrosaurids comprise one of the most abundant dinosaur clades in the Dinosaur Park Formation, but taxonomic affinities of hadrosaurid specimens remain poorly understood in the Judith River Formation. Corythosaurus is the most common hadrosaurid in the Dinosaur Park Formation and, to date, has been restricted to this formation. This study reports the first definitive Corythosaurus specimens from the Judith River Formation, which were discovered on two private ranches in northern Montana. The attribution of the most complete skeleton to Corythosaurus is indicated by: wide crest-snout angle, presence of premaxilla-nasal fontanelle, dorsoventrally expanded nasal, laterally exposed ophthalmic canal of the laterosphenoid, and tall neural spines. A second specimen preserves a large ilium that can be positively identified as Corythosaurus based on its associated skull, which is now in private hands. The specimens were recovered from the Coal Ridge Member of the Judith River Formation, which is approximately time equivalent to the Dinosaur Park Formation. Thus, the discovery of Corythosaurus in the Judith River Formation extends the biogeographic range of this genus and establishes a framework for future interformational biostratigraphic studies of Late Cretaceous dinosaur faunas in North America.

Osteology of the axial skeleton of Aucasaurus garridoi: phylogenetic and paleobiological inferences.

Aucasaurus garridoi is an abelisaurid theropod from the Anacleto Formation (lower Campanian, Upper Cretaceous) of Patagonia, Argentina. The holotype of Aucasaurus garridoi includes cranial material, axial elements, and almost complete fore- and hind limbs. Here we present a detailed description of the axial skeleton of this taxon, along with some paleobiological and phylogenetic inferences. The presacral elements are somewhat fragmentary, although these show features shared with other abelisaurids. The caudal series, to date the most complete among brachyrostran abelisaurids, shows several autapomorphic features including the presence of pneumatic recesses on the dorsal surface of the anterior caudal neural arches, a tubercle lateral to the prezygapophysis of mid caudal vertebrae, a marked protuberance on the lateral rim of the transverse process of the caudal vertebrae, and the presence of a small ligamentous scar near the anterior edge of the dorsal surface in the anteriormost caudal transverse process. The detailed study of the axial skeleton of Aucasaurus garridoi has also allowed us to identify characters that could be useful for future studies attempting to resolve the internal phylogenetic relationships of Abelisauridae. Computed tomography scans of some caudal vertebrae show pneumatic traits in neural arches and centra, and thus the first reported case for an abelisaurid taxon. Moreover, some osteological correlates of soft tissues present in Aucasaurus and other abelisaurids, especially derived brachyrostrans, underscore a previously proposed increase in axial rigidity within Abelisauridae.

100 million years of turtle paleoniche dynamics enable the prediction of latitudinal range shifts in a warming world.

Past responses to environmental change provide vital baseline data for estimating the potential resilience of extant taxa to future change. Here, we investigate the latitudinal range contraction that terrestrial and freshwater turtles (Testudinata) experienced from the Late Cretaceous to the Paleogene (100.5-23.03 mya) in response to major climatic changes. We apply ecological niche modeling (ENM) to reconstruct turtle niches, using ancient and modern distribution data, paleogeographic reconstructions, and the HadCM3L climate model to quantify their range shifts in the Cretaceous and late Eocene. We then use the insights provided by these models to infer their probable ecological responses to future climate scenarios at different representative concentration pathways (RCPs 4.5 and 8.5 for 2100), which project globally increased temperatures and spreading arid biomes at lower to mid-latitudes. We show that turtle ranges are predicted to expand poleward in the Northern Hemisphere, with decreased habitat suitability at lower latitudes, inverting a trend of latitudinal range contraction that has been prevalent since the Eocene. Trionychids and freshwater turtles can more easily track their niches than Testudinidae and other terrestrial groups. However, habitat destruction and fragmentation at higher latitudes will probably reduce the capability of turtles and tortoises to cope with future climate changes.

Coryphoid palms from the K-Pg boundary of central India and their biogeographical implications: Evidence from megafossil remains.

Ten palm leaf impressions are documented from the latest Maastrichtian (late Cretaceous) to early Danian (earliest Paleocene) sediments (K-Pg, c. 66-64 Ma) of the Mandla Lobe of the Deccan Inter-trappean Beds, Madhya Pradesh, central India. The palmate leaf shape along with a definite well-preserved costa support their placement in the subfamily Coryphoideae of the family Arecaceae. We place all recovered palm leaf specimens in the fossil genus Sabalites, report seven species of coryphoid palms and describe two new species namely, Sabalities umariaensis sp. nov. and Sabalites ghughuaensis sp. nov. The fossils indicate that coryphoid palms were highly diverse in central India by the latest Cretaceous. These and earlier reported coryphoid palm fossils from the same locality indicate that they experienced a warm and humid tropical environment during the time of deposition. These discoveries confirm the presence of a diversity of Coryphoideae in Gondwana prior to the India-Eurasia collision and provide information about coryphoid biogeographical history over geological time. Based on megafossil remains, we trace coryphoid palm migration pathways from India to mainland Southeast (SE) Asia and other parts of Asia after the docking of the Indian subcontinent with Eurasia early in the Paleogene.

A New Species of the Pythonomorph Carentonosaurus from the Cenomanian of Algora (Guadalajara, Central Spain).

The Cenomanian (lowermost Upper Cretaceous) faunal assemblages are of high interest in understanding the turnovers that took place between the Early and the Late Cretaceous, resulting in significant differences. In this context, the analysis of the association of reptiles found in the Algora fossil site (Guadalajara Province, Central Spain) is of great interest since it represents the first European Cenomanian site with a high concentration of macrovertebrate remains. A new pythonomorph 'lizard' from Algora, Carentonosaurus algorensis sp. nov., is described here. It is the second representative of this European genus. Its microanatomical study reveals that an extreme pachyosteosclerosis affected at least its dorsal vertebrae, suggesting adaptations for slow-swimming habits in shallow-water environments. Consequently, this new taxon is interpreted as a slow swimmer, hovering near the bottom of near-shore marine environments of the Late Cretaceous European Archipelago and, more specifically, along the shores of the larger Iberian Island for that period. This is in concordance with the high diversification of 'pachyostotic' pythonomorphs recorded during the Cenomanian, allowing the subsequent adaptation of this lineage to open marine environments.

Calcareous dinoflagellate blooms during the Late Cretaceous 'greenhouse' world-a case study from western Ukraine.

The Late Cretaceous was a unique period in the history of the Earth characterized by elevated sea levels, reduced land area, and significantly high concentrations of atmospheric CO2 resulting in increased temperatures across the globe-a 'Greenhouse World'. During this period, calcareous dinoflagellate cysts (c-dinocysts) flourished and became a ubiquitous constituent of calcifying plankton around the world. An acme in calcareous dinocysts during the Albian to the Turonian coincided with the highest recorded seawater surface temperatures and was possibly linked to conditions that favored calcification and a highly oligotrophic system in European shelf seas. This study examines the potential applicability of c-dinocysts as a proxy for paleoenvironmental conditions based on their assemblage changes plotted against foraminiferal occurrences and microfacies analysis. The material was extracted from the upper Turonian chalk of the Dubivtsi region in western Ukraine. An inverse correlation was observed between species diversity and the number of c-dinocyst specimens. Nutrient availability gradients apparently determined important changes in the calcareous dinocysts distribution. These trophic changes were likely caused by the interplay of eustatic sea-level fluctuations and Subhercynian tectonic activity leading to changeable nutrient inputs from the nearby land.