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The upper Campanian–lower Maastrichtian site of Poyos (Guadalajara, Spain) has yielded an abundant fossil record of reptiles, including several cranial and postcranial elements of theropod dinosaurs. Here we present a study, based on statistical and cladistic analyses as well as on detailed description, of a sample of isolated theropod teeth collected from this site. The sample comprises twenty relatively complete and well-preserved tooth crowns, belonging to mesial and lateral teeth. The combination of morphological and morphometric features is consistent with the identification of these specimens as belonging to a medium-sized abelisaurid theropod. These specimens resemble the teeth associated with the holotype of Arcovenator escotae (upper Campanian of France) and some isolated teeth assigned to Arcovenator sp. from different temporal correlative localities of Spain. These similarities suggest the presence of an abelisaurid closely related to Arcovenator in Poyos, expanding the fossil record of this lineage of abelisaurids to the upper Campanian-lower Maastrichtian in the Iberian Peninsula. The currently known fossil record shows that abelisaurids were one of the most abundant groups of non-coelurosaurian theropods in the Upper Cretaceous of Europe and possibly the only medium-to large-size carnivorous dinosaurs in the Ibero-Armorican realm from the upper Cenomanian to the upper Maastrichtian. The increasing abundance of abelisaurids during the Late Cretaceous and the vanishing of other large theropods that dominated the Early Cretaceous faunas of Ibero-Armorica seem to be part of a faunistic turnover that can be related to a climate change to semi-arid conditions. [Display omitted] • Morphometric and cladistic analyses are performed on isolated abelisaurid teeth. • Contribution for a better knowledge on the Late Cretaceous theropods of Iberia. • Late Cretaceous abelisaurids from Ibero-Armorica are closely related to each other. • Abelisaurids dominated different Europeans landmasses during the Late Cretaceous. • Abundance of abelisaurids in the Ibero-Armorica is related to semi-arid conditions. [ABSTRACT FROM AUTHOR]

This study focuses on the analysis of the first dinosaur tracks discovered in the Mulichinco Formation, Neuquén Basin, Argentina. The deposition of this unit occurred during the early Valanginian, Early Cretaceous, making it the oldest known record of dinosaur tracks for that period in the basin. The aim of this study is to provide a paleoenvironmental interpretation of the area and potential trackmakers based on the morphology of the tracks and the facies analysis of the depositional system. The depositional system evolved from a moderately sinuous fluvial system in the lower interval to a braid distal plain system with the development of bodies of water without marine influence, culminating in an estuary with marine influence in the upper interval. The paleoenvironmental conditions during the deposition of the unit were favourable for the presence and interaction of diversity large continental vertebrates. The track-bearing surfaces in the lower interval suggest that the organisms exploited the temporary gaps created between channel migration and floodplain formation as areas for transit or water sources. In the middle interval, the abundant presence of traces fossils of invertebrates and symmetrical ripples suggest a more stable depositional system where fluctuations in the water column were common. The co-occurrence of various track-makers and remains of large vertebrates described in the Mulichinco Formation is unusual among track sites at the basin. Overall, this study provides new insights into the Early Cretaceous paleoenvironmental conditions of the Neuquén Basin and the diversity of large vertebrates that inhabited the region during this time. • The first analysis of dinosaur footprint-bearing surfaces from the Valanginian of the Neuquén Basin is presented. • The great abundance of footprint-bearing levels suggests high diversity of continental vertebrates. • The dinosaur footprints on different surfaces adjust interpretation of depositional dynamics. [ABSTRACT FROM AUTHOR]

Abstract A new peirosaurid crocodyliform from the Upper Cretaceous (Santonian) of South America, Barrosasuchus neuquenianus gen. et sp. nov. is here described. Barrosasuchus is distinguished by a combination of features that include: presence of a foramen at the mid-point of the dorsal surface of the mandibular symphysis; quadratojugal dorsally broad, extensively contacting the postorbital articulation; absence of ventral exposure of splenials along mandibular rami, posterior to the symphysis; mid to posterior teeth with roots and crowns highly compressed laterally; presence of longitudinal depressions on palatal surface of maxillae; and anterior dentary alveoli strongly procumbent. The holotype specimen of Barrosasuchus neuquenianus , MCF-PVPH-413 is represented by an almost complete skull and most of the articulated postcranial skeleton. Thus, Barrosasuchus is currently the most complete peirosaurid taxon known from Patagonia, and represents a key element for future reviews of the phylogeny of the group. Peirosauridae represents a successful clade in Gondwana, and particularly in Patagonia, with at least six distinct genera currently recorded. Graphical abstract Image 1 Highlights • Barrosasuchus neuquenianus is a new South American Upper Cretaceous peirosaurid crocodile. • Barrosasuchus is the most complete peirosaurid crocodile recorded in Patagonia at present. • Barrosasuchus is a member of the major Upper Cretaceous diversity of peirosaurids. [ABSTRACT FROM AUTHOR]

Abstract A new dicraeosaurid sauropod, Pilmatueia faundezi gen. et sp. nov. from the Mulichinco Formation (Valanginian, Lower Cretaceous, Neuquén Basin, Argentina) is based on isolated skeletal remains collected from a single stratigraphic level, relatively close to each other, with unquestionable dicraeosaurid features in the axial elements. Pilmatueia faundezi is diagnosed by a unique combination of several features that include cervico-dorsal vertebrae with dorsoventrally oriented ridges on the anterior surfaces of the anterior centrodiapophyseal laminae, and posterior dorsal vertebrae with deep fossae at the bases of the bifid neural spines separated by a thick, low, sagittal lamina. Pilmatueia is recovered as the sister taxon of the late Early Cretaceous Amargasaurus cazaui. Pilmatueia increases our knowledge about the record of sauropods during the Valanginian, a period in which dinosaur diversity worldwide is poorly known. Highlights • A new taxon of the intriguing sauropod family Dicraeosauridae, Pilmatueia faundezi is described. • Pilmatueia is the first recognized Valangininan dicraeosaur sauropod taxon. • Pilmatueia represents the earliest recorded Cretaceous dicraeosaurid sauropods. • Pilmatueia was part of a South American Upper Jurassic-Lower Cretaceous dicraeosaurid radiation. [ABSTRACT FROM AUTHOR]

Elasmosaurids are a monophyletic group of cosmopolitan plesiosaurs with extremely long necks. Although abundant elasmosaurid material has been collected from the Upper Cretaceous of Antarctica, skull material is extremely rare. Here, new elasmosaurid cranial material from the lower Maastrichtian levels of the Cape Lamb Member (Snow Hill Island Formation) on Vega Island, Antarctica is described. The studied specimen (MLP 15-I-7-6) is a non-aristonectine elasmosaurid but shows a palate morphology characterized by the absence of a posterior interpterygoid symphysis and a posterior plate-like extension of the pterygoids, features previously associated with the aristonectine palatal structure. The specimen MLP 15-I-7-6 thus provides an indication that these palatal features are also present in non-aristonectine Weddellian elasmosaurids, and makes available additional evidence of the close phylogenetical relationship between the aristonectines and some Weddellian non-aristonectine elasmosaurids. [ABSTRACT FROM AUTHOR]

The first Podocarpaceae wood record is described from the Mulichinco Formation (Valanginian, Lower Cretaceous), Neuquén Basin, Argentina. The specimen was directly associated with a middle caudal vertebra of a diplodocid sauropod dinosaur. A new species – Podocarpoxylon prumnopityoides – is proposed based on features that include the presence of abietinean wood type (tracheid radial pitting), plus podocarpoid (cupressoid type) and some dacrydioid (taxodioid type) cross-field pits, diffuse axial parenchyma and low rays. This combination of anatomical characters is comparable to both Prumnopitys and Podocarpus , whereas the type of pits in the cross-fields resembles some members of the extant Prumnopitys . This is the first unequivocal record of the Family Podocarpaceae in the Valanginian of South America and confirms the hypothesis that the divergence between the “ Podocarpoid-Dacrydioid ” and “ Prumnopityoid ” clades occurred earlier than the Early Cretaceous. [ABSTRACT FROM AUTHOR]

Abstract: A new ornithopod dinosaur from Antarctica, Trinisaura santamartaensis n. gen. et n. sp. is diagnosed by a unique combination of characters that includes a scapula with a spike-like acromial process with a strong and sharp lateral crest and longer than other ornithopods, a humerus with a rudimentary deltopectoral crest represented as a thickening on the anterolateral margin of the humerus, and shaft strongly bowed laterally, and an ischium gently curved along its entire length. The holotype specimen comprises vertebral and appendicular elements. The presence of axially elongate distal caudal vertebrae, pubis with long prepubic and postpubic processes, as well as a femur with a distinct anterior trochanter, pendant 4th trochanter and shallow anterior intercondylar groove constitute a combination of characters present in the Late Cretaceous Patagonian Gasparinisaura, Anabisetia and Talenkahuen. The materials were found on the surface enclosed in a hard sandstone concretion collected near the Santa Marta Cove, James Ross Island, from the lower levels of the Snow Hill Island Formation (Campanian). This is the first ornithopod taxon identified from this unit, and the second ornithischian dinosaur, after the ankylosaur Antarctopelta oliveroi. However, other ornithopod reports from nearby localities of James Ross and Vega islands in outcrops of the overlying Lopez de Bertodano Formation suggest that this clade was widely represented in the Campanian and Maastrichtian of the James Ross Basin, Antarctic continent. [Copyright &y& Elsevier]

Abstract: An incomplete braincase from the Upper Cretaceous Portezuelo Formation of northwestern Patagonia (Neuquén Province, Argentina) is described. The specimen preserves the lateral walls formed by the laterosphenoid, probably part of the orbitosphenoid, prootic, the exoccipital-opisthotic complex and fragments of the frontal, parietal and basisphenoid. Both inner ears are preserved allowing the production of latex endocasts. The external and internal morphology of the laterosphenoid and the prootic, the absence of a floccular recess, and the morphology and position of the cranial nerves V–VII, the oval window and the metotic foramen indicate that the new braincase belongs to a sauropod dinosaur, probably a titanosaur. The morphology of the inner ear is also reminiscent of that of Sauropoda, which is characterized by the presence of a simple, short and conical lagena, a posterior semicircular canal that is larger than the lateral semicircular canal, an anterior semicircular canal that is larger than the other two, and an angle between the vertical semicircular canals (anterior and posterior) of approximately 90°. [Copyright &y& Elsevier]

Abstract: Twenty three different sites in two areas of Río Negro Province (Salitral Ojo de Agua and Salitral de Santa Rosa-Salinas de Trapalcó), preserving eggs and eggshells from the Allen Formation (Upper Cretaceous) were studied, and five egg levels were identified. Three different types of eggshell were recognized. Eggs possessing thick eggshells of Type 1 are abundant in both areas, sometimes associated with eggs having thinner shells. Eggs of eggshell Type 1 are included in the oofamily Faveoloolithidae of the parataxonomic classification. Eggshell Type 2 is subdivided into two groups (Types 2A and 2B), mostly based on the mean thickness of the eggshells and other parameters. Eggs of eggshell Type 2 are assigned to the oofamily Megaloolithidae of the parataxonomic classification, and ascribed to titanosaurs. A third type of eggshell (Type 3) is only recorded at one of the localities (Salitral Ojo de Agua, egg level 2). This type is intimately associated with theropod bones, and its microstructure agrees with an assignation to the Theropoda. It is assigned to the oofamily Elongatoolithidae. [Copyright &y& Elsevier]

The bone histology of the Antarctic ornithopods Trinisaura santamartaensis and Morrosaurus antarcticus from the Upper Cretaceous (Campanian-Maastrichtian) is here studied. With the purpose to obtain information regarding their growth pattern, we analyse the bone histology of appendicular elements from the holotype specimens of both species. The cortical bone of the studied elements is constituted by fibro-lamellar tissue, with vascular canals mostly showing in a longitudinal and reticular arrangement, suggesting an accelerated growth. The cortical bone tissue is interrupted by lines of arrested growth (LAGs) and annuli. The study reveals that both the holotypes of Trinisaura and Morrosaurus were sexually mature subadults at the time of death (i.e. they died before reach somatic maturity). The growth pattern of these Antarctic ornithopods is similar to that reported for the related taxon Gasparinisaura , which lived in lower latitudes, as well as for the Australian ornithopods, taxa that inhabited polar latitudes during the Early Cretaceous. This contrasts with the pattern reported for more derived ornithopods (i.e. hadrosaurids) and ceratopsians from the Northern Hemisphere, whose growth dynamics vary in different latitudes. In this regard, Gondwanan ornithopods would present a preadaptation for endure in environments with great temperature changes along the year. [ABSTRACT FROM AUTHOR]

A new carcharodontosaurid taxon, Lajasvenator ascheriae gen. et sp. nov. is described. The new taxon is based on two specimens: MLL-PV-Pv-005 is a partial skeleton represented by a portion of the snout, partially articulated presacral vertebral series, four articulated caudal vertebra and fragments of the pelvic girdle; MLL-PV-Pv-007 includes the anterior ends of both dentaries, a quadratojugal, and fragments of cervical vertebrae, ribs and a possible tarsal bone. Lajasvenator is unique in having anterior projections on cervical prezygapophyses, lip-like crests on the lateral surfaces of cervical postzygapophyses, and bilobed anterior processes on cervical ribs. Lajasvenator material was collected from the terrestrial sandstones of the Valanginian Mulichinco Formation. It is the oldest carcharodontosaurid record from South America. This medium sized theropod was found associated with remains of the dicraeosaurid sauropod Pilmatueia , indeterminate diplodocid remains, and a yet unidentified iguanodontian-like ornithopod. Image 1 • A new genus and species of carcharodontosaurid theropod (Lajasvenator ascheriae) is described. • Lajasvenator is the oldest Cretaceous carcharodontosaurid record. • Lajasvenator represents the first Lower Cretaceous, South American carcharodontosaurid. [ABSTRACT FROM AUTHOR]

A new ceratosaurian theropod dinosaur, Huinculsaurus montesi gen. et sp. nov., is described here. This taxon is based on the last three dorsal vertebrae and the first and second sacral vertebrae found in association at Aguada Grande, Neuquén Province, Argentina. Although fragmentary, Huinculsaurus shows a unique mix of features which differentiates it from all other theropods, including the sympatric abelisaurid Ilokelesia , and is diagnosed by prezygapophyseal articular facets twice longer than wide, anterior centroparapophyseal lamina strongly developed as an extensive lateral lamina in the posterior dorsal vertebrae, pneumatic foramina located ventrally to the postzygodiapophyseal lamina in the posterior dorsal vertebrae, posteriorly tapering postzygapophysis pointed posteriorly, and an accessory lamina bisecting the parapophyseal centrodiapophyseal fossa in the posterior dorsal neural arches. Phylogenetic analyses recovered Huinculsaurus as most closely related to the Late Jurassic Elaphrosaurus than to other Cretaceous abelisauroids, suggesting the persistence of the elaphrosaurine lineage in South America up to the early Late Cretaceous. • A new abelisauroid theropod Huinculsaurus is described. • Huinculsaurus fills the Barremian-Santonian gap of noasaurid record. • Elaphrosaurine lineage survived in South America up to the early Upper Cretaceous. [ABSTRACT FROM AUTHOR]

A detailed histological study of Antarctopelta oliveroi , from the Upper Cretaceous of Antarctica, is performed in order to increase our knowledge of the ankylosaur bone histology and its taxonomical and paleobiological implications. The main goals of this contribution are: to infer the ontogenetic stage of the holotype of Antarctopelta oliveroi (MLP 86-X-28-1); to evaluate the degree of interelemental histological variation; to compare its histology with that of other ankylosaurs; to provide information about the phylogenetic affinities of Antarctopelta regarding dermal armor histology; and to evaluate the influence of a high latitude, strongly seasonal ecosystem on the growth of Antarctopelta. The sample includes several postcranial elements from the holotype (e.g. osteoderms, appendicular bones, dorsal ribs, ossified tendons). Bone histology reveals that the specimen was sexually mature at its time of death. Although a distinct Outer Circumferential Layer is not evident in all the sampled elements, the bone microstructure suggests quite slow appositional growth (i.e. most of the growth had already occurred) at the time of death. Primary cortical bone of the sampled elements, mostly composed of fibrolamellar bone tissue interrupted by growth marks, reveals a cyclical growth strategy as reported for other ankylosaurs and non-avian dinosaurs. The bone histology of Antarctopelta indicates that, as with other Southern Hemisphere polar dinosaurs, there are no apparent differences in growth strategy compared with its low latitude relatives. Therefore, no evident physiological modifications appears to be linked with the distribution of ankylosaurs and other non-avian dinosaurs at higher latitudes (>60° S). [ABSTRACT FROM AUTHOR]