A new Late Cretaceous crocodyliform from the western margin of Gondwana (La Rioja Province,Argentina)

The Cretaceous witnessed the greatest diversity of Gondwanan notosuchian crocodyliforms, which displayed high levels of diversity and a notable array of specialized forms that developed in different ecological niches. Among this diversity, the advanced notosuchians are a clade of mid body sized forms which displays a remarkable abundance but is restricted to two lithological units from the Late Cretaceous of South America, the Adamantina Formation in southeastern Brazil and the Bajo de la Carpa Formation in Patagonia (Argentina). The only exceptions known so far were the Late Cretaceous Labidiosuchus from the Marilia Formation in Brazil and Yacarerani from the Cajones Formation in Bolivia. Herein we report a new Cretaceous crocodyliform, Llanosuchus tamaensis gen. nov. et sp. nov., found in the Los Llanos Formation (Campanian?) in northwestern Argentina (La Rioja Province). The small specimen includes well preserved fragments of the cranium and mandible with an estimated skull size of about 9 cm lengths. This crocodyliform shares several derived characters with Notosuchus terrestris from the Bajo de la Carpa Formation (Patagonia) and it was found in a weakly developed sandy paleosol profile formed in wet local conditions but in a region characterized by semi-arid climate and active eolian sedimentation. The presence of a new advanced notosuchian in the Cretaceous of western Gondwana, and its intermediate geographical region between the known South American species (Brazil, Argentina and Bolivia), has interesting implications, and adds another record of an advanced notosuchian in deposits with inferred warm climates and semi-arid paleoenvironments. Finally, Llanosuchus tamaensis supports a Late Cretaceous age for Los Llanos Formation with important geological implications for La Rioja Province.     

The first crocodyliform from the Chubut Group (Chubut Province, Argentina) and its phylogenetic position within basal Mesoeucrocodylia

A new crocodyliform specimen is presented here found in the Cerro Castaño Member of the Cerro Barcino Formation (Chubut Group). The material consists of cranial and postcranial remains that represent a new taxon that has strong affinities with Peirosauridae, but also shares derived features present in Araripesuchus. The phylogenetic relationships of this new taxon were tested through a cladistic analysis depicting it as a member of the Peirosauridae. The inclusion of Barcinosuchus within this clade of basal mesoeucrocodylians is supported by the presence of hypapophyses up to the third or fourth dorsal vertebrae, anterolateral facing edge on postorbital, quadrate dorsal surface divided in two planes by a ridge; mandibular symphysis tapering anterirorly in ventral view, lateral surface of dentary convex anterior to mandibular fenestra, distal body of quadrate well developed, anteroposteriorly thin and lateromedially broad. The new specimen broadens the temporal and geographical distribution of Peirosauridae during the Cretaceous of Gondwana, representing the southern-most and the most ancient record of the group in Patagonia. The new material also provides insights on the postcranial anatomy of peirosaurids, a group that has been so far studied almost exclusively from cranial material.     

Review of the Late Cretaceous-early Paleogene crocodylomorphs of Europe: Extinction patterns across the K-PG boundary

Although the European dinosaur succession during the latest Cretaceous and its relationship with the Cretaceous-Paleogene (K-Pg) mass extinction has been the focus of recent work, other continental vertebrates, such as crocodylomorphs, have received less attention. The European continental record of crocodylomorphs in general, and of eusuchians in particular, is relatively dense through the Maastrichtian until the K-Pg boundary. Traditionally it has been argued that continental crocodylomorphs were minimally impacted by the K-Pg extinction, but they were substantially affected in Europe with the disappearance of endemic eusuchians such as Hylaeochampsidae, Allodaposuchus and their close relatives, and non-eusuchians such as Doratodon or Theriosuchus. Despite extensive sampling in Danian continental deposits, only scarce fragmentary crocodylomorph remains have been cited. It is not until the late Paleocene and Eocene that a recovery in continental crocodylomorphs is observed. The presence of taxa such as planocraniids, the alligatoroids Diplocynodon and Hassiacosuchus, and stem crocodyloids during this period provide the first reliable continental records of Crocodylia in Europe and is best explained by post-extinction immigration from Asia or North America. By contrast, marine forms such as Thoracosaurus are found on both sides of the K-Pg boundary in Europe. The adaptation of these marine animals to different environments, from shallow seas to more transitional or fluvial environments, could be the key to their success and survival across the K-Pg boundary, as seen in other marine crocodylomorph clades such as Dyrosauridae.     

A gigantic caenagnathid oviraptorosaurian (Dinosauria: Theropoda) from the Upper Cretaceous of the Gobi Desert,Mongolia

A large, isolated symphyseal region of fused dentaries of an oviraptorosaurian was found in the Upper Cretaceous Bayn Shire Formation at Tsagaan Teg in the Mongolian Gobi Desert. A phylogenetic analysis places this specimen within Caenagnathidae. This specimen is comparable in size and morphology to the gigantic caenagnathid Gigantoraptor erlianensis from the Iren Dabasu Formation in China and is likely closely related to it. The occurrence of the specimen with possible affinities to G. erlianensis in the Bayn Shire Formation is consistent with the hypothesized correlation between the Bayn Shire and Iren Dabasu formations based on the co-occurrences of vertebrate fossils, especially turtles.     

Osteoderms of Montealtosuchus arrudacamposi (Crocodyliformes,Peirosauridae) from the Turonian-Santonian (Upper Cretaceous) of Bauru Basin,Brazil

The skin of Crocodyliformes is characterized by osteoderms of various sizes and shapes. It plays roles in defence, thermoregulation, sexual attraction, calcium reserves, and locomotion. This study presents the morphometric characteristics of osteoderms preserved in the nuchal, dorsal, ventral and appendicular shield of Montealtosuchus arrudacamposi, a Peirosauridae crocodyliform from the Turonian-Santonian (Upper Cretaceous) of Adamantina Formation, Bauru Basin, Brazil. The results of the analysis show that its dermal shield had protective and thermoregulatory functions and a well-defined mechanical function allowing terrestrial locomotion and enabling good agility and capacity for movement.     

Gondwanasuchus scabrosus gen. et sp. nov., a new terrestrial predatory crocodyliform (Mesoeucrocodylia: Baurusuchidae) from the Late Cretaceous Bauru Basin of Brazil

Baurusuchids are among the most common and diverse crocodyliform fossils from the Late Cretaceous Bauru Basin of Brazil. This inland continental basin was the habitat of a rich crocodyliform fauna containing five mesoeucrocodylian families, of which the Baurusuchidae represents highly specialized predatory crocodyliforms of terrestrial habits as indicated by their dental, cranial, and postcranial features. The large size they achieved, together with likely predatory adaptations, would suggest they competed and occupied theropod ecological niches in the Bauru Basin. Here we describe Gondwanasuchus scabrosus gen. et sp. nov., a medium-sized baurusuchid with a strongly laterally compressed skull, bearing unique dentition with deep apicobasal sulci and probably well-developed binocular vision. The cranial and dental features in Gondwanasuchus suggest that this active predator would have fed on small vertebrates and took the role of small theropods in terrestrial guild. Gondwanasuchus is the most distinctive baurusuchid known to date and enriches the knowledge on these important Gondwanan terrestrial predatory crocodyliforms.     

Lower Cretaceous Mesoeucrocodylians from Scandinavia (Denmark and Sweden)

The crocodyliform faunas of the lowermost Cretaceous Rabekke and Jydegård Formations on the Baltic island of Bornholm, Denmark, and the Annero Formation of Skåne, southernmost Sweden, are represented by isolated teeth, osteoderms, and vertebrae. The rich Berriasian assemblage of the Rabekke Formation includes at least three distinctive taxa: Bernissartia sp., Theriosuchus sp., and Goniopholis sp., an association that is also known from several other contemporaneous European vertebrate localities. In contrast to this fauna, the Jydegård and Annero Formations have yielded only rare mesoeucrocodylian remains, which are assigned to Theriosuchus sp. and an undetermined mesoeucrocodylian taxon, possibly Pholidosaurus. Geographically, the Scandinavian localities represent the easternmost and northernmost distribution of typical continental Jurassic-Cretaceous crocodyliform communities in Europe.     

A new Cenomanian vertebrate tracksite at Tamajón (Guadalajara,Spain): Palaeoichnology and palaeoenvironmental implications

A new Upper Cretaceous vertebrate tracksite has been discovered at Tamajón (Iberian Ranges, Guadalajara, Spain). The track level is a relatively smooth and slightly undulating sandy ferruginous crust, corresponding to an erosive surface at the base of a small meandering channel. It is incised into the underlying planar cross-bedded sandstones of coastal bars located at the middle-upper part of the Utrillas Formation (middle-upper Cenomanian). The site shows an extraordinary concentration of vertebrate tracks, among which numerous sets of two to five isolated digit impressions (“swim tracks”) and, at least, two trackways referred to crocodyliforms, and a single tridactyl footprint probably produced by a theropod dinosaur can be recognized. There are also several long traces (epichnial grooves) revealing sharp direction changes (up to 90°) which seem to be fish fin traces (Undichna unisulca), although crocodyliforms (tail marks) and/or fish invertebrates cannot be rejected as possible tracemakers. Some crocodyliform tracks reveal a thin raised rim, due to the displacement of the sediment by the pressure produced by the feet. Several impressions are moderately deformed by small sediment slides, only preserving their deepest part (claw marks). This is clearly indicative of a soft substrate with a high degree of plasticity and water content at the time of the track registration. Nevertheless, the sediment was hard enough to preserve manus and pes print morphologies and also possible crocodyliform tail and/or fish fin traces. Small rhizoliths can also be recognized and may belong to herbaceous wetland vegetation. The morphology of the palaeochannel, the sedimentary context and the track preservation seem to indicate that the tracks were impressed in a shallow channel located near the coast, under wet conditions and in different moments of time. This discovery represents the first occurrence of vertebrate ichnites in the Utrillas Formation, a stratigraphic unit where osteological and ichnological remains are relatively scarce, and it confirms that some crocodyliforms lived in near coast channels during the deposition of this unit.     

New pterosaurian remains from the Late Cretaceous (Santonian) of Hungary (Iharkút, Csehbánya Formation)

The Late Cretaceous (Santonian) continental vertebrate locality of Iharkút, western Hungary has provided numerous azhdarchid pterosaur remains including the recently described, Bakonydraco galaczi. Since the first report of these fossils, additional remains have been discovered that improve considerably our knowledge of some aspects of the anatomy of azhdarchid pterosaurs. New cranial material described here indicates an edentulous, non-crested premaxillary rostrum in Bakonydraco similar to that of Quetzalcoatlus and reveals that this rostrum was considerably thinner and more lightly built than the relatively massive, pointed mandibular symphysis. In addition, the contact surface of the upper and lower jaws of Bakonydraco at least in the symphyseal region was more similar to Tapejara wellnhoferi than to other azdarchids: the contact is irregular and the premaxilla does not fit closely the rostral part of the mandible. Among the postcranial material the atlas-axis complex possessing lateral pneumatic foramina is of great importance because it further supports the notion of interspecific variability of vertebral pneumaticity among pterosaurs.     

The first record of redfieldiiform fish (Actinopterygii) from the Upper Triassic of Korea: Implications for paleobiology and paleobiogeography of Redfieldiiformes

A new genus and species of redfieldiiform fish, Hiascoactinus boryeongensis gen. et sp. nov., is described based on a nearly complete specimen from the Upper Triassic Amisan Formation of South Korea. Hiascoactinus is distinguished from other redfieldiiforms by having a barely ornamented dermal skull surface except for the snout region, two heteromorphic suborbitals arranged vertically behind the postorbital, a pistol-shaped suprascapular, and dorsal and anal fins with divided fin membranes between rays. The morphological features of the snout region and dorsal and anal fins of Hiascoactinus provide important clues to understand its feeding and swimming behavior. All previously proposed Asian redfieldiiform fossils are inaccurately classified, and consequently, Hiascoactinus is regarded as the only valid redfieldiiform taxon in Asia. Hiascoactinus is assigned to the basal group of redfieldiiforms primarily based on the presence of an antopercle. The basal phylogenetic position of Hiascoactinus indicates that basal redfieldiiforms dispersed from the southern Gondwanaland to the easternmost Laurasia through the terrestrial water system, and these two landmasses were connected during the Late Triassic.     

Taphonomy of a Baurusuchus (Crocodyliformes,Baurusuchidae) from the Adamantina Formation (Upper Cretaceous,Bauru Basin), Brazil: Implications for preservational modes,time resolution and paleoecology

Upper Cretaceous vertebrate accumulations from the Adamantina Formation are known due to their high taxonomic diversity. On the other hand, taphonomic analyses still are rare, limiting the understanding of processes related to the biostratinomic and fossildiagenetic histories of this lithostratigraphic unit. In 2005, fossils were collected from an outcrop located at Jales municipality, state of São Paulo, southeastern Brazil. From this outcrop, a well-preserved Baurusuchus was recovered, which displays a peculiar set of taphonomic signatures. This paper identifies and interprets taphonomic features of a specimen of Baurusuchus (Crocodyliformes, Baurusuchidae; UFRJ DG 418-R) from the Adamantina Formation (Upper Cretaceous of the Bauru Basin), in Jales municipality, state of São Paulo. Brief taphonomic comparisons with other specimens previously studied (crocodiles and dinosaurs) and a lithofaciological analysis of the outcrop were undertaken in order to enhance the knowledge of the stratigraphy and paleoenvironment and improve the time resolution for the Adamantina Formation in the region of Jales. Furthermore, paleoecological data were interpreted based on the taphonomic analysis.The fossil is composed of an articulated segment of vertebral column, ribs, part of the pelvic girdle and gastralia. There is no hydraulic equivalence between both the specimen of Baurusuchus and the size of quartz grain predominant in the fossiliferous layer, suggesting death in situ or short transport as a “water carcass”. Teeth marks identified on the pubes were assigned to a small/juvenile baurusuchid crocodyliform or a theropod dinosaur. The repositioning of some elements (ribs and dorsal osteoderms) is suggestive of mummification. Desiccation marks were observed and attributed to the stage 1 of weathering. These features suggest subaerial exposure of the carcass prior to burial, however, probably after the mummification. On the other hand, the subaerial exposure was short, because the individual was not fully disarticulated. Furthermore, the degrees of articulation and preservation of the specimen nullify the hypothesis of reworking.Lithofaciological and taphonomic analyses suggest a well-drained floodplain as the burial environment and an arid or semi-arid climate in the region of Jales outcrop. In addition, the taphonomic signatures seem to indicate a time resolution about 10⁰–10⁴ years for the layer where the crocodyliforms were collected, but it seems to have, within this time limit, temporal-mixing among terrestrial crocodiles and dinosaurs collected from the same layer, suggesting time-averaging in this outcrop.     

New Spanish Late Cretaceous eusuchian reveals the synchronic and sympatric presence of two allodaposuchids

The recently described clade Allodaposuchidae includes European eusuchian crocodyliforms restricted to the Late Cretaceous (Campanian and Maastrichtian). A new allodaposuchid crocodyliform is here described based on two specimens from the upper Campanian–lower Maastrichtian fossil site of Lo Hueco (Cuenca, Spain). This new taxon, Agaresuchus fontisensis gen. et sp. nov., is described by two complete skulls and a lower jaw associated with one of them. This new species can be distinguished unambiguously from Lohuecosuchus megadontos, the other allodaposuchid known from the same fossil site. The presence of two allodaposuchid crocodyliforms in Lo Hueco allows the recognition of the synchronic and sympatric existence of two representatives of this clade for the first time. The new genus Agaresuchus, comprises a previously described Iberian allodaposuchid species, “Allodaposuchus” subjuniperus, as Agaresuchus subjuniperus, new combination.     

A thick-skulled theropod (Dinosauria,Saurischia) from the Upper Cretaceous of Morocco with implications for carcharodontosaurid cranial evolution

In this study, we erect Sauroniops pachytholus gen. et sp. nov., a large-bodied theropod dinosaur from the Cenomanian (Upper Cretaceous) of Morocco, on the basis of an almost complete frontal showing a unique combination of features including a naso–frontal suture extended along 40% of the frontal length, a thick dome in the anterolateral corner of the dorsal surface, a trapezoidal prefrontal facet that is restricted to the anterodorsal margin of the lateral surface of the frontal with no participation in the orbital roof and separated from the lacrimal facet by a narrow vertical lamina, a hypertrophied ‘D-shaped’ lacrimal facet that is four times the anterior depth of the postorbital facet, and a raised posteromedial margin of the dorsal surface describing a saddle with the anterolateral dome and confluent with a series of anteromedial rugosities. Phylogenetic analysis found robust support for placing Sauroniops among the basal carcharodontosaurids and related to Eocarcharia, showed that some of the unusual features of the new theropod were convergently acquired by abelisaurids, and revealed a mosaic pattern in the evolution of the carcharodontosaurid skull table. The frontals of Sauroniops and Carcharodontosaurus, both from the ‘Kem Kem compound assemblage’ of Morocco, show comparable size but differ in the extent of the naso–frontal articulation, the shape and disposition of the prefrontal and lacrimal articulations, the development of dorsal ornamentation and the morphology of the supratemporal fossa. Among carcharodontosaurids, the skull table developed unique configurations among each lineage and appears diagnostic at the species-level. The dome-like frontal in Sauroniops may indicate head-butting behaviour in this taxon or evolved for visual display.     

Multicusped crocodyliform teeth from the Upper Cretaceous (São José do Rio Preto Formation,Bauru Group) of São Paulo,Brazil

The six peculiar multicusped teeth described here were collected from sediments of the Upper Cretaceous of São José do Rio Preto Formation, near Ibirá (northeastern São Paulo, Brazil). Their bulbous crowns are slightly labio-lingual compressed, and bear a main plus two accessory cusps, which conceal a well developed cingulum. Wear facets are seen on the main and distal accessory cusps. Comparison to the known Crocodyliformes with multicusped teeth show that the new material is not referable to “protosuchians” or eusuchians, nor related to two unnamed forms from Morocco and “notosuchians” such as Uruguaysuchus, Chiamaerasuchus, and Simosuchus. On the other hand, possible affinities with Candidodon and Malawisuchus were maintained based on shared traits. This includes teeth with the main cusp and some accessory cusps arranged in more than one axis, a previously defined unambiguous apomorphy of the putative clade composed of Candidodon plus Malawisuchus. The term Candidodontidae can be applied to this group, and defined as all taxa closer to Candidodon itapecuruensis than to Notosuchus terrestris, Uruguaysuchus aznarezi, Comahuesuchus brachybuccalis, Sphagesaurus huenei, Baurusuchus pachecoi, and Crocodylus niloticus.     

Dentaries of a caenagnathid (Dinosauria: Theropoda) from the Nemegt Formation of the Gobi Desert in Mongolia

A symphyseal region of the fused dentaries of a caenagnathid theropod is described from the Upper Cretaceous Nemegt Formation at the Bugin Tsav locality in the Mongolian Gobi Desert. In contrast to the high diversity of Caenagnathidae in the upper Campanian to Maastrichtian in North America, only specimens of a single caenagnathid, Elmisaurus raurus, have been reported in the coeval strata in Asia. Although dentaries are commonly-found bones in the fossil record of Caenagnathidae, the present specimen is the first discovery of caenagnathid dentaries from the upper Campanian to Maastrichtian in Asia. The Nemegt Formation is unique for its diverse oviraptorosaurian fauna that includes both Caenagnathidae and Oviraptoridae as well as the non-caenagnathoid Avimimus portentosus. Hypothesized coexistence of eolian and fluvial environments in the Gobi Basin during the deposition of the Nemegt Formation might explain such co-occurrence of Caenagnathidae and Oviraptoridae.     

A new titanosaur (Dinosauria,Sauropoda) from the Upper Cretaceous of Lo Hueco (Cuenca,Spain)

The upper Campanian-lower Maastrichtian site of Lo Hueco (Cuenca, Spain) has provided a set of well-preserved partial skeletons in anatomical connection or with a low dispersion of their skeletal elements. One partial skeleton is herein described and a new titanosaurian sauropod is established, Lohuecotitan pandafilandi. This titanosaur is diagnosed by eight autapomorphic features: dorsally and ventrally widened or bifurcated posterior centrodiapophyseal lamina in anterior and middle dorsal vertebrae; short postspinal lamina with a transversely expanded distal end represented by smooth scars in the dorsal vertebrae; anteriormost caudals with the medial spinoprezygapophyseal and medial spinopostzygapophyseal laminae ventrally connected with the prespinal and postspinal laminae, respectively; anterior caudal neural spines with a dorsal projection of the prespinal and postspinal laminae; anterior caudal neural spines bears a “greek-cross”-like cross-section; middle caudal centra having two round and rough structures in the dorsal edge of the posterior articulation, which extends to the dorsal surface of the centrum; the articular ends of the rami of the haemal arches are divided in two articular surfaces; and tuberosity between the anterior and the lateral trochanter of the fibula. The herein performed phylogenetic analysis considered L. pandafilandi as a member of Lithostrotia more derived than Malawisaurus. The known palaeodiversity of the Late Cretaceous Ibero-Armorican titanosaurs is increasing, and further analyses focused on this group will be necessary to better understand the evolutionary history of European titanosaurs and to clarify their relationships within Titanosauria.     

A New Lizard (Lepidosauria: Squamata) from the Upper Cretaceous of Henan, China

Funiusaurus luanchuanensis gen. et sp. nov. was described on the basis of an incomplete skull from the Upper Cretaceous Qiupa Formation of the Tantou Basin in Luanehuan County, Henan Province. It is the second representative of lizards known from Luanchuan and adds a new member to the Luanchuan Fauna. F. luanchuanensis is a small-sized lizard and systematically assigned to the Polyglyphanodontidae of the Teiioidea because of the presence of a caniniform tooth and an elongate posterior process of the postorbital. It is distinctive in that the heterodont dentition bears 19 teeth in both the upper and lower jaws, the 3^rd maxillary tooth is large and caniniform, the post-caniniform teeth in maxilla and those posterior to the 3^rd dentary tooth are chisel-like in lateral view, the prefrontal possesses a fossa on its lateral surface, the postorbital with an extremely elongate posterior process and the well-developed retroarticular process has a deep fossa on its dorsal surface. In phylogeny, our analysis suggests a close relationship of Funiusaurus to the large-sized Tianyusaurus from the same basin within the Tuberocephalosaurinae. The discovery of Funiusaurus is significant in confirming the status of the Tuberocephalosaurinae, which includes a group of the Asian members of the Polyglyphanodontidae only.     

Cranial anatomy of Pholidosaurus purbeckensis from the Lower Cretaceous of France and its bearing on pholidosaurid affinities

New and nearly complete cranial remains of Pholidosaurus purbeckensis are described on the basis of specimens recovered from the Berriasian locality of Cherves-de-Cognac, France. Two skulls, associated mandibles and a set of dorsal osteoderms are available and allow a refinement of the anatomy of the genus, known otherwise from coeval deposits in Germany and England. Because of its longirostrine morphology, convergent with other crocodylomorph lineages, the phylogenetic relationships of Pholidosaurus are likely to be affected by Long Branch Attraction problems. Various tests of removing/excluding longirostrine lineages confirm that Dyrosauridae have a labile position and that their affinities with Pholidosauridae are weakly supported. Results from comparative anatomy and phylogenetic analyses recover Pholidosaurus as the basalmost member of Pholidosauridae, a group closely related to Goniopholididae. Pholidosaurus is recovered together with abundant remains of Goniopholis and with more limited remains of Theriosuchus. The paleoecology of Pholidosaurus and more generally, of Pholidosauridae, is discussed.     

The shape of pebbles

A theory of pebble erosion is presented, based on the assumption that the rate of erosion at a point on the surface is a function Vof the curvature there. It is proved that for physically reasonable functions V,the sphere is the only shape of pebble which can maintain its proportions as it wears away. An argument is given which leads to a particular form for the function Vand a few qualitative consequences of this form are indicated. The surface of the pebble at time tmay be described using spherical polar coordinates θ, Φ by the radius function r (θ, Φ, t). This function is given by a highly nonlinear partial differential equation. However, in the case of the erosion of a deformed sphere, when terms which are of second order or higher in the deformation are neglected, the equation becomes linear and is a version of the diffusion equation. The stability of the spherical shape against deformations of the various harmonic types is then easily analyzed.