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Ophiuroids, also called brittle stars, are an important component of modern marine benthos, yet their fossil record is still poorly understood. Here, we describe new finds of ophiuroids from the Upper Sinemurian (Lower Jurassic) of Asturias, Spain. The material consists of several articulated specimens showing all relevant anatomical details to allow for an exhaustive description. The specimens belong to a new species, Arenorbis santameraensis sp. nov., adding a Jurassic species to the genus Arenorbis previously known exclusively from the Middle Triassic of central Europe. We show that Arenorbis has characters typically found in the suborder Ophiodermatina. The new Jurassic occurrence of Arenorbis shows remarkable parallels with its Middle Triassic equivalents in terms of sedimentologic and taphonomic context, suggesting niche conservatism in Arenorbis. In contrast to the wide geographical distribution of the genus in the Middle Triassic, the new species is currently only known from a restricted area, suggesting that it represents a Jurassic relict of a formerly widespread Triassic lineage.

A stratigraphic study of the carbonate deposits from the interval between the uppermost Sinemurian and the base of the Upper Pliensbachian is presented herein. For this purpose, four expanded sections of the Asturian Basin, in Northern Spain, were sampled. The sections are located between Rodiles E section (Villaviciosa municipality) and Playa de Vega section (Ribadesella municipality). The ammonites recorded in over 100 successive levels of this sector enabled the substantial improvement of the biochronostratigraphic scale of reference; making it comparable with those defined for other basins of the Iberian Peninsula and other areas of the western Tethys. The lower boundary of the Pliensbachian is indicated by the first appearance of Gemmellaroceras aff. aenigmaticum (Gemmellaro) below the first appearance of the genus Apoderoceras. The upper boundary is defined by the first record of the Protogrammoceras. (Matteiceras) subgenus which in some levels is associated with Amaltheus stokesi (Sowerby). The boundaries between the zones and subzones were able to be established accurately in most cases. The ammonite assemblages are similar to those established for the NW European Province. Some intervals, however, include species typical of the Mediterranean Province. Among these, the Taylori Subchronozone (Gemmellaroceras) and the transition between the Jamesoni Subchronozone and the Valdani Subchronozone (Tropidoceras) can be highlighted. Additionally, taking into consideration the succession between of ammonite genera and species, 27 horizons were identified, 24 of which correspond to the Lower Pliensbachian, and the other 3 to the uppermost Sinemurian and the lowermost part of the Upper Pliensbachian. Moreover, the identification of 3 of the Lower Pliensbachian horizons were based upon the evolution of the Mediterranean Tropidoceras.

We thank the journal reviewers and the editors for valuable criticism. Luis Alfonso Fernandez Perez and Beatriz Gonzalez Santano helped in the field, Marcus Poschmann provided feedback at an early stage of this research, and Kai Zhou and Javier Dorador assisted with data processing. Research by M.G. Mangano and L.A. Buatois was supported by Natural Sciences and Engineering Research Council (NSERC) Discovery Grants 311727-15 and 311726-13, respectively. J. Ortega-Hernandez acknowledges support from a Herchel Smith Research Fellowship at the Department of Zoology and Emmanuel College, both University of Cambridge (UK). Financial support for L. Pinuela and J. C. Garcia-Ramos was provided by the Principado de Asturias. Financial support for F.J. Rodriguez-Tovar was provided by project CGL2015-66835-P (Secretaria de Estado de I + D + I, Spain), Research Group RNM-178 (Junta de Andalucia), and Scientific Excellence Unit UCE-2016-05 (Universidad de Granada)., Trace fossils represent the primary source of information on the evolution of animal behaviour through deep time, and provide exceptional insights into complex life strategies that would be otherwise impossible to infer from the study of body parts alone. Here, we describe unusual trace fossils found in marginal-marine, storm- and river-flood deposits from the Middle Devonian Naranco Formation of Asturias (northern Spain) that constitute the first evidence for infaunal moulting in a non-trilobite euarthropod. The trace fossils are preserved in convex hyporelief, and include two main morphological variants that reflect a behavioural continuum. Morphotype 1 consists of a structure that superficially resembles a Rusophycus with an oval outline that possesses a distinctly three lobed axis with an elevated central ridge and regularly spaced transverse furrows that convey the appearance of discrete body segments. The anterior part is the most irregular region of the structure, and it is not always recorded. Morphotype 2 displays more elongated, tubular morphology. Careful observation, however, reveals that it comprises up to three successive morphotype 1 specimens organised in a linear fashion and partially truncating each other. Trilobate morphology and effaced transverse furrows are locally evident, but the predominant morphological feature is the continuous, elevated ridge. The detailed morphology of morphotype 1 and well-preserved, discrete segments of morphotype 2 closely resemble the dorsal exoskeleton of the enigmatic late Carboniferous euarthropod Camptophyllia, suggesting the possible affinities of the producer. Comparisons with patterns of Devonian phacopid trilobite exuviation suggest that the Naranco Formation trace fossils may have been produced by the infaunal activities of an euarthropod that anchored its dorsal exoskeleton in the firm sediment during the body inversion moult procedure. Our findings expand the phylogenetic and environmental occurrence of infaunal moulting in Palaeozoic euarthropods, and suggest a defensive strategy against predation, previously only known from trilobites preserved in open-marine deposits., Natural Sciences and Engineering Research Council of Canada 311727-15 311726-13, Herchel Smith Research Fellowship at the Department of Zoology, University of Cambridge (UK), Herchel Smith Research Fellowship at the Emmanuel College, University of Cambridge (UK), Principado de Asturias, Secretaria de Estado de I + D + I, Spain CGL2015-66835-P, Junta de Andalucia RNM-178, Scientific Excellence Unit (Universidad de Granada) UCE-2016-05

A newly discovered assemblage of lizard tracks from the Lower Cretaceous Jinju Formation (Sindong Group, Gyeongsang Basin) Korea is the largest yet reported from the Cretaceous. It consists of at least 95 tracks comprising five trackways, including a meter-long trackway (T1) with 50 footprints assigned to the new ichnotaxon Neosauroides innovatus ichnosp. nov. Two other trackways (T2 and T3) are designated N. innovatus paratypes characterized by strong heteropody, relatively wide trackways and small narrow manus tracks. These morphological characteristics distinguish Neosauroides innovatus from the previously reported lizard trackways Sauripes hadongensis from the Hasandong Formation and Neosauroides koreaensis from the Haman Formation, both also from the Gyeongsang Basin. These three lizard track assemblages from the Korean Cretaceous constitute the entire global lizard track record for this period. The Mesozoic record of lizard tracksites is more localized than the lizard body fossil record. This limited distribution suggests bias in the track record and the fossil record more generally. However, due to deposition of fine-grained substrates, suitable for high definition track registration, the Jinju Formation is increasingly well known as an ichnological window on small tetrapod activity and based on diversity, abundance and high-quality preservation, is regarded as an exceptional Konservat-Lagerstätten.

Se estudia la cronoestratigrafía, biosedimentación y, en particular, la sucesión de los ammonoideos que, con un registro relativamente pobre, se encuentra en varias secciones del Sinemuriense superior (cronozonas Obtusum y Oxynotum) de la costa de Asturias, entre la Playa de Peñarrubia (Gijón) y la Playa de Vega (Ribadesella). Si se exceptúa el límite inferior de la cronozona Obtusum, todas las unidades cronoestratigráficas han podido ser caracterizadas con bastante precisión. En la cronozona Obtusum (subcronozonas Obtusum y Stellare) se suceden en el tiempo siete especies de Asteroceras (A. aff. confusum-A. confusum-A. obtusum-A. cf. margaritoides-A. stellare-A. blakei) y Aegasteroceras (A. sagittarium), que de forma puntual pueden estar asociadas a escasos Epophioceras, Xipheroceras, Promicroceras y Cymbites. La subcronozona Denotatus se caracteriza por la sucesión de tres especies de Eparietites (E. undaries-E. impendens-E. glaber) asociadas a raros Promicroceras. En la cronozona Oxynotum se registran Palaeoechioceras, Gagaticeras (G. cf. exortum-G. gagateum) y Oxynoticeras (O. simpsoni) en la subcronozona Simpsoni y Oxynoticeras (O. oxynotum) asociado a Cheltonia (C. accipitris) en la subcronozona Oxynotum. En la parte media y superior de esta subcronozona, se registran asimismo escasos Paroxynoticeras y escasos Bifericeras y Gleviceras. En el aspecto paleobiogeográfico, la sucesión obtenida es típica de la Provincia del NO Europeo con la inclusión de algunos elementos más propios de la Provincia Mediterránea en la parte media y superior de la cronozona Obtusum (Asteroceras cf. suevicum, E. glaber) y en la parte media de la cronozona Oxynotum (Paroxynoticeras salisburgense).

Detailed bed-by-bed ichnological and sedimentological analysis of the early Toarcian Oceanic Anoxic Event (T-OAE) in two sections from the Asturian Basin – Rodiles and Lastres – reveals changes in the macrobenthic tracemaker community mainly induced by oxygen fluctuations. Ichnological analysis enabled us to document an abundant and diverse trace fossil assemblage, with ten ichnogenera, probably corresponding to alternations between the Zoophycos ichnofacies and the distal expression of the Glossifungites ichnofacies: Arenicolites, Chondrites, Diplocraterion, Halimedides, Palaeophycus, Planolites, Rhizocorallium, Thalassinoides, Trichichnus and Zoophycos. Six ichnofabrics were differentiated: laminated?, Diplocraterion–Thalassinoides, Chondrites-mottled, Chondrites–Palaeophycus–Planolites, Chondrites–Halimedides–Planolites and Chondrites-laminated. Ichnological features (including ichnodiversity, distribution of traces and cross-cutting relationships) allowed us to characterise a well-developed multi-tiered macrobenthic tracemaker community, as well as distinguish different tiering models associated with variations in bottom- and pore-water oxygenation. Anoxic conditions associated with the T-OAE corresponded mainly, but not exclusively, to black shale facies. Minor-order oxygen fluctuations from suboxic/anoxic to disoxic/oxic conditions developed during the middle part of the T-OAE. Laminated intra-T-OAE dark and light grey marls show lithological features similar to those of bioturbated pre- and post-event marls; thus, the ichnological information provides evidence that the T-OAE had a larger effect on biota than on depositional features., We would like to thank Dr. Catherine Chagué (Editor) and two anonymous reviewers for their helpful comments and suggestions on a previous version of this manuscript. This research was funded by Projects CGL2015-66835-P and PID2019-104625RB-100 (Secretaría de Estado de I+D+I, Spain), B-RNM-072-UGR18 (FEDER Andalucía) and P18-RT-4074 (Junta de Andalucía), the Scientific Excellence Unit UCE-2016-05 (Universidad de Granada) and Sociedad Pública de Gestión y Promoción Turística y Cultural del Principado de Asturias. We also would like to thank Serafín Montes, laboratory technician from the Departamento de Estratigrafía y Paleontología (University of Granada). J. Fernández-Martínez specially thanks his beloved father for joining him during field trips.

The Pliensbachian–Toarcian transition has been considered a major bottleneck in the early evolution of belemnites, probably related to major palaeoenvironmental and climatic changes during the Early Toarcian. Previous research has focused on the study of belemnites from higher, temperate latitudes, while high-resolution studies on diversity and size of subtropical belemnite assemblages in the northwest Tethys are comparatively rare. The lack of high-resolution (ammonoid subzone) abundance data on diversity and size distributions of belemnite assemblages does not allow separating changes during the Pliensbachian–Toarcian boundary event from those during the Toarcian anoxic event. Sample standardized diversity analyses on new data from Iberian sections suggest the Pliensbachian–Toarcian corresponds to a slight decrease in diversity and an adult size decrease within dominant species. Cluster and non-metric multidimensional scaling analyses, however, indicate that the largest changes in diversity and palaeogeographic distribution of belemnite assemblages occurred during the Toarcian oceanic anoxic event (TOAE) rather than the Pliensbachian–Toarcian boundary. In southern basins like the Lusitanian Basin and Riff Mountains, belemnites even disappear entirely during the TOAE. More generally, the TOAE corresponds with an increase in body size of belemnite assemblages driven by species turnover. The lack of widespread anoxia in southern basins of the northwest Tethys indicates that direct impact of warming or increased pCO2 triggered by volcanism as well as indirect effects on nutrient availability and productivity might have played an important role during both crises.

The well-preserved trackway of a lacertiform, lizard-like trackmaker from the Haman Formation (Cretaceous) of Korea is described as Neosauroides koreaensis ichnogen. et ichnosp. nov. This is the only example of a Cretaceous lacertiform or lizard-like trackway currently known in the global track record. Although lacertiform trackways, mostly assigned to the ichnogenus Rhynchosauroides , are common in the global Triassic, they are almost entirely absent in the Jurassic and Cretaceous. Moreover, ichnological classification criteria allow that Neosauroides is morphologically distinct from Rhynchosauroides at the genus level, and more like the tracks of the extant lizard Sceloporus . The reasons for the conspicuous lack of post-Triassic occurrences are not certain, but not due to a post-Triassic lack of potential lizard trackmakers. Thus, the preservation biases are likely due to paleobiological factors such as trackmaker ecology and paleoenvironmental preference.

Body size changes have been investigated through episodes of environmental crisis among several groups of organisms but the relative contribution of within-lineage size changes, selective extinction and origination of taxa on these patterns is still being debated. Rapid warming, anoxia, and perturbations of the carbon cycle linked with volcanic activity, as well as their impact on marine diversity are well documented for the Pliensbachian-Toarcian (Pli-Toa) boundary and for the Toarcian Oceanic Anoxic Event (T-OAE). Belemnites were a very abundant and successful cephalopod group in the Mesozoic oceans playing a paramount role in the oceanic trophic webs. Belemnites have mainly been studied from a geochemical perspective during this interval. Newly collected data from three northern and western Iberian sections (Peniche, Rodiles and Lastres) allowed an analysis of the belemnite body size dynamics across the Pli-Toa boundary and the T-OAE and a comparison with other European basins. In Peniche (Lusitanian Basin, Portugal), a significant reduction in belemnite body size was recognized across the Pli-Toa boundary at the assemblage level (i.e. community scale of organization). From the analysis of the different taxa recorded, it seems that adult specimens of Pseudohastites longiformis are driving the body size pattern observed (13% rostrum size decrease). The uppermost Polymorphum-Levisoni zones interval is characterized by a dramatic decrease on both belemnite abundance and diversity. Only 4 specimens of the genus Acrocoelites were found, increasing the body size at the assemblage level. In the Asturian Basin (N Spain), on the other hand, a body size increase at the assemblage level is recognized across the Pli-Toa boundary caused by a within-lineage effect mainly related to adult specimens of Passaloteuthis and Pseudohastites genera. During the onset of the T-OAE, belemnite body size increases due to the appearance of Acrocoelites genus. To summarize, the increase in rostrum size at the assemblage level across the T-OAE is associated with the radiation of a large-sized taxon (Acrocoelites genus) and the extinction of various other species. On the other hand, across the Pli-Toa boundary, the belemnite body size changes are dominated by within-lineage mechanisms. This suggests that species might have been able to cope within the early warming phase (Pli-Ta boundary), but were more affected by the subsequent warming and anoxia during the T-OAE. Our preliminary results indicate that this pattern might also be recognized in other western European sections, such as Cleveland Basin, western Paris Basin (Normandy) and Southern Germany sections. The biotic and abiotic drivers of belemnite body size changes still need to be comprehensively analyzed.

The Principality of Asturias (or simply Asturias) is a region located in the North of Spain (SW of Europe) limited by the Cantabrian Sea in the North and the Castilla y Leon, Cantabria and Galicia regions in the South, East and West respectively. The Asturias Coast represents around 30% of the Cantabrian Coast, the northern limit of the Iberian Peninsula, and is surrounded by the Cantabrian Sea. This sea represents the transition of the Atlantic Ocean to the Biscay Gulf, between Spain and France. Towards the South, the Cantabrian Coast is limited by the Cantabrian Mountains, up to 2,648 m altitude, which axis is located only at 20–50 km from the sea.

Luancaia igen. nov. and its two new ichnospecies, L. candasensis and L. elongata, from the Middle Devonian Naranco Formation of Asturias, northern Spain, record infaunal molting. The new ichnogenus has an elongate to oblong outline, and displays a distinctly trilobate appearance that includes an axial longitudinal lobe characterized by a distinctive ridge flanked by lateral lobes at each side. Well-defined transverse ridges convey a metameric-like appearance consisting of up to nine distinct segments. The anterior-most part is more variable, but consistently features a pair of oval strongly convex, or a subtriangular fan-like ridge in well-preserved specimens. Luancaia is similar to Rusophycus in its general segmented appearance, suggesting a euarthropod producer, but differs in the presence of a distinctive axial ridge and in the absence of scratch imprints. Luancaia closely resembles the dorsal side of the enigmatic Carboniferous oniscid-like euarthropod Camptophyllia. We propose that Luancaia records supine (i.e. upside-down) infaunal molting of a euarthropod with a dorsal exoskeletal morphology similar to Camptophyllia, in which exuviation was facilitated by dorsal anchoring on a firm muddy substrate. The Naranco Formation records sedimentation in a shallow- and marginal-marine setting that at times was affected by fluvial discharge most likely during storm floods. In particular, Luancaia is preserved in storm-flood beds that accumulated in relative proximity to a river mouth. These latter deposits consist of sparsely bioturbated sandstone and mudstone that reflect deposition under stressful conditions, such as salinity stress, erosion and by pass high sedimentation rate, and turbidity. By burrowing into the sediment, the producer avoided the stressed physical conditions of the sediment surface. Marginal-marine settings, where competition and predation pressures were significantly lower than in adjacent fully marine environments, may have served as safe molting sites during the mid-Paleozoic marine radiation.

At least four parallel trackways of medium-sized and robust ornithopods are described from the Upper Jurassic Terenes tracksite in Asturias (N. Spain). While the tracks and trackways of small and gracile ornithopods are common in the Jurassic record, large ornithopods are very rare in this period. Ornithopod gregarious behavior has been recorded from many Cretaceous ichnoassemblages, but there are few examples from the Jurassic, and these always relate to small individuals. The Asturian tracks are quite different from known ichnogenera, but they are not sufficiently well preserved to propose a new one. Medium-large Jurassic ornithopods with robust feet such as Draconyx or Cumnoria are the best candidates to be the trackmakers.

We constructed a geological map, a 3D model and cross-sections, carried out a structural analysis, determined the stress fields and tectonic transport vectors, restored a cross section and performed a subsidence analysis to unravel the kinematic evolution of the NE emerged portion of the Asturian Basin (NW Iberian Peninsula), where Jurassic rocks crop out. The major folds run NW-SE, normal faults exhibit three dominant orientations: NW-SE, NE-SW and E-W, and thrusts display E-W strikes. After Upper Triassic-Lower Jurassic thermal subsidence, Middle Jurassic doming occurred, accompanied by normal faulting, high heat flow and basin uplift, followed by Upper Jurassic high-rate basin subsidence. Another extensional event, possibly during Late Jurassic-Early Cretaceous, caused an increment in the normal faults displacement. A contractional event, probably of Cenozoic age, led to selective and irregularly distributed buttressing and fault reactivation as reverse or strike-slip faults, and folding and/or offset of some previous faults by new generation folds and thrusts. The Middle Jurassic event could be a precursor of the Bay of Biscay and North Atlantic opening that occurred from Late Jurassic to Early Cretaceous, whereas the Cenozoic event would be responsible for the Pyrenean and Cantabrian ranges and the partial closure of the Bay of Biscay.

Ichnological analysis of deep-sea trace fossil assemblages from the Cenozoic turbiditic succession of the Campo de Gibraltar Complex (Cadiz Province, southern Spain) is presented. A relatively diverse and abundant trace fossil assemblage is recognized, with 20 ichnogenera belonging to the nongraphoglyptid assemblage and 12 to the graphoglyptid assemblage. Nongraphoglyptid traces are dominated by Chondrites, Halopoa, Helminthopsis, Lophoctenium, Nereites, Ophiomorpha, Phycosiphon, Planolites, Scolicia, Thalassinoides and Zoophycos, while Gordia and Tubotomaculum are common, and Cladichnus, Gyrophyllites, Polykampton, Rotundusichnium, Rutichnus, Spirophycus and Stelloglyphus are scarce or rare. Except for Helminthopsis and Spirophycus, all ichnotaxa are post-depositional structures, with feeding forms (pacichnia and fodinichnia) dominant. The graphoglyptid assemblage consists of agrichnia, predepositional trace fossils, with abundant Desmograpton, and Paleodictyon; in turn, Helminthorhaphe, Megagrap...

The MUJA (Museo del Jurásico de Asturias, Jurassic Museum of Asturias) has an interesting collection of theropod tracks that show similarities with the ichnogenera assigned to the Eubrontes-Grallator plexus. In this paper we describe in detail the morphology of 21 specimens recovered from different localities on “The Dinosaur Coast” of Asturias, plus four specimens preserved in outcrops in the sea cliffs of Les Vinaes (Villaviciosa). All the specimens are from the outcrops of the Lastres Formation, which is Kimmeridgian in age. The general morphology of the tracks, the footprint length-width ratio, the mesaxony, low divarication of the digits (II-IV) and the absence of hallux and metatarsophalangeal impressions suggest that the tracks are more similar to Grallator than to any other theropod ichnotaxa. Geometric morphometric analysis (principal component analysis, PCA) based on 2D landmark techniques suggests that they differ from Kalohipus bretunensis (as yet the only Grallator-like ichnotaxon described in the Iberian Peninsula) mainly in the divarication angles and in the projection of digit III

Ongoing studies of a multiple track-bearing horizons from massive excavations in the Jinju Formation (Lower Cretaceous) of South Korea have yielded a remarkable diversity of avian, non-avian dinosaur, pterosaur, crocodilian and mammal tracks, many very small and well preserved. Here we report diminutive, didactyl tracks (~1.0 cm long) assigned to a new dromaeosaurid ichnogenus Dromaeosauriformipes, which resembles the larger, but still quite small, ichnogenus Dromaeosauripus, also from the same formation only 30 km away. These diminutive tracks are consistent with the foot size of smaller dromaeosaurid taxa like Early Cretaceous Microraptor from China, and may represent diminutive species or juveniles of larger species. The association of tracks with lakeshore sediments is consistent with the evidence that Microraptor was a fish eater. Two trackways and isolated tracks indicate variable trackmaker gaits and speeds. If oviparous, as assumed for most non-avian dinosaur neonates, the trackmakers must have hatched from tiny eggs. Previous studies of the Korean Cretaceous indicate the presence of other diminutive (~1.0 cm long) theropod tracks (Minisauripus). Such occurrences strongly suggest that small tracks attributed to juveniles, or very small tetrapod species, are more common than previously supposed especially where suitable preservation conditions prevailed.

Early Jurassic ichthyosaurs are well-known based on the abundant and exquisitely preserved European records of the Western Tethys. For example, faunas from Southern England and the Toarcian Posidonia shales of Holzmaden and surrounding areas (Germany) are known worldwide. However, between these areas there are still gaps and/or under-sampled localities from the northern coast of Europe. In recent years as a result of systematic palaeontological and geological explorations of Pliensbachian fossiliferous localities along the coast of Asturias (northern Spain), ichthyosaur specimens have been collected. One of them can be identified at lower taxonomic levels and it is referred to Leptonectes sp. These new findings highlight the richness of the fossil record of the northern coast of Spain and suggest that the abundance of Pliensbachian ichthyosaurs worldwide may have been underestimated., Facultad de Ciencias Naturales y Museo

A re-description of the Early Cretaceous Zhaojue dinosaur tracksite (Sichuan Province, China) is the major focus of the present work. The tracksite is located in an active copper mine, and a dinosaur track-bearing surface of about 1500 m2 (named tracksite I) initially discovered in 1991, has since almost completely collapsed due to ongoing quarry activities. Only about 5% of the initial surface still remains in place (named “remaining tracksite”), while due to the collapse a few new but rather poorly-preserved tracks were unearthed on an underlying level. While the tracks still in place were studied using common field techniques, a schematic tracksite map of the collapsed surface was drawn based on a “corrected orthophotograph” that was generated from overview photographs and from video frames. Fortunately, the resolution of some of the close-up video frames is sufficiently high to observe general track morphology, and to re-interpret previously wrongly identified trackways. Here, we report a quite diverse ichnocoenosis consisting of sauropod, ornithopod, theropod, and pterosaur trackways and isolated tracks. The sauropod trackways belong to the Brontopodus-type and were possibly left by medium-sized titanosaurs. One of the sauropod trackways turns around and makes an astonishingly narrow turn of more than 180° with very pronounced “off-tracking” of the manus with respect to the pes. Such unusual trackways are important for the reconstruction of sauropod locomotion. The theropod trackways were left by small and medium-sized animals with the imprint morphology being similar to that of the ichnogenera Grallator and Eubrontes. Large tridactyl tracks with blunt toes are tentatively identified as ornithopod tracks and may be described as Caririchnium-type tracks. Pterosaur tracks can be assigned to Pteraichnus. The association of pterosaur with small theropod tracks is rather unusual, and this tracksite further corroborates the frequent presence of large ornithopods in inland environmental settings.

The Yangouxia dinosaur tracksites are well known for a diverse assemblage of tetrapod tracks preserved as natural impressions (concave epireliefs) on large bedding planes, representing a locally widespread surface marking the transition from a sand- to a mud-dominated sequence in the Hekou Group. Previous ichnological studies at these large sites have focused on the morphology and ichnotaxonomy of the tracks, including a single trackway representing the first pterosaur tracks reported from China. Here, we report a distinctly different assemblage associated with minor sandstones in the mud-dominated sequence 20 m above the main tracksite level. This assemblage consists of at least 20 pterosaur manus track casts attributed to a single ichnotaxon (Pteraichnus). No pes tracks have been identified. These tracks mostly occur in random orientations, although one possible trackway segment is inferred, to represent walking progression. Manus-only pterosaur track assemblages are common and likely reflect differential registration depths of manus and pes and/or sub optimal preservation conditions. The tracks are associated with distinctive invertebrate traces including Cochlichnus, Spongeliomorpha and Paleophycus and suggest the pterosaurs were likely feeding on the invertebrate tracemakers.

Deposit-feeding strategies recorded in the ichnogenus Phymatoderma from the Lower Jurassic shelf-sea deposits in central (Dotternhausen, southwest Germany) and western Europe (Asturias, north Spain) are revealed by geochemical and microscopic analyses. Thin-section observations showed that the trace-maker of Phymatoderma from Asturias ingested bioclastic skeletal sediments, and that from Dotternhausen ingested fine-grained siliciclastic sediments. Geochemical analysis elucidated that the trace-makers of Phymatoderma from both Asturias and Dotternhausen were non-selective deposit feeders (i.e., indiscriminately ingesting sediment particles on the seafloor), although the ingested sediments were significantly different in lithology. Microscopic analysis revealed that the Early Jurassic Phymatoderma-producers mainly fed on calcareous nannoplankton, i.e., coccolithophores, dinoflagellates, as well as their phytodetritus. Here, we demonstrate a substrate-independent feeding mode in the Early Jurassic Phymatoderma-producers, which accords with the similar morphologic, paleogeographic, and chronologic context of Phymatoderma from Asturias and Dotternhausen.

A detailed structural analysis was carried out on the Jurassic rocks cropping out along the cliffs of La Conejera Inlet (Asturias, Spain). It includes a geological map and a distortion-free cross-section constructed via photogrammetric methods. La Conejera Inlet is located within the Asturian Basin, a Permian–Mesozoic extensional basin partially formed during the opening of the Bay of Biscay. It suffered selective basin inversion during a Cenozoic contraction responsible for the Pyrenees and its western prolongation along the north margin of the Iberian Peninsula. The study of the structures (folds, faults, joints and veins) of the hangingwall of two normal faults with opposite dip senses reveals that it underwent a later compressional stage in which one fault block acted as a buttress. The contractional deformation in the hangingwall, interpreted as a deformed rollover anticline with an associated antithetic fault, diminishes on moving away from one of the main faults. The positive inversion tectonics produced not only a buttressing effect, but it also involved a certain amount of reverse reactivation of one of the main faults that still preserves a normal displacement. The original normal motion would have taken place during the Middle?–Late Jurassic, related to an embryonic stage of the opening of the Bay of Biscay. The later contractional stage would have been caused by the Cenozoic Alpine shortening. The good outcrop quality allows a relative chronology for the observed structures to be established. Employing all the available information we tried to reconstruct the structure at depth and predict the detachment depth, and to estimate the amounts of extension (the present-day value and that before the compression) and compression.

The Vega Formation (Upper Jurassic, Asturias, Spain) contains two Kimmeridgian outcrops – the Abeu and Huerres sections – with bivalves coated with carbonate microbialites (oncoids). The bivalve shells in the Abeu section were replaced early by calcite, while those of the Huerres section were dissolved and the moulds filled by late diagenetic cements. For the Abeu shells, there was a loss of Sr and a gain of Mg, Fe and Mn during the replacement process, but much of the original organic matter was retained. Part of the S present can be linked to this organic matter, and part to the sulphate that replaced the carbonate groups in the calcite. The thin microbialites inside the shells of some of the Huerres bivalves have allowed us to estimate the influence of the growth rate on the incorporation of trace elements in calcite. With an approximately six times lower growth rate, the internal microbialite incorporates less Mg and S and more Fe and Mn than the external one, while maintaining the Sr content. The trace element content (Mg, S, Sr, Fe and Mn) of the Huerres and Abeu microbialites are similar; these coatings may therefore have been formed in the same type of freshwater but in different microenvironments. Given the substantial sulphate content of the microbialites from both sections, this freshwater probably came from hot springs. However, the high Fe/Mn ratio of the Abeu microbialites suggests a reducing environment during their formation. Indeed, δ18O and δ13C data confirm that the Abeu and Huerres microbialites were formed in different microenvironments: the positive covariance for δ18O and δ13C of the Abeu microbialites and replaced shells (r2 = 0.83) and the wide range of variation for δ18O (2.80‰) together suggest that the microbialite crusts grew in isolated ponds where evaporation was dominant. In the Huerres microbialites the positive covariance for δ18O and δ13C (r2 = 0.59) and the narrow range of variation for δ18O (0.74‰) indicate that the Huerres section was formed in a more open environmental system where degassing predominated over evaporation., Museo Geominero, Instituto Geológico y Minero de España, España, Museo del Jurásico de Asturias, España

In the last three decades vertebrate ichnology went through a renaissance due the discovery of new tracksites and the application of rigorous analytic methods (e.g., synapomorphy analyses). This finally allowed full hypothesis testing and a better integration of vertebrate ichnology in paleobiologic, paleoecologic and paleobiogeographic studies. In this chapter we provide a review of recent advances in vertebrate ichnology, focusing on Mesozoic terrestrial reptiles.

This study focuses on new records of freshwater bivalves from the Late Jurassic Vega, Tere~nes and Lastres formations of Asturias, northern Spain. Five new taxa Mujanaia abeuensis gen. et sp. nov., ‘Unio’ asturianus sp. nov., Margaritifera? lagriega sp. nov., Asturianaia colunghensis gen. et sp. nov. and Asturianaia lastrensis gen. et sp. nov. are described and included in the families Unionidae and Margaritiferidae (Unionida); they are compared and contrasted with other European, Asiatic and North American species. Their discovery constitutes the oldest records of Unionida in Spain, and they provide new palaeogeographical data on the distribution and origin of this group in Europe. These taxa are also an effective tool for the environmental reconstruction of the Jurassic ecosystems of Spain’s Dinosaur Coast., Museo Geominero, Instituto Geológico y Minero de España, España, Department of Earth Sciences, The Natural History Museum, Reino Unido, Museo del Jurásico de Asturias, España

The late Kimmeridgian Tereñes Formation, exposed on the coast of Asturias, northern Spain, displays a complex pattern of directed changes of grain size, carbonate content, and skeletal concentrations. In its upper part, here investigated, the formation represents a protected shelf lagoon in which four major facies types are distinguished: The Nanogyra virgula mudstone (1) and the Corbulomima concentrations (2) are characterized by concentrations of small bivalves. The carbonate mudstone (3) contains pseudomorphs after gypsum crystals and thin crusts of gypsum, occasionally in connection with thin microbial layers. Finally, the silty to fine-sandy marlstone and micrite and marly silt (4) is highly bioturbated and contains a moderately diverse benthic macrofauna. These facies indicate a generally quiet environment punctuated by brief episodes of high water energy. Two low-diversity macrobenthic assemblages can be recognized, each of them strongly dominated by a single bivalve taxon. The Nanogyra virgula assemblage exhibits a higher diversity than the near-monospecific Corbulomima assemblage. The former lived in well aerated waters of slightly reduced salinity, and the latter in dysoxic waters of more strongly reduced salinity. The environmental stress responsible for the extremely low species richness and evenness is thought to be multifactorial, produced by reduced salinity, dysoxic conditions, and a soft substrate, and resulted in simple food chains. The eurytopic opportunist Corbulomima was the only element of the shelly macrobenthos that was able to thrive in the shelf lagoon under these conditions. It occurs in countless mm- to cm-thick pavements and shell beds which show evidence of winnowing, influence of weak currents, and occasionally of distal storms, as can be deduced from the orientation pattern of shells. These rhythmic Corbulomima concentrations are explained as reflecting small-scale climatic fluctuations between wetter, stormier conditions leading to mixing of the water masses and enabling colonization of the lagoonal floor by the bivalve, and drier, more tranquil conditions. The latter resulted in a stratified water mass and anoxia at the bottom. Superimposed on this rhythmic alternation are three higher orders of cycles which are partly climatic controlled, partly reflect changes in relative sea level, FG Paläoumwelt, GeoZentrum Nordbayern der Universität Erlangen, Alemania, Bayerische Staatssammlung für Geologie und Paläontologie, Alemania, Instituto Geológico y Minero de España, España, Museo del Jurásico de Asturias, España, Área de Didáctica de las Ciencias Experimentales, Departamento de Educación, Universidad de Cantabria, España

The new ichnosubspecies Rhizocorallium jenense spinosus from the Late Sinemurian (Early Jurassic) of Asturias (northern Spain) is described. This ichnotaxon occurs in three outcrops (El Puntal, Punta Rodiles and Punta La Llastra), near the Villaviciosa estuary, belonging to the Buerres Member of the Rodiles Formation. Rhizocorallium jenense spinosus is similar in shape and size to the ichnospecies Rhizocorallium jenense (herein ichnosubspecies R. jenense jenense) in comprising short and more or less straight U-shaped spreite burrows, commonly obliquely oriented with respect to the bedding plane, but is characterized by the presence of spine-shaped protuberances on the outer margin of the arm. Number of observed spine-shaped protuberances per specimen is variable, being commonly 2–4. Protuberances form obtuse, equilateral or acute triangles. The apical end of the spine-shaped protuberance varies from pointed to rounded. The specimens were emplaced in soft or slightly stiffer substrates to firmgrounds. Recurrent distribution of the spine-shaped protuberances reveals a well programmed behavioural pattern of the tracemaker, previously unknown in Rhizocorallium. Several strategies are envisaged: (a) a cache strategy, implying that the tracemaker collected organic matter during favourable times and subsequently stored material in the spine-shaped protuberances for resource-poorer times, (b) a farming strategy, the spine-shaped protuberances being used for concentration of micro-organisms (bacteria, fungi), and (c) a brooding strategy of the tracemaker, revealing a relationship between brood care and oxygen provision, with the location of the spine-shaped protuberances on the external margin of the arms related to a better water circulation.

The Kimmeridgian Vega, Tereñes and Lastres formations of Asturias have yielded a rich vertebrate fauna, represented by both abundant tracks and osteological remains. However, skeletal remains of theropod dinosaurs are rare, and the diversity of theropod tracks has only partially been documented in the literature. Here we describe the only non-dental osteological theropod remain recovered so far, an isolated anterior caudal vertebra, as well as the largest theropod tracks found. The caudal vertebra can be shown to represent a megalosaurine megalosaurid and represents the largest theropod skeletal remain described from Europe so far. The tracks are also amongst the largest theropod footprints reported from any setting and can be assigned to two different morphotypes, one being characterized by its robustness and a weak mesaxony, and the other characterized by a strong mesaxony, representing a more gracile trackmaker. We discuss the recently proposed distinction between robust and gracile large to giant theropod tracks and their possible trackmakers during the Late Jurassic-Berriasian. In the absence of complete pedal skeletons of most basal tetanurans, the identity of the maker of Jurassic giant theropod tracks is difficult to establish. However, the notable robustness of megalosaurine megalosaurids fits well with the described robust morphotypes, whereas more slender large theropod tracks might have been made by a variety of basal tetanurans, including allosaurids, metriocanthosaurids or afrovenatorine megalosaurids, or even exceptionally large ceratosaurs. Concerning osteological remains of large theropods from the Late Jurassic of Europe, megalosaurids seem to be more abundant than previously recognized and occur in basically all Jurassic deposits where theropod remains have been found, whereas allosauroids seem to be represented by allosaurids in Western Europe and metriacanthosaurids in more eastern areas. Short-term fluctuations in sea level might have allowed exchange of large theropods between the islands that constituted Europe during the Late Jurassic.

The diagenetic overprint in rhythmic hemipelagic successions can either enhance or change the original distribution of CaCO3, but it is difficult to evaluate its effect because in most field examples, it is not possible to distinguish between sedimentary and diagenetic features. The rhythmic succession of the Pliensbachian of Asturias (Spain) shows alternation of bioclastic and laminated/burrowed intervals. The original content of carbonate brought by storms from shallow areas was larger in the bioclastic horizons. However, there is a widespread mismatch between facies alternations and the observed lithological rhythms. The diagenetic redistribution of CaCO3 resulted in successive limestone–marl/clay couplets that do not match (either in number or in the location of the boundaries) the sedimentary cycles defined by facies alternations. We conclude that interpreting the limestone–marl rhythms as a direct response to primary changes is highly questionable, unless there is unequivocal proof of a sedimentary origin of the alternation of the two lithologies.

NATHALIE BARDET,*'1 MARTA FERNANDEZ,2 JOSE CARLOS GARCIA-RAMOS, XABIER PEREDA SUBERBIOLA,4 LAURA PIN9UELA,3 JOSE IGNACIO RUIZ-OMEN9ACA,3 and PEGGY VINCENT'; 'UMR 5143 du CNRS, Ddpartement Histoire de la Terre, Mus6um National d'Histoire Naturelle, 8 rue Buffon, 75005 Paris, France, bardet@mnhn.fr, pvincent@mnhn.fr; 2Departamento Paleontologia Vertebrados, Museo de La Plata, Paseo del Bosque, 1900 La Plata, Argentine, martafer@museo.fcnym.unlp.edu.ar; 3Museo del Jurisico de Asturias, 33328 Colunga, Spain, jcgramos@geol.uniovi.es, lpinuela@geol.uniovi.es, jigruiz@unizar.es; 4Universidad del Pais Vasco/Euskal Herriko Unibersitatea, Facultad de Ciencia y Tecnologfa, Departamento de Estratigraffa y Paleontologia, Apdo. 644, 48080 Bilbao, Spain, xabier.pereda@lg.ehu.es

The type material of the ichnospecies Gigantosauropus asturiensis Mensink and Mertmann 1984 is re-examined and shown to represent a sauropod rather than a theropod. This interpretation confirms the recent suggestions of several authors. We describe the trackway in detail but conclude that it is not diagnostic at any taxonomic level, below the general category of sauropod. Thus, G. asturiensis may legitimately be considered a nomen dubium, and the name should be restricted to the original material and not extended to formally describe other poorly preserved specimens. Claims that the largest pes tracks are 1.35 or even 1.5 m in length are incorrect. Pes length ranges from 98–125 cm (mean 110.75 cm). Hispanosauropus hauboldi Mensink and Mertmann 1984 is also of doubtful utility as previously defined. The holotype, a field specimen, which clearly represents a theropod dinosaur, cannot be located, and may be lost to erosion. The paratype is a sauropod track and therefore has no relevance to the ichno-species ...

Some small and medium-sized crocodylomorph footprints are described from the Late Jurassic (Kimmeridgian) coastal and deltaic units of the northern Spain (Asturias). There are at least four footprint morphotypes. Three of them, with well preserved trackways, are included in the ichnogenus Crocodylopodus (Crocodylopodus isp. and Crocodylopodus meijidei); the fourth one, documented by some isolated large footprints, is referable to the ichnogenus Hatcherichnus. This ichnoassociation confirms the presence of small crocodilians in palaeoenvironments apparently dominated by dinosaurs. The presence of Hatcherichnus seems to confirm the affinity between the Iberian and North American ichnofaunas.

We study the NE emerged portion of the Asturian Basin, a Permian-Mesozoic extensional basin (NW Iberia) partially inverted during the Cenozoic as a result of a contractional event. A geological map, a 3D model, cross sections, a structural analysis and a 3D photogrammetric study were performed. Our goal is to comprehend the relevance, relative timing and behaviour of the extensional and contractional structures formed during the tectonic events defining its current framework. A Mesozoic extensional episode characterized by fault activity, increase of thermal flow and uplift and a Cenozoic contractional episode responsible for reverse and strike-slip reactivation of old faults and generation of few thrusts and folds occurred. The information obtained here should assist with the study of worse exposed inland parts of the basin and the seismic interpretation of offshore data. Additionally, understanding the structural configuration of the Jurassic rocks cropping out in the zone might be of interest as an analogue for hydrocarbon industry, given that some of them may be potential hydrocarbon source rocks. Additionally, unravelling their structure is essential considering the recent request for a hydrocarbon exploration permit by an oil company including this area which, in turn, belongs to a state reserve acreage for CO2 storage.