Laura Piñuela

Shrinking the World's Largest Dinosaur Tracks: Observations on the Ichnotaxonomy of Gigantosauropus asturiensis and Hispanosauropus hauboldi from the Upper Jurassic of Asturias, Spain

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 description. Therefore, we select a new paralectotype and provide a more detailed description of specimens that can be assigned to this ichnotaxon. Hispanosauropus is similar to tracks recently described under the label Megalosauripus. However, the status of this latter ichnogenus, and the spectrum of track types to which it refers, is disputed. Thus, we provisionally restrict the name Hispanosauropus to the original illustrated holotype and a paralectotype from the same locality. On the grounds of morphological similarity, the name may be applied to similar material from elsewhere in the Upper Jurassic of Asturias.

Crocodylomorph Tracks from the Late Jurassic of Asturias (Spain)

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.

An Ornithopod-Dominated Tracksite from the Lower Cretaceous Jiaguan Formation (Barremian–Albian) of Qijiang, South-Central China: New Discoveries, Ichnotaxonomy, Preservation and Palaeoecology

The historically-famous Lotus Fortress site, a deep 1.5–3.0-meter-high, 200-meter-long horizonal notch high up in near-vertical sandstone cliffs comprising the Cretaceous Jiaguan Formation, has been known since the 13th Century as an impregnable defensive position. The site is also extraordinary for having multiple tetrapod track-bearing levels, of which the lower two form the floor of part of the notch, and yield very well preserved asseamblages of ornithopod, bird (avian theropod) and pterosaur tracks. Trackway counts indicate that ornithopods dominate (69%) accounting for at least 165 trackmakers, followed by bird (18%), sauropod (10%), and pterosaur (3%). Previous studies designated Lotus Fortress as the type locality of Caririchnium lotus and Wupus agilis both of which are recognized here as valid ichnotaxa. On the basis of multiple parallel trackways both are interpreted as representing the trackways of gregarious species. C. lotus is redescribed here in detail and interpreted to indicate two age cohorts representing subadults that were sometimes bipedal and larger quadrupedal adults. Two other previously described dinosaurian ichnospecies, are here reinterpreted as underprints and considered nomina dubia. Like a growing number of significant tetrapod tracksites in China the Lotus Fortress site reveals new information about the composition of tetrapod faunas from formations in which the skeletal record is sparse. In particular, the site shows the relatively high abundance of Caririchium in a region where saurischian ichnofaunas are often dominant. It is also the only site known to have yielded Wupus agilis. In combination with information from other tracksites from the Jiaguan formation and other Cretaceous formations in the region, the track record is proving increasingly impotant as a major source of information on the vertebrate faunas of the region. The Lotus Fortress site has been developed as a spectacular, geologically-, paleontologically- and a culturally-significant destination within Qijiang National Geological Park.

First report of a Late Jurassic lizard-like footprint (Asturias, Spain)

This report describes an isolated footprint preserved as a natural cast (convex hyporelief) from the Lastres Fm. (Late Jurassic) of northern Spain. The track consists of a small isolated pentadactyl ectaxonic right manus footprint. It is very asymmetric, plantigrade, with digits and palm deeply marked on the substrate. Digit IV is the longest, digits II and I are nearly equal in length and only a little shorter than III and IV. The footprint morphology is typical of a lizard – like or “lacertoid” track .The general outline of the footprint, the width to length ratio approximately equal to 1, the marked plantigrady and the substantial similarity in length of digits IV-I are coherent with a Rhynchosauroidea manual print. The global record of Rhynchosauroides ichnogenus shows that this specimen represents the latest occurrence of the ichnogenus. The most probable trackmaker was possibly a rhyncocephalian reptile.

Reanalysis of Wupus agilis (Early Cretaceous) of Chongqing, China as a Large Avian Trace: Differentiating between Large Bird and Small Non-Avian Theropod Tracks

Trace fossils provide the only records of Early Cretaceous birds from many parts of the world. The identification of traces from large avian track-makers is made difficult given their overall similarity in size and tridactyly in comparison with traces of small non-avian theropods. Reanalysis of Wupus agilis from the Early Cretaceous (Aptian-Albian) Jiaguan Formation, one of a small but growing number of known avian-pterosaur track assemblages, of southeast China determines that these are the traces of a large avian track-maker, analogous to extant herons. Wupus, originally identified as the trace of a small non-avian theropod track-maker, is therefore similar in both footprint and trackway characteristics to the Early Cretaceous (Albian) large avian trace Limiavipes curriei from western Canada, and Wupus is reassigned to the ichnofamily Limiavipedidae. The reanalysis of Wupus reveals that it and Limiavipes are distinct from similar traces of small to medium-sized non-avian theropods (Irenichnites, Columbosauripus, Magnoavipes) based on their relatively large footprint length to pace length ratio and higher mean footprint splay, and that Wupus shares enough characters with Limiavipes to be reassigned to the ichnofamily Limiavipedidae. The ability to discern traces of large avians from those of small non-avian theropods provides more data on the diversity of Early Cretaceous birds. This analysis reveals that, despite the current lack of body fossils, large wading birds were globally distributed in both Laurasia and Gondwana during the Early Cretaceous.

Rosselia socialis from the Ordovician of Asturias (Northern Spain) and the Early Evolution of Equilibrium Behavior in Polychaetes

ABSTRACT Stacked specimens of Rosselia socialis from the Middle to Upper Ordovician Castro Formation of Asturias, northern Spain represent an example of an infaunal community able to move upwards simultaneously to avoid burial due to sedimentation from unidirectional currents. This ichnofabric is similar to those described from younger deposits and attributed to equilibrium structures produced by polychaetes belonging to the Order Terebellida. Although high density of specimens has been documented in Cambrian Rosselia suites, the Ordovician occurrence from Asturias is so far the oldest example of a Rosselia ichnofabric recording synchronous equilibrium behaviour of a whole community. Despite uncertainties derived from their patchy fossil record and potential for behavioral convergence, trace-fossil evidence seems to indicate that some groups of polychaetes were efficient burrowers since the early Cambrian. Rosselia ichnofabrics reflect an increased complexity of the trophic web and the ability of infaunal polychaete communities to colonize sandy, relatively high-energy settings by the early Paleozoic.

First Record of Gregarious Behavior in Robust Medium-Sized Jurassic Ornithopods: Evidence from the Kimmeridgian Trackways of Asturias (N. Spain) and Some General Considerations on Other Medium-Large Ornithopod Tracks in the Mesozoic Record

ABSTRACT At least four parallel trackways of medium-sized and robust ornithopods are described from the Upper Jurassic Tereñes 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.

The ichnogenus Tubotomaculum: an enigmatic pellet-filled structure from Upper Cretaceous to Miocene deep-marine deposits of southern Spain

Abstract The trace-fossil name Tubotomaculum has been extensively used to refer to spindle-shaped pellet-filled tubes present in Upper Cretaceous to Miocene deep-marine deposits of the western Mediterranean region. However, it has never been formally diagnosed, and accordingly it was regarded as a nomen nudum. In this paper, we formally introduce the ichnogenus Tubotomaculum, including the new ichnospecies Tubotomaculum mediterranensis. Bioglyphs, represented by scratch traces that may be present on the basal and lateral surfaces of the structure, suggesting production by crustaceans. The functional meaning of these structures challenges the simple model of a mining strategy. Instead, the storing of pellets to use them as a bacteria-enriched resource during times when organic detritus was scarce is suggested. The association with chemoautothrophic bacteria in modern analogs of Tubotomaculum provides a crucial piece of evidence to support the cache model. Integration of information from modern environments and the fossil record points to a connection between Tubotomaculum, mud volcanism, fluid venting, and hydrocarbon seeps. The presence of bioglyphs suggests firmgrounds that may have resulted from bottom current scouring of the sea sediment, leading to erosional exhumation of previously buried compacted sediment, which was therefore available for colonization by the infauna. However, an alternative scenario involves enriched fluids related to mud-volcanism resulting in reducing conditions that favored carbonate precipitation and nodule formation just a few centimeters below the sediment-water interface.

The Mesozoic Vertebrate Radiation in Terrestrial Settings

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.

Trace Fossils Assemblages from the Cenozoic “Flysch Units” of the Campo de Gibraltar Complex (Southern Spain)

ABSTRACT Ichnological analysis of deep-sea trace fossil assemblages from the Cenozoic turbiditic succession of the Campo de Gibraltar Complex (Cádiz 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, Megagrapton and Urohelminthoida are common, and the rest, including Belorhaphe, Cosmorhaphe, Glockerichnus, Helicolithus, Lorenzinia, Paleomeandron and Spirorhaphe, are scarce or rare. Trace fossil assemblages can be attributed to the Nereites ichnofacies, with dominance of the Nereites ichnosubfacies, but the Ophiomorpha rudis ichnosubfacies and the Paleodictyon ichnosubfacies could be associated to different depositional settings into the deep-marine basin-floor and the deep-sea fan. Together with the tectonic activity and climate, variations in the petrology of the source area, inducing differences in clay mineral composition, may influence the input and deposition of organic matter, affecting graphoglyptid composition. The graphoglyptid assemblage is dominated by winding and meandering structures, some branched, as well as networks; while radial structures and spiral structures are scarce and little diversified. The studied successions are of special interest for interpreting paleoenvironmental and evolutionary changes affecting graphoglyptid assemblages from Paleocene to Miocene in the Campo de Gibraltar Complex.