Los Cayos Dinosaur Tracksite: An Overview on the Lower Cretaceous Ichno-Diversity of the Cameros Basin (Cornago,La Rioja Province,Spain)

The Los Cayos dinosaur tracksite is located at the eastern sector of the Cameros Basin (Cornago Township, La Rioja province), NE Spain. The sediments consist of interbedded terrigenous siliciclastics and carbonates belonging to the Enciso Group (Early Cretaceous, Aptian in age). The sedimentological and faunal evidence suggests that these sediments were deposited in a low gradient lacustrine environment. Los Cayos constitutes a relatively wide area with at least 6 localities that have yielded dinosaur tracks. More than 2,000 dinosaur tracks have been discovered to date. Medium to large theropod dinosaurs constitute about 95% of the ichnofauna. Ornithopod dinosaur tracks have been reported from only one of the outcrops (Los Cayos D). Los Cayos S has yielded theropod and sauropod tracks. One sauropod trackway shows a narrow-gauge locomotion pattern and a manus print morphology suggesting that the trackmaker was a titanosaurid, or at least a titanosauriform sauropod. Some pterosaur manus impressions, avian-like footprints of small size and possible turtle tracks complete the assemblage of one of the most impressive and best-preserved dinosaur tracksites of the European Lower Cretaceous.     

Simulating sauropod manus-only trackway formation using finite-element analysis

The occurrence of sauropod manus-only trackways in the fossil record is poorly understood, limiting their potential for understanding locomotor mechanics and behaviour. To elucidate possible causative mechanisms for these traces, finite-element analyses were conducted to model the indentation of substrate by the feet of Diplodocus and Brachiosaurus. Loading was accomplished by applying mass, centre of mass and foot surface area predictions to a range of substrates to model track formation. Experimental results show that when pressure differs between manus and pes, as determined by the distribution of weight and size of respective autopodia, there is a range of substrate shear strengths for which only the manus (or pes) produce enough pressure to deform the substrate, generating a track. If existing reconstructions of sauropod feet and mass distributions are correct, then different taxa will produce either manus- or pes-only trackways in specific substrates. As a result of this work, it is predicted that the occurrence of manus- or pes-only trackways may show geo-temporal correlation with the occurrence of body fossils of specific taxa.     

Probable crocodilian tracks and traces from the Morrison Formation (Upper Jurassic) of eastern Utah

A tetradactyl pes impression and tridactyl manus impression are described as the type specimen of Hatcherichnus sanjuanensis ichnogen. et ichnosp. nov., a probable large crocodilian ichnite from the Salt Wash Member of the Upper Jurassic Morrison Formation in eastern Utah. A similar pes track from the Morrison Formation at Garden Park, Colorado, may also belong to this ichnogenus. The type specimen from Utah consists of plaster replicas of natural casts of a left pes impression and a left manus impression. Associated with the type specimen were possible tail and body drag impressions. The tracks do not appear to be part of a walking trackway and may be swim tracks associated with an animal in shallow water. The tracks occur at a visible contact between slightly fining‐upward channel sandstone units.     

Pterosaur Stance and Gait and the Interpretation of Trackways

The tracks ascribed to pterosaurs from the Late Jurassic limestones at Crayssac, France, must be pterosaurian because the manus prints are so far outside those of the pes, the pes print is four times longer than wide, and the manus prints appear to preserve distinct traces of a posteromedially directed wing-finger. These tracks are different in important ways from previously described Pteraichnus trackways, which have been variably considered pterosaurian, crocodilian, or indeterminate. No Pteraichnus (sensu stricto: those not from Crayssac) tracks have diagnostic features of pterosaurs and in none can a complete phalangeal or digital formula be reconstructed; however, all published Pteraichnidae tracks fulfill the criteria of poor preservation, and some have some diagnostic features of crocodile tracks. Reconstructions of pterosaurs walking in pteraichnid tracks do not fit those tracks well, but crocodiles do. In contrast, the Crayssac tracks demonstrate the erect stance and parasagittal gait previously reconstructed for pterosaurs. They also demonstrate that the footfall pattern was not as in typical reptiles (LH-RF-RH-LF), but that the manus must have been raised before the next forward step of the ipselateral foot (LH-LF-RH-RF), suggesting that the quadrupedal pattern was secondary. The metatarsus in pterosaurs was set low at the beginning of a stride, as it is in crocodilians and basal dinosaurs. The diagnosis of the Ichnofamily Pteraichnidae comprises features of possible crocodilian trackmakers, but not of possible pterosaurian trackmakers. Trackways considered for attribution to pterosaurs should show (1) manus prints up to three interpedal widths from midline of body, and always lateral to pes prints, (2) pes prints four times longer than wide at the metatarso-phalangeal joint, and (3) penultimate phalanges longest among those of the pes.     

Technical note: A volumetric method for measuring the longitudinal arch of human tracks and feet

Fossil footprints (i.e., tracks) were believed to document arch anatomical evolution, although our recent work has shown that track arches record foot kinematics instead. Analyses of track arches can thereby inform the evolution of human locomotion, although quantifying this 3-D aspect of track morphology is difficult. Here, we present a volumetric method for measuring the arches of 3-D models of human tracks and feet, using both Autodesk Maya and Blender software. The method involves generation of a 3-D object that represents the space beneath the longitudinal arch, and measurement of that arch object's geometry and spatial orientation. We provide relevant tools and guidance for users to apply this technique to their own data. We present three case studies to demonstrate potential applications. These include, (1) measuring the arches of static and dynamic human feet, (2) comparing the arches of human tracks with the arches of the feet that made them, and (3) direct comparisons of human track and foot arch morphology throughout simulated track formation. The volumetric measurement tool proved robust for measuring 3-D models of human tracks and feet, in static and dynamic contexts. This tool enables researchers to quantitatively compare arches of fossil hominin tracks, in order to derive biomechanical interpretations from them, and/or offers a different approach for quantifying foot morphology in living humans.     

“Keep your feet on the ground”: Simulated range of motion and hind foot posture of the Middle Jurassic sauropod Rhoetosaurus brownei and its implications for sauropod biology

The biomechanics of the sauropod dinosaur pes is poorly understood, particularly among the earliest members of the group. To date, reasonably complete and articulated pedes in Early Middle Jurassic sauropods are rare, limited to a handful of taxa. Of these, Rhoetosaurus brownei, from eastern Australia, is currently the only one from the Gondwanan Middle Jurassic that preserves an articulated pes. Using Rhoetosaurus brownei as a case exemplar, we assessed its paleobiomechanical capabilities and pedal posture. Physical and virtual manipulations of the pedal elements were undertaken to evaluate the range of motion between the pedal joints, under both bone-to-bone and cartilaginous scenarios. Using the results as constraints, virtual reconstructions of all possible pedal postures were generated. We show that Rhoetosaurus brownei was capable of significant digital mobility at the osteological metatarsophalangeal and distal interphalangeal joints. We assume these movements would have been restricted by soft tissue in life but that their presence would have helped in the support of the animal. Further insights based on anatomy and theoretical mechanical constraints restricted the skeletal postures to a range encompassing digitigrade to subunguligrade stances. The approach was extended to additional sauropodomorph pedes, and some validation was provided via the bone data of an African elephant pes. Based on the resulting pedal configurations, the in-life plantar surface of the sauropod pes is inferred to extend caudally from the digits, with a soft tissue pad supporting the elevated metatarsus. The plantar pad is inferred to play a role in the reduction of biomechanical stresses, and to aid in support and locomotion. A pedal pad may have been a key biomechanical innovation in early sauropods, ultimately resulting in a functionally plantigrade pes, which may have arisen during the Early to Middle Jurassic. Further mechanical studies are ultimately required to permit validation of this long-standing hypothesis.     

Trackway Ratio: A New Look at Trackway Gauge in the Analysis of Quadrupedal Dinosaur Trackways and its Implications for Ichnotaxonomy

A new parameter, the Trackway Ratio (TR), is proposed to supplement the previously used trackway gauge to describe and quantify the relative width of trackways in dinosaur quadrupedal gaits. It is expressed as the ratio of the width of the tracks relative to the total width of the trackway (both measured perpendicular to the long axis of the trackway). The ratio may be used with either pes (PTR) or manus (MTR) tracks. The PTR range of values for wide-, medium- and narrow-gauge trackways of previous authors are provisionally suggested to be ≤35%, 36–49% and ≥50%, respectively. The application of such a ratio would permit a more consistent ichnotaxonomy to be adopted where both track morphology and trackway parameters are used to define ichnotaxa.

Determination of the TR, as well as other parameters, will be affected by track preservation quality. Recent experiments on track simulation in the laboratory have shed further light on observations made in the field concerning the value of track measurements (in particular track length and width) recorded from below the surface on which the maker was moving. Experimental track simulations in the laboratory have shown that the dimensions of transmitted tracks preserved below the surface on which the foot was impressed may vary from 65% to 135% of the true dimensions of the indenter. Two case studies are presented that quantify the errors that may be made on calculating TR and the size, gait and speed of the maker, from trackways if the preservation of the tracks are not fully understood.

It is shown that in individual trackways the PTR may vary along the length of the trackway; so that part of the trackway may be classified as wide-gauge and other parts medium-gauge. There is a relationship between variation in PTR and that of pace angulation along the length of a single trackway. An analysis of 42 trackways, principally sauropod, shows a temporal distribution that does not agree closely with previous suggestions relating to narrow- and wide-gauge trackways.     

A NEW WIDE-GAUGE SAUROPOD TRACK SITE FROM THE LATE CRETACEOUS OF MENDOZA, NEUQUÉN BASIN, ARGENTINA

Abstract:  Agua del Choique is a new Late Cretaceous sauropod track site from Mendoza Province, Neuquén Basin, Argentina. It is situated in the Loncoche Formation, late Campanian – early Maastrichthian in age, and is one of the youngest sauropod tracks site recorded in the world. Agua del Choique represents a lake setting and river-dominated delta deposits, and comprises at least 160 well-preserved tracks, located on a calcareous sandstone bed. A new ichnotaxon, Titanopodus  mendozensis ichnogen. et ichnosp. nov., is erected for the footprints of this track site. Titanopodus  mendozensis exhibits the following association of features: (1) wide-gauge trackway (manus and pes trackway ratios of 18–22 and 26–31 per cent respectively), (2) pronounced heteropody (manus-pes area ratio of 1:3), (3) outer limits of trackway defined, in some cases, by the manus tracks, and (4) manus impression with an asymmetrical crescent contour and acuminate external border. Titanopodus  mendozensis is an excellent case study of the wide-gauge style of locomotion produced by Late Cretaceous derived titanosaurs that have no impression of manual phalanges. These features, and the fossil record from the Loncoche Formation, suggest that the trackmakers were, probably, middle size saltasaurine or aeolosaurine titanosaurs (14–16 m long).     

Extant Lizard Tracks: Variation and Implications for Paleoichnology

In this study, I collected tracks and trackways from nine species of extant lizards representing all five major lizard clades. Previously, tracks from species of only two of these clades were described. Lizard tracks conventionally are regarded as having curved digit imprints that progressively increase in length from digit I to IV, with a smaller digit V directing antero-laterally. However, the zygodactylous feet of chameleons (Calumma parsonii and Furcifer pardalis), the posteriorly directed digit V in the pes of ground-dwelling geckos (Eublepharis macularius) and the rounded feet of blue-tongued skinks (Tiliqua scincoides) did not make “typical” lizard tracks, and demonstrate that even within a limited taxonomic sample there can be considerable variation in the morphologies of lizard tracks. Among the lizards examined, mode of locomotion and how the feet function have more influence on the morphology of tracks than does the phylogenetic affinities of the trackmaker. This preliminary neoichnological study increases the known variation in lizard tracks and aids in interpreting the fossil trackway record by providing comparative information that can be used to identify fossil tracks made by lizards.     

Complex In-Substrate Dinosaur (Sauropoda,Ornithopoda) Foot Pathways Revealed by Deep Natural Track Casts from the Lower Cretaceous Xiagou and Zhonggou Formations,Gansu Province,China

Several new Early Cretaceous tracksites from the Lower Cretaceous Xiagou Formation of Gansu Province (China) with tracks of large sauropods and ornithopods are described. Previously reported bird tracks were missing due to human negligence. The studied specimens are preserved as impressions and shallow and deep natural track casts. These dinosaur tracks are first reported from the Jiuquan area in the Changma Basin, matching well with the skeletal record of diverse non-avian dinosaur-bird faunas of this region. Moreover, they add new data to the dinosaur ichnofaunas of the Lanzhou-Minhe Basin (Gansu Province) and indicate a wide distribution of dinosaur-bird assemblages in the Early Cretaceous. Regarding morphology, sauropod, and ornithopod tracks from the Lanzhou-Minhe Basin and the Jiuquan area are very similar to each other. Titanosauriform trackmakers are assumed for the sauropod tracks and possibly iguanodontids have left the large, tridactyl ornithopod tracks. Of particular interest are well-preserved, deep natural track casts of large ornithopods and sauropods preserving ridges and grooves as well as striation marks on the lateral sides of the casts that allow the reconstruction of complex pathways of the foot within the substrate. One particular sauropod pes–manus track cast even indicates lateral and vertical sliding within the sediment because of the presence of “double impressions of digits” on the bottom.     

Intra-Trackway Morphological Variations Due to Substrate Consistency: The El Frontal Dinosaur Tracksite (Lower Cretaceous,Spain)

An ichnological and sedimentological study of the El Frontal dinosaur tracksite (Early Cretaceous, Cameros basin, Soria, Spain) highlights the pronounced intra-trackway variation found in track morphologies of four theropod trackways. Photogrammetric 3D digital models revealed various and distinct intra-trackway morphotypes, which reflect changes in footprint parameters such as the pace length, the track length, depth, and height of displacement rims. Sedimentological analyses suggest that the original substrate was non-homogenous due to lateral changes in adjoining microfacies. Multidata analyses indicate that morphological differences in these deep and shallow tracks represent a part of a continuum of track morphologies and geometries produced by a gradient of substrate consistencies across the site. This implies that the large range of track morphologies at this site resulted from similar trackmakers crossing variable facies. The trackways at the El Frontal site present an exemplary case of how track morphology, and consequently potential ichnotaxa, can vary, even when produced by a single trackmaker.     

Chirothere Footprint Sites from the Otter Sandstone Formation (Middle Triassic,late Anisian) of Devon,United Kingdom

Three chirothere footprint sites are documented from the Middle Triassic (Anisian) fluvial Otter Sandstone Formation of Sidmouth, Devon, UK. One site, on the foreshore below Peak Hill, has revealed numerous tracks, including a probable manus imprint, which are recorded here. Another site, also beneath Peak Hill, has produced a single probable manus track from a higher horizon. The third site, on the foreshore below Salcombe Hill Cliff, has yielded a small number of pes tracks similar to those from Peak Hill. The footprints at all sites are interpreted as belonging to a large Chirotherium ichnospecies, perhaps C. barthii Kaup. Unusually, the tracks are preserved in mudstone, often in convex epirelief, and are inferred to have been generated subaqueously. The apparent restriction of the footprints to the higher part of the Otter Sandstone Formation supports other evidence, such as a greater abundance of vertebrate skeletal material, subhorizontal rather than vertical rhizocretions, and a greater frequency of lacustrine facies, for a less arid climate and higher water table than lower in the sequence.     

Thinopus and a Critical Review of Devonian Tetrapod Footprints

Devonian tetrapod tracks and trackways can be recognized by three criteria: morphology of the manus and pes impressions that matches known Devonian tetrapod skeletal morphology, manus smaller than pes, and the alternating trackway pattern that results from lateral sequence walking in quadrupedal tetrapod locomotion. The first reported Devonian tetrapod track, named Thinopus antiquus, from Pennsylvania, is not a tetrapod track and is likely an impression of a fish coprolite(s). A critical review of the published Devonian track record indicates only three can be verified as produced by a tetrapod trackmaker—Genoa River, Australia; Easter Ross, Scotland; and Valentia Island, Ireland. The supposed tetrapod tracks from the Middle Devonian of the Zache?mie quarry, Poland, fail the criteria for identification as Devonian tetrapod tracks. Indeed, no convincing case has been made that the Zache?mie structures are tetrapod tracks. Instead, they are reinterpreted as fish nests/feeding traces (ichnogenus Piscichnus). The oldest Devonian tetrapod trackway is Givetian and this is the oldest record of a tetrapod, but the sparse record of Devonian tetrapod tracks is of no other biostratigraphic and little paleobiogeographic significance. Bona fide Devonian tetrapod tracks are from nonmarine facies, so they do not support a marginal marine origin of tetrapods. They indicate lateral sequence walking and pelvic-limb-propelled, fully terrestrial (subaerial) locomotion in freshwater environments by at least some Devonian tetrapods.     

Traditional Versus Multivariate Methods for Identifying Jaguar,Puma, and Large Canid Tracks

ABSTRACT The jaguar (Panthera onca) and puma (Puma concolor) are the largest felids of the American Continent and live in sympatry along most of their distribution. Their tracks are frequently used for research and management purposes, but tracks are difficult to distinguish from each other and can be confused with those of big canids. We used tracks from pumas, jaguars, large dogs, and maned wolves (Chrysocyon brachyurus) to evaluate traditional qualitative and quantitative identification methods and to elaborate multivariate methods to differentiate big canids versus big felids and puma versus jaguar tracks (n = 167 tracks from 18 zoos). We tested accuracy of qualitative classification through an identification exercise with field-experienced volunteers. Qualitative methods were useful but there was high variability in accuracy of track identification. Most of the traditional quantitative methods showed an elevated percentage of misclassified tracks (≥20%). We used stepwise discriminant function analysis to develop 3 discriminant models: 1 for big canid versus big felid track identification and 2 alternative models for jaguar versus puma track differentiation using 1) best discriminant variables, and 2) size-independent variables. These models had high classification performance, with <10% of error in the validation procedures. We used simpler discriminant models in the elaboration of identification keys to facilitate track classification process. We developed an accurate method for track identification, capable of distinguishing between big felids (puma and jaguar) and large canids (dog and maned wolf) tracks and between jaguar and puma tracks. Application of our method will allow a more reliable use of tracks in puma and jaguar research and it will help managers using tracks as indicators of these felids' presence for conservation or management purposes.     

Triassic turtle tracks and the origin of turtles

Turtle (Testudines) tracks, Chelonipus torquatus, reported from the early Middle Triassic (Anisian) of Germany, and Chelonipus isp. from the late Early Triassic (Spathian) of Wyoming and Utah, are the oldest fossil evidence of turtles, but have been omitted in recent discussions of turtle origins. These tracks provide significant clues as to how early the turtle Bauplan originated. Turtle trackways are quite distinctive: the manus and pes form tracks nearly parallel to the midline and indicate an unusually wide gait in which the trackway width is nearly equal to the stride length. These tracks do not fit what would be expected to be made by Triassic Pappochelys or Odontochelys, a supposed prototurtle and an early turtle, respectively. In contrast, these tracks are consistent with what would be expected from the Triassic turtles Proganochelys and Palaeochersis. The features inferred to be present in Triassic turtle tracks support the notion that Odontochelys is a derived aquatic branch of the turtle stem lineage rather than the ancestral state of all turtles. Chelonipus also resembles the Permian track Pachypes dolomiticus, generally assigned to a pareiasaur trackmaker. These revelations highlight the need to consider all available evidence regarding turtle origins, rather than just the body fossils.     

Oldest known avian footprints from Australia: Eumeralla Formation (Albian), Dinosaur Cove,Victoria

Two thin‐toed tridactyl tracks in a fluvial sandstone bed of the Eumeralla Formation (Albian) at Dinosaur Cove (Victoria, Australia) were likely made by avian trackmakers, making these the oldest known fossil bird tracks in Australia and the only Early Cretaceous ones from Gondwana. These tracks, which co‐occur on the same surface with a slightly larger nonavian theropod track, are distinguishable by their anisodactyl form, hallux impressions and wide digit II–IV divarication angles. A lengthy hallux impression and other deformational structures associated with one track indicate foot movement consistent with an abrupt stop, suggesting its tracemaker landed after either flight or a hop. The single nonavian theropod track is similar to other tracks described from the Eumeralla Formation at another locality. The avian footprints are larger than most Early Cretaceous avian tracks recorded worldwide, indicating sizeable enantiornithine or ornithurine species in formerly polar environments of Australia. The avian tracks further supplement scant body fossil evidence of Early Cretaceous birds in southern Australia, which includes a furcula from the Wonthaggi Formation. Because of this discovery, Dinosaur Cove, previously known for its vertebrate body fossils, is added to a growing list of Early Cretaceous vertebrate tracksites in southern Australia.     

A New Pterosaur Tracksite from the Jurassic Summerville Formation,Near Ferron,Utah

Pterosaur tracks (cf. Pteraichnus) from the Summerville Formation of the Ferron area of central Utah add to the growing record of Pteraichnus tracksites in the Late Jurassic Summerville Formation and time-equivalent, or near time-equivalent, deposits. The site is typical in revealing high pterosaur track densities, but low ichnodiversity suggesting congregations or “flocks” of many individuals. Footprint length varies from 2.0 to 7.0 cms. The ratio of well-preserved pes:manus tracks is about 1:3.4. This reflects a bias in favor of preservation of manus tracks due to the greater weight-bearing role of the front limbs, as noted in other pterosaur track assemblages. The sample also reveals a number of well-preserved trackways including one suggestive of pes-only progression that might be associated with take off or landing, and another that shows pronounced lengthening of stride indicating acceleration.

One well-preserved medium-sized theropod trackway (Therangospodus) and other larger theropod track casts (cf. Megalosauripus) are associated with what otherwise appears to be a nearly monospecific pterosaur track assemblage. However, traces of a fifth pes digit suggest some tracks are of rhamphorynchoid rather than pterodactyloid origin, as usually inferred for Pteraichnus. The tracks occur at several horizons in a thin stratigraphic interval of ripple marked sandstones and siltstones. Overall the assemblage is similar to others found in the same time interval in the Western Interior from central and eastern Utah through central and southern Wyoming, Colorado, northeastern Arizona, and western Oklahoma. This vast “Pteraichnus ichnofacies,” with associated saurischian tracks, remains the only ichnological evidence of pre-Cretaceous pterosaurs in North America and sheds important light on the vertebrate ecology of the Summerville Formation and contiguous deposits.     

A Catalog of Pterosaur Pedes for Trackmaker Identification

The matching of ichnites to extinct trackmakers has been done successfully with a variety of taxa, from basal hominids to basal tetrapods. Traces attributed to pterosaurs have been studied for more than 50 years, but little interest has been shown in the pedes themselves. While ichnites can vary greatly in their correspondence to their trackmaker, most pterosaur tracks appear to preserve sufficient detail to assess their origins. This report presents a catalog of pterosaur pedal skeletons that can be matched to a wider spectrum of ichnites, including digitigrade and bipedal ichnites previously not associated with pterosaurs. A variety of pedal characters separate several putative genera into distinct clades, some only distantly related to one another. Distinct pedal characters indicate certain tiny pterosaurs were not juveniles of dissimilar adults, but were separate taxa and likely adults themselves. A squamate and fenestrasaur origin for pterosaurs is supported. These new insights overturn long-standing paradigms. The pterosaur pes contains a wealth of data that should not be ignored. Application of this data enables a more precise identification of both skeletal taxa and ichnotaxa.