Vertebrate Tracks Research Articles

Formation and preservation of vertebrate tracks in semi‐liquid sediments: Insights from tidal flats and laboratory experiments

Formation and preservation of vertebrate tracks in semi‐liquid sediments: Insights from tidal flats and laboratory experiments

The John Wesley Powell Fossil Track Block—theropod tracks with ornithopod-like morphology from the Early Jurassic Navajo Sandstone, Glen Canyon National Recreation Area, Utah-Arizona

A large fallen block of Early Jurassic Navajo Sandstone located at Lake Powell, within Glen Canyon National Recreation Area, south-central Utah, displays natural casts of vertebrate tracks. The footprints occur on at least three track-bearing horizons preserved on and between stromatolitic sandstone beds. Two large, parallel trackways, plus a third, divergent trackway, on the main track layer (MTL) superficially resemble ornithopod footprints; however, they were produced by large-sized theropod dinosaurs, ratherthan ornithischians, and we identify these as Eubrontes. Small coelophysoid theropod tracks (Grallator) are the most common vertebrate ichnofossils on all track-bearing horizons, with approximately 50 footprints preserved on the MTL, six on the highest surface, and three on thinner float slabs stratigraphically lower in section. An additional 12 tracks in three trackways of Anchisauripus size occur on the MTL, but they superficially resemble Kayentapus in having wider divarication angles than typical Anchisauripus. The MTL also preserves at least five closely associated tetradactyl footprints that we identify as cf. Brasilichnium. A nearby, smaller fallen block preserves distinct Batrachopus tracks, which are rare in eolian environments. The microbial (possibly endoevaporitic) mats and stromatolitic horizons on which the animals had walked produced a distinct ichnomorphologic variation because of substrate consistency and the elastic properties of the mats, resulting in differential compaction of the bedding surfaces. Lithic compaction of the finer-grained sediments between denser, more resistant sandstone beds pre- and/or post-lithification resulted in additional deformation of the tracks, followed by natural erosion. We interpret these natural cast footprints on the MTL as possible transmitted tracks. The track-bearing, microbial-mat surfaces represent interdunal pooling of water, probably during periods of increased precipitation and/or rising water tables during wet seasons.

A Glimpse Through Time: Preliminary Report of the Andre’s Alcove Tracksite, Lower Jurassic Navajo Sandstone, Glen Canyon National Recreation Area, Utah

In November 2018, a team of researchers from the National Park Service and the St. George Dinosaur Discovery Site documented fossil vertebrate tracks at the Andre’s Alcove Tracksite (AAT) in the Lower Jurassic (?190–185 Ma) Navajo Sandstone in Glen Canyon National Recreation Area, Utah. The tracks at the AAT were photo-documented for photogrammetric processing using Agisoft Photoscan Professional to enable the track surface to be studied remotely. Ichnotaxa already identified at the AAT include those of small ornithischian dinosaurs (Anomoepus), theropod dinosaurs (Grallator, Eubrontes), and protosuchian crocodylomorphs (Batrachopus). Vertebrate body fossils are rarer in the Navajo Sandstone than in underlying, earlier Jurassic strata; the AAT site therefore provides important insights into late Early Jurassic vertebrate diversity and behaviors at the onset of the Navajo Erg in the American Southwest.

New Vertebrate Tracks from the Neogene Río Negro Formation (Río Negro Province, Argentina)

Nuevas huellas de tetrápodos han sido descubiertas cerca de Pozo Salado, en la costa atlántica al oeste del área de Punta Mejillón (provincia de Río Negro, Argentina). Las huellas están conservadas sobre la superficie de una arenisca de grano fino incluida en una sección estratigráfica perteneciente a la Formación Río Negro, de edad neógena. Las huellas son abundantes pero la icnodiversidad es relativamente baja. Tanto la morfología de las huellas como la extra-morfología asociada sugieren que la superficie y el espesor de sedimento involucrado fueron impresos por productores de diferentes clases de tamaño durante un tiempo relativamente largo de exposición. Las huellas suficientemente bien preservadas para permitir una asignación icnotaxonómica se clasificaron como Gruipeda maxima, Gruipeda cf. maxima, cf. Porcellusignum isp. y huellas indeterminadas asignadas a Eutardigrada. Las trazas se pueden relacionar con aves gruiformes/ciconiiformes, roedores hidroquéridos y perezosos terrestres, respectivamente. El nuevo hallazgo, a más de 100 km al SO de las típicas localidades portadoras de huellas de la costa atlántica, enriquece el registro de huellas de vertebrados de la Formación Río Negro y registra una icnoespecie adicional, no reportada hasta ahora.

Coprolites in Cemented Pleistocene Deposits on the Cape South Coast of South Africa

Helm, C.W.; Bamford, M.K.; Carr, A.S.; Cawthra, H.C.; De Vynck, J.C.; Dixon, M.G.; Quick, L.J., and Stear, W., 2023. Coprolites in cemented Pleistocene deposits on the Cape south coast of South Africa. Journal of Coastal Research, 39(2), 221–233. Charlotte (North Carolina), ISSN 0749-0208. Ichnology, the study of trace fossils, has the potential to complement information from traditional body fossil studies. Six ichnosites, containing an array of features interpreted with varying degrees of confidence as vertebrate coprolites, have recently been identified on the Cape south coast of South Africa. They are embedded in Pleistocene deposits from Marine Isotope Stage 6 or 5e through Marine Isotope Stage 5a. Bovid, carnivoran, elephant, and reptile origins are inferred. In the majority of cases, vertebrate tracks occur in association with the coprolites. Petrography studies confirm an organic component in all samples, confirming the potential of coprolites to contribute to palaeoenvironmental reconstruction. Although initial palynology and phytolith studies were negative, a diligent search for further sites and further testing may help in realizing this potential. More broadly, the six ichnosites demonstrate the capacity of cemented dune and beach surfaces on the Cape south coast to preserve coprolites in open-air settings, compared with previously known coprolite records from carnivore dens and archaeological sites.

Invertebrate trace fossils from Paleogene fluvial strata in Western Washington, USA

Fluvial strata in the Paleogene Chuckanut Formation contain a wealth of trace fossils that include both vertebrate and invertebrate ichnofossils. Vertebrate traces have received careful scrutiny, but invertebrate traces have not previously been described. Trace fossils occur in two sediment types. Mudstones deposited in subaqueous environments include highly bioturbated layers that are dominated by horizontal meniscate burrows. Siltstone and fine-grained sandstone beds primarily contain vermiform trails on bedding surfaces, with sparse vertical traces. Some of these sandy beds also contain vertebrate tracks. Chuckanut Formation beds commonly show rapid facies changes in sediments that were deposited along a meandering river during a time of semitropical climate. Transitions from subaqueous to subaerial conditions may have been related to changing water levels caused by variations in seasonal precipitation or episodic flood events. Other possible factors include ponds created by abandonment of channels, overbank sediment s deposited by floods, and breaching of levees to form crevasse splay deposits. Trace fossil assemblages show local variations in the diverse depositional environments of the Chuckanut Formation. Many of the ichnofossil suites clearly represent Scoyenia Ichnofacies, but some occurrences may involve overprinting of Scoyenia and Mermia ichnofacies.

Microbially induced sedimentary structures and the preservation of vertebrate tracks on the Colorado River delta in Lake Powell, Hite, Utah

Microbially induced sedimentary structures (MISS) increase the preservation potential of vertebrate and invertebrate ichnofossils. The Colorado River forms a delta in Lake Powell at Hite, Utah, and the deltaic shoreline provides a natural laboratory to examine the development of MISS and their influence on vertebrate track preservation. Two types of MISS were identified: pustular and blister. Pustular MISS occur in proximity to the June 2020 high water line. The pustular morphology is characterized by mm-scale small mounds, or pimple-like shapes. Field emission scanning electron microscopy (FESEM) examination identified preserved filamentous cyanobacteria intertwined with fine silt- and clay-sized sediment and well-preserved freshwater diatoms. Branta canadensis (Canada goose) tracks are well developed and they vary from single tridactyl tracks to trampled horizons. Blister MISS, in contrast to pustular MISS, are present in lower elevations, forming in deeper water, greater than 0.5 m. Blisters are mm- to cm-scale irregular mounds that consist of arching mats that are detached from the underlying sediment creating a pore space. Through time the blister mat mounds are destroyed by fragmentation due to desiccation combined with wind processes. FESEM and energy-dispersive spectroscopy system (EDS) analyses indicate the presence of filamentous cyanobacteria on the exterior and palisade Bacillus-type bacteria are in the interior of the blister arch, and gypsum crystals within the mat arch. Freshwater diatoms are present in both mat types. A single human track and multiple trackways of Canis latrans (coyote) were identified on the blister mats. Weakly impressed Canada goose tracks are present. Tracks cross cutting or modifying the pustular MISS have preserved MISS surface textures except in the heavily trampled areas, whereas tracks linked to the blister mat typically do not have reserved mat texture, and usually contain fragmented mat within the impression. Because of fluctuating lake levels and desiccation, these track types had a limited temporal window where they may be produced when moisture conditions permitted MISS development, about two months. Any vertebrates through the area out of the “track window” were not recorded in sediment and mat modification. Tracks imprinted on pustular MISS in lacustrine environments will have a high preservation potential if there are annual fluctuations in lake levels.

New evidence for avian and small non-avian theropod ichnotaxa from the Lower Cretaceous of Canada: Implications for theropod ichnodiversity

A diverse continental ichnofauna from the Lower Cretaceous (Aptian) Gething Formation occurs at the Ninesting Creek site in northeastern British Columbia. Vertebrate tracks including Wupus and Saurexallopus are inferred to represent medium-sized (footprint length ∼10 cm) tridactyl avian and larger (footprint length ∼15–17 cm), gracile, tetradactyl non-avian theropod trackmakers respectively. Shape, length-to-width and divarication ratios, suggest two morphotypes that are distinct from the poorly known, and infrequently-cited, Gething Formation ichnogenera Columbosauripus and Irenichnites (footprint lengths ∼12.5 and ∼15.0 cm respectively). This suggests a diverse theropod ichnofauna representing size classes which are quite distinct from the better-known large theropod ichnogenus Irenesauripus with footprint lengths in the range of ∼38.0–53.5 cm. Thus, current evidence suggests that the ichnodiversity of smaller avian and non-avian theropod tracks (footprint length ∼<15.0 cm) outnumbers large ‘megatheropod’ morphotypes by about 7:1. The implications of this distribution are consistent with recently proposed palaeoecological models. The assemblage also includes probable pterosaur tracks and distinctive arcuate compound Archaeonassa-Lockeia traces, attributed to freshwater unionid bivalves. The trace fossils comprise a composite Mermia-Scoyenia Ichnofacies assemblage. Palaeoenvironmentally the site represents the low energy margin of an open lake basin or floodplain pond, or a fluvial point bar.

Vertebrate tracks from the Permian of Gonfaron (Provence, Southern France) and their implications for the late Capitanian terrestrial extinction event

The Guadalupian was a key epoch for the evolution of tetrapod faunas. It includes the earliest unambiguous occurrences of therapsids and stereospondyls (groups that later became dominant in terrestrial and freshwater environments, respectively) and the late Capitanian mass extinction event. The low-latitude faunas from this time interval, where sufficiently dated, comprise rare tetrapod body fossils whereas the most complete records are provided by ichnoassociations, especially coming from the Provence basins of France. In this paper, we revise the tetrapod ichnoassociation from the Pélitique Formation of the Le Luc Basin of Provence, identifying the following tetrapod ichnotaxa: Batrachichnus salamandroides (temnospondyls/lepospondyls), Capitosauroides talus comb. nov. (therocephalian therapsids), Dicynodontipus isp. (cynodont therapsids), Varanopus isp. (bolosaurian parareptiles), Hyloidichnus bifurcatus (captorhinomorph eureptiles) and Rhynchosauroides isp. (neodiapsid eureptiles). According to our revised ichnotaxonomy and stratigraphic correlations, we date the Pélitique Formation as late Capitanian and assign its tetrapod ichnoassociation to the newly defined Association V (Dicynodontipus sub-biochron of the Erpetopus biochron). The Pélitique Formation ichnoassociation shows a typical composition for a post-dinocephalian extinction ichnofauna, as shown by preliminary multivariate statistics on Guadalupian–Lopingian tetrapod ichnoassociations. It is similar to the contemporaneous skeletal faunas described from the mid- to high-latitude sites of Russia and South Africa and is arguably the earliest evidence of post-dinocephalian extinction recovery at low-latitudes. Our results confirm the global and abrupt impact of the late Capitanian terrestrial mass extinction and the subsequent recovery in the low-latitude realm. This extinction was probably time-equivalent with a global benthic marine mass extinction, and both events may have been linked to climatic perturbation caused by the Emeishian volcanic activity in China, which reached its peak around 260 Ma.

Inventory and Conservation of Triassic Vertebrate Tracks in the Monts d’Ardèche UNESCO Global Geopark, France

The Regional Natural Park (RNP) of the Monts d'Ardeche, located in south-eastern France, became the Monts d’Ardeche UNESCO Global Geopark in September 2014. This territory possesses significant geological structures, including numerous and rich Middle-Late Triassic vertebrate tracksites. The UNESCO Global Geopark label helped to formalize a long-standing partnership for the study of this ichnological patrimony between the RNP of the Monts d'Ardeche and the University of Burgundy. Developing scientific research, protection, training and outreach are the main lines of the agreement signed in 2015. The strategy is to make a detailed and sedimentologically contextualized inventory of vertebrate tracks in the Geopark and its surroundings, establish conservation and protection priorities, set up geosites for the public and involve local people in all these activities. To date, 15 tracksites and nearly a thousand individual tracks have been inventoried. The locality “Le Sartre” stands out as being the first recognized geosite amongst the remarkable tracksites in Ardeche. After four years of scientific investigations and fitting out works, it was inaugurated in October 2020. This geosite is the first equipped locality in France to show Late Triassic dinosaur tracks and to be freely accessible to the public. This success was made possible by the intellectual, logistic and social involvement of local people throughout, by acknowledgement of these contributions, and by the capacity of all actors to collaborate efficiently with each other. With more than 1000 fossil vertebrate tracks still awaiting to be valorized in Ardeche, the designation as a UNESCO Global Geopark clearly marked a turning point from academic-only to articulated research, conservation and geotouristic initiatives involving local communities.

Construction of Vertebral Body Tracking Algorithm Based on Dynamic Imaging Parameter Measurement and Its Application in the Treatment of Lumbar Instability

Static imaging measurements could not truly reflect the dynamic panorama of the lumbar movement process, and the abnormal activities between the lumbar vertebrae and their dynamic balance could not be observed, resulting in difficulties in the mechanism analysis of lumbar instability and the efficacy evaluation of manipulation therapy. Therefore, this paper constructed a vertebral tracking algorithm based on dynamic imaging parameter measurement through imaging parameter measurement and calculation. According to the imaging data obtained by vertebral body tracking algorithm, the corresponding statistical methods were used to compare the functional scores before and after manipulation and the changes of imaging data, so as to evaluate the therapeutic effect of manipulation on lumbar instability. Through the clinical observation and imaging analysis of 15 patients with lumbar instability before and after manipulation treatment, it is verified that the vertebra tracking algorithm is effective in the vertebra tracking and plays a positive role in the treatment of lumbar instability.

New record of Late Cretaceous vertebrate tracks from the Yacoraite Formation (Juella, Quebrada de Humahuaca, northwestern Argentina): aerial drone survey, preservation and sedimentary context

The Yacoraite Formation is a worldwide known unit due to the diversity and abundance of vertebrate ichnological record. The complex tectono-sedimentary evolution related to the Andean Cycle generated high dip angles of bedding and, consequently, large tracksites are not easily accessible, making hard the ichnological analysis. Here, we describe a new tracksite named “La Banderita”, near Juella town (Quebrada de Humahuaca, Jujuy, Argentina), where abundant vertebrate and invertebrate trace fossils have been identified on different high slope surfaces. A small, portable unmanned aerial vehicle (UAV) equipped with a digital camera was employed to overcome difficulties in studying traces. After the aerial survey, digital photogrammetry was applied to get 3D models of the trampled surfaces (about 7700 m2) and to obtain track distribution maps (more than 100 tracks). As a complement, a detailed 3D model of an easily accessible small area was also made (about 315 m2). Trace fossils were preserved within three facies intervals from subtidal/lower intertidal (Intervals I-II) to intertidal (Interval III) settings. In this last interval, quadrupedal (probably sauropod), bipedal (theropod) and undetermined tracks, differently preserved as undertracks, true tracks and natural casts, are identified. These three modes are product of narrow preservational windows, which have prevented weathering destruction process after original trampling. Ichnological and sedimentological data are coherent with those of other localities from the Yacoraite Formation, and suggest that dinosaurs moved along peritidal settings. This contribution highlights the use of aerial drone survey and 3D photogrammetric models, which besides traditional ichnological and sedimentological techniques, allowed a detailed reconstruction of track formation and preservation, contextualizing the trampled surfaces in their palaeoenvironmental setting.

A new ichnofauna from the Permian of the Zat Valley in the Marrakech High Atlas of Morocco

A new ichnofauna from the Permian of Morocco is described in details: it is the first Palaeozoic ichnofauna from the Zat Valley in Marrakech High Atlas. The new tracksite was found in the Tighdouine region, in the middle-upper Permian of the Cham-el-Houa Siltstone Formation. An abundant and diverse ichnoassemblage composed of both protostomian (probably arthropods and annelids) traces and vertebrate tracks is recorded. The presence of protostomian burrows and traceways, associated with tetrapod tracks corresponds to the Scoyenia ichnofacies. Protostomian traces are ascribed to Diplichnites gouldi, Diplopodichnus biformis, Scoyenia cf. gracilis and Spongeliomorpha carlsbergi. Tetrapod tracks include more than 70 tracks attributed to Amphisauropus, Erpetopus, Hyloidichnus, Characichnos, and indeterminate tracks. The co-occurrence of tetrapod tracks (both walking and swimming tracks), protostomian traces, mudcracks, ripple marks, as well as the lithological features of the track-bearing levels, indicate regularly inundated depositional environments during periods of high discharge under a local seasonal climate. A sedimentological analysis shows that the depositional environments evolved from braided-meandering systems to alluvial floodplains. The track-bearing surfaces are mainly preserved in crevasse splays, levees and pond deposits. This newly discovered ichnofauna helps to better reconstruct the palaeoenvironments of the Marrakech High Atlas in Morocco during the Permian, and enlarges the palaeogeographic distribution of important ichnotaxa.

First vertebrate tracks and palaeoenvironment in a MIS-5 context in the Doñana National Park (Huelva, SW Spain)

A Late Pleistocene surface full of tracks and trackways (named ‘Matalascañas Trampled Surface’) has been exposed at the base of the ‘El Asperillo’ cliff (Doñana National Park, Matalascañas, Huelva, southwestern Spain) as a result of recent storms. This surface has been identified as the bottom of the unit AU1, according to the local stratigraphic section, and originated during the marine stage MIS-5 (∼106 ± 19 kyr). This trampled surface records exceptional tracks and trackways of different terrestrial vertebrates. In particular, three morphotypes of tracks ascribed to Artiodactyla (the auroch Bos primigenius? the red deer Cervus elaphus and wild boar Sus scrofa), one to Elephantidae (Palaeoloxodon antiquus), one of Canidae (Canis lupus), and three to waterbirds (geese, Anserinae, and waders, Charadrii) have been identified. This ichnoassociation is characteristic of a shorebird ichnofacies. We interpret this trampled surface to have been related to puddled areas of shallow waters in an inter-dune position, similar to present day examples in the Doñana National Park.

Tracking the last elephants in Europe during the Würm Pleniglacial: the importance of the Late Pleistocene aeolianite record in SW Iberia

In his short joint ventures across the world of vertebrate tracks, Richard Bromley recognized the aeolian sands as unsuitable soft substrates for their preservation. Only after his work in the Balearic Islands, a more systematic study of coastal aeolianites worldwide revealed that these depositional systems could preserve a highly important record of behavioural trace fossils for the evolution of vertebrates, especially in the Pleistocene, including extinct megafauna and the escalation of the Homo. Here we describe coastal aeolianites from the upper Pleistocene of SW Iberia, namely SW Portugal and Gibraltar, with trackways, tracks and trampled surfaces of the last elephants in mainland Europe. Photogrammetric 3 D modelling and analysis of the relevant proboscidean track levels allowed revision of and support for previous ichnotaxonomic identification to Proboscipeda panfamilia and behavioural interpretations of the producer. Smaller and very large trackways and footprints attributed to Palaeoloxodon antiquus are described and discussed according to new and recent, but always rare findings. The seeming progressive and definitive extinction of this species towards southern Iberia, following the same pattern for the replacement of the Neanderthals during the last initial Pleniglacial (until ca. 28 ka), suggests evidence for co-evolution.

Tracking the Pliensbachian–Toarcian Karoo firewalkers: Trackways of quadruped and biped dinosaurs and mammaliaforms

The Karoo igneous rocks represent one of the largest continental flood basalt events (by volume) on Earth, and are not normally associated with fossils remains. However, these Pliensbachian–Toarcian lava flows contain sandstone interbeds that are particularly common in the lower part of the volcanic succession and are occasionally fossiliferous. On a sandstone interbed in the northern main Karoo Basin, we discovered twenty-five tridactyl and tetradactyl vertebrate tracks comprising five trackways. The tracks are preserved among desiccation cracks and low-amplitude, asymmetrical ripple marks, implying deposition in low energy, shallow, ephemeral water currents. Based on footprint lengths of 2–14 cm and trackway patterns, the trackmakers were both bipedal and quadrupedal animals of assorted sizes with walking and running gaits. We describe the larger tridactyl tracks as “grallatorid” and attribute them to bipedal theropod dinosaurs, like Coelophysis, a genus common in the Early Jurassic of southern Africa. The smallest tracks are tentatively interpreted as Brasilichnium-like tracks, which are linked to synapsid trackmakers, a common attribution of similar tracks from the Lower to Middle Jurassic record of southern and southwestern Gondwana. The trackway of an intermediate-sized quadruped reveals strong similarities in morphometric parameters to a post-Karoo Zimbabwean trackway from Chewore. These trackways are classified here as a new ichnogenus attributable to small ornithischian dinosaurs as yet without a body fossil record in southern Africa. These tracks not only suggest that dinosaurs and therapsids survived the onset of the Drakensberg volcanism, but also that theropods, ornithischians and synapsids were among the last vertebrates that inhabited the main Karoo Basin some 183 Ma ago. Although these vertebrates survived the first Karoo volcanic eruptions, their rapidly dwindling habitat was turned into a land of fire as it was covered by the outpouring lavas during one of the most dramatic geological episodes in southern Africa.

Multi-aged social behaviour based on artiodactyl tracks in an early Miocene palustrine wetland (Ebro Basin, Spain)

We present a new locality with at least 880 vertebrate tracks found at the top of a limestone bed from the lower Miocene Tudela Formation (Spain). The trampled surface was formed by artiodactyls that crossed a muddy carbonate accumulated under the influence of water level variations in a palustrine environment. The tracks reflect different types of morphological preservation. The well-preserved tracks have tetradactyl digit impressions caused by both manus and pes, and are the type series of a new artiodactyl ichnotaxon, Fustinianapodus arriazui ichnogen. nov. and ichnosp. nov. The rest of the tracks, which are not as well preserved, are didactyl and were classified as undetermined artiodactyl tracks. According to their preservation, morphology, size, arrangement and orientation, we propose that this tracksite is the product of a social behaviour, particularly gregariousness, of a multi-age group of artiodactyls ~19 Ma ago. The morphologic and palaeoecologic data presented here suggest that the trackmakers were a group of anthracotheres with a livelihood similar to current hippos. They crossed, periodically, a fresh water palustrine area along some preferential pathways (trails).

Late Permian-Early Jurassic vertebrate tracks from patagonia: Biochronological inferences and relationships with southern african realms

In recent years, new studies about vertebrate tracks found in the late Permian-Triassic Los Menucos Complex and Early Jurassic Marifil Volcanic Complex (Río Negro province, Patagonia, Argentina) have been published. In those studies, the chronostratigraphic information of each track-bearing unit has been discussed and the relationships between the record from Patagonia and southern Africa have been highlighted. With the aim of deepening both subjects, the biochronological and palaeobiogeographical information of the main ichnotaxa found in the lower Mesozoic units of Patagonia, Dicynodontipus, Pentasauropus and Anomoepus-like tracks, have been analysed. Moreover, the updated chronological data from the Vera Formation, Los Menucos Complex, in the Tscherig and Yancaqueo farm areas, and from the Marifil Volcanic Complex near Perdomo farm, have been studied. The entire biochronological, chronological and tectonic evidence suggests that within the Los Menucos Complex there are two sequences: a lower one, Wuchiapingian-Olenekian in age, near the Tscherig farm and bearing Dicynodontipus tracks, and an upper sequence of Anisian-Rhaetian (?Norian) age, in the Yancaqueo farm and bearing Pentasauropus tracks. This suggests that the rocks historically defined as Vera Formation have different ages in different areas and span a longer time interval than previously thought. In the case of the Anomoepus-like tracks found in the Marifil Volcanic Complex, the biochronological and geological data are consistent with an Early Jurassic age. According to ichnological information and geological background we propose a correlation between Patagonia and southern Africa constrained in three main phases: 1. Lopingian to Early Triassic, Vera Formation (Tscherig farm) and Balfour Formation, respectively; 2. Middle to Late Triassic, Vera Formation (Yancaqueo farm) and lower Elliot Formation, respectively; and 3. Early Jurassic, Marifil Volcanic Complex and upper Elliot Formation, respectively. In addition, this correlation is supported by a similarity in palaeoclimatic settings that allow inferring a homogeneous distribution of trackmakers in both realms of southern Gondwana. Finally, the palaeobiogeographic information of the studied ichnotaxa and their putative trackmakers is consistent and shows an extensive distribution, during a geotectonic moment with most of the continents assembled forming Pangaea.

The oldest record of a tyreophoran track in Gondwana: Geological implications of subaerial exposure in the lower part of the Lajas Formation at the Covunco section (Neuquén Basin), Patagonia, Argentina

The outcrops of the Lajas Formation at the Covunco section expose a succession that contrasts with the classical localities for the unit, due to subaerial exposure confirmed by a vertebrate track documented in the basal section of the unit. The stacking pattern, facies distribution, subaerial exposure in the previously interpreted prodelta facies and the documented unconformity in the middle part of the unit are incompatible with the continuous deltaic evolution suggested previously for the studied locality. Regardless of the absence of a precise age for the succession, the regional literature of subsurface data, the paleontological remains and the intra-Callovian unconformity at the top of the unit, suggest a Bathonian (late?) up to Early Callovian age for the unit in the area. It is younger than the classical deltaic deposits extensively studied in outcrops or subsurface to the north-east and south of the Huincul High and confirms the diachronism between the south and north of the high and it sheds light on the late evolution of the unit. The younger age in Covunco section is compatible with the suggested age differences. The sedimentary record in the logged section was divided in three parts: a lower section containing marginal-marine deposits with tidal features like sigmoidal structures and muddy and coaly drapes, marine trace fossils (Asteriacites quinquefolius) and bioclastic deposits that are transitionally overlying the Los Molles Formation and end with fluvial deposits containing the vertebrate track. It is documentedat the top of an interval with3D dunes. The track is tridactyl and assigned to cf. Deltapodus. It constitutes the oldest record in Gondwana of a track attributed to tyreophorans. Isaberrysaura (Neoornitischia/Tyreophora) is the candidate producer, taking into account the stratigraphic and geographical proximity of the underlying Los Molles Formation that contains the skeletal remains. The track has some morphological features that suggest a possible swimming-wading behaviour as was previously proposed for stegosaurs. Overlying the fluvial interval, the middle section is composed of transgressive deposits containing abundant bioclastic conglomerates and channels with trunks. The upper section was deposited after a facies dislocation overlying a previously interpreted unconformity that suggests an abrupt change in the sedimentary record, containing pebbly sandstones intercalated with sandstone beds with Skolithos resembling “pipe rocks”. They are replaced upward by fine-grained sandstones with HCS, suggesting open marine conditions over the storm wave base level and a deepening upward trend. Then, the succession becomes sandier and highly bioturbated with abundant Rhizocorallium specimens and some lenticular channels with lateral accretion and abundant symmetrical wave ripple levels developed during a regressive phase.

Study of lumbar spine activity regularity based on Kanade-Lucas-Tomasi algorithm

Abstract The diagnosis of lumbar spine pathologies such as lower back pain (LBP) is extremely difficult, and a consensus regarding a diagnostic standard has not yet been reached. Accurate measurement of intervertebral kinematic parameters helps to understand the etiology and diagnosis of related diseases, and to evaluate the subsequent treatment. Quantitative fluoroscopy (QF) which can obtain continuous, dynamic image sequences of lumbar motion at low radiation doses were introduced. The estimation of intervertebral kinematics depends on the precise localization of lumbar vertebrae. Usually, vertebral corners are identified and tracked by automated methods or manual method. This study presents a novel method for vertebral tracking based on the KLT (Kanade-Lucas-Tomasi, KLT) algorithm for intervertebral kinematics analysis. Accuracy of the proposed method was tested using a sagittal human image which contained two vertebral bodies, and the average errors achieved for displacement and angle were within 0.25 mm and 0.3°, respectively. To test the proposed method under clinical conditions, totally 11 volunteers were recruited and a result of more smoothness and stability in the intervertebral kinematics was obtained with comparing to the manual method by an experienced and trained clinician. In conclusion, the proposed method is an effective, accurate way to assess lumbar vertebrae tracking.