Dinosaur Trackways Research Articles

Stops and turns: Uncommonly preserved theropod locomotive behavior patterns in an Upper Cretaceous tracksite from Torotoro National Park, Bolivia

The Carreras Pampa tracksite from the Upper Maastrichtian of Bolivia preserves one of the world's largest concentrations of dinosaur trackways. Thus far, we have assigned all but a small number of these trackways to theropod trackmakers. With such a high concentration of trackways, the Carreras Pampa tracksite is an excellent place to find evidence of a diversity of uncommonly preserved dinosaur locomotive behaviors. To date, we have found four trackways with turns ranging from 44° to 84° and describe a fifth trackway with a turn of 38° that contains unusual features. Four trackways have been found that indicate the trackmaker was walking, stopped or paused, and then began walking again. One of the trackways that records a stop also shows evidence that the trackmaker was limping. Another trackway shows that the trackmaker made a sudden, abrupt change in its direction of movement, probably in response to an unknown obstacle, and then gradually returned to its original orientation. One series of fossil traces is reported that we believe is best interpreted as a crouching trace involving multiple tracks and tail traces. These tracks were made by theropods of various sizes, with track lengths ranging from 7.3 to 32.4 cm. These trackways show that a diversity of locomotive behavior patterns occurred during the formation of the Carreras Pampa tracksite.

Uncovering hidden footprints: revision of the Lower Jurassic (Sinemurian) Razorback Beds – home to Australia’s earliest reported dinosaur trackway

ABSTRACT This investigation uses archival data (circa 1954) to elucidate new details on Australia’s first scientifically described dinosaur trackway, located at the Fireclay Caverns-Site A, Mount Morgan, Queensland. A high-resolution archival photograph reveals two additional prints, extending the known sequence from four to six tracks. Leveraging this extended dataset, we have quantified temporospatial variations to assess the trackmaker’s locomotion. Our findings reveal a decrease in stride and step lengths towards the end of the trackway, accompanied by a slight directional shift from east-southeast to east and a reduction in walking speed from a maximum of 3.8–1.8 km/hr. The life reconstruction animation of the Fireclay Caverns-Site A trackmaker supports the walking gait calculated from the relative stride data and demonstrates biomechanically plausible limb movements. By incorporating non-traditional methods, such as temporal trackway analysis and its translation as a trackmaker animation, we establish a broader framework for conventional ichnological studies. This approach enhances our interpretation of the dynamic record encapsulated in fossil trackways, enabling us to visualise and scientifically scrutinise the behaviour of extinct trackmakers.

Analysing trackway-based speed calculations to infer dinosaur locomotive capabilities and behaviours

ABSTRACT Dinosaur trackway studies provide valuable insights into extinct animals’ locomotor behaviour. Despite limitations arising from the inability to directly observe these trackmakers, speed and gait estimation formulae have become standard tools in the field of dinosaur ichnology. Stride length has traditionally been used to estimate dinosaur average speed and intra-trackway speed variations, but its unilateral focus can overlook some nuances within trackways. Alternatively, the contralateral measure pace length may not always align with the direction of travel. Analysing data from the Mancheon-ri tracksite and others, our results show that step length aligns advantageously along the trackway axis and captures nuanced speed variations. Incorporating additional parameters such as cadence and step duration enriches our understanding of the trackmaker’s movements. Cadence summarises the overall rhythm of movement across trackways, and step duration reveals temporal variations between individual steps, offering potential for 3D animated reconstructions of dinosaur behaviour. Despite these methodologies’ inherent limitations and assumptions, they provided a more refined understanding of dinosaur locomotion and behavioural patterns. Acknowledging the limitations of studying unobservable trackmakers, our estimations – based on established formulas for hip height and speed – are both rooted in accepted methodologies and remain informative, enhancing our understanding of dinosaur trackmaker behaviours.

Paleoecology and paleoenvironment of the Early Cretaceous theropod-dominated ichnoassemblage of the Los Corrales del Pelejón tracksite, Teruel Province, Spain

The earliest Cretaceous (mid-late Berriasian) tracksite Los Corrales del Pelejón is an important dinosaur trackway site in Teruel Province in Spain. The ichnoassemblage occurs in the Galve Formation (Galve sub-basin, Maestrazgo Basin) and comprises around 40 tracks assigned to theropods and ornithopods. In this paper, we undertake a paleoenvironmental analysis of the succession, which includes the overbank deposits of a fluvial environment, and discuss the implications of these findings for trackway preservation and orientation. The track-bearing unit is composed of fine- to very fine-grained, thinly bedded sandstone layers with wave ripples and traces of the Mermia ichnofacies, which were deposited as splay deposits within an ephemeral overbank pond. Two different theropod ichnotaxa (Megalosauripus cf. transjuranicus and Grallatoridae indet.) of three different size classes occur as small-, medium-, and large-sized tracks. The ornithopod tracks are classified as cf. Iguanodontipus isp. Five theropod trackways (M. cf. transjuranicus) show a bimodal orientation pattern with a similar orientation to NE-SW wave ripple crests, suggesting that these animals were walking parallel to the shoreline of the ephemeral overbank pond. Three of them walked in a similar subparallel orientation, but there is no evidence suggesting gregarious behavior as they have slightly different orientations and/or speed values. The Los Corrales del Pelejón site is an example of environmental influence on dinosaur behavior.

Diversity of dinosaur tracks and swim traces in a new site in the Upper Cretaceous El Molino Formation, Torotoro National Park, Bolivia

In January 2021, a new site containing dinosaur trackways was uncovered at kilometer 99 during the Anzaldo to Torotoro highway construction. The trackways were found on two beds of ooid and ostracod-bearing quartz arenites of about 160 m2, each separated by roughly 2 m of calcareous siltstone. In the lower layer, five theropod and five sauropod trackways were identified, three trackways of uncertain identity, and three trackways of didactyl tracks. Due to time constraints, only the upper layer containing a rich assemblage of theropod tracks and traces was thoroughly studied before road construction removed the bed. The upper bed contained 493 tracks in 88 trackways. Of those trackways, 21 consisted of a single, isolated track. In addition to tracks, 73 swim traces from 14 trackways were characterized. We distinguished five track morphotypes based on the morphology of the digits and pedal impression. Swim traces occurred in three distinct morphotypes. Invertebrate burrowing and sediment collapse, after the kick-off phase of track formation, partially modified most tracks. Before substrate stabilization, the water level rose, and dinosaurs swam in the area, leaving characteristic swim trackways with their feet scratching the bottom. This report records abundant theropod tracks and swim traces in a fortuitous exposure that is no longer accessible and comments on behavioral and paleoenvironmental implications. This location adds to the significance of the dinosaur track record of the Parque Nacional Torotoro (Torotoro National Park), Bolivia.

The first hadrosaurid trackway from the horseshoe canyon formation (campanian/maastrichtian) of Alberta, Canada

The Horseshoe Canyon Formation has provided a wealth of vertebrate skeletal fossils over the past 100 years of collection. Vertebrate trace fossils such as footprints and trackways, however, have been markedly underrepresented. Trackways can provide a wealth of information regarding behaviour and soft tissues reflective of autopodial anatomy. Discovery of several giant, high-fidelity ichnites in series from the Morrin Member represents the first definitive dinosaur trackway reported from the Horseshoe Canyon Formation. The trackway is composed of three footprint casts in series, alongside 22 associated ichnites. The ichnites were formed in soft sediment molds along a non-uniform walking surface. The deep substrates allowed for the preservation of both the plantar surface and dorsal components of the trackmakers’ feet. Some ichnites show soft tissue morphologies like interdigital webbing, toe pads, and skin impressions. Presence of these features and small kidney-shaped forelimb prints allow referral to Hadrosauropodus langstoni. The preservation of the trackway demonstrates asymmetries useful for comparison of the relief and impression surfaces of prints using both discrete and morphometric characteristics, improving confidence in identifying partial or isolated Hadrosauropodus prints of various modes of formation.

Dinosaur trackways from the Upper Cretaceous Nichkesai Formation near Mayluu Suu City, Southern Tien Shan Mountains, north-western Kyrgyzstan.

Trackways provide essential data on the biogeographic distribution, locomotion and behaviour of dinosaurs. Cretaceous dinosaur trackways are abundant in the Americas, Europe, North Africa and East Asia, but are less well documented in Central Asia despite extensive exposure of Cretaceous terrestrial sedimentary rocks in the region. Here we report the presence of bipedal, tridactyl dinosaur trackways near the city of Mayluu Suu, Jalal Abad Oblast, north-western Kyrgyzstan, the first discovery of dinosaur trace fossils within the country. The trackways are situated on a steep slope uncovered by a landslide around the year 2000 in a highly landslide-affected area. Photogrammetry is used to digitally analyse and conserve the trace fossils. We infer a shoreface setting for the trackways based on the locality sedimentology, discuss the identity of the track makers and highlight the potential for future trackway discovery in the area. This discovery contributes vital data to an otherwise sparse record on the spatio-temporal distribution of dinosaurs in Kyrgyzstan, and to the dinosaur trackway record of Central Asia.

North America’s largest assemblage of Late Jurassic dinosaur trackways, a new look at the Purgatoire Valley dinosaur tracksite (Dinosaur Lake), Morrison Formation, southeastern Colorado, United States

ABSTRACT The Purgatoire Valley dinosaur tracksite (‘Dinosaur Lake’) is North America’s largest assemblage of Late Jurassic dinosaur tracks. Roughly 1,300 tracks representing ~100 trackways were reported from a 5,600 m2 area in 1986. Extensive new excavations have revealed more than 800 additional tracks in a 2,600 m2 area. Less abraded tracks farther from the river channel, excavated below bed rock not alluvium, provide high-quality-of-preservation morphometric data. Sauropod (Parabrontopodus) trackways up to 88 m long, some with over 100 successive pes prints, comprise nearly 500 manus and pes tracks. Parallel sauropod trackways confirm previous interpretations of gregarious behaviour, now including a mixed herd of subadult and adult individuals. A preferred westward trackway progression trend likely suggests a single or short-lived episode of gregarious movement along a lake shoreline. Nearly 300 newly recorded tridactyl (theropod) tracks range from 25 to 40 cm in length, with several trackways exceeding 25 or more successive steps. Theropod tracks are assigned to ichnogenus Megalosauripus, also known from the Late Jurassic of Utah, Europe, Central Asia and North Africa. Other theropodan ichnogenera (Hispanosauropus and Therangospodus) from this epoch and region have not been identified. Cross-cutting (over-printing) trackway relationships help constrain the sequence of track registration events.

A theropod trackway providing evidence of a pathological foot from the exceptional locality of Las Hoyas (upper Barremian, Serranía de Cuenca, Spain).

We describe a trackway (LH-Mg-10-16) occurring in laminated carbonated limestones of the Las Hoyas locality, Serranía de Cuenca, Spain. It is unmistakably a large theropod dinosaur trackway encompassing two unusual aspects, namely, wide-steps, and a set of equally deformed left footprints (with a dislocated digit). The layer also preserves other vertebrate trails (fish Undichna) and different impressions in the sediment. To address these complex settings, we devised a multidisciplinary approach, including the ichnological and taphonomical descriptions, characterisation of the rock lithofacies using thin-sections, 3D structured-light digitalisation with a high precision of 200–400 μm, and a geometric morphometric comparison with a large sample of bipedal dinosaur trackways. Sedimentary analyses showed that the trackway was produced in a humid, benthonic microbial mat, the consistency and plasticity of which enabled the preservation of the details of the movement of the animal. The results of the geometric analysis indicate that the “wide-steps” of the trackway is not unusual compared to other trackways, providing evidence that it was made by a single individual with an estimated hip height approximately 2 m. Analogous pathologies in extant archosaurs that yield the combination of wide steps and deformed digits in the same trackway were considered. All results mutually support the hypothesis that a large theropod dinosaur, with a pathological foot, generated the trackway as it crossed an area of shallow water while slowly walking towards the main water source, thus stepping steadily over the benthonic mat over which multiple fish were swimming.

Darting towards Storm Shelter: A minute dinosaur trackway from southern Africa

Theropod dinosaurs are considered the main terrestrial carnivores in the Jurassic and Cretaceous. Their rise to dominance has been linked to, among others, body size changes in their early history, especially across the Triassic–Jurassic boundary. However, to qualitatively assess such temporal trends, robust skeletal and trace fossil data sets are needed globally. The richly fossiliferous southern African continental rock record in the main Karoo Basin offers an unparalleled perspective for such investigations. Herein, by documenting a newly discovered Early Jurassic trackway of very small, functionally tridactyl tracks near Storm Shelter (Eastern Cape) in South Africa, the track record can be expanded. Based on ichnological measurements at the ichnosite and digital 3D models, the footprint dimensions (length, width, splay), locomotor parameters (step length, stride, speed), and body size estimates of the trackmaker are presented. In comparison to other similar tracks, these footprints are not only the smallest Grallator-like tracks in the Clarens Formation, but also the most elongated dinosaur footprints in southern Africa to date. The tracks also show that the small-bodied bipedal trackmaker dashed across the wet sediment surface at an estimated running speed of ~12.5 km/h. During the dash, either as a predator or as a prey, the trackmaker’s small feet sunk hallux-deep into the sediment. The tracking surface is overgrown by fossilised microbial mats, which likely enhanced the footprint preservation. Based on track morphometrics and the regional dinosaur skeletal record, the trackmakers are attributed to Megapnosaurus rhodesiensis (formerly Syntarsus rhodesiensis), a small-to-medium-sized, early theropod common in southern Africa.Significance:
 
 A newly discovered Early Jurassic theropod trackway in South Africa contains not only the smallest tracks in the Clarens Formation, but also the most elongated dinosaur footprints in southern Africa to date.
 The tracks show that the small bipedal trackmaker dashed across the wet sediment surface at an estimated running speed of ~12.5 km per hour.
 During the run, the trackmaker’s feet sunk so deeply into the sediment that even the forwards-directed halluces were impressed.
 
 Open data set: https://doi.org/10.6084/m9.figshare.13007240.v1

Darting towards Storm Shelter: a minute dinosaur trackway from southern Africa

Theropod dinosaurs are considered the main terrestrial carnivores in the Jurassic and Cretaceous. Their rise to dominance has been linked to, among others, body size changes in their early history, especially across the Triassic–Jurassic boundary. However, to qualitatively assess such temporal trends, robust skeletal and trace fossil data sets are needed globally. The richly fossiliferous southern African continental rock record in the main Karoo Basin offers an unparalleled perspective for such investigations. Herein, by documenting a newly discovered Early Jurassic trackway of very small, functionally tridactyl tracks near Storm Shelter (Eastern Cape) in South Africa, the track record can be expanded. Based on ichnological measurements at the ichnosite and digital 3D models, the footprint dimensions (length, width, splay), locomotor parameters (step length, stride, speed), and body size estimates of the trackmaker are presented. In comparison to other similar tracks, these footprints are not only the smallest Grallator-like tracks in the Clarens Formation, but also the most elongated dinosaur footprints in southern Africa to date. The tracks also show that the small-bodied bipedal trackmaker dashed across the wet sediment surface at an estimated running speed of ~12.5 km/h. During the dash, either as a predator or as a prey, the trackmaker’s small feet sunk hallux-deep into the sediment. The tracking surface is overgrown by fossilised microbial mats, which likely enhanced the footprint preservation. Based on track morphometrics and the regional dinosaur skeletal record, the trackmakers are attributed to Megapnosaurus rhodesiensis (formerly Syntarsus rhodesiensis), a small-to-medium-sized, early theropod common in southern Africa.Significance: A newly discovered Early Jurassic theropod trackway in South Africa contains not only the smallest tracks in the Clarens Formation, but also the most elongated dinosaur footprints in southern Africa to date. The tracks show that the small bipedal trackmaker dashed across the wet sediment surface at an estimated running speed of ~12.5 km per hour. During the run, the trackmaker’s feet sunk so deeply into the sediment that even the forwards-directed halluces were impressed. Open data set: https://doi.org/10.6084/m9.figshare.13007240.v1

Lower Cretaceous Dinosaur Trackways Exposed by Water Erosion in Sichuan Province, China

A newly discovered saurischian dominated tracksite in the Lower Cretaceous Jiaguan Formation in southeastern Sichuan province reveals 13 sauropod trackway segments representing ichnogenus Brontopodus and three theropod trackways. This is a typical Type 1 Jiaguan Formation deposit dominated by tetrapod tracks with no significant tetrapod body fossils. The tracks occur in a river channel exposure of feldspathic quartz sandstone about 20–25 m wide and ~ 60 m long. The trackways are exposed on both banks but eroded away in the central channel area. The sauropod tracks represent relatively small animals with pes print lengths ranging from 24.5 cm to 33.9 cm. The theropod trackways include a large example (footprint length 46.5 cm with metatarsal traces) and two smaller parallel trackways with footprint lengths less than 20 cm. The author also discussed the erosion of tracks and trackways by water erosion, especially their morphological changes.

Tortuous trackways: evidence and implications of deviations, turns and changes in direction by dinosaurian trackmakers

ABSTRACT Dinosaur trackways that show changes in direction are reported from Jurassic and Cretaceous sites in North and South America, Europe and Asia. Such changes in direction can be defined as tortuosity, and categorised in 45° quadrants. To date only six tortuous theropod trackways have been reported with changes in direction exceeding ¼ -¾ turns (~ 45° – ~135°). Likewise, six tortuous sauropod trackways show turns between ~ 65° and ~180°, and two of these show turns of more than 180°, thus crossing their own trackways. Dinosaur trackways with measured deviations between ~20° and 30° are also commonly reported. The reasons for trackway tortuosity cannot be inferred confidently, although a vast, potentially relevant biological cybernetics literature exists on possible extrinsic and intrinsic influences on directional changes. These are explored and listed as multiple working hypotheses. The potential to find tortuous trackways is inferred to increase with the size of track-bearing exposures. The lack of empirical information on tortuous trackways registered by large extant tetrapods, and the extrinsic environmental and or intrinsic behavioural reasons for such tortuosity, needs to be further explored and better understood as a step towards improved interpretation of the behaviour of extinct dinosaurian trackmakers.

Applications of 3D Paleontological Data at the Florida Museum of Natural History

The past decade has seen an exponential increase of innovative applications of 3D technology in the geosciences. Here, we present a case study from the Florida Museum of Natural History applied to the multidisciplinary field of paleontology. We have deployed 3D scanning and printing techniques for the purposes of scientific research, formal education, and informal outreach. Depending on the application of the 3D file, different techniques are utilized to create high-fidelity models of physical fossil specimens or geologic field sites. These techniques include X-ray CT scans, surface scans, and photogrammetry, all of which produce 3D models that vary in resolution and scale. Novel paleontological research applied non-destructive CT scanning to explore the internal anatomy of fossil museum specimens, additionally, 3D models are being used to create K–12 curricula aligned with national and state-specific education standards that are implemented in formal classroom settings. Many of these lessons are part of the NSF-funded iDigFossils project, which aims to evaluate students’ motivation and interest towards science, technology, engineering, and mathematics after participating in integrated 3D printing and paleontology lessons. Specifically, lessons on dinosaur trackways, horse evolution, and the Great American Biotic Interchange teach geologic concepts such as deep time, taphonomy, plate tectonics, and evolutionary trends. The same 3D models developed for these K–12 lessons have been used during Florida Museum’s outreach events to engage broad audiences with hands-on exhibits and activities. All 3D files are stored on open-access, online repositories, providing accessibility to fossil specimens and field sites. The application of 3D technology for the study of fossils and paleontology will continue to expand the impact of scientific discoveries for basic research as well as for broader impacts on society.

Unusual dinosaur trackway preservation as clues to paleo-landscape and behavior from the Lower Cretaceous Luohe Formation, Shaanxi Province, China

Poorly preserved tracks have limited ichnotaxonomic or biotaxon utility, but may reveal useful information about the paleoenvironment, behavior and track taphonomy. Eight mostly parallel to sub parallel trackway segments (T1–T8) were registered on a truncation surface in the Lower Cretaceous Luohe Formation of Shaanxi Province. These attest to the passage of several bipeds, probably all theropods, in a paleo-contour-parallel, south-north direction in an arid setting. Quality of preservation in these trackways is poor, but notably superior in two additional trackways (T9–T10) on a foreset surface. Trackway T9 indicates a didactyl trackmaker, probably a deinonychosaurian, heading north to south. This is the 13th report of deinonychosaurian tracks from the Lower Cretaceous of China. If any or all the eight south-north oriented trackway segments represent continuations of other segments in the same trackways, the total number of individual trackmakers heading in this direction may have been as low as three. Although the trackway pattern and sedimentological evidence could indicate a physically controlled pathway influencing the direction taken by these trackmakers, the possibility that the trackways also represented small social or gregarious group cannot be ruled out.

Microbial structures and dinosaur trackways from a Cretaceous coastal environment (Dakota Group, Colorado, U.S.A.)

ABSTRACT Microbially induced sedimentary structures may help preserve unique glimpses of ancient shoreline habitats, but are little known from Mesozoic epicontinental settings. To help fill this knowledge gap, we describe a diverse suite of microbial structures from the Upper Cretaceous “J” Sandstone (South Platte Formation, Dakota Group) that are spectacularly exposed at Dinosaur Ridge in Morrison, Colorado, USA. Structures include “tattered” bed surfaces and ferruginous sand chips in supratidal flat facies. A large over-flip structure is preserved in a channel locally known as Crocodile Creek. In upper-intertidal facies, multidirectional ripple marks occur. Perhaps the most well-known microbial structures are exposed on extensive bedding surfaces known as “Slimy Beach,” where lower supratidal-flat facies are dominated by decimeter-scale erosional remnants and pockets. Morphologies and superposition of the structures allows identification of three generations of erosional pockets. Generation A of these erosional pockets exhibit size similarities to ornithomimid, sauropod, and ornithopod dinosaur tracks from adjacent bedding planes, raising the question of whether initial disturbance of the mat-bound surface could have been from track making. Generation B erosional pockets are older and record continuous erosion of the initial pockets until they were eventually overgrown and sealed by microbial mats. Generation C pockets are the oldest ones, exposing wide areas of barren sediment that could not be overgrown by microbial mats anymore. In concert, the microbial structures point to seasonally variable meteorological conditions along the coastline of the Western Interior Seaway and indicate that the “Slimy Beach” bedding plane represents a multi-year record of dinosaur locomotion.

Recently Discovered Basilosaurid, Baluchithere Rhinoceros, Horses, Sea Cow, Proboscidean, Eucrocodile, Pterosaurs, Plesiosaur, Fishes, Invertebrates and Wood Fossils, Tracks and Trackways of Dinosaurs from Pakistan; Comparison of Recognized Four Titanosaur Taxa of Indo-Pakistan with Madagascar

Recent Geological and Paleontological exploration during the start of new/third millennium (from 2000 to 2019) yielded 45 taxa of vertebrates and invertebrates from Mesozoic and Tertiary (except a jawless fish from Cambrian and a trilobite from Permo-Triassic boundary) strata of Pakistan like dinosaurs, mesoeucrocodiles, eucrocodiles, pterosaurs-light bodied flying reptiles, plesiosaurs-broad bodied and ichthyosaurs-streamlined bodied reptiles and fishes, basilosaurid whale, Baluchithere rhinoceroses and paleo-horses mammals, invertebrates (hippurites/rudists, oysters, mussels and other bivalves, ammonites, belemnites nautilides and gastropods Mollusca, starfish echinoids, nummulites, assilina and alveolina foraminifers, arthropods and corals), algae, sponge and wood fossils. Here described new fossil records would attract widespread interests.

A new narrow-gauge sauropod trackway from the Cenomanian Candeleros Formation, northern Patagonia, Argentina

Dinosaurs are extremely abundant in the Upper Cretaceous Neuquén Group of the Neuquén Basin (Argentina). Nevertheless, while osteological remains are rich the ichnological record is more restricted. A new sauropod dinosaur trackway with five manus-pes imprint sets discovered in the Cenomanian Candeleros Formation is described here. The trackway belongs to the narrow-gauge type that is identified for the first time in the Cenomanian and possibly for the Late Cretaceous. It is preserved as concave epirelief in fine-grained sandstones from floodplain deposits. The tracks, which are large in size (average length of 98 cm), include conspicuous rims with very well-preserved symmetrical ripples on top that are documented for the first time in the track record. Due to their preservation and the absence of clear anatomical details, the trackway was not assigned to any particular ichnotaxon. Taking into account the presence of rebbachisaurid diplodocoid remains in the Candeleros Formation, the classical association of narrow-gauge trackways with diplodocoids and the inferred gleno-acetabular distance, it is suggested that the studied trackway might belong to a large-sized rebbachisaurid. The worldwide record of Cenomanian dinosaur tracks includes only a few records of sauropod tracks. Thus, this new finding contributes to increase the knowledge about the early Late Cretaceous sauropods and their tracks.

A new fossil assemblage shows that large angiosperm trees grew in North America by the Turonian (Late Cretaceous).

The diversification of flowering plants and marked turnover in vertebrate faunas during the mid-Cretaceous transformed terrestrial communities, but the transition is obscured by reduced terrestrial deposition attributable to high sea levels. We report a new fossil assemblage from multiple localities in the Upper Cretaceous Ferron Sandstone Member of the Mancos Shale Formation in Utah. The fossils date to the Turonian, a severely underrepresented interval in the terrestrial fossil record of North America. A large silicified log (maximum preserved diameter, 1.8 m; estimated height, ca. 50 m) is assigned to the genus Paraphyllanthoxylon; it is the largest known pre-Campanian angiosperm and the earliest documented occurrence of an angiosperm tree more than 1.0 m in diameter. Foliage and palynomorphs of ferns, conifers, and angiosperms confirm the presence of mixed forest or woodland vegetation. Previously known terrestrial vertebrate remains from the Ferron Sandstone Member include fish teeth, two short dinosaur trackways, and a pterosaur; we report the first turtle and crocodilian remains and an ornithopod sacrum. Previous studies indicate that angiosperm trees were present by the Cenomanian, but this discovery demonstrates that angiosperm trees approaching 2 m in diameter were part of the forest canopies across southern North America by the Turonian (~92 million years ago), nearly 15 million years earlier than previously thought.

LIDAR-based characterization and conservation of the first theropod dinosaur trackways from Arkansas, USA.

LIDAR-based analyses of the first theropod dinosaur trackways known from the state of Arkansas, USA are reported. The trackways were found on a limestone bedding plane in the Albian De Queen Formation in an active gypsum quarry. Because limited access precluded thorough field study, fieldwork focused on preserving the entire site digitally with ground-based LIDAR, and detailed measurements were later taken digitally from point cloud data. The site contains eight tridactyl trackways associated with sauropod trackways and numerous isolated tracks. Although there appear to be two different tridactyl morphotypes, we show that the tracks are all likely from a single species of trackmaker. We apply a simple method of estimating substrate consistency by comparing the differences between true track dimensions and apparent track dimensions. The tridactyl tracks at the southern end of the site are preserved with significantly greater differences in true vs. apparent dimensions and are shallower than the rest of the tridactyl tracks at the site, which we interpret as the result of outward expansion of the soft tissues of the foot upon contact with a firm substrate. We interpret the firm substrate as having high bulk density and high shear strength, which also explain associated manus-only sauropod tracks. We show that the tridactyl tracks are likely from theropod trackmakers and that footprint lengths, trackway paces, stride lengths, and pace angulations of the De Queen trackways are statistically indistinguishable from equivalent measurements of theropod trackways in the Glen Rose Formation. The Glen Rose tracks are attributed to the large-bodied theropod, Acrocanthosaurus and we likewise attribute the De Queen tracks to Acrocanthosaurus, which is known from skeletal remains in temporally equivalent units and from the mine itself.