Primates are unusual among terrestrial quadrupedal mammals in that at walking speeds they prefer ... more Primates are unusual among terrestrial quadrupedal mammals in that at walking speeds they prefer diagonal rather than lateral gaits. A number of reasons have been proposed for this preference in relation to the arboreal ancestry of modern primates: stability, energetic cost, neural control, skeletal loading, and limb interference avoiding. However, this is a difficult question to explore experimentally since most primates only occasionally use anything other than diagonal gaits. An alternative approach is to produce biologically realistic computer simulations of primate gait that enable the constraints of biomechanical loading and the energetics of different modes of locomotion to be explored. In this paper we describe such a model for the chimpanzee Pan troglodytes. The simulation is able to produce spontaneous quadrupedal locomotion, and the footfall sequences generated are split between lateral and diagonal footfall sequences with no obvious energetic benefit associated with either option. However, out of 10 successful simulation runs, 5 were lateral sequence/lateral couplet gaits indicating a preference for a specific lateral footfall sequence with a relatively tightly constrained phase difference between the fore- and hindlimbs. This suggests that the choice of diagonal walking gaits in chimpanzees is not a simple mechanical phenomenon and that diagonal walking gaits in primates are selected for by multiple factors.
Fossil evidence for longitudinal arches in the foot is frequently used to con- strain the origins... more Fossil evidence for longitudinal arches in the foot is frequently used to con- strain the origins of terrestrial bipedality in human ancestors. This approach rests on the prevailing concept that human feet are unique in functioning with a relatively stiff lateral mid-foot, lacking the significant flexion and high plantar pressures present in non-human apes. This paradigm has stood for more than 70 years but has yet to be tested objectively with quan- titative data. Herein, we show that plantar pressure records with elevated lateral mid-foot pressures occur frequently in healthy, habitually shod humans, with magnitudes in some individuals approaching absolute maxima across the foot. Furthermore, the same astonishing pressure range is present in bonobos and the orangutan (the most arboreal great ape), yield- ing overlap with human pressures. Thus, while the mean tendency of habitual mechanics of the mid-foot in healthy humans is indeed consistent with the traditional concept of the lateral mid-foot as a relatively rigid or stabilized structure, it is clear that lateral arch stabilization in humans is not obligate and is often transient. These findings suggest a level of detach- ment between foot stiffness during gait and osteological structure, hence fossilized bone morphology by itself may only provide a crude indication of mid-foot function in extinct hominins. Evidence for thick plantar tissues in Ardipithecus ramidus suggests that a human-like combination of active and passive modulation of foot compliance by soft tissues extends back into an arboreal context, supporting an arboreal origin of hominin bipedalism in compressive orthogrady. We propose that the musculoskeletal conformation of the modern human mid-foot evolved under selection for a functionally tuneable, rather than obligatory stiff structure.
Human footprints provide some of the most publically emotive and tangible evidence of our ancesto... more Human footprints provide some of the most publically emotive and tangible evidence of our ancestors. To the scientific community they provide evidence of stature, presence, behaviour and in the case of early hominins potential evidence with respect to the evolution of gait. While rare in the geological record the number of footprint sites has increased in recent years along with the analytical tools available for their study. Many of these sites are at risk from rapid erosion, including the Ileret footprints in northern Kenya which are second only in age to those at Laetoli (Tanzania). Unlithified, soft-sediment footprint sites such these pose a significant geoconservation challenge. In the first part of this paper conservation and preservation options are explored leading to the conclusion that to ‘record and digitally rescue’ provides the only viable approach. Key to such strategies is the increasing availability of three-dimensional data capture either via optical laser scanning and/or digital photogrammetry. Within the discipline there is a developing schism between those that favour one approach over the other and a requirement from geoconservationists and the scientific community for some form of objective appraisal of these alternatives is necessary. Consequently in the second part of this paper we evaluate these alternative approaches and the role they can play in a ‘record and digitally rescue’ conservation strategy. Using modern footprint data, digital models created via optical laser scanning are compared to those generated by state-of-the-art photogrammetry. Both methods give comparable although subtly different results. This data is evaluated alongside a review of field deployment issues to provide guidance to the community with respect to the factors which need to be considered in digital conservation of human/hominin footprints.
The study of a small sauropod trackway from the Late Cretaceous Fumanya tracksite (southern Pyren... more The study of a small sauropod trackway from the Late Cretaceous Fumanya tracksite (southern Pyrenees, Catalonia) and further comparisons with larger trackways from the same locality suggest a causative relationship between gait, gauge, and body proportions of the respective titanosaur trackmakers. This analysis, conducted in the context of scaling predictions and using geometric similarity and dynamic similarity hypotheses, reveals similar Froude numbers and relative stride lengths for both small and large trackmakers from Fumanya. Evidence for geometric similarity in these trackways suggests that titanosaurs of different sizes moved in a dynamically similar way, probably using an amble gait. The wide gauge condition reported in trackways of small and large titanosaurs implies that they possessed similar body (trunk and limbs) proportions despite large differences in body size. These results strengthen the hypothesis that titanosaurs possessed a distinctive suite of anatomical characteristics that are well reflected in their tracks and trackways.
The skeletons of dinosaurs, particularly large-bodied, enigmatic forms like Tyrannosaurus and Tri... more The skeletons of dinosaurs, particularly large-bodied, enigmatic forms like Tyrannosaurus and Triceratops, are awe inspiring and have been brought ‘back-to-life’ in numerous animated and motion picture productions. But how did these animals really stand and move in life and how rigorously can scientists reconstruct their locomotion? In recent years, traditional approaches, such as morphological comparisons and limb bone scaling, have been combined with new computational modelling methods to provide rich insight into dinosaur locomotion and how it may have changed during the group's long evolutionary history. However, many significant challenges remain and currently it is still difficult to constrain how any one dinosaur moved. Unknown factors, such as body mass and muscle anatomy, make it difficult to reliably reconstruct the motions and capabilities (e.g. running speeds) of dinosaurs based on data available from fossils. Thus, future work must continue to integrate information on dinosaur anatomy with principles of locomotion established in living animals, as well as embracing a range of methodological approaches.
Footprints are the most direct source of evidence about locomotor biomechanics in extinct vertebr... more Footprints are the most direct source of evidence about locomotor biomechanics in extinct vertebrates. One of the principal suppositions underpinning biomechanical inferences is that footprint geometry correlates with dyna- mic foot pressure, which, in turn, is linked with overall limb motion of the trackmaker. In this study, we perform the first quantitative test of this long-standing assumption, using topological statistical analysis of plantar pressures and experimental and computer-simulated footprints. In computer-simulated footprints, the relative distribution of depth differed from the distribution of both peak and pressure impulse in all simulations. Analysis of footprint samples with common loading inputs and similar depths reveals that only shallow footprints lack significant topological differences between depth and pressure distributions. Topological comparison of plantar pressures and experimental beach footprints demonstrates that geometry is highly depen- dent on overall print depth; deeper footprints are characterized by greater relative forefoot, and particularly toe, depth than shallow footprints. The high- lighted difference between ‘shallow’ and ‘deep’ footprints clearly emphasizes the need to understand variation in foot mechanics across different degrees of substrate compliance. Overall, our results indicate that extreme caution is required when applying the ‘depth equals pressure’ paradigm to hominin footprints, and by extension, those of other extant and extinct tetrapods.
Integrated laser scanning and photogrammetry - remote methods of collecting three dimensional (3D... more Integrated laser scanning and photogrammetry - remote methods of collecting three dimensional (3D) spatial and geometrical data - has to-date been under-utilized in palaeontology. Laser scanning provides a dense point cloud that represents a precisely sampled replica of an object’s surface geometry. Integrating a digital camera into the scanning unit allows photographic images to be combined with these point clouds to produce interactive photo-realistic 3D models. The Differential Global Positioning System (DGPS) also built into the unit provides sub-metre global position information and allows data to be integrated with other georeferenced datasets. As a non-invasive method of attaining geometrically precise 3D digital models, these techniques enable palaeontologists to explore fossils and fossil sites on the desktop where an exceptional level of visualization can be combined with analytical facilities unique to the digital environment. 3D geological mapping using integrated laser scanning and photogrammetry has provided the necessary framework for interpretation of fossiliferous localities in the context of their 3D sedimentary facies, improving understanding of the stratigraphic and palaeoenvironmental context of fossil sites. Highresolutionphoto-realistic models also offer remote interactive access through virtual fieldtrips, and may contribute significantly to conservation and education at palaeontological heritage sites. Building on its use to model the 3D geometry of fossil dinosaur tracks, we have also recently used laser scanning to digitize skeletal mounts of theropod dinosaurs, producing scale models that have been used to examine the mass, inertial properties and locomotor mechanics of these animals.
In 1940 R.T. Bird of the American Museum of Natural History collected segments of a sauropod and ... more In 1940 R.T. Bird of the American Museum of Natural History collected segments of a sauropod and a theropod trackway from a site in the bed (Glen Rose Formation; Lower Cretaceous) of the Paluxy River, in what is now Dinosaur Valley State Park (Glen Rose, Texas, USA). However, Bird left undocumented thousands of other dinosaur footprints from this and other Paluxy tracksites. In 2008 and 2009 our international team carried out fieldwork to create detailed photomosaics of extant Paluxy tracksites, using GIS technology to combine these with historic maps and photographs. We also made photographs, tracings, LiDAR images, and measurements of individual footprints and trackways. Paluxy dinosaur tracksites occur in more than one tracklayer, but the largest and most spectacular footprints occur in the Main Tracklayer, a 20-30 cm thick, homogeneous dolomudstone that is thickly riddled with vertical invertebrate burrows (Skolithos). There are two dinosaur footprint morphotypes in the Main Tracklayer: spectacular sauropod trackways (Brontopodus ) and the far more numerous tridactyl footprints, most or all of which were made by large theropods (possible ornithopod prints occur in a tracklayer stratigraphically higher than the Main Tracklayer). Tridactyl footprints are highly variable in quality; Paluxy tracksites collectively constitute a natural laboratory for investigating how trackmaker-substrate interactions create extensive extramorphological variability from a single foot morphology. Trackways of bipedal dinosaurs show a “mirror-image” distribution, suggesting movement of animals back and forth along a shoreline. In contrast, most sauropod trackways head in roughly the same direction, suggesting passage of a group of dinosaurs. The trackways collected by R.T. Bird suggest that at least one theropod was following a sauropod.
Finite-element analysis was used to investigate the extent of bias in the ichnological fossil rec... more Finite-element analysis was used to investigate the extent of bias in the ichnological fossil record attributable to body mass. Virtual tracks were simulated for four dinosaur taxa of different sizes (Struthiomimus, Tyrannosaurus, Brachiosaurus and Edmontosaurus), in a range of substrate conditions. Outlines of autopodia were generated based upon osteology and published soft-tissue reconstructions. Loads were applied vertically to the feet equivalent to the weight of the animal, and distributed accordingly to fore- and hindlimbs where relevant. Ideal, semi-infinite elastic–plastic substrates displayed a ‘Goldilocks’ quality where only a narrow range of loads could produce tracks, given that small animals failed to indent the substrate, and larger animals would be unable to traverse the area without becoming mired. If a firm subsurface layer is assumed, a more complete assemblage is possible, though there is a strong bias towards larger, heavier animals. The depths of fossil tracks within an assemblage may indicate thicknesses of mechanically distinct substrate layers at the time of track formation, even when the lithified strata appear compositionally homogeneous. This work increases the effectiveness of using vertebrate tracks as palaeoenvironmental indicators in terms of inferring substrate conditions at the time of track formation. Additionally, simulated undertracks are examined, and it is shown that complex deformation beneath the foot may not be indicative of limb kinematics as has been previously interpreted, but instead ridges and undulations at the base of a track may be a function of sediment displacement vectors and pedal morphology.
The occurrence of sauropod manus-only trackways in the fossil record is poorly understood, limiti... more 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.
The taxonomy and systematics of the earliest plesiosaurians is poorly resolved. This limits our u... more The taxonomy and systematics of the earliest plesiosaurians is poorly resolved. This limits our understanding of the diversification of one of the most successful clades of secondarily aquatic tetrapods. Here we provide a robust diagnosis of Thalassiodracon hawkinsii from the Pre-planorbis Beds (Triassic–Jurassic boundary interval) of the United Kingdom, and suggest that at least two other, previously unrecognized plesiosaurians are present in the same deposits. Computed tomography of an exceptionally preserved skull, and examination of previously undescribed (or briefly described) specimens yields new anatomical data. Thalassiodracon has a dorsomedian ridge on the premaxilla, a squamosal bulb, four premaxillary teeth, and a heterodont maxillary dentition. Several features of Thalassiodracon, including the squmosal bulb, broad anterior termination of the pterygoids, heterodont dentition, and single foramen in the lateral surface of the exoccipital, are plesiomorphic or represent pliosauroid synapomorphies. Among pliosauroids, Thalassiodracon shares a parietal that extends far anteriorly, a broad, interdigitating posterior termination of the premaxilla, and a short posteroventral process of the postorbital with Hauffiosaurus and pliosaurids. Thus, we suggest pliosaurid affinities for Thalassiodracon, in contrast to most recent phylogenetic studies. The early stratigraphic position of Thalassiodracon coincides with the earliest occurrence of Rhomaleosauridae (the sister taxon of Pliosauridae). The relatively long neck and small skull of Thalassiodracon indicate that the robust skeleton and macropredaceous habits of rhomaleosaurids and pliosaurids were derived independently.
Body mass reconstructions of extinct vertebrates are most robust when complete to near-complete s... more Body mass reconstructions of extinct vertebrates are most robust when complete to near-complete skeletons allow the reconstruction of either physical or digital models. Digital models are most efficient in terms of time and cost, and provide the facility to infinitely modify model properties non-destructively, such that sensitivity analyses can be conducted to quantify the effect of the many unknown parameters involved in reconstructions of extinct animals. In this study we use laser scanning (LiDAR) and computer modelling methods to create a range of 3D mass models of five specimens of non-avian dinosaur; two near-complete specimens of Tyrannosaurus rex, the most complete specimens of Acrocanthosaurus atokensis and Strutiomimus sedens, and a near-complete skeleton of a sub-adult Edmontosaurus annectens. LiDAR scanning allows a full mounted skeleton to be imaged resulting in a detailed 3D model in which each bone retains its spatial position and articulation. This provides a high resolution skeletal framework around which the body cavity and internal organs such as lungs and air sacs can be reconstructed. This has allowed calculation of body segment masses, centres of mass and moments or inertia for each animal. However, any soft tissue reconstruction of an extinct taxon inevitably represents a best estimate model with an unknown level of accuracy. We have therefore conducted an extensive sensitivity analysis in which the volumes of body segments and respiratory organs were varied in an attempt to constrain the likely maximum plausible range of mass parameters for each animal. Our results provide wide ranges in actual mass and inertial values, emphasizing the high level of uncertainty inevitable in such reconstructions. However, our sensitivity analysis consistently places the centre of mass well below and in front of hip joint in each animal, regardless of the chosen combination of body and respiratory structure volumes. These results emphasize that future biomechanical assessments of extinct taxa should be preceded by a detailed investigation of the plausible range of mass properties, in which sensitivity analyses are used to identify a suite of possible values to be tested as inputs in analytical models.
MOR693, nicknamed ‘Big Al,’ is the most complete skeleton of the non-avian
theropod Allosaurus an... more MOR693, nicknamed ‘Big Al,’ is the most complete skeleton of the non-avian theropod Allosaurus and therefore provides the best opportunity to investigate the mass properties of this important Jurassic theropod through accurate physical or digital volumetric models. In this study, laser scanning and computer modelling software have been used to construct volumetric models of MOR693. A long-range laser scanner has been used to digitize the mounted cast of MOR693, allowing the reconstruction of body volumes and respiratory structures around and within the three-dimensional (3D) skeletal model. The digital medium offered the facility to modify model properties nondestructively in a detailed sensitivity analysis to quantify the effects of the many unknown parameters involved in such reconstructions. In addition to varying the volumes of body segments and respiratory structures, we also extend the sensitivity analysis to include uncertainties regarding osteological articulations in non-avian dinosaurs, including effects of inter-vertebral spacing and the orientation or ‘flare’ of the rib cage in MOR693. Results suggest body mass and inertial values are extremely uncertain and show a wide range in plausible values, whilst the CM (centre of mass) position is well constrained immediately in front and below the hip joint in MOR693, consistent with similar reconstructions of non-avian theropods.
Light Detection And Range (LiDAR) imaging provides a means to model the 3D geometry of fossil tra... more Light Detection And Range (LiDAR) imaging provides a means to model the 3D geometry of fossil tracks in the field with high accuracy. This represents a considerable advance for the science of vertebrate ichnology in which traditional field methods suffer from a significant degree of abstraction and lack the resolution required to interpret tracks quantitatively. Three-dimensional LiDAR models provide additional morphometric information and allow the application of new analytical tools unique to the digital environment. The method will enable fossil track morphometrics to develop into an iterative process that combines 3D visualization and multivariate statistical methods, blending qualitative and quantitative approaches and allowing track morphologies to be compared holistically. Modelling of trackways from Fumanya (south-east Pyrenees) using LiDAR has enabled variation in linear track dimensions to be explained by the varied contribution of different modes of shear with increasing depth below the foot ⁄ sediment interface. Features in the relief of pes traces indicate that subsurface zones within their track volumes are defined by the interaction of puncture and local shear, below a surface zone of liquefaction failure now lost to erosion. This model of mechanical failure enables a preliminary review of the pedal kinematics of titanosaurid sauropod dinosaurs and suggests multiphase loading of the sediment by the titanosaurid pes. However, from inspection of these 3D surfaces alone it is not possible to differentiate between the possibility of one or two discrete phases of pedal motion preceding the toe-off event at the maximum height of the support phase. By integrating LiDAR models with analogue modelling within a 3D digital environment it will be possible to clarify such interpretations of fossil tracks and the locomotor mechanics of extinct animals.
Increasing political and social awareness of the importance of protecting the geological heritage... more Increasing political and social awareness of the importance of protecting the geological heritage is compelling geoscientists to consider new methods for reconciling conservation and exploration of their research sites. Terrestrial Light Detection And Range (LiDAR) imaging is an accurate method of collecting 3D spatial data that has so far been under-utilized in the geological sciences. This aim of this paper is to assess the value of integrated LiDAR and photogrammetric imaging as a tool for synchronizing scientific exploration with conservation of geological heritage sites. Fumanya (Catalonia) is one of the most important Cretaceous tracksites in Europe, but the nature of exposure of the track-bearing surface has hindered quantitative documentation of the ichnites. Using integrated Light Detection And Range (LiDAR) imaging and photogrammetry it has been possible to construct highresolution Digital Outcrop Models (DOM) of the tracksites. Photo-textured DOMs are a powerful visualization tool and function as fully 3D interactive databases that preserve information about the site that would otherwise be lost to erosion. LiDAR-derived DOMs have the potential to contribute profoundly to future geoconservation projects, particularly as a tool for documenting and monitoring heritage sites and promoting education and tourism. LiDAR scanning also provides sufficient resolution to perform robust quantitative analysis of dinosaur tracks.
Public engagement and the promotion of science to a wider non-academic
audience form an integral ... more Public engagement and the promotion of science to a wider non-academic audience form an integral role of the professional scientist in the twenty-first century. The high level of public interest in palaeontology means that the Earth’s prehistoric past can provide an important medium through which to communicate information concerning contemporary scientific issues. Here we explain how modern computer techniques can be used to enhance public understanding of complex palaeontological issues
Constructing musculoskeletal models of extinct vertebrates requires subjective assumptions about ... more Constructing musculoskeletal models of extinct vertebrates requires subjective assumptions about soft tissue parameters rarely preserved in the fossil record. Despite these necessary assumptions about fundamental input values, paleobiologists rarely perform objective tests of best-estimate models before reaching conclusions based on predicted results. The extent to which lack of knowledge on soft tissue anatomy limits the accuracy of running speed estimates of extinct dinosaurs is therefore poorly understood. In this study, a sensitivity analysis is performed on an evolutionary robotics model of the non-avian theropod dinosaur Allosaurus, used previously to estimate maximum running speed in this extinct animal. A range of muscle parameters were varied over the range observed in extant vertebrates, whereas mass-related parameters were altered across the range of published estimates for Allosaurus. Muscle parameters have a linear relationship with maximum running speed, whereas surprisingly total body mass and torso center of mass have little effect. Muscle force values produced the greatest range in predicted running speeds (4.5–10.7 m/s) and stride lengths (4–5.8 m) in the sensitivity analysis, equating to 65.9% and 30.7% variation about the original ‘best-estimate’ prediction, a relatively high potential margin of error. These results highlight the importance of sensitivity analyses in biomechanical modeling of extinct taxa, particularly where values for soft tissues parameters are not tightly constrained. The current range in plausible values for soft tissue properties makes a robust quantitative assessment of behavioral ecology and species interactions in dinosaurian communities extremely difficult.
The large theropod dinosaur Tyrannosaurus rex underwent remarkable changes during its growth from... more The large theropod dinosaur Tyrannosaurus rex underwent remarkable changes during its growth from ,10 kg hatchlings to .6000 kg adults in ,20 years. These changes raise fascinating questions about the morphological transformations involved, peak growth rates, and scaling of limb muscle sizes as well as the body’s centre of mass that could have influenced ontogenetic changes of locomotion in T. rex. Here we address these questions using three-dimensionally scanned computer models of four large, well-preserved fossil specimens as well as a putative juvenile individual. Furthermore we quantify the variations of estimated body mass, centre of mass and segment dimensions, to characterize inaccuracies in our reconstructions. These inaccuracies include not only subjectivity but also incomplete preservation and inconsistent articulations of museum skeletons. Although those problems cause ambiguity, we conclude that adult T. rex had body masses around 6000–8000 kg, with the largest known specimen (‘‘Sue’’) perhaps ,9500 kg. Our results show that during T. rex ontogeny, the torso became longer and heavier whereas the limbs became proportionately shorter and lighter. Our estimates of peak growth rates are about twice as rapid as previous ones but generally support previous methods, despite biases caused by the usage of scale models and equations that underestimate body masses. We tentatively infer that the hindlimb extensor muscles masses, including the large tail muscle M. caudofemoralis longus, may have decreased in their relative size as the centre of mass shifted craniodorsally during T. rex ontogeny. Such ontogenetic changes would have worsened any relative or absolute decline of maximal locomotor performance. Regardless, T. rex probably had hip and thigh muscles relatively larger than any extant animal’s. Overall, the limb ‘‘antigravity’’ muscles may have been as large as or even larger than those of ratite birds, which themselves have the most muscular limbs of any living animal.
Bite mechanics and feeding behaviour in Tyrannosaurus rex are controversial. Some contend that a ... more Bite mechanics and feeding behaviour in Tyrannosaurus rex are controversial. Some contend that a modest bite mechanically limited T. rex to scavenging, while others argue that high bite forces facilitated a predatory mode of life. We use dynamic musculoskeletal models to simulate maximal biting in T. rex.Models predict that adult T. rex generated sustained bite forces of 35 000–57 000 N at a single posterior tooth, by far the highest bite forces estimated for any terrestrial animal. Scaling analyses suggest that adult T. rex had a strong bite for its body size, and that bite performance increased allometrically during ontogeny. Positive allometry in bite performance during growth may have facilitated an ontogenetic change in feeding behaviour in T. rex, associated with an expansion of prey range in adults to include the largest contemporaneous animals.
Primates are unusual among terrestrial quadrupedal mammals in that at walking speeds they prefer ... more Primates are unusual among terrestrial quadrupedal mammals in that at walking speeds they prefer diagonal rather than lateral gaits. A number of reasons have been proposed for this preference in relation to the arboreal ancestry of modern primates: stability, energetic cost, neural control, skeletal loading, and limb interference avoiding. However, this is a difficult question to explore experimentally since most primates only occasionally use anything other than diagonal gaits. An alternative approach is to produce biologically realistic computer simulations of primate gait that enable the constraints of biomechanical loading and the energetics of different modes of locomotion to be explored. In this paper we describe such a model for the chimpanzee Pan troglodytes. The simulation is able to produce spontaneous quadrupedal locomotion, and the footfall sequences generated are split between lateral and diagonal footfall sequences with no obvious energetic benefit associated with either option. However, out of 10 successful simulation runs, 5 were lateral sequence/lateral couplet gaits indicating a preference for a specific lateral footfall sequence with a relatively tightly constrained phase difference between the fore- and hindlimbs. This suggests that the choice of diagonal walking gaits in chimpanzees is not a simple mechanical phenomenon and that diagonal walking gaits in primates are selected for by multiple factors.
Fossil evidence for longitudinal arches in the foot is frequently used to con- strain the origins... more Fossil evidence for longitudinal arches in the foot is frequently used to con- strain the origins of terrestrial bipedality in human ancestors. This approach rests on the prevailing concept that human feet are unique in functioning with a relatively stiff lateral mid-foot, lacking the significant flexion and high plantar pressures present in non-human apes. This paradigm has stood for more than 70 years but has yet to be tested objectively with quan- titative data. Herein, we show that plantar pressure records with elevated lateral mid-foot pressures occur frequently in healthy, habitually shod humans, with magnitudes in some individuals approaching absolute maxima across the foot. Furthermore, the same astonishing pressure range is present in bonobos and the orangutan (the most arboreal great ape), yield- ing overlap with human pressures. Thus, while the mean tendency of habitual mechanics of the mid-foot in healthy humans is indeed consistent with the traditional concept of the lateral mid-foot as a relatively rigid or stabilized structure, it is clear that lateral arch stabilization in humans is not obligate and is often transient. These findings suggest a level of detach- ment between foot stiffness during gait and osteological structure, hence fossilized bone morphology by itself may only provide a crude indication of mid-foot function in extinct hominins. Evidence for thick plantar tissues in Ardipithecus ramidus suggests that a human-like combination of active and passive modulation of foot compliance by soft tissues extends back into an arboreal context, supporting an arboreal origin of hominin bipedalism in compressive orthogrady. We propose that the musculoskeletal conformation of the modern human mid-foot evolved under selection for a functionally tuneable, rather than obligatory stiff structure.
Human footprints provide some of the most publically emotive and tangible evidence of our ancesto... more Human footprints provide some of the most publically emotive and tangible evidence of our ancestors. To the scientific community they provide evidence of stature, presence, behaviour and in the case of early hominins potential evidence with respect to the evolution of gait. While rare in the geological record the number of footprint sites has increased in recent years along with the analytical tools available for their study. Many of these sites are at risk from rapid erosion, including the Ileret footprints in northern Kenya which are second only in age to those at Laetoli (Tanzania). Unlithified, soft-sediment footprint sites such these pose a significant geoconservation challenge. In the first part of this paper conservation and preservation options are explored leading to the conclusion that to ‘record and digitally rescue’ provides the only viable approach. Key to such strategies is the increasing availability of three-dimensional data capture either via optical laser scanning and/or digital photogrammetry. Within the discipline there is a developing schism between those that favour one approach over the other and a requirement from geoconservationists and the scientific community for some form of objective appraisal of these alternatives is necessary. Consequently in the second part of this paper we evaluate these alternative approaches and the role they can play in a ‘record and digitally rescue’ conservation strategy. Using modern footprint data, digital models created via optical laser scanning are compared to those generated by state-of-the-art photogrammetry. Both methods give comparable although subtly different results. This data is evaluated alongside a review of field deployment issues to provide guidance to the community with respect to the factors which need to be considered in digital conservation of human/hominin footprints.
The study of a small sauropod trackway from the Late Cretaceous Fumanya tracksite (southern Pyren... more The study of a small sauropod trackway from the Late Cretaceous Fumanya tracksite (southern Pyrenees, Catalonia) and further comparisons with larger trackways from the same locality suggest a causative relationship between gait, gauge, and body proportions of the respective titanosaur trackmakers. This analysis, conducted in the context of scaling predictions and using geometric similarity and dynamic similarity hypotheses, reveals similar Froude numbers and relative stride lengths for both small and large trackmakers from Fumanya. Evidence for geometric similarity in these trackways suggests that titanosaurs of different sizes moved in a dynamically similar way, probably using an amble gait. The wide gauge condition reported in trackways of small and large titanosaurs implies that they possessed similar body (trunk and limbs) proportions despite large differences in body size. These results strengthen the hypothesis that titanosaurs possessed a distinctive suite of anatomical characteristics that are well reflected in their tracks and trackways.
The skeletons of dinosaurs, particularly large-bodied, enigmatic forms like Tyrannosaurus and Tri... more The skeletons of dinosaurs, particularly large-bodied, enigmatic forms like Tyrannosaurus and Triceratops, are awe inspiring and have been brought ‘back-to-life’ in numerous animated and motion picture productions. But how did these animals really stand and move in life and how rigorously can scientists reconstruct their locomotion? In recent years, traditional approaches, such as morphological comparisons and limb bone scaling, have been combined with new computational modelling methods to provide rich insight into dinosaur locomotion and how it may have changed during the group's long evolutionary history. However, many significant challenges remain and currently it is still difficult to constrain how any one dinosaur moved. Unknown factors, such as body mass and muscle anatomy, make it difficult to reliably reconstruct the motions and capabilities (e.g. running speeds) of dinosaurs based on data available from fossils. Thus, future work must continue to integrate information on dinosaur anatomy with principles of locomotion established in living animals, as well as embracing a range of methodological approaches.
Footprints are the most direct source of evidence about locomotor biomechanics in extinct vertebr... more Footprints are the most direct source of evidence about locomotor biomechanics in extinct vertebrates. One of the principal suppositions underpinning biomechanical inferences is that footprint geometry correlates with dyna- mic foot pressure, which, in turn, is linked with overall limb motion of the trackmaker. In this study, we perform the first quantitative test of this long-standing assumption, using topological statistical analysis of plantar pressures and experimental and computer-simulated footprints. In computer-simulated footprints, the relative distribution of depth differed from the distribution of both peak and pressure impulse in all simulations. Analysis of footprint samples with common loading inputs and similar depths reveals that only shallow footprints lack significant topological differences between depth and pressure distributions. Topological comparison of plantar pressures and experimental beach footprints demonstrates that geometry is highly depen- dent on overall print depth; deeper footprints are characterized by greater relative forefoot, and particularly toe, depth than shallow footprints. The high- lighted difference between ‘shallow’ and ‘deep’ footprints clearly emphasizes the need to understand variation in foot mechanics across different degrees of substrate compliance. Overall, our results indicate that extreme caution is required when applying the ‘depth equals pressure’ paradigm to hominin footprints, and by extension, those of other extant and extinct tetrapods.
Integrated laser scanning and photogrammetry - remote methods of collecting three dimensional (3D... more Integrated laser scanning and photogrammetry - remote methods of collecting three dimensional (3D) spatial and geometrical data - has to-date been under-utilized in palaeontology. Laser scanning provides a dense point cloud that represents a precisely sampled replica of an object’s surface geometry. Integrating a digital camera into the scanning unit allows photographic images to be combined with these point clouds to produce interactive photo-realistic 3D models. The Differential Global Positioning System (DGPS) also built into the unit provides sub-metre global position information and allows data to be integrated with other georeferenced datasets. As a non-invasive method of attaining geometrically precise 3D digital models, these techniques enable palaeontologists to explore fossils and fossil sites on the desktop where an exceptional level of visualization can be combined with analytical facilities unique to the digital environment. 3D geological mapping using integrated laser scanning and photogrammetry has provided the necessary framework for interpretation of fossiliferous localities in the context of their 3D sedimentary facies, improving understanding of the stratigraphic and palaeoenvironmental context of fossil sites. Highresolutionphoto-realistic models also offer remote interactive access through virtual fieldtrips, and may contribute significantly to conservation and education at palaeontological heritage sites. Building on its use to model the 3D geometry of fossil dinosaur tracks, we have also recently used laser scanning to digitize skeletal mounts of theropod dinosaurs, producing scale models that have been used to examine the mass, inertial properties and locomotor mechanics of these animals.
In 1940 R.T. Bird of the American Museum of Natural History collected segments of a sauropod and ... more In 1940 R.T. Bird of the American Museum of Natural History collected segments of a sauropod and a theropod trackway from a site in the bed (Glen Rose Formation; Lower Cretaceous) of the Paluxy River, in what is now Dinosaur Valley State Park (Glen Rose, Texas, USA). However, Bird left undocumented thousands of other dinosaur footprints from this and other Paluxy tracksites. In 2008 and 2009 our international team carried out fieldwork to create detailed photomosaics of extant Paluxy tracksites, using GIS technology to combine these with historic maps and photographs. We also made photographs, tracings, LiDAR images, and measurements of individual footprints and trackways. Paluxy dinosaur tracksites occur in more than one tracklayer, but the largest and most spectacular footprints occur in the Main Tracklayer, a 20-30 cm thick, homogeneous dolomudstone that is thickly riddled with vertical invertebrate burrows (Skolithos). There are two dinosaur footprint morphotypes in the Main Tracklayer: spectacular sauropod trackways (Brontopodus ) and the far more numerous tridactyl footprints, most or all of which were made by large theropods (possible ornithopod prints occur in a tracklayer stratigraphically higher than the Main Tracklayer). Tridactyl footprints are highly variable in quality; Paluxy tracksites collectively constitute a natural laboratory for investigating how trackmaker-substrate interactions create extensive extramorphological variability from a single foot morphology. Trackways of bipedal dinosaurs show a “mirror-image” distribution, suggesting movement of animals back and forth along a shoreline. In contrast, most sauropod trackways head in roughly the same direction, suggesting passage of a group of dinosaurs. The trackways collected by R.T. Bird suggest that at least one theropod was following a sauropod.
Finite-element analysis was used to investigate the extent of bias in the ichnological fossil rec... more Finite-element analysis was used to investigate the extent of bias in the ichnological fossil record attributable to body mass. Virtual tracks were simulated for four dinosaur taxa of different sizes (Struthiomimus, Tyrannosaurus, Brachiosaurus and Edmontosaurus), in a range of substrate conditions. Outlines of autopodia were generated based upon osteology and published soft-tissue reconstructions. Loads were applied vertically to the feet equivalent to the weight of the animal, and distributed accordingly to fore- and hindlimbs where relevant. Ideal, semi-infinite elastic–plastic substrates displayed a ‘Goldilocks’ quality where only a narrow range of loads could produce tracks, given that small animals failed to indent the substrate, and larger animals would be unable to traverse the area without becoming mired. If a firm subsurface layer is assumed, a more complete assemblage is possible, though there is a strong bias towards larger, heavier animals. The depths of fossil tracks within an assemblage may indicate thicknesses of mechanically distinct substrate layers at the time of track formation, even when the lithified strata appear compositionally homogeneous. This work increases the effectiveness of using vertebrate tracks as palaeoenvironmental indicators in terms of inferring substrate conditions at the time of track formation. Additionally, simulated undertracks are examined, and it is shown that complex deformation beneath the foot may not be indicative of limb kinematics as has been previously interpreted, but instead ridges and undulations at the base of a track may be a function of sediment displacement vectors and pedal morphology.
The occurrence of sauropod manus-only trackways in the fossil record is poorly understood, limiti... more 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.
The taxonomy and systematics of the earliest plesiosaurians is poorly resolved. This limits our u... more The taxonomy and systematics of the earliest plesiosaurians is poorly resolved. This limits our understanding of the diversification of one of the most successful clades of secondarily aquatic tetrapods. Here we provide a robust diagnosis of Thalassiodracon hawkinsii from the Pre-planorbis Beds (Triassic–Jurassic boundary interval) of the United Kingdom, and suggest that at least two other, previously unrecognized plesiosaurians are present in the same deposits. Computed tomography of an exceptionally preserved skull, and examination of previously undescribed (or briefly described) specimens yields new anatomical data. Thalassiodracon has a dorsomedian ridge on the premaxilla, a squamosal bulb, four premaxillary teeth, and a heterodont maxillary dentition. Several features of Thalassiodracon, including the squmosal bulb, broad anterior termination of the pterygoids, heterodont dentition, and single foramen in the lateral surface of the exoccipital, are plesiomorphic or represent pliosauroid synapomorphies. Among pliosauroids, Thalassiodracon shares a parietal that extends far anteriorly, a broad, interdigitating posterior termination of the premaxilla, and a short posteroventral process of the postorbital with Hauffiosaurus and pliosaurids. Thus, we suggest pliosaurid affinities for Thalassiodracon, in contrast to most recent phylogenetic studies. The early stratigraphic position of Thalassiodracon coincides with the earliest occurrence of Rhomaleosauridae (the sister taxon of Pliosauridae). The relatively long neck and small skull of Thalassiodracon indicate that the robust skeleton and macropredaceous habits of rhomaleosaurids and pliosaurids were derived independently.
Body mass reconstructions of extinct vertebrates are most robust when complete to near-complete s... more Body mass reconstructions of extinct vertebrates are most robust when complete to near-complete skeletons allow the reconstruction of either physical or digital models. Digital models are most efficient in terms of time and cost, and provide the facility to infinitely modify model properties non-destructively, such that sensitivity analyses can be conducted to quantify the effect of the many unknown parameters involved in reconstructions of extinct animals. In this study we use laser scanning (LiDAR) and computer modelling methods to create a range of 3D mass models of five specimens of non-avian dinosaur; two near-complete specimens of Tyrannosaurus rex, the most complete specimens of Acrocanthosaurus atokensis and Strutiomimus sedens, and a near-complete skeleton of a sub-adult Edmontosaurus annectens. LiDAR scanning allows a full mounted skeleton to be imaged resulting in a detailed 3D model in which each bone retains its spatial position and articulation. This provides a high resolution skeletal framework around which the body cavity and internal organs such as lungs and air sacs can be reconstructed. This has allowed calculation of body segment masses, centres of mass and moments or inertia for each animal. However, any soft tissue reconstruction of an extinct taxon inevitably represents a best estimate model with an unknown level of accuracy. We have therefore conducted an extensive sensitivity analysis in which the volumes of body segments and respiratory organs were varied in an attempt to constrain the likely maximum plausible range of mass parameters for each animal. Our results provide wide ranges in actual mass and inertial values, emphasizing the high level of uncertainty inevitable in such reconstructions. However, our sensitivity analysis consistently places the centre of mass well below and in front of hip joint in each animal, regardless of the chosen combination of body and respiratory structure volumes. These results emphasize that future biomechanical assessments of extinct taxa should be preceded by a detailed investigation of the plausible range of mass properties, in which sensitivity analyses are used to identify a suite of possible values to be tested as inputs in analytical models.
MOR693, nicknamed ‘Big Al,’ is the most complete skeleton of the non-avian
theropod Allosaurus an... more MOR693, nicknamed ‘Big Al,’ is the most complete skeleton of the non-avian theropod Allosaurus and therefore provides the best opportunity to investigate the mass properties of this important Jurassic theropod through accurate physical or digital volumetric models. In this study, laser scanning and computer modelling software have been used to construct volumetric models of MOR693. A long-range laser scanner has been used to digitize the mounted cast of MOR693, allowing the reconstruction of body volumes and respiratory structures around and within the three-dimensional (3D) skeletal model. The digital medium offered the facility to modify model properties nondestructively in a detailed sensitivity analysis to quantify the effects of the many unknown parameters involved in such reconstructions. In addition to varying the volumes of body segments and respiratory structures, we also extend the sensitivity analysis to include uncertainties regarding osteological articulations in non-avian dinosaurs, including effects of inter-vertebral spacing and the orientation or ‘flare’ of the rib cage in MOR693. Results suggest body mass and inertial values are extremely uncertain and show a wide range in plausible values, whilst the CM (centre of mass) position is well constrained immediately in front and below the hip joint in MOR693, consistent with similar reconstructions of non-avian theropods.
Light Detection And Range (LiDAR) imaging provides a means to model the 3D geometry of fossil tra... more Light Detection And Range (LiDAR) imaging provides a means to model the 3D geometry of fossil tracks in the field with high accuracy. This represents a considerable advance for the science of vertebrate ichnology in which traditional field methods suffer from a significant degree of abstraction and lack the resolution required to interpret tracks quantitatively. Three-dimensional LiDAR models provide additional morphometric information and allow the application of new analytical tools unique to the digital environment. The method will enable fossil track morphometrics to develop into an iterative process that combines 3D visualization and multivariate statistical methods, blending qualitative and quantitative approaches and allowing track morphologies to be compared holistically. Modelling of trackways from Fumanya (south-east Pyrenees) using LiDAR has enabled variation in linear track dimensions to be explained by the varied contribution of different modes of shear with increasing depth below the foot ⁄ sediment interface. Features in the relief of pes traces indicate that subsurface zones within their track volumes are defined by the interaction of puncture and local shear, below a surface zone of liquefaction failure now lost to erosion. This model of mechanical failure enables a preliminary review of the pedal kinematics of titanosaurid sauropod dinosaurs and suggests multiphase loading of the sediment by the titanosaurid pes. However, from inspection of these 3D surfaces alone it is not possible to differentiate between the possibility of one or two discrete phases of pedal motion preceding the toe-off event at the maximum height of the support phase. By integrating LiDAR models with analogue modelling within a 3D digital environment it will be possible to clarify such interpretations of fossil tracks and the locomotor mechanics of extinct animals.
Increasing political and social awareness of the importance of protecting the geological heritage... more Increasing political and social awareness of the importance of protecting the geological heritage is compelling geoscientists to consider new methods for reconciling conservation and exploration of their research sites. Terrestrial Light Detection And Range (LiDAR) imaging is an accurate method of collecting 3D spatial data that has so far been under-utilized in the geological sciences. This aim of this paper is to assess the value of integrated LiDAR and photogrammetric imaging as a tool for synchronizing scientific exploration with conservation of geological heritage sites. Fumanya (Catalonia) is one of the most important Cretaceous tracksites in Europe, but the nature of exposure of the track-bearing surface has hindered quantitative documentation of the ichnites. Using integrated Light Detection And Range (LiDAR) imaging and photogrammetry it has been possible to construct highresolution Digital Outcrop Models (DOM) of the tracksites. Photo-textured DOMs are a powerful visualization tool and function as fully 3D interactive databases that preserve information about the site that would otherwise be lost to erosion. LiDAR-derived DOMs have the potential to contribute profoundly to future geoconservation projects, particularly as a tool for documenting and monitoring heritage sites and promoting education and tourism. LiDAR scanning also provides sufficient resolution to perform robust quantitative analysis of dinosaur tracks.
Public engagement and the promotion of science to a wider non-academic
audience form an integral ... more Public engagement and the promotion of science to a wider non-academic audience form an integral role of the professional scientist in the twenty-first century. The high level of public interest in palaeontology means that the Earth’s prehistoric past can provide an important medium through which to communicate information concerning contemporary scientific issues. Here we explain how modern computer techniques can be used to enhance public understanding of complex palaeontological issues
Constructing musculoskeletal models of extinct vertebrates requires subjective assumptions about ... more Constructing musculoskeletal models of extinct vertebrates requires subjective assumptions about soft tissue parameters rarely preserved in the fossil record. Despite these necessary assumptions about fundamental input values, paleobiologists rarely perform objective tests of best-estimate models before reaching conclusions based on predicted results. The extent to which lack of knowledge on soft tissue anatomy limits the accuracy of running speed estimates of extinct dinosaurs is therefore poorly understood. In this study, a sensitivity analysis is performed on an evolutionary robotics model of the non-avian theropod dinosaur Allosaurus, used previously to estimate maximum running speed in this extinct animal. A range of muscle parameters were varied over the range observed in extant vertebrates, whereas mass-related parameters were altered across the range of published estimates for Allosaurus. Muscle parameters have a linear relationship with maximum running speed, whereas surprisingly total body mass and torso center of mass have little effect. Muscle force values produced the greatest range in predicted running speeds (4.5–10.7 m/s) and stride lengths (4–5.8 m) in the sensitivity analysis, equating to 65.9% and 30.7% variation about the original ‘best-estimate’ prediction, a relatively high potential margin of error. These results highlight the importance of sensitivity analyses in biomechanical modeling of extinct taxa, particularly where values for soft tissues parameters are not tightly constrained. The current range in plausible values for soft tissue properties makes a robust quantitative assessment of behavioral ecology and species interactions in dinosaurian communities extremely difficult.
The large theropod dinosaur Tyrannosaurus rex underwent remarkable changes during its growth from... more The large theropod dinosaur Tyrannosaurus rex underwent remarkable changes during its growth from ,10 kg hatchlings to .6000 kg adults in ,20 years. These changes raise fascinating questions about the morphological transformations involved, peak growth rates, and scaling of limb muscle sizes as well as the body’s centre of mass that could have influenced ontogenetic changes of locomotion in T. rex. Here we address these questions using three-dimensionally scanned computer models of four large, well-preserved fossil specimens as well as a putative juvenile individual. Furthermore we quantify the variations of estimated body mass, centre of mass and segment dimensions, to characterize inaccuracies in our reconstructions. These inaccuracies include not only subjectivity but also incomplete preservation and inconsistent articulations of museum skeletons. Although those problems cause ambiguity, we conclude that adult T. rex had body masses around 6000–8000 kg, with the largest known specimen (‘‘Sue’’) perhaps ,9500 kg. Our results show that during T. rex ontogeny, the torso became longer and heavier whereas the limbs became proportionately shorter and lighter. Our estimates of peak growth rates are about twice as rapid as previous ones but generally support previous methods, despite biases caused by the usage of scale models and equations that underestimate body masses. We tentatively infer that the hindlimb extensor muscles masses, including the large tail muscle M. caudofemoralis longus, may have decreased in their relative size as the centre of mass shifted craniodorsally during T. rex ontogeny. Such ontogenetic changes would have worsened any relative or absolute decline of maximal locomotor performance. Regardless, T. rex probably had hip and thigh muscles relatively larger than any extant animal’s. Overall, the limb ‘‘antigravity’’ muscles may have been as large as or even larger than those of ratite birds, which themselves have the most muscular limbs of any living animal.
Bite mechanics and feeding behaviour in Tyrannosaurus rex are controversial. Some contend that a ... more Bite mechanics and feeding behaviour in Tyrannosaurus rex are controversial. Some contend that a modest bite mechanically limited T. rex to scavenging, while others argue that high bite forces facilitated a predatory mode of life. We use dynamic musculoskeletal models to simulate maximal biting in T. rex.Models predict that adult T. rex generated sustained bite forces of 35 000–57 000 N at a single posterior tooth, by far the highest bite forces estimated for any terrestrial animal. Scaling analyses suggest that adult T. rex had a strong bite for its body size, and that bite performance increased allometrically during ontogeny. Positive allometry in bite performance during growth may have facilitated an ontogenetic change in feeding behaviour in T. rex, associated with an expansion of prey range in adults to include the largest contemporaneous animals.
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Papers by Karl Bates
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.
theropod Allosaurus and therefore provides the best opportunity to investigate the mass properties of this important Jurassic theropod through accurate physical or digital volumetric models. In this study, laser scanning and computer modelling software have been used to construct volumetric models of MOR693. A long-range laser scanner has been used to digitize the mounted cast of MOR693, allowing the reconstruction of body volumes and respiratory structures around and within the three-dimensional (3D) skeletal model. The digital medium offered the facility to modify model properties nondestructively in a detailed sensitivity analysis to quantify the effects of the many unknown parameters involved in such reconstructions. In addition to varying the volumes of body segments and respiratory structures, we also extend the sensitivity analysis to include uncertainties regarding osteological articulations in non-avian dinosaurs, including effects of inter-vertebral spacing and the orientation or ‘flare’ of the rib cage in MOR693. Results suggest body mass and inertial values are extremely uncertain and show a wide range in plausible values, whilst the CM (centre of mass) position is well constrained immediately in front and below the hip joint in MOR693, consistent with similar reconstructions of non-avian theropods.
The method will enable fossil track morphometrics to develop into an iterative process that combines 3D visualization and multivariate statistical methods, blending qualitative and quantitative approaches and allowing track
morphologies to be compared holistically. Modelling of trackways from Fumanya (south-east Pyrenees) using LiDAR has enabled variation in linear track dimensions to be explained by the varied contribution of different modes of shear with increasing depth below the foot ⁄ sediment interface.
Features in the relief of pes traces indicate that subsurface zones within their track volumes are defined by the interaction of puncture and local shear, below a surface zone of liquefaction failure now lost to erosion. This model of
mechanical failure enables a preliminary review of the pedal kinematics of titanosaurid sauropod dinosaurs and suggests multiphase loading of the sediment by the titanosaurid pes. However, from inspection of these 3D surfaces alone it is not possible to differentiate between the possibility of one or two discrete phases of pedal motion preceding the toe-off event at the maximum height of the support phase. By integrating LiDAR models with analogue modelling within a 3D digital environment it will be possible to clarify such interpretations of fossil tracks and the locomotor mechanics of
extinct animals.
otherwise be lost to erosion. LiDAR-derived DOMs have the potential to contribute profoundly to future geoconservation projects, particularly as a tool for documenting and monitoring heritage sites and promoting education and tourism. LiDAR scanning also provides sufficient resolution to perform robust quantitative analysis of dinosaur tracks.
audience form an integral role of the professional scientist in the twenty-first
century. The high level of public interest in palaeontology means that the
Earth’s prehistoric past can provide an important medium through which to
communicate information concerning contemporary scientific issues. Here
we explain how modern computer techniques can be used to enhance public
understanding of complex palaeontological issues
the non-avian theropod dinosaur Allosaurus, used previously to estimate maximum running speed in this extinct animal. A range of muscle parameters were varied over the range observed in extant vertebrates, whereas mass-related parameters were altered across the range of published estimates for Allosaurus. Muscle parameters have a linear relationship with maximum running speed, whereas surprisingly total body mass and torso center of mass have little effect. Muscle force values produced the greatest range in predicted running speeds (4.5–10.7 m/s) and stride lengths (4–5.8 m) in the sensitivity analysis, equating to 65.9% and 30.7% variation about the original ‘best-estimate’ prediction, a relatively high potential margin of error. These results highlight the importance of sensitivity analyses in biomechanical modeling of extinct taxa, particularly where values
for soft tissues parameters are not tightly constrained. The current range in plausible values for soft tissue properties makes a robust quantitative assessment of behavioral ecology and species interactions in dinosaurian communities extremely difficult.
have decreased in their relative size as the centre of mass shifted craniodorsally during T. rex ontogeny. Such ontogenetic
changes would have worsened any relative or absolute decline of maximal locomotor performance. Regardless, T. rex probably had hip and thigh muscles relatively larger than any extant animal’s. Overall, the limb ‘‘antigravity’’ muscles may have been as large as or even larger than those of ratite birds, which themselves have the most muscular limbs of any living animal.
size, and that bite performance increased allometrically during ontogeny. Positive allometry in bite performance during growth may have facilitated an ontogenetic change in feeding behaviour
in T. rex, associated with an expansion of prey range in adults to include the largest contemporaneous animals.
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.
theropod Allosaurus and therefore provides the best opportunity to investigate the mass properties of this important Jurassic theropod through accurate physical or digital volumetric models. In this study, laser scanning and computer modelling software have been used to construct volumetric models of MOR693. A long-range laser scanner has been used to digitize the mounted cast of MOR693, allowing the reconstruction of body volumes and respiratory structures around and within the three-dimensional (3D) skeletal model. The digital medium offered the facility to modify model properties nondestructively in a detailed sensitivity analysis to quantify the effects of the many unknown parameters involved in such reconstructions. In addition to varying the volumes of body segments and respiratory structures, we also extend the sensitivity analysis to include uncertainties regarding osteological articulations in non-avian dinosaurs, including effects of inter-vertebral spacing and the orientation or ‘flare’ of the rib cage in MOR693. Results suggest body mass and inertial values are extremely uncertain and show a wide range in plausible values, whilst the CM (centre of mass) position is well constrained immediately in front and below the hip joint in MOR693, consistent with similar reconstructions of non-avian theropods.
The method will enable fossil track morphometrics to develop into an iterative process that combines 3D visualization and multivariate statistical methods, blending qualitative and quantitative approaches and allowing track
morphologies to be compared holistically. Modelling of trackways from Fumanya (south-east Pyrenees) using LiDAR has enabled variation in linear track dimensions to be explained by the varied contribution of different modes of shear with increasing depth below the foot ⁄ sediment interface.
Features in the relief of pes traces indicate that subsurface zones within their track volumes are defined by the interaction of puncture and local shear, below a surface zone of liquefaction failure now lost to erosion. This model of
mechanical failure enables a preliminary review of the pedal kinematics of titanosaurid sauropod dinosaurs and suggests multiphase loading of the sediment by the titanosaurid pes. However, from inspection of these 3D surfaces alone it is not possible to differentiate between the possibility of one or two discrete phases of pedal motion preceding the toe-off event at the maximum height of the support phase. By integrating LiDAR models with analogue modelling within a 3D digital environment it will be possible to clarify such interpretations of fossil tracks and the locomotor mechanics of
extinct animals.
otherwise be lost to erosion. LiDAR-derived DOMs have the potential to contribute profoundly to future geoconservation projects, particularly as a tool for documenting and monitoring heritage sites and promoting education and tourism. LiDAR scanning also provides sufficient resolution to perform robust quantitative analysis of dinosaur tracks.
audience form an integral role of the professional scientist in the twenty-first
century. The high level of public interest in palaeontology means that the
Earth’s prehistoric past can provide an important medium through which to
communicate information concerning contemporary scientific issues. Here
we explain how modern computer techniques can be used to enhance public
understanding of complex palaeontological issues
the non-avian theropod dinosaur Allosaurus, used previously to estimate maximum running speed in this extinct animal. A range of muscle parameters were varied over the range observed in extant vertebrates, whereas mass-related parameters were altered across the range of published estimates for Allosaurus. Muscle parameters have a linear relationship with maximum running speed, whereas surprisingly total body mass and torso center of mass have little effect. Muscle force values produced the greatest range in predicted running speeds (4.5–10.7 m/s) and stride lengths (4–5.8 m) in the sensitivity analysis, equating to 65.9% and 30.7% variation about the original ‘best-estimate’ prediction, a relatively high potential margin of error. These results highlight the importance of sensitivity analyses in biomechanical modeling of extinct taxa, particularly where values
for soft tissues parameters are not tightly constrained. The current range in plausible values for soft tissue properties makes a robust quantitative assessment of behavioral ecology and species interactions in dinosaurian communities extremely difficult.
have decreased in their relative size as the centre of mass shifted craniodorsally during T. rex ontogeny. Such ontogenetic
changes would have worsened any relative or absolute decline of maximal locomotor performance. Regardless, T. rex probably had hip and thigh muscles relatively larger than any extant animal’s. Overall, the limb ‘‘antigravity’’ muscles may have been as large as or even larger than those of ratite birds, which themselves have the most muscular limbs of any living animal.
size, and that bite performance increased allometrically during ontogeny. Positive allometry in bite performance during growth may have facilitated an ontogenetic change in feeding behaviour
in T. rex, associated with an expansion of prey range in adults to include the largest contemporaneous animals.