I'm a computational palaeontologist focusing on track formation and associated limb dynamics of dinosaurs. I currently hold a Marie Curie International Outgoing Fellowship, between Brown University (USA) and the Royal Veterinary College, London (UK)
Publications are also available from my Mendeley page:
Abstract: 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.
Abstract: The 3D digitisation of palaeontological resources is of tremendous use to the field, providing the means to archive, analyse, and visualise specimens that would otherwise be too large to handle, too valuable to destructively sample, or simply in a different geographic location. Digitisation of a specimen to produce a 3D digital model often requires the use of expensive laser scanning equipment or proprietary digital reconstruction software, making the technique inaccessible to many workers. Presented here is a guide for producing high resolution 3D models from photographs, using freely available open-source software. To demonstrate the accuracy and flexibility of the approach, a number of examples are given, including a small trilobite (~0.04 m), a large mounted elephant skeleton (~3 m), and a very large fossil tree root system (~6 m), illustrating that the method is equally applicable to specimens or even outcrops of all sizes. The digital files of the models produced in this paper are included. The results demonstrate that production of digital models from specimens for research or archival purposes is available to anyone, and it is hoped that an increased use of digitisation techniques will facilitate research and encourage collaboration and dissemination of digital data.
Abstract: 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.
Abstract: 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.
Abstract: The depth to which a vertebrate track is indented can provide a wealth of information, being a direct result of the weight, duty factor, and limb kinematics of the animal as well as media (=substrate or sediment) consistency. In order to recreate the formation of the track and elucidate media consistency at the time of track formation, such factors as animal mass, duty factor, and foot morphology must be taken into consideration. This study uses Finite Element Analysis and physical modeling to demonstrate for the first time that the shape of the foot is an important factor that influences the depth to which the sediment is penetrated. In cohesive sediment, less compact morphology allows more sediment to move vertically upwards at the edges of the foot, dissipating force at the surface, and retarding transmission of load vertically down into the sediment. The reverse of this effect is seen in noncohesive sediment. Foot morphology, therefore, has a direct impact on preservation potential, both of surface tracks and undertracks, that is irrespective of the pressure exerted on the sediment surface by the foot and independent of mass and duty factor.
Abstract: The Hot Springs Mammoth Site, South Dakota, USA, has been excavated for over three decades, during which time numerous body fossils have been recorded. The site is particularly well known for the skeletal remains of mammalian megafauna. Bedding plane surfaces were studied that displayed the first record of small vertebrate (avian) and invertebrate traces. While large vertebrate tracks, often observed in cross-section, are well known at the site, the new traces form a hitherto unstudied assemblage. xD; xD;The presence of distinct didactyl and tridactyl avian tracks from the site are described here for the first time. The small (∼20 mm long) tracks and associated invertebrate traces suggest relatively high moisture content in the substrate on surfaces that experienced aerial or subaerial exposure. This is consistent with the interpretation that the upper layers of the site represent the latter stages of a sinkhole setting with a pond undergoing cyclical drying out.
Abstract: 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 non-destructively 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.
Notes: ISI Document Delivery No.: 525QL xD;Times Cited: 0 xD;Cited Reference Count: 24 xD;Bates, Karl T. Falkingham, Peter L. Breithaupt, Brent H. Hodgetts, David Sellers, William I. Manning, Phillip L. xD;COQUINA PRESS
Abstract: A track from the Late Cretaceous previously described as being generated by a semi-palmate bird was studied with the aid of high resolution laser scanning. Substrate conditions at the time of track formation were diagnosed (fine-grained, soft, waterlogged sediment) and used to constrain a finite element track simulator. The indentation of a non-webbed virtual tridactyl foot in such conditions created a resultant track with features analogous to [`]webbing' between digits. This [`]webbing' was a function of sediment deformation and subsequent failure in 3D, specific to rheology. Variation of substrate conditions and interdigital angle was incrementally stepped. Apparent webbing impressions were clearly developed only within a limited range of sediment conditions and pedal geometry. The implications of this work are that descriptions of [`]webbed' tracks should account for the possibility that webbing was indirectly formed through sediment failure and not necessarily the direct impression of a webbed foot. Additionally, dating the earliest occurrence of webbed feet in the fossil record, and potentially extending phylogenetic ranges, should be treated with caution when based upon evidence from tracks.
Abstract: Dromaeosaurid theropod dinosaurs, such as Velociraptor, possess strongly recurved, hypertrophied and hyperextensible ungual claws on the pes (digit II) and manus. The morphology of these unguals has been linked to the capture and despatching of prey. However, the mechanical properties or, more importantly, the mechanical potential of these structures have not been explored. Generation of a 3D finite element (FE) stress/strain contour map of a Velociraptor manual ungual has allowed us to evaluate quantitatively the mechanical behavior of a dromaeosaurid claw for the first time. An X-ray microtomography scan allowed construction of an accurate 3D FE mesh. Analogue material from an extant avian theropod, the pedal digit and claw of an eagle owl (Bubo bubo), was analyzed to provide input data for the Velociraptor claw FE model (FEM). The resultant FEM confirms that dromaeosaurid claws were well-adapted for climbing as they would have been resistant to forces acting in a single (longitudinal) plane, in this case due to gravity. However, the strength of the unguals was limited with respect to forces acting tangential to the long-axis of the claw. The tip of the claw functioned as the puncturing and gripping element of the structure, whereas the expanded proximal portion transferred the load stress through the trabeculae and cortical bone. Enhanced climbing abilities of dromaeosaurid dinosaurs supports a scansorial phase in the evolution of flight.
Abstract: Dinosaurs successfully conjure images of lost worlds and forgotten lives. Our understanding of these iconic, extinct animals now comes from many disciplines, not just the science of palaeontology. In recent years palaeontology has benefited from the application of new and existing techniques from physics, biology, chemistry, engineering, but especially computational science. The application of computers in palaeontology is highlighted in this chapter as a key area of development in studying fossils. The advances in high performance computing (HPC) have greatly aided and abetted multiple disciplines and technologies that are now feeding paleontological research, especially when dealing with large and complex data sets. We also give examples of how such multidisciplinary research can be used to communicate not only specific discoveries in palaeontology, but also the methods and ideas, from interrelated disciplines to wider audiences. Dinosaurs represent a useful vehicle that can help enable wider public engagement, communicating complex science in digestible chunks.
Abstract: Fossilised tracks are widely cited as providing evidence of behaviour, biomechanics and
ecology of vertebrates, thus complementing and supplementing the osteological record.
However, trackways are often overlooked in macroevolutionary studies. The loading of the
foot is a direct result of the limb motion relative to the centre of mass of the animal, and
variations in limb motion or centre of mass may be expressed in the 3D morphology of any
resultant track. For example, variations in centre of mass of quadrupedal animals will result
in differential loading between manus and pes, which when combined with the relative
surface areas of fore- and hind-feet, may produce drastically different under-foot pressures.
If a substrate exhibits an elastic-plastic behaviour, a specific load will be required to exceed
the elastic response of the substrate and cause it to plastically deform and produce tracks.
We show that predicted underfoot pressures of different sauropod dinosaurs preferentially
produce either manus-dominated or pes-dominated trackways depending on whether the
centre of mass is more anterior or posteriorly positioned. The temporal distribution of these
taxa correlates with a significantly greater number of pes-dominated sauropod tracks from
Jurassic age rocks, followed by a switch to manus-dominated trackways in the Cretaceous.
We interpret this as being the result of sauropods evolving to be more ‘front heavy’ through-
out the course of their evolution. Additionally, the substrate types in which manus- or pes-
dominated tracks occurred were noted. There is no association between tracks and substrate
in the Jurassic. However, in the Cretaceous, manus-dominated tracks are most commonly
recorded in cohesive substrates (e.g. mudstones), whereas pes-dominated tracks tend to be
restricted to non-cohesive substrates (e.g. sandstones). This may be the result of niche parti-
tioning among sauropods, associated with the Cretaceous diversification of the anatomically
and environmentally specialised titanosaurs
Abstract: In 1940 R.T. Bird of the American Museum of Natural History (New York) collected segments of trackways of an herbivorous sauropod and a carnivorous theropod from a tracksite in the bed (Glen Rose Formation) of the Paluxy River, in what is now Dinosaur Valley State Park. However, Bird left undocumented thousands of other dinosaur footprints in several other Paluxy tracksites. In 2008 and 2009 we carried out fieldwork to create detailed photomosaics of extant Paluxy tracksites, using GIS technology to combine these with historic maps and photographs of older tracksites. In addition, photographs, tracings, and measurements were made of individual footprints and trackways at numerous tracksites.
Although there are multiple tracklayers, the largest number and most spectacular footprints occur in a thick (ca. 20-25 cm) "main " tracklayer that is also densely dotted by vertical invertebrate burrows. The diversity of dinosaur footprint morphotypes is limited to tracks of the quadrupedal sauropods, and the far more numerous tridactyl prints, most or all of which were probably made by theropods. Some tridactyl prints show beautiful morphological details that are readily interpretable in terms of trackmaker foot structure, but more commonly the prints are distorted, with variably collapsed toe marks. Some tridactyl prints include long "heel" impressions.
Beyond documenting ichnological diversity, our project seeks to estimate the minimum number of individual dinosaurs recorded by the Paluxy tracksites. Are there patterns in the orientation, distribution, and association of trackways that suggest group behavior on the part of either sauropods or theropods? Can we support/refute Bird’s hypothesis that one or more of the theropods was pursuing one or more of the sauropods? The Paluxy tracksites constitute one of the world’s largest concentrations of dinosaur footprints. Our research will facilitate systematic comparison of Glen Rose dinosaur tracks with those from other footprint faunas, and will shed new light on the movements and behavior of the great reptiles.
