Stephen M. Gatesy

Stephen M. Gatesy
Brown University · Department of Ecology and Evolutionary Biology

PhD

About

144
Publications
37,615
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Introduction
Stephen M. Gatesy currently works at the Department of Ecology and Evolutionary Biology, Brown University. Stephen does research in Anatomy, Paleobiology and Zoology.

Publications

Publications (144)
Article
Full-text available
Living birds (Aves) have bodies substantially modified from the ancestral reptilian condition. The avian pelvis in particular experienced major changes during the transition from early archosaurs to living birds1,2. This stepwise transformation is well documented by an excellent fossil record2–4; however, the ontogenetic alterations that underly it...
Article
Full-text available
The stance phase of walking is when forces are applied to the environment to support, propel, and maneuver the body. Unlike solid surfaces, deformable substrates yield under load, allowing the foot to sink to varying degrees. For bipedal birds and their dinosaurian ancestors, a shared response to walking on these substrates has been identified in t...
Article
Paleobiological reconstructions of joint mobility are an essential component of functional analyses of extinct animals. Over the past half-decade, the methods underlying mobility studies have advanced rapidly in three main areas: increasing complexity of virtual joint manipulation, formalizing pose viability criteria, and constructing more rigorous...
Article
Full-text available
The last common ancestor of birds and crocodylians plus all of its descendants (clade Archosauria) dominated terrestrial Mesozoic ecosystems, giving rise to disparate body plans, sizes, and modes of locomotion. As in the fields of vertebrate morphology and paleontology more generally, studies of archosaur skeletal structure have come to depend on t...
Article
Virtual and augmented reality (VR/AR) are new technologies with the power to revolutionize the study of morphology. Modern imaging approaches such as computed tomography, laser scanning, and photogrammetry have opened up a new digital world, enabling researchers to share and analyze morphological data electronically and in great detail. Because thi...
Article
Full-text available
The emergence of bipedalism had profound effects on human evolutionary history, but the evolution of locomotor patterns within the hominin clade remains poorly understood. Fossil tracks record in vivo behaviours of extinct hominins, and they offer great potential to reveal locomotor patterns at various times and places across the human fossil recor...
Article
Paleobiologists typically exclude impossible joint poses from reconstructions of extinct animals by estimating the rotational range of motion (ROM) of fossil joints. However, this ubiquitous practice carries the assumption that osteological estimates of ROM consistently overestimate true joint mobility. Because studies founded on ROM‐based exclusio...
Article
Full-text available
Feet must mediate substrate interactions across an animal's entire range of limb poses used in life. Metatarsals, the ‘bones of the sole,’ are the dominant pedal skeletal elements for most tetrapods. In plantigrade species that walk on the entirety of their sole, such as living crocodylians, intermetatarsal mobility offers the potential for a conti...
Article
Full-text available
Reconstructions of movement in extinct animals are critical to our understanding of major transformations in vertebrate locomotor evolution. Estimates of joint range of motion (ROM) have long been used to exclude anatomically impossible joint poses from hypothesized gait cycles. Here we demonstrate how comparative ROM data can be harnessed in a dif...
Article
Starting with his first report on fossil footprints from the Connecticut Valley over 180 years ago, Edward Hitchcock described what he interpreted as a burgeoning ancient fauna founded on ever-increasing nominal track diversity. For three decades, Hitchcock made countless contributions to ichnology, but his inference of thin-toed animals (Leptodact...
Article
Full-text available
Whilst bones present a static view of extinct animals , fossil footprints are a direct record of the activity and motion of the track maker. Deep footprints are a particularly good record of foot motion. Such footprints rarely look like the feet that made them; the sediment being heavily disturbed by the foot motion. Because of this, such tracks ar...
Article
ABSTRACT Three-dimensional studies of range of motion currently plot joint poses in an "Euler space" whose axes are angles measured in the joint's three rotational degrees of freedom. Researchers then compute the volume of a pose cloud to measure rotational mobility. However, pairs of poses that are equally different from one another in orientation...
Article
Full-text available
The feet of ground-dwelling birds retain many features of their dinosaurian ancestry. Experiments with living species offer insights into the complex interplay among anatomy, kinematics and substrate during the formation of Mesozoic footprints. However, a key aspect of the track-making process, sub-surface foot movement, is hindered by substrate op...
Article
Extant archosaurs exhibit highly divergent articular soft tissue anatomies between avian and crocodilian lineages. However, the general lack of understanding of the dynamic interactions among archosaur joint soft tissues has hampered further inferences about the function and evolution of these joints. Here we use contrast-enhanced computed tomograp...
Article
We present the results of a two-year design study to developing virtual reality (VR) flow visualization tools for the analysis of dinosaur track creation in a malleable substrate. Using Scientific Sketching methodology, we combined input from illustration artists, visualization experts, and domain scientists to create novel visualization methods. B...
Poster
We present a two-year design study of developing virtual reality (VR) flow visualization tools for the analysis of dinosaur track creation using the Scientific Sketching design methodology. We involved 25 art and computer science students from a VR design course in a rapid visualization sketching cycle, guided by paleontologist collaborators throug...
Article
Drone footage of a large American crocodile bottom walking in shallow coastal water off Costa Rica was used to estimate oblique pace and stride lengths and pace angulations from autopodial touchdowns. The crocodile's pes stride lengths were longer but more variable than expected for an individual of comparable size high-walking on land, due in part...
Article
Recent discoveries have made hominin tracks an increasingly prevalent component of the human fossil record, and these data have the capacity to inform long-standing debates regarding the biomechanics of hominin locomotion. However, there is currently no consensus on how to decipher biomechanical variables from hominin tracks. These debates can be l...
Article
Full-text available
The collection and dissemination of vertebrate ichnological data is struggling to keep up with techniques that are becoming commonplace in the wider palaeontological field. A standard protocol is required to ensure that data is recorded, presented and archived in a manner that will be useful both to contemporary researchers, and to future generatio...
Data
Figure S2. Estimated rotation centres for the patellofemoral joint, shown in the plane‐of‐best‐fit for patella motion.
Data
Table S2. Moment arms calculated for M. iliotibialis cranialis (IC), M. iliotibialis lateralis preacetabularis (ILPR) and M. femorotibialis intermedius (FT) about patellofemoral rotation centres estimated by second‐order curve fitting (Curve Centres), circular arc fitting (Circle Centre) or median planar movement poles (Median Pole), with numbered...
Data
Figure S1. Mean knee joint flexion/extension angles for specimens of Numida running at various speeds (see Kambic et al., 2015) averaged from time‐normalized data from all recorded strides, plotted against percentage stance and swing phases.
Data
Figure S4. Mean values of r ET/r PT, taken to be a proxy for mechanical advantage (see Materials and methods).
Data
Table S1. Flexion‐extension angles in degrees for the hip and knee joints, with numbered limb phases. See Skeletal Kinematics section of Materials and methods for details.
Data
Figure S3. Mean values of r ET/r PT, taken to be a proxy for mechanical advantage (see Materials and methods).
Article
Full-text available
Measuring range of motion (ROM) is a valuable technique that can link bone morphology to joint function in both extant and extinct taxa. ROM results are commonly presented as tables or graphs of maxima and minima for each rotational degree of freedom. We investigate the interactions among three degrees of freedom using X-ray reconstruction of movin...
Article
Full-text available
Human patellae (kneecaps) are thought to act as gears, altering the mechanical advantage of knee extensor muscles during running. Similar sesamoids have evolved in the knee extensor tendon independently in birds, but it is unknown if these also affect the mechanical advantage of knee extensors. Here, we examine the mechanics of the patellofemoral j...
Article
As purely sedimentary structures, fossil footprints are all about shape. Correctly interpreting the significance of their surface topography requires understanding the sources of morphological variation. Differences among specimens are most frequently attributed to either taxonomy (trackmaker) or to preservation quality. ‘Well-preserved’ tracks are...
Article
Full-text available
Marker-based XROMM requires software tools for: (1) correcting fluoroscope distortion; (2) calibrating X-ray cameras; (3) tracking radio-opaque markers; and (4) calculating rigid body motion. In this paper we describe and validate XMALab, a new open-source software package for marker-based XROMM (C++ source and compiled versions on Bitbucket). Most...
Article
Full-text available
Horse racing is a multi-billion-dollar industry that has raised welfare concerns due to injured and euthanized animals. Whilst the cause of musculoskeletal injuries that lead to horse morbidity and mortality is multifactorial, pre-existing pathologies, increased speeds and substrate of the racecourse are likely contributors to foot disease. Horse h...
Data
Maximum principal stress (MPa) distribution results for the shod and the unshod horse foot, in dorsal view Bones shown from top to bottom are the P1, P2 and P3. Warm (red) and cold (blue) colours show higher and lower maximum principal stresses respectively.
Data
Ground reaction force (GRF) data in Newtons for the unshod (n = 4) and shod (n = 4) conditions
Data
Minimum principal stress (MPa) distribution results for the shod and the unshod horse foot, in dorsal view Bones shown from top to bottom are the P1, P2 and P3. Warm (red) and cold (blue) colours show higher and lower minimum principal stresses respectively.
Data
Sensitivity analysis on the P1 constraints BC1 constraints are applied on the entire distal joint surface of the P1 and fixed in all axes. BC2 constraints involve fix constraining 3 nodes at the distal joint surface on the centroid axis of the load. The remainder nodes are fixed on the long axis of the bone only. Transparent and non-transparent ima...
Data
Sensitivity analysis on the location of the P3 constraints and the respective von Mises stresses patterns on the palmar and dorsal views Warm (red) and cold (blue) colours show higher and lower von Mises stresses respectively.
Data
Raw speed data for the unshod (n = 4) and shod (n = 4) conditions Column A shows the conditions. Column B lists the name and date of the steps. Column C lists the horse’s hip height in meters. Column D lists the frame rate of the Sony camera used for the speed calculations. Columns E and F list the start and end frame of each trial and each conditi...
Data
The position of the custom-designed calibration cube used during the fluoroscopy experiments to calibrate the 3D space in the XROMM analysis
Data
Loading (in red) and boundary (in orange) locations for the P1, P2 and P3 bones (see Methods: Loads and constraints)
Data
Maximum principal stress (MPa) distribution results for the shod and the unshod horse foot, in palmar view Bones shown from top to bottom are the P1, P2 and P3. Warm (red) and cold (blue) colours show higher and lower maximum principal stresses respectively.
Data
Minimum principal stress (MPa) distribution results for the shod and the unshod horse foot, in palmar view Bones shown from top to bottom are the P1, P2 and P3. Warm (red) and cold (blue) colours show higher and lower minimum principal stresses respectively.
Data
Degrees of motion for proximal interphalangeal (PIP) and distal interphalangeal (DIP) joints for the shod (n = 4) and unshod (n = 4) conditions about the flexion-extension axis
Article
Full-text available
Horse racing is a multi-billion-dollar industry that has raised welfare concerns due to disabled and euthanized animals. Whilst the cause of musculoskeletal injuries that lead to horse morbidity and mortality is multifactorial, pre-existing pathologies, increased speeds and substrate of the racecourse are likely contributors to foot disease. The ho...
Article
Full-text available
Horse racing is a multi-billion-dollar industry that has raised welfare concerns due to disabled and euthanized animals. Whilst the cause of musculoskeletal injuries that lead to horse morbidity and mortality is multifactorial, pre-existing pathologies, increased speeds and substrate of the racecourse are likely contributors to foot disease. The ho...
Article
Full-text available
In avian bipeds performing steady locomotion, right and left limbs are typically assumed to act out of phase, but with little kinematic disparity. However, outwardly appearing steadiness may harbor previously unrecognized asymmetries. Here, we present markerbased XROMM data showing that guineafowl on a treadmill routinely yaw away from their direct...
Article
Full-text available
As one of the earliest-known mammaliaforms, Haramiyavia clemmenseni from the Rhaetic (Late Triassic) of East Greenland has held an important place in understanding the timing of the earliest radiation of the group. Reanalysis of the type specimen using high-resolution computed tomography (CT) has revealed new details, such as the presence of the de...
Conference Paper
Full-text available
Foot anatomy and mechanics vary among herbivorous quadrupeds. Horses have one toe ending in a rigid hoof, which is effective for fast-running but generates large impact vibrations. The feet of the elephants and rhinoceroses have five and three toes, respectively, bound within a digital cushion, which absorbs locomotor forces, yet is heavy and thus...
Article
Full-text available
Locomotion over deformable substrates is a common occurrence in nature. Footprints represent sedimentary distortions that provide anatomical, functional, and behavioral insights into trackmaker biology. The interpretation of such evidence can be challenging, however, particularly for fossil tracks recovered at bedding planes below the originally ex...
Article
Full-text available
Ground-dwelling birds are typically characterized as erect bipeds having hind limbs that operate parasagittally. Consequently, most previous research has emphasized flexion/extension angles and moments as calculated from a lateral perspective. Three-dimensional motion analyses have documented non-planar limb movements, but the skeletal kinematics u...
Article
Crocodylians occupy a key phylogenetic position for investigations of archosaur locomotor evolution. Compared to the well-studied hindlimb, relatively little is known about the skeletal movements and mechanics of the forelimb. In this study, we employed manual markerless XROMM (X-ray Reconstruction Of Moving Morphology) to measure detailed 3-D kine...
Article
Full-text available
Theropod dinosaurs show striking morphological and functional tail variation; e.g., a long, robust, basal theropod tail used for counterbalance, or a short, modern avian tail used as an aerodynamic surface. We used a quantitative morphological and functional analysis to reconstruct intervertebral joint stiffness in the tail along the theropod linea...
Article
Full-text available
Past studies have shown that birds use their wings not only for flight, but also when ascending steep inclines. Uphill flap-running or wing-assisted incline running (WAIR) is used by both flight-incapable fledglings and flight-capable adults to retreat to an elevated refuge. Despite the broadly varying direction of travel during WAIR, level, and de...
Data
Average WAIR (blue) verses AF (red) in a sternal reference frame. (WMV)
Data
WAIR (blue) verses AF in a global reference frame. (WMV)
Data
Single trial of each behavior comparing WAIR (blue) verses AF in a sternal reference frame. (WMV)