author={Tai Kubo and Michael J. Benton},
  • T. Kubo, M. Benton
  • Published 1 November 2007
  • Geography, Biology, Environmental Science
  • Palaeontology
Abstract:  During the Triassic, some 250–200 million years ago, the basal archosaurs showed a transition from sprawling to erect posture. Past studies focused on changes in bone morphology, especially on the joints, as they reorientated from a sprawling to an erect posture. Here we introduce a biomechanical model to estimate the magnitude of femur stress in different postures, in order to determine the most reasonable postures for five basal archosaurs along the line to crocodiliforms (the… 
The trackmaker of Apatopus (Late Triassic, North America): implications for the evolution of archosaur stance and gait
Abstract:  For some decades, a major focus of research has been on how locomotor modes changed in some archosaurian reptiles from a more or less ‘sprawling’ to an ‘erect’ posture, whether there were
Convergences and Trends in the Evolution of the Archosaur Pelvis
The evolutionary model fitting supports the early-burst model for iliac and pubic metrics in more inclusive archosaur clades, indicating that larger changes ofarchosaur pelves occurred in early times of the clade's history.
Elbow joint adductor moment arm as an indicator of forelimb posture in extinct quadrupedal tetrapods
A new, quantitatively based forelimb posture index that is applicable to a majority of extant tetrapods is outlined and Triceratops, Anhanguera and desmostylian mammals are categorized as upright/sagittally locomoting taxa.
Evolution of limb bone loading and body size in varanid lizards
Findings suggest that evolution from sprawling to upright posture did not occur in archosaurs as a response to larger size; rather, these archosaurs likely became upright first and larger later.
Reassessment of the postcranial anatomy of Prozostrodon brasiliensis and implications for postural evolution of non-mammaliaform cynodonts
It is confirmed that the evolution of an erect posture and a new muscular orientation of the hind limb occurred within Cynodontia before the appearance of the clade Mammaliaformes.
Articular soft tissue anatomy of the archosaur hip joint: Structural homology and functional implications
The osteological correlates identified here will inform systematic and functional analyses of archosaur hindlimb evolution and provide the anatomical foundation for biomechanical investigations of joint tissues.
Pelvic and hindlimb myology of the basal archosaur Poposaurus gracilis (archosauria: Poposauroidea)
This reconstruction is based on the direct examination of the osteology and myology of phylogenetically relevant extant taxa in conjunction with osteological correlates from the skeleton of P. gracilis and provides a foundation for subsequent examination of variation in myological orientation and function based on pelvic and hindlimb morphology, across the basal archosaur lineage leading to extant crocodilians.
A reconstruction of the thigh musculature of the extinct pseudosuchian Prestosuchus chiniquensis from the Dinodontosaurus Assemblage Zone (Middle Triassic Epoch), Santa Maria 1 Sequence, southern Brazil
Abstract Prestosuchus chiniquensis is an extinct species of terrestrial archosaur from the Middle Triassic Epoch restricted to southern Brazil. In this paper the thigh musculature of P. chiniquensis
Origin of feathered flight
A new approach is developed, combining terrestrial and arboreal hypotheses of the origin of flight, which indicates that for the development of true flapping avian flight, a key role was played by the initial universal anisodactylous foot of birds.
Trends in Ecology & Evolution
Hair and feathers likely evolved in the Early Triassic ancestors of mammals and birds, at a time when synapsids and archosaurs show independent evidence of higher metabolic rates (erect gait and endothermy), as part of a major resetting of terrestrial ecosystems following the devastating end-Permian mass extinction.


Evolution of hindlimb posture in nonmammalian therapsids: biomechanical tests of paleontological hypotheses
  • R. Blob
  • Biology, Geography
  • 2001
A biomechanical model is derived to test the hypothesis that the use of multiple postures was ancestral to the more upright posture typical of most mammals, and indicates that the axial rotation of the femur typical in sprawling locomotion can reduce peak bending stresses.
In vivo locomotor strain in the hindlimb bones of alligator mississippiensis and iguana iguana: implications for the evolution of limb bone safety factor and non-sprawling limb posture
  • Blob, Biewener
  • Biology
    The Journal of experimental biology
  • 1999
Measurements of in vivo locomotor strain from the limb bones of lizard and crocodilian species, animals from previously unsampled phylogenetic lineages with non-parasagittal limb posture and kinematics suggest that, in some lineages, strain magnitudes may not have been maintained at constant levels through the evolution of a non-sprawling posture.
The hind limb step cycle of Caiman sclerops and the mechanics of the crocodile tarsus and metatarsus
Crocodiles use two distinct hind limb step cycles: an erect pattern seen in the high walk and a more sprawling lizard-like pattern. These differ in the amount of abduction of the femur and rotation
Basal Archosaurs: Phylogenetic Relationships and Functional Implications
Erect posture has been identified as the key adaptation (possibly associated with locomotor stamina) that resulted in the archosaurian radiation.
  • Ashley-Ross
  • Biology
    The Journal of experimental biology
  • 1994
A quantitative study of hindlimb kinematics during terrestrial locomotion in a non-specialized salamander was undertaken to allow comparisons with limb movements in other groups of tetrapods. Five
Interspecific scaling of the hindlimb skeleton in lizards, crocodilians, felids and canids: does limb bone shape correlate with limb posture?
  • R. Blob
  • Biology, Environmental Science
  • 2000
During locomotion, lizards and crocodilians generally use a more sprawling limb posture than most mammals and experience substantial axial rotation of the femur. Consequently, the limb bones of most
Limb posture and locomotion in the Virginia opossum (Didelphis marsupialis) and in other non‐cursorial mammals
Walking movements in eight mammalian species were studied cineradiographically with particular attention given to limb posture and excursion relative to the parasagittal and horizontal planes.
Locomotion in rauisuchid thecodonts
ABSTRACT The systematic approach to the Rauisuchidae suggests that the lowest level of locomotor organization of the Thecodontia is represented by the Proterosuchidae, which can be regarded as
Biomechanics and kinematics of limb-based locomotion in lizards: review, synthesis and prospectus.
  • A. Russell, V. Bels
  • Biology, Engineering
    Comparative biochemistry and physiology. Part A, Molecular & integrative physiology
  • 2001
Wing bone stresses in free flying bats and the evolution of skeletal design for flight
The data demonstrate that torsion and shear are unique and crucial features of skeletal biomechanics during flight, and suggest that the evolution of skeletal design in bats and other flying vertebrates may be driven by the need to resist these loads.