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Cited by 209Paleontology and Evolutionary BiologyMorphological variations and asymmetryEvolution and Paleontology Studies

Bipedalism, flight, and the evolution of theropod locomotor diversity

Gatesy, Stephen M., Middleton, Kevin M.·1997·Journal of Vertebrate Paleontology
DOI 10.1080/02724634.1997.10010977
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Abstract

The evolution of theropod flight has been characterized as a shift from one to three locomotor modules. Basal theropods, which were terrestrial bipeds, had a single locomotor module composed of the hind limb and tail. In birds, aerial locomotion was acquired with the origination of the wing module and a decoupling of the hind limb and tail into separate pelvic and caudal modules. This increase in modularity is thought to have granted birds more locomotor “options” than non-avian theropods. More specifically, an aerial locomotor system could have eased constraints on the hind limb and allowed specialization for habitats and lifestyles unavailable to non-birds. If so, bird hind limbs should be more disparate than those of non-avian theropods. We addressed this hypothesis by visualizing one aspect of limb design, the proportions of the three main segments, using ternary diagrams. Our results show that avian hind limb proportions are much more disparate than those of non-avian theropods. This broad range of limb design correlates with a radiation in locomotor diversity founded on three locomotor modules. We propose that birds have reached regions of proportion morphospace that are off limits to bipeds with only one locomotor module. In comparison, the limbs of non-avian theropods are conservatively proportioned. Despite great variation in body size, theropods other than birds do not exhibit specializations for locomotion other than terrestrial bipedalism. Although other aspects of size and shape need to be analyzed, the relationship between modular flexibility and morphological disparity appears to play an important role in theropod locomotor evolution.

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  • The proportions of the manual phalanges are consistent with a specialized grasping function present in deinonychosaurs.

    “The proportions of the manual phalanges are consistent with a specialized grasping function present in deinonychosaurs [65].”

    From The ecology of Archaeopteryx (2026) · cites this paper as [65]

  • Pedal phalanges in Archaeopteryx are shorter distally within each digit, and pedal proportions plot intermediate between arboreal and terrestrial species, close to extant columbiforms, suggesting broad and generalized locomotive capabilities.

    “Pedal phalanges are shorter distally within each digit and pedal proportions plot intermediate between arboreal and terrestrial species, close to taxa like extant columbiforms, suggesting broad and generalized locomotive capabilities [65].”

    From The ecology of Archaeopteryx (2026) · cites this paper as [65]

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Authors
Gatesy, S. M., & Middleton, K. M.
Affiliations
Brown University (US)
ORCID
Venue
Journal of Vertebrate Paleontology
Publisher
Informa UK Limited
Published
1997-06-19
Volume
17
Issue
2
Pages
308-329
ISSN
  • 0272-4634 (ISSN-L)
  • 1937-2809
DOI
10.1080/02724634.1997.10010977
OpenAlex
W2028889824
Cited by
209
References
78
Citations by year
2026: 7 · 2025: 7 · 2024: 9 · 2023: 18 · 2022: 11 · 2021: 11 · 2020: 12 · 2019: 7 · 2018: 17 · 2017: 7 · 2016: 11 · 2015: 4 · 2014: 7 · 2013: 9 · 2012: 9
FWCI
4.81
Type
journal article
Language
en
Open access
closed
Locations
Journal of Vertebrate Paleontology (publishedVersion)
Topics
  • Physical Sciences › Earth and Planetary Sciences › Paleontology › Paleontology and Evolutionary Biology
  • Physical Sciences › Mathematics › Geometry and Topology › Morphological variations and asymmetry
  • Physical Sciences › Earth and Planetary Sciences › Paleontology › Evolution and Paleontology Studies
Keywords
theropod dinosaurs, bipedalism, morphological disparity, flight evolution, morphospace

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