Dinosaur Locomotion

Abstract

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.

Key concepts:

  • Dinosaurs represent a unique and interesting system for studying adaptation and locomotion due to their diverse morphologies, body sizes and changes in posture during their long evolutionary history.

  • It is difficult to constrain how dinosaurs moved because there are so many unknown factors such as their body mass and muscle anatomy.

  • Fossil skeletons and footprints reveal that dinosaurs used an ‘erect posture’ and restricted most limb movements to a plane parallel to the body (parasagittal gait).

  • Comparative anatomy and limb bone scaling allows general comparisons between locomotion in dinosaurs and living mammals and, for example, suggests both predominantly drove limb motion from the hip (versus the knee and ankle in birds).

  • Computer modelling approaches are becoming widely used to investigate dinosaur locomotion and biomechanics in extinct animals in general.

  • Computer modelling approaches allow the role of individual muscles in dinosaur limbs to be investigated, and thus it is possible to compare how muscles might have functioned in dinosaurs and their closest relatives (in other words to investigate how muscle function evolved).

  • Biomechanical models and computer simulations have been used to investigate how dinosaurs might have moved and what kind of locomotor behaviours they might have been capable of (e.g. running ability).

  • Biomechanical approaches require explicit specification of muscle properties for dinosaurs. Because most if not all of these parameters are unknown for dinosaurs, and in many cases only broadly estimable, researchers have used sensitivity analysis to quantify the potential margin of error in their predictions. This results in a broad range of predicted running gaits and top speeds for dinosaurs.

  • To address these challenges and better understand dinosaur locomotion, future work must be highly integrative, combining methods and evidence from anatomy, trackways and biomechanical modelling with better understanding of locomotion in living animals.

Keywords: dinosaur; locomotion; biomechanics; scaling; bird

Figure 1.

Evolution of dinosaur locomotion. Broad changes in locomotor function are plotted on to these ‘phylogenies’ of dinosaurs. (a) Dinosaur phylogeny showing the divergence of dinosaurs into ornithischians, sauropods and theropods and a few key changes within these lineages. In theropods, ‘1’ indicates the origin of feathers, a furcula (wishbone), and other preflight specialisations; ‘2’ indicates the secondary increase of size in tyrannosaurs and a concomitant reduction of running ability; ‘3’ indicates the evolution of more preflight features (elongate feathers and large sternum or breastbone), a more crouched pose and a reduction of body size and ‘4’ indicates the origin of true powered flight in birds, and subsequent elaborations of terrestrial and aerial locomotion. (b) Ornithischian phylogeny focusing on the three or more independent origins of large size and quadrupedalism. All colour dinosaur illustrations are from Joe Tucciarone (http://members.aol.com/Dinoplanet/dinosaur.html), used with permission. © Joe Tucciarone.

Figure 2.

Trackway evidence for walking and perhaps running. A 163‐million‐year‐old trackway of a medium‐sized theropod (carnivorous) dinosaur from England. The animal was walking slowly (a), then sped up perhaps to a run (b), and then later slowed down. Left (L) and right (R) footprints can be seen, and the stride length (SL) and angulation (ANG) can be measured. Notice, how the SL and ANG increase in the faster tracks in (b) This might have been a running gait, but was not an extraordinarily fast one, and is not the fastest one known (see Table ; this trackway is from the second theropod in that list). Reproduced from Day et al. with permission from Nature Publishing Group.

Figure 3.

Reconstruction of the pelvis and hind limb musculature of Lesothosaurus diagnosticus (based on Maidment and Barrett, ). (a and b) Pelvis in: (a) lateral and (b) medial views. (c–f) Femur in: (c) cranial, (d) medial, (e) caudal and (f) lateral views. (g) This muscle reconstruction, developed by looking at the bones of Lesothosaurus and other dinosaurs and comparing them to those of living crocodilians and birds, was used to produce a 3D musculoskeletal model of Lesothosaurus (shown in right lateral view; see Bates et al., for muscle abbreviations and more information). This model was used to estimate the moments arm of hind limb muscles in Lesothosaurus and subsequently to draw comparisons about muscle function with other dinosaurs and living birds. For example, (h) the iliofemoralis group muscle moment arms for hip (left graph) flexion–extension, (central graph) abduction–adduction and (right graph) long axis rotation over a range of hip joint flexion–extension angles. This muscle group is shown below the graphs (i) in the models of (left) Lesothosaurus, (central) Allosaurus and (right) an ostrich (not to scale). The main finding in this case was that IFMa is located much farther cranial (forwards) to the joint centre in the ostrich causing higher medial rotation moment arms (right graph). This difference in muscle function is thought to be important distinction between the way primitive dinosaurs controlled their limbs during stance and the way birds do in the present day. Abbreviations: ABD–ADD, abduction/adduction; CFB, caudofemoral brevis; CFL, caudoemoralis longus; FL, femoral length; Flex–Ext, flexion/extension; FMTL, femorotibialis lateralis; FMTM, femorotibialis medialis; FTI, flexor tibialis internus; IFB, iliofibularis; IFMa, iliofemoralis anterior; ISTR, ischiotrochantericus; ITB, iliotibialis; LAR, long axis rotation; MA, moment arm; PIFE, puboischiofemoralis externus and PIFI, puboischiofemoralis internus. Images from Bates et al..

Figure 4.

Biomechanics of dinosaur locomotion. (a) A tyrannosaur is shown at the midpoint of support during running, in a pose with particular pelvic, hip, knee, ankle and toe angles. (b) In any pose one can calculate the forces (F) and moments (M; rotational forces equal to a force F times a moment arm R). The weights of the body segments directed downwards (W) and the ground reaction force (GRF) pushing up against the foot are included. For example, to support its body while running at 20 m s−1 (72 km h−1) in the pose shown, a Tyrannosaurus would have needed approximately 86% of its body mass as leg muscles. This is far more than the body could have contained; thus, large tyrannosaurs and other large dinosaurs presumably had to move more slowly, perhaps 5–11 m s−1 at most (18–40 km h−1) and used a more upright pose, not such a crouched pose. Reproduced from Hutchinson and Garcia, . © Nature Publishing Group.

Figure 5.

(a) 3D musculoskeletal model of the large theropod dinosaur Acrocanthosaurus. (b) Dynamic computer simulations of running initially predicted a maximum running speed of 6.8 m s−1 for Acrocanthosaurus. However, sensitivity analysis, in which a number of uncertain parameters (e.g. muscle mass and muscle fibre lengths) were varied across a reasonable range of alternative values, suggested that top speed may have between 4.5 and 7.6 m s−1 (Bates, ).

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Further Reading

Biewener AA (1990) The biomechanics of mammalian terrestrial locomotion. Science 250: 1097–1103.

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Dial KP (2002) Wing‐assisted incline running and the evolution of flight. Science 299: 402–404.

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Sellers WI and Manning PL (2007) Estimating dinosaur maximum running speeds using evolutionary robotics. Proceedings of the Royal Society B 274: 2711–2716.

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How to Cite close
Bates, Karl T(Mar 2013) Dinosaur Locomotion. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0003320.pub2]