Adaptations for Bipedal Locomotion of Lizards

Snyder, Richard C.

doi:10.1093/icb/2.2.191

Cited by 144 publications

(126 citation statements)

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“…Many lizard species switch between quadrupedal and bipedal running posture during locomotion (Snyder, 1952(Snyder, , 1962. The alteration of running posture constitutes a change in locomotor behavior, particularly if in response to a consistent variable such as an obstacle.…”

Section: Introductionmentioning

confidence: 99%

“…A bipedal posture may decrease energy expenditure by having only two limbs in motion (Kohlsdorf and Biewener, 2006;Snyder, 1952Snyder, , 1962. Alternatively, a bipedal posture may be a mechanical consequence of rapid initial acceleration.…”

Section: Introductionmentioning

confidence: 99%

“…Tail elevation is likely important, as a horizontal tail could aid in locomotion over the obstacle (Hsieh, 2003;Self, 2012). In the case of the basilisk lizard, holding the tail horizontally acts as a counterbalance in forward locomotion and generates thrust to propel the animal forward during bipedal running on water (Snyder, 1962;Hsieh, 2003). Or, a horizontal tail may counterbalance the weight of the increased body angle during bipedal running, as it would position the COM of the tail as far as possible from the center of the hip (Irschick and Jayne, 1999b), thus providing a potential benefit for lizards using a bipedal running posture.…”

Section: Introductionmentioning

confidence: 99%

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The effects of multiple obstacles on the locomotor behavior and performance of a terrestrial lizard

Parker

McBrayer

2016

Journal of Experimental Biology

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Negotiation of variable terrain is important for many small terrestrial vertebrates. Variation in the running surface resulting from obstacles (woody debris, vegetation, rocks) can alter escape paths and running performance. The ability to navigate obstacles likely influences survivorship through predator evasion success and other key ecological tasks (finding mates, acquiring food). Earlier work established that running posture and sprint performance are altered when organisms face an obstacle, and yet studies involving multiple obstacles are limited. Indeed, some habitats are cluttered with obstacles, whereas others are not. For many species, obstacle density may be important in predator escape and/or colonization potential by conspecifics. This study examines how multiple obstacles influence running behavior and locomotor posture in lizards. We predict that an increasing number of obstacles will increase the frequency of pausing and decrease sprint velocity. Furthermore, bipedal running over multiple obstacles is predicted to maintain greater mean sprint velocity compared with quadrupedal running, thereby revealing a potential advantage of bipedalism. Lizards were filmed running through a racetrack with zero, one or two obstacles. Bipedal running posture over one obstacle was significantly faster than quadrupedal posture. Bipedal running trials contained fewer total strides than quadrupedal ones. But on addition of a second obstacle, the number of bipedal strides decreased. Increasing obstacle number led to slower and more intermittent locomotion. Bipedalism provided clear advantages for one obstacle, but was not associated with further benefits for an additional obstacle. Hence, bipedalism helps mitigate obstacle negotiation, but not when numerous obstacles are encountered in succession.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The effects of multiple obstacles on the locomotor behavior and performance of a terrestrial lizard

Parker

McBrayer

2016

Journal of Experimental Biology

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“…In modern Aves, knee flexion is more important to locomotion than femoral retraction (Gatesy and Biewener, 1991;Carrano, 1998;Farlow et al, 2000), and the M. caudofemoralis is greatly reduced in most birds and altogether absent in others (Gatesy, 1990). In crocodilians and the majority of non-serpente squamates, however, the M. caudofemoralis is both the primary and the single largest retractor muscle of the hind limb (Snyder, 1962;Gatesy, 1990). Electromyographic studies of walking and running crocodiles have shown the M. caudofemoralis to be consistently active at all speeds, whenever femoral retraction occurs (Gatesy, 1997).…”

mentioning

confidence: 99%

The Tail of Tyrannosaurus: Reassessing the Size and Locomotive Importance of the M. caudofemoralis in Non‐Avian Theropods

Persons

Currie

2010

The Anatomical Record

165

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Unlike extant birds and mammals, most non-avian theropods had large muscular tails, with muscle arrangements similar to those of modern reptiles. Examination of ornithomimid and tyrannosaurid tails revealed sequential diagonal scarring on the lateral faces of four or more hemal spines that consistently correlates with the zone of the tail just anterior to the disappearance of the vertebral transverse processes. This sequential scarring is interpreted as the tapering boundary between the insertions of the M. caudofemoralis and the M. ilioischiocaudalis. Digital muscle reconstructions based on measurements of fossil specimens and dissections of modern reptiles showed that the M. caudofemoralis of many non-avian theropods was exceptionally large. These high caudofemoral mass estimates are consistent with the elevation of the transverse processes of the caudal vertebra above the centrum, which creates an enlarged hypaxial region. Dorsally elevated transverse processes are characteristic of even primitive theropods and suggest that a large M. caudofemoralis is a basal characteristic of the group. In the genus Tyrannosaurus, the mass of the M. caudofemoralis was further increased by dorsoventrally lengthening the hemal arches. The expanded M. caudofemoralis of Tyrannosaurus may have evolved as compensation for the animal's immense size. Because the M. caudofemoralis is the primary hind limb retractor, large M. caudofemoralis masses and the resulting contractile force and torque estimates presented here indicate a sizable investment in locomotive muscle among theropods with a range of body sizes and give new evidence in favor of greater athleticism, in terms of overall cursoriality, balance, and turning agility. Anat Rec, 294:119-131, 2011. V V C 2010 Wiley-Liss, Inc.

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“…The relation of the vertebral column to the movement of the sacrum was discussed by Wei si (1954) who concentrated on the articular surfaces On a more comparative basis, the relation of the morphology of the limbs and vertebral column to movement was discussed by Stapley (1912), Snyder (1954Snyder ( , 1961Snyder ( , 1962 and S 1 i j p e r (1946). Stapley concentrated on the cervical region, Snyder studied the morphology of bipedal lizards from a functional point of view and S 1 i j p e r studied in detail the vertebral column and spinal musculature in mammals.…”

mentioning

confidence: 99%

Contributions to the biomechanics of the vertebral column. II. Rotatory system induced in the thoraco-lumbar curvature by the epaxial musculature

Tucker¹

1964

Acta Theriol.

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Adaptations for Bipedal Locomotion of Lizards

Cited by 144 publications

References 9 publications

The effects of multiple obstacles on the locomotor behavior and performance of a terrestrial lizard

The effects of multiple obstacles on the locomotor behavior and performance of a terrestrial lizard

The Tail of Tyrannosaurus: Reassessing the Size and Locomotive Importance of the M. caudofemoralis in Non‐Avian Theropods

Contributions to the biomechanics of the vertebral column. II. Rotatory system induced in the thoraco-lumbar curvature by the epaxial musculature

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