Great Transformations in Vertebrate Evolution

Dial, Kenneth P.; Shubin, Neil; Brainerd, Elizabeth L.

doi:10.7208/chicago/9780226268392.001.0001

Cited by 26 publications

(27 citation statements)

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“…When animals transition between air and water, they must cope with dramatic changes to their sensory perception, their respiration and the force regime to which they are subjected (Dial et al, 2015;Fish, 2016). Despite these challenges, the phylogeny of birds provides abundant examples of secondary adaption to life in water (Vermeij and Dudley, 2000).…”

Section: Introductionmentioning

confidence: 99%

Upstroke-based acceleration and head stabilization are the norm for the wing-propelled swimming of alcid seabirds

Lapsansky

Tobalske

2019

Journal of Experimental Biology

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Alcids, a family of seabirds including murres, guillemots and puffins, exhibit the greatest mass-specific dive depths and durations of any birds or mammals. These impressive diving capabilities have motivated numerous studies on the biomechanics of alcid swimming and diving, with one objective being to compare stroke-acceleration patterns of swimming alcids with those of penguins, where upstroke and downstroke are used for horizontal acceleration. Studies of free-ranging, descending alcids have found that alcids accelerate in the direction of travel during both their upstroke and downstroke, but only at depths <20 m, whereas studies of alcids swimming horizontally report upstroke-based acceleration to be rare (≤16% of upstrokes). We hypothesized that swimming trajectory, via its interaction with buoyancy, determines the magnitude of acceleration produced during the upstroke. Thus, we studied the strokeacceleration relationships of five species of alcid swimming freely at the Alaska SeaLife Center using videography and kinematic analysis. Contrary to our prediction, we found that upstroke-based acceleration is very common (87% of upstrokes) during both descending and horizontal swimming. We reveal that head-dampingwherein an animal extends and retracts its head to offset periodic accelerationsis common in swimming alcids, underscoring the importance of head stabilization during avian locomotion.

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Section: Introductionmentioning

confidence: 99%

Upstroke-based acceleration and head stabilization are the norm for the wing-propelled swimming of alcid seabirds

Lapsansky

Tobalske

2019

Journal of Experimental Biology

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“…Developing birds challenge this adultocentric view because fledglings with very rudimentary anatomies begin flapping and producing aerodynamic forces long before acquiring “flight” aptations and the “avian” body plan characteristic of adults [ 10 , 18 , 56 ]. Juveniles in species with a diverse array of wing-leg morphologies and life history strategies frequently recruit their legs and incipient wings cooperatively to avoid predators or reach refuges ([ 57 – 59 ]; AMH, KPD, and Tom Martin, personal observations; see juvenile birds in: https://www.youtube.com/watch?v=k94EDd8aKng and https://www.youtube.com/watch?v=3USAC-Ky25s ), by flap-running up slopes (wing-assisted incline running / walking; WAIR) and controlling aerial descents [ 53 , 54 ], swimming and steaming across water [ 55 ], and/or jumping into brief flapping flights [ 20 ]. In fact, in at least some precocial species, the development of flight capacity (~18–20 days in Alectoris chukar ) precedes the development of an adult-like musculoskeletal apparatus (close to ~100 days) by a substantial and biologically relevant margin [ 10 , 20 ].…”

Section: Introductionmentioning

confidence: 99%

Flapping before Flight: High Resolution, Three-Dimensional Skeletal Kinematics of Wings and Legs during Avian Development

et al. 2016

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Some of the greatest transformations in vertebrate history involve developmental and evolutionary origins of avian flight. Flight is the most power-demanding mode of locomotion, and volant adult birds have many anatomical features that presumably help meet these demands. However, juvenile birds, like the first winged dinosaurs, lack many hallmarks of advanced flight capacity. Instead of large wings they have small “protowings”, and instead of robust, interlocking forelimb skeletons their limbs are more gracile and their joints less constrained. Such traits are often thought to preclude extinct theropods from powered flight, yet young birds with similarly rudimentary anatomies flap-run up slopes and even briefly fly, thereby challenging longstanding ideas on skeletal and feather function in the theropod-avian lineage. Though skeletons and feathers are the common link between extinct and extant theropods and figure prominently in discussions on flight performance (extant birds) and flight origins (extinct theropods), skeletal inter-workings are hidden from view and their functional relationship with aerodynamically active wings is not known. For the first time, we use X-ray Reconstruction of Moving Morphology to visualize skeletal movement in developing birds, and explore how development of the avian flight apparatus corresponds with ontogenetic trajectories in skeletal kinematics, aerodynamic performance, and the locomotor transition from pre-flight flapping behaviors to full flight capacity. Our findings reveal that developing chukars (Alectoris chukar) with rudimentary flight apparatuses acquire an “avian” flight stroke early in ontogeny, initially by using their wings and legs cooperatively and, as they acquire flight capacity, counteracting ontogenetic increases in aerodynamic output with greater skeletal channelization. In conjunction with previous work, juvenile birds thereby demonstrate that the initial function of developing wings is to enhance leg performance, and that aerodynamically active, flapping wings might better be viewed as adaptations or exaptations for enhancing leg performance.

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“…Contrarily to what was stated about therapsid posture in the past (Charig, 1980; Bonaparte, 1982), therapsid-grade limb osteology was characterized by several important modifications, which indicate a more parasagittal stance of the limbs (Romer, 1956; Boonstra, 1967; Jenkins Jr, 1971), especially if compared with the prevalent sprawling posture of non-therapsid synapsids (Romer, 1956; Hopson, 2015). Modifications of the scapula and the glenoid have allowed the elbow to rotate inwardly, bringing the humerus closer to the sagittal plane (Walter, 1986).…”

Section: Discussionmentioning

confidence: 97%

“…For example, it must be noted that non therapsid-synapsids with sprawling posture could have left trackways in which the left and right tracks lie near to the axial midline (i.e., narrow internal trackway width mirroring a semi-erect to erect posture of the trackmaker) by adopting side to side flexion of the trunk (Hopson, 2015). The same was described for a therapsid trackway by Smith (1993).…”

Section: Track Recordmentioning

confidence: 99%

“…Some degree of lateral undulation of the vertebral column causing swing of the hips has been also described on the basis of skeletal remains (Fröbisch, 2006: p. 1305). However, in sprawling trackmakers adopting trunk flexion and producing narrow trackways, tracks are mainly inwardly oriented with respect to the trackway midline (see Hopson, 2015: Fig 8.1). In the studied material, the orientation of footprint axis (passing through digit III) is parallel to the travel direction.…”

Section: Track Recordmentioning

confidence: 99%

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Triassic pentadactyl tracks from the Los Menucos Group (Río Negro province, Patagonia Argentina): possible constraints on the autopodial posture of Gondwanan trackmakers

Citton

Díaz-Martínez

Valais

et al. 2018

PeerJ

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The Los Menucos locality in Patagonia, Argentina, bears a well-known ichnofauna mostly documented by small therapsid footprints. Within this ichnofauna, large pentadactyl footprints are also represented but to date were relatively underinvestigated. These footprints are here analyzed and discussed based on palaeobiological indications (i.e., trackmaker identification). High resolution digital photogrammetry method was performed to achieve a more objective representation of footprint three-dimensional morphologies. The footprints under study are compared with Pentasauropus from the Upper Triassic lower Elliot Formation (Stormberg Group) of the Karoo Basin (Lesotho, southern Africa). Some track features suggest a therapsid-grade synapsid as the potential trackmaker, to be sought among anomodont dicynodonts (probably Kannemeyeriiformes). While the interpretation of limb posture in the producer of Pentasauropus tracks from the Los Menucos locality agrees with those described from the dicynodont body fossil record, the autopodial posture does not completely agree. The relative distance between the impression of the digital (ungual) bases and the distal edge of the pad trace characterizing the studied tracks likely indicates a subunguligrade foot posture (i.e., standing on the last and penultimate phalanges) in static stance, but plantiportal (i.e., the whole foot skeleton and related soft tissues are weight-bearing) during the dynamics of locomotion. The reconstructed posture might have implied an arched configuration of the articulated metapodials and at least of the proximal phalanges, as well as little movement capabilities of the metapodials. Usually, a subunguligrade-plantiportal autopod has been described for gigantic animals (over six hundreds kilograms of body weight) to obtain an efficient management of body weight. Nevertheless, this kind of autopod is described here for large but not gigantic animals, as the putative trackmakers of Pentasauropus were. This attribution implies that such an autopodial structure was promoted independently from the body size in the putative trackmakers. From an evolutionary point of view, subunguligrade-plantiportal autopods not necessarily must be related with an increase in body size, but rather the increase in body size requires a subunguligrade or unguligrade, plantiportal foot. Chronostratigraphically, Pentasauropus was reported from Upper Triassic deposits of South Africa and United States, and from late Middle Triassic and Upper Triassic deposits of Argentina. Based on the stratigraphic distribution of the ichnogenus currently accepted, a Late Triassic age is here proposed for the Pentasauropus-bearing levels of the Los Menucos Group.

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Great Transformations in Vertebrate Evolution

Cited by 26 publications

References 0 publications

Upstroke-based acceleration and head stabilization are the norm for the wing-propelled swimming of alcid seabirds

Upstroke-based acceleration and head stabilization are the norm for the wing-propelled swimming of alcid seabirds

Flapping before Flight: High Resolution, Three-Dimensional Skeletal Kinematics of Wings and Legs during Avian Development

Triassic pentadactyl tracks from the Los Menucos Group (Río Negro province, Patagonia Argentina): possible constraints on the autopodial posture of Gondwanan trackmakers

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