![]() On sait cependant peu de choses sur l'anatomie fonctionnelle des ailes des pingouins non-volants, car tous sont éteints et leur morphologie est presque exclusivement représentée par des restes squelettiques. Chez les oiseaux, l'évolution de la plongée propulsée par les ailes, associée à une perte de la capacité de vol, est devenue un exemple classique de convergence, apparue dans des lignées disparates telles que les manchots (Sphenisciformes) et les pingouins (Pan-Alcidae, Charadriiformes). La reconstruction de la musculature des ailes d’espèces éteintes de pingouins non-volants ( Pinguinus et Mancalla) révèle une convergence incomplète avec les manchots (Spheniscidae) expliquée par des états ancestraux différentsMalgré un intérêt de longue date pour l'évolution convergente, les facteurs limitant l’evolution de phénotypes entièrement convergents restent mal compris. ![]() Detailed investigations such as this one may indicate that, even in the face of similar functional demands, courses of phenotypic evolution are dictated to an important degree by ancestral starting points. Thus, the wings of these flightless wing-propelled divers can be described as convergent as overall functional units, but are incompletely convergent at lower levels of anatomical organization-a result of retaining differing conditions from each group’s respective volant ancestors. However, the conformations of individual muscles and ligaments underlying these specializations differ markedly between penguins and flightless auks, instead resembling those in each respective group’s close relatives. The results suggest that the wings of both flightless auk taxa were characterized by an increased mechanical advantage of wing elevator/retractor muscles, and decreased mobility of distal wing joints, both of which are likely advantageous for wing-propelled diving and parallel similar functional specializations in penguins. Extensive anatomical data were gathered from dissections of 12 species of extant charadriiforms and 4 aequornithine waterbirds including a penguin. Here, in order to re-evaluate the extent of evolutionary convergence among flightless wing-propelled divers, wing muscles and ligaments were reconstructed in two extinct flightless auks, representing independent transitions to flightlessness: Pinguinus impennis (a crown-group alcid), and Mancalla (a stem-group alcid). Nevertheless, little is known about the functional anatomy of the wings of flightless auks because all such taxa are extinct, and their morphology is almost exclusively represented by skeletal remains. In birds, the evolution of flightless wing-propelled diving has emerged as a classic example of convergence, having arisen in disparate lineages including penguins (Sphenisciformes) and auks (Pan-Alcidae, Charadriiformes). Despite longstanding interest in convergent evolution, factors that result in deviations from fully convergent phenotypes remain poorly understood.
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