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The vertebrate limb is a dynamic structure that has evolved into many diverse forms to facilitate complex behavioural adaptations. The principle molecular and cellular processes that underlie development of the vertebrate limb are well characterised. However, how these processes are altered to drive differential limb development between vertebrates is less well understood. Several vertebrate models are being utilized to determine the developmental basis of differential limb morphogenesis, though these typically focus on later patterning of the established limb bud and may not represent the complete developmental trajectory. Particularly, heterochronic limb development can occur prior to limb outgrowth and patterning but receives little attention. This review summarises the developmental regulation of vertebrate forelimb diversity, with particular focus on wing reduction in the flightless emu as a model for studying limb heterochrony. These studies highlight that wing reduction is complex, with heterochronic cellular and genetic events influencing the major stages of limb development. Together, these studies provide a broader picture of how different limb morphologies may be established during development.
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The aim of the study is to calculate the swimming capability of the extinct penguin Inkayacu paracasensis in terms of estimated maximum swimming speed, based on a theoretical biomechanical (fluid mechanics) method, which was previously applied to Mesozoic marine reptiles and living cetaceans. For comparison purposes, this parameter is also calculated for the African black-footed penguin Spheniscus demersus and the Emperor penguin Aptenodytes forsteri. Results show an estimated maximum speed of 2.8-3.4 m/s, 2.8-3.5 m/s and 3.0-3.7 m/s for the three species respectively. Studies with species in captivity and in the wild allows corroborating the estimated values for the living species, with a maximum error of about 10% in the case of A. forsteri. Therefore, the Emperor penguin and Inkayacu have developed similar swimming velocities. It is suggested that wing beat frequency, stride length and gliding phases are similar in both large bodied species, in contrast of the small ones. In addition, it is also analyzed the influence of the fow model (ReynoldÂs number) in the three penguin species. It is suggested that skull morphology of Inkayacu could be an advantage in locomotion with respect of the Emperor penguin.
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San Marcos: paleontÃlogo realiza el primer estudio de biofÃsica aplicada a fÃsiles de PerÃ
Extinct birds of the family Pelagornithidae were large gliding seabirds that inhabited the planet from the late Paleocene to the Pliocene. This investigation studies the fight capacity of a species of pelagornithids, Pelagornis chilensis. Using the sustenance formula and allometric formulas it was shown that different speeds of the fossil bird are significantly greater than Thalassarche chrysostoma, the gray-headed albatross, which is the more morphologically close extant bird to P. chilensis. In addition, consistent with the previous results, it was determined that the parasitic power, the induced power, the muscular strength and the Reynolds number of P. chilensis are significantly greater than the same variables of T. chrysostoma. The method was used in the albatross Diomedea exulans, to check the proximity of the observed values with the calculated ones and estimate the error, obtaining a difference between these results of 2.7%. Finally, the conditions and form of fight and their possible application to the fight are studied; it is hypothesized that due to the large size of both birds and morphology, these fight patterns would have been similar.
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