Répteis alados pré-históricos 'saltavam com vara' antes de voar

quarta-feira, novembro 17, 2010

Prehistoric Winged Reptiles 'Pole-Vaulted' Into Flight

ScienceDaily (Nov. 15, 2010) — Controversial claims that enormous prehistoric winged beasts could not fly have been refuted by the most comprehensive study to date which asserts that giant pterosaurs were skilled in flight.

Image by Dr Mark Witton of 'Pteranodon, a pterosaur with a 7 m wingspan, mid launch. Note that the legs have already cleared the ground and the arms are being used to push the animal into the air.' (Credit: Dr Mark Witton)

The study, by Dr. Mark Witton from the University of Portsmouth in the UK and Dr Michael Habib from Chatham University in Pittsburgh, PA, contradicts recent assertions that the creatures were flightless and explains how they took to the air.

They state that the giant reptiles took off by using all four of their limbs and effectively 'pole-vaulting' over their wings using their leg muscles and pushing from the ground using their powerful arm muscles. Once airborne they could fly huge distances and even cross continents. Their research is published in the Public Library of Science journalPLoS ONE.

The debate about whether extinct giant pterosaurs, the largest of which were the height of giraffes, could fly has divided palaeontologists in recent years. Previous suggestions that they were flightless were based on assumptions that they were too heavy or because they would have taken off like birds, by running or leaping into their air using just their hind limbs.

Dr Witton said: "Most birds take off either by running to pick up speed and jumping into the air before flapping wildly, or if they're small enough, they may simply launch themselves into the air from a standstill. Previous theories suggested that giant pterosaurs were too big and heavy to perform either of these manoeuvres and therefore they would have remained on the ground.

Read more here/Leia mais aqui: Science Daily


On the Size and Flight Diversity of Giant Pterosaurs, the Use of Birds as Pterosaur Analogues and Comments on Pterosaur Flightlessness

Mark P. Witton1*, Michael B. Habib2

1 School of Earth and Environmental Sciences, University of Portsmouth, Portsmouth, United Kingdom, 2 Department of Sciences, Chatham University, Pittsburgh, Pennsylvania, United States of America


The size and flight mechanics of giant pterosaurs have received considerable research interest for the last century but are confused by conflicting interpretations of pterosaur biology and flight capabilities. Avian biomechanical parameters have often been applied to pterosaurs in such research but, due to considerable differences in avian and pterosaur anatomy, have lead to systematic errors interpreting pterosaur flight mechanics. Such assumptions have lead to assertions that giant pterosaurs were extremely lightweight to facilitate flight or, if more realistic masses are assumed, were flightless. Reappraisal of the proportions, scaling and morphology of giant pterosaur fossils suggests that bird and pterosaur wing structure, gross anatomy and launch kinematics are too different to be considered mechanically interchangeable. Conclusions assuming such interchangeability—including those indicating that giant pterosaurs were flightless—are found to be based on inaccurate and poorly supported assumptions of structural scaling and launch kinematics. Pterosaur bone strength and flap-gliding performance demonstrate that giant pterosaur anatomy was capable of generating sufficient lift and thrust for powered flight as well as resisting flight loading stresses. The retention of flight characteristics across giant pterosaur skeletons and their considerable robustness compared to similarly-massed terrestrial animals suggest that giant pterosaurs were not flightless. Moreover, the term ‘giant pterosaur’ includes at least two radically different forms with very distinct palaeoecological signatures and, accordingly, all but the most basic sweeping conclusions about giant pterosaur flight should be treated with caution. Reappraisal of giant pterosaur material also reveals that the size of the largest pterosaurs, previously suggested to have wingspans up to 13 m and masses up to 544 kg, have been overestimated. Scaling of fragmentary giant pterosaur remains have been misled by distorted fossils or used inappropriate scaling techniques, indicating that 10–11 m wingspans and masses of 200–250 kg are the most reliable upper estimates of known pterosaur size.

Citation: Witton MP, Habib MB (2010) On the Size and Flight Diversity of Giant Pterosaurs, the Use of Birds as Pterosaur Analogues and Comments on Pterosaur Flightlessness. PLoS ONE 5(11): e13982.

Editor: Vincent Laudet, Ecole Normale Supérieure de Lyon, France

Received: March 20, 2010; Accepted: October 21, 2010; Published: November 15, 2010

Copyright: © 2010 Witton, Habib. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Funding: The authors have no support or funding to report.

Competing interests: The authors have declared that no competing interests exist.

* E-mail: mark.witton@port.ac.uk