On the Origin of Birds
The discovery of a new bird-like fossil challenges longstanding theories about which species of dinosaur gave rise to the avian lineage.
By Cristina Luiggi | July 27, 2011
This year marks the 150th anniversary of the discovery of one of the most iconic dinosaur fossils of all time: Archaeopteryx. Unearthed in 1861 in southern Germany, it has long been considered the missing link between dinosaurs and birds: it has the skeleton of a reptile—including a long bony tail and teeth—combined with what are considered hallmarks of modern birds—feathers and a wishbone.
But the discovery of a new bird-like dinosaur, Xiaotingia zhengi, in China threatens to dethrone Archaeopteryx as the most primitive of birds.
The inclusion of the new fossil in a comprehensive phylogenetic analysis of dinosaurs and early birds, published today (July 27) in Nature, resulted in a rearrangement of evolutionary relationships—removing Archaeopteryx from the avian family and placing it in a closely related family of non-avian dinosaurs.
“For the past 150 years, Archaeopteryx has been this filter through which we’ve run every idea about the early evolution of birds,” said Lawrence Witmer, a paleontologist at Ohio University who was not involved with the study. The new fossil will force researchers to re-evaluate avian origins from a different perspective, he added.
Roughly the size of a chicken, Xiaotingia zhengi is morphologically very similar to Archaeopteryx, sporting long arms and (most likely) four wings. Like Archaeopteryx, it also walked, or possibly glided, across the Earth during the Late Jurassic Period around 150 million years ago—right at the genesis of birds.
“It’s an amazing fossil,” said lead author Xing Xu, a paleontologist at the Institute of Vertebrate Paleontology and Paleoanthropology in China. “The information recovered from this fossil will have a tremendous impact on our understanding of bird origins.”
+++++
Read more here/Leia mais aqui: The Scientist
+++++
+++++
An Archaeopteryx-like theropod from China and the origin of Avialae
Xing Xu, Hailu You, Kai Du & Fenglu Han
Affiliations
Contributions
Corresponding Author
Nature 475, 465–470 (28 July 2011)
doi:10.1038/nature10288
Received 16 November 2010 Accepted 10 June 2011 Published online 27 July 2011
Abstract
Archaeopteryx is widely accepted as being the most basal bird, and accordingly it is regarded as central to understanding avialan origins; however, recent discoveries of derived maniraptorans have weakened the avialan status of Archaeopteryx. Here we report a new Archaeopteryx-like theropod from China. This find further demonstrates that many features formerly regarded as being diagnostic of Avialae, including long and robust forelimbs, actually characterize the more inclusive group Paraves (composed of the avialans and the deinonychosaurs). Notably, adding the new taxon into a comprehensive phylogenetic analysis shifts Archaeopteryx to the Deinonychosauria. Despite only tentative statistical support, this result challenges the centrality of Archaeopteryx in the transition to birds. If this new phylogenetic hypothesis can be confirmed by further investigation, current assumptions regarding the avialan ancestral condition will need to be re-evaluated.
Subject terms: Evolution
+++++
+++++
Professores, pesquisadores e alunos de universidades públicas e privadas com acesso ao site CAPES/Periódicos (mais de 300) podem ler gratuitamente este artigo da Nature e de mais 22.440 publicações científicas.
+++++
+++++
NOTA DESTE BLOGGER:
O bom em ciência é que a verdade de hoje pode ser encontrada em descompasso com a verdade das evidências amanhã. Em ciência, nada como um dia atrás do outro, onde verdades dogmáticas são esfareladas pelo rigor do contexto de justificação teórica.
Contexto de justificação teórica? Os darwinistas ortodoxos fundamentalistas xiitas odeiam isso... e a Galera dos meninos e meninas de Darwin talvez nem saiba o que é isso...
Fui, nem sei por que, nem um pouco surpreendido, pois o Archaeopteryx era tido pela Nomenklatura científica como o ELO de ligação entre dinossauros e aves apesar da montanha de evidências contrárias a esta POTOCA. Mas, quando a questão é Darwin, o que é uma, duas, três, quatro, cinco, seis mentiras para favorecer o fato, Fato, FATO da evolução?
Eu sei do que estou falando, e eles também...
Contexto de justificação teórica? Os darwinistas ortodoxos fundamentalistas xiitas odeiam isso... e a Galera dos meninos e meninas de Darwin talvez nem saiba o que é isso...
Fui, nem sei por que, nem um pouco surpreendido, pois o Archaeopteryx era tido pela Nomenklatura científica como o ELO de ligação entre dinossauros e aves apesar da montanha de evidências contrárias a esta POTOCA. Mas, quando a questão é Darwin, o que é uma, duas, três, quatro, cinco, seis mentiras para favorecer o fato, Fato, FATO da evolução?
Eu sei do que estou falando, e eles também...
