Saturday, December 6, 2014

[Paleontology • 2014] New Specimen of Archaeopteryx provides Insights into The Evolution of Pennaceous Feathers | The Flight for First Bird

Archaeopteryx’s status is changing, but the animal is still key to the dinosaur–bird transition.
Illustration by Emily Willoughby; Graphics: Jasiek Krzysztofiak/Nature;
doi: 10.1038/nature13467 10.1038/516018a

The iconic status of Archaeopteryx, the first animal discovered with both bird and dinosaur features, is under attack. More-recently discovered rival species show a similar mix of traits. But Archaeopteryx still hogged the opening symposium at the 2014 Society of Vertebrate Paleontology meeting in Berlin last month, and even festooned the official conference beer glasses.

As the simplistic idea of a ‘first’ bird gives way to a messy evolutionary transition, newly discovered fossils and improved analysis techniques put Archaeopteryx in prime position to unravel the details. “Research on Archaeopteryx is really catching a new breath,” says palaeobiologist Martin Kundrat of Uppsala University in Sweden, who co-organized the symposium at the November meeting.

The first Archaeopteryx fossil specimens turned up in limestone quarries in Bavaria, southern Germany, in the early 1860s. Until recently, they were the only fossil specimens found to mix bird- and dinosaur-like features. On the one hand, they are small — the fossils show juvenile creatures about the size of a magpie, which as adults may have been raven-sized — and have broad feathered wings that look good for gliding; on the other, they have a jaw with sharp teeth, dinosaur-like claws and a bony tail. These features led to the idea of the first bird, and generations of scientists have treated the 145-million-year-old animal as a ‘transitional species’ — the key piece of evidence linking birds and dinosaurs (Archaeopteryx is Greek for ‘ancient feather’, whereas its German name, ‘Urvogel’, means ‘first bird’).



Discoveries of bird-like theropod dinosaurs and basal avialans in recent decades have helped to put the iconic ‘Urvogel’ Archaeopteryx into context and have yielded important new data on the origin and early evolution of feathers. However, the biological context under which pennaceous feathers evolved is still debated. Here we describe a new specimen of Archaeopteryx with extensive feather preservation, not only on the wings and tail, but also on the body and legs. The new specimen shows that the entire body was covered in pennaceous feathers, and that the hindlimbs had long, symmetrical feathers along the tibiotarsus but short feathers on the tarsometatarsus. Furthermore, the wing plumage demonstrates that several recent interpretations are problematic. An analysis of the phylogenetic distribution of pennaceous feathers on the tail, hindlimb and arms of advanced maniraptorans and basal avialans strongly indicates that these structures evolved in a functional context other than flight, most probably in relation to display, as suggested by some previous studies. Pennaceous feathers thus represented an exaptation and were later, in several lineages and following different patterns, recruited for aerodynamic functions. This indicates that the origin of flight in avialans was more complex than previously thought and might have involved several convergent achievements of aerial abilities.

Christian Foth, Helmut Tischlinger and Oliver W. M. Rauhut. 2014. New Specimen of Archaeopteryx provides Insights into The Evolution of Pennaceous Feathers. Nature. 511, 79–82. doi: 10.1038/nature13467

Amy M. Balanoff, Gabe S. Bever, Timothy B. Rowe and Mark A. Norell. 2013. Evolutionary origins of the avian brain. Nature. 501, 93–96 doi:
Ryan M. Carney, Jakob Vinther, Matthew D. Shawkey, Liliana D'Alba and Jörg Ackermann. 2012. New evidence on the colour and nature of the isolated Archaeopteryx feather. Nature Communications. 3, Article number: 637 doi: 10.1038/ncomms1642

Ewen Callaway. 2014. Rival Species recast significance of ‘First Bird’. Nature516, 18–19 (04 December 2014) doi: 10.1038/516018a