Archaeopteryx must be one of the most familar images associated with the origins and evolution of birds. Famously, it was first described one hundred years ago in 1861 from a single feather in 150-million year old Jurasssic limestone from Solnhofen in Bavaria.
The first skeletal fossil of Archaeopteryx was found in 1861 and purchased by the British Museum (part of which later became the Natural History Museum) for £700 in 1862. This specimen was described by the then Superintendent of the Museum's Natural History Departments, Richard Owen, in 1863. A further nine fossils have been found since then and are found in various museums. Although the first fossil found was of a feather, it is not now certain that the feather was from the same species as the body fossils. When first found, Archaeopteryx was uniquely important in showing the connection between birds and other reptiles - but since then, evidence from many other fossils has supported the scientific view of the origins of birds.
These fossils have traditionally been seen as those of a very early bird at the very base of the current avian branch of the Tree of Life. The birds emerged by the evolution and diversification of a group of reptiles in the late Jurassic period - just over 161 million years ago. From a current scientific viewpoint, the basal group of reptiles - the Paraves - split to form two groups: the Avialae (becoming birds over time); and the Deinonychosauria.
However, a new paper in the journal Nature by Xing Xu et al. has involved examination of a newly discovered fossil species from this group, Xiaotingia, from China. This organism was very similar to Archaeopteryx and the question arose of whether Archaeopteryx should be placed in the Avialae or the Deinonychosauria: which branch? Systematic scientific investigation of several Archaeopteryx fossils, Xiaotingia, and other fossils, suggests initially that Achaeopteryx does not fall into the same group as the birds - the Avialae. This involved examination of the NHM Archaeopteryx, illustrating the importance of collections as a continuing reference resource for science.
The research suggests that Archaeopteryx is not an ancestral bird in the Avialae, but should instead be seen as a member of the Deinonychosauria, along with Xiaotingia. This finding will cause considerable controversy in science as results are scrutinised and discussed and further evidence amassed. Future fossil findings will add further data that may add detail and support for different positions, but reference to the original fossils will continue to be essential. One point of interest will be that the characteristic feathers and skeleton of Archaeopteryx show that this character combination may not have been restricted to birds alone, but seems to have been found in a wider group of reptiles.
Witmer L M Palaeontology: An icon knocked from its perch Nature 475, 458–459 (28 July 2011) doi:10.1038/475458a Published online 27 July 2011
Xing Xu,Hailu You,Kai Du & Fenglu Han An Archaeopteryx-like theropod from China and the origin of Avialae Nature 475, 465–470 (28 July 2011) doi:10.1038/nature10288 Published online 27 July 2011