From the Zoological Journal of the Linnean Society:
The tenth skeletal specimen of Archaeopteryx …Solnhofen, where Archaeopteryx was found: here.We describe the tenth skeletal specimen of the Upper Jurassic Archaeopterygidae.
The almost complete and well-preserved skeleton is assigned to Archaeopteryx siemensii Dames, 1897 and provides significant new information on the osteology of the Archaeopterygidae.
As is evident from the new specimen, the palatine of Archaeopteryx was tetraradiate as in non-avian theropods, and not triradiate as in other avians.
Also with respect to the position of the ectopterygoid, the data obtained from the new specimen lead to a revision of a previous reconstruction of the palate of Archaeopteryx.
The morphology of the coracoid and that of the proximal tarsals is, for the first time, clearly visible in the new specimen.
The new specimen demonstrates the presence of a hyperextendible second toe in Archaeopteryx.
This feature is otherwise known only from the basal avian Rahonavis and deinonychosaurs (Dromaeosauridae and Troodontidae), and its presence in Archaeopteryx provides additional evidence for a close relationship between deinonychosaurs and avians.
The new specimen also shows that the first toe of Archaeopteryx was not fully reversed but spread medially, supporting previous assumptions that Archaeopteryx was only facultatively arboreal.
Archaeopteryx finds since the 19th century: here.
How birds learned how to fly: here.
A fossil brain from the Cretaceous of European Russia and avian sensory evolution: here.
The earliest known bird, the magpie-sized Archaeopteryx lithographica, was able to hear like a modern emu: here.
Solnhofen fossils, mainly of invertebrates: here.
Earliest birds acted more like turkeys than common cuckoos
The earliest birds acted more like turkeys than common cuckoos, according to a new report in the November 6th issue of Current Biology, a publication of Cell Press. By comparing the claw curvatures of ancient and modern birds, the researchers provide new evidence that the evolutionary ancestors of birds primarily made their livings on the ground rather than in trees.
“The claws of Mesozoic birds and their immediate ancestors, the non-avian theropods, are relatively ‘straight’—most like [those] of birds that are now either specialized for walking on the ground or have a preference for it, rather than the highly curved claws of birds that spend a lot of time in trees,” said Christopher Glen of the University of Queensland. “We were particularly surprised by the fact that all the fossil species, representing evolutionary lineages from non-flying ancestors to early flying birds, had claws more like modern birds that spend most of their time on the ground.”
The origin and early evolution of birds has long been a major topic of debate in evolutionary biology, the researchers said. Throughout the 20th century, the issue was generally polarized into those who argued that birds had a ground-based ancestor and those who believed birds evolved from an arboreal ancestor, a “false dichotomy that has hindered progress in the field,” they continued.
In the new study, Glen and his colleagues suggest that part of the problem is the loose categorization of many living bird species as either ground- or tree-dwellers on the basis of their hind limbs when, in reality, these are not mutually exclusive alternatives. Rather, birds exhibit differing degrees of ground- and tree-based behaviors and would be better placed along a continuum according to the proportion of time spent on ground versus tree foraging.
To test the idea, Glen’s group first analyzed the toe claws of 249 species of recent birds, revealing that their claw curvatures increase, becoming more hooked, as tree foraging becomes more predominant. They then compared the claw curvatures of modern birds to those of the fossilized ancestors of birds.
“In summary,” they concluded, “since claw angle is independent of body size and the evolutionary relationships among species, it is a reliable indicator of the predominant behavior reliant upon hind-limb locomotion, and can make an important contribution to reconstructing the ‘ecomorphology’ of fossil species—how they lived and used their environments. Our findings suggest early birds foraged predominantly on the ground, rather than supporting previous suggestions of arboreal claw adaptations, which appear to have evolved later in the lineage.”
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The researchers include Christopher L. Glen, and Michael B. Bennett, of the School of Biomedical Sciences, The University of Queensland, St. Lucia, Queensland 4072, Australia.
http://www.eurekalert.org/pub_releases/2007-11/cp-eba103107.php
Comment by Administrator — November 5, 2007 @ 8:38 pm