Wednesday, 21 June 2017

Cretaceous Bird Mocks Creationists

Bird caught in amber 100 million years ago is best ever found | New Scientist.

It's not often we get to look at creatures from 100 million years ago, displayed in such detail. Normally we have to make do with distorted stone fossils which been subjected to all sorts of pressures and stresses, leaching by water and slow replacement by minerals over centuries. It's sometimes surprising that very much detail has been retained at all.

Preservation in amber is quite another matter, however. The specimen is trapped and coated in resin in a matter of minutes and sealed quickly away from any bacteria other than those trapped with it, and isolated from oxygen, other than the minuscule quantities that can slowly diffuse through the amber. It's almost as though the specimen has been sealed in a time capsule.

But not quite. The amazing detail we can see in this example of a fledgling bird-like enantiornithine published in Gondwana Research is actually a detailed impression made in the amber itself. The flesh, including any DNA, has long since turned to a carbon residue. The structures of the feathers however have been preserved in remarkable detail.

Regrettably, and all the more bizarrely given that the full paper is available to read on line, the publishers, Elsevier, again want money for me to save you the trouble of going there to read it by reprinting the abstract here.

This specimen, embedded in Burmese amber, is from a group of birds that existed contemporaneously with late dinosaurs, known as the 'opposite birds' that were a sister clade to the ancestors of modern birds, the neornithines. The difference was that, whereas modern birds all have a ball and socket shoulder joint, these had a socket and ball joint (there is a difference). The relatively well-developed flight feathers in so young a fledgling, characteristic of this group of birds, suggests a high level of independence probably from hatching and a low level of parental care and supervision.

They had claws on their wings and, like the ancestors of modern birds at that time, they had jaws with teeth. A surprising feature of this specimen, in contrast to the well-developed flight feathers, is the lack of body plumage. The fledgling appear to have been almost naked yet probably capable of fluttering flight. What body feathers there are, suggest fledgling birds of this species had a mixture of the contour feathers seen on adult modern birds and the filamentous proto-feathers found on feathered dinosaurs.

What we have is a species with a dinosaur jaw and teeth and a mixture of dinosaur-like proto-feathers and proper bird feathers. If that's not an example of what creationist dogma says don't exist, a 'transitional' species, then it's difficult to know what is. We also know from the DNA of modern birds that not only do they still carry the genes for making a dinosaur jaw with teeth but also a dinosaur foot. Disconcertingly for 'Intelligent (sic) Design' advocates, these can be reactivated in the embryo. What is intelligent about putting redundant genes in a genome and then having to deactivate them?

This group gave rise to a wide diversity of birds during the Cretaceous, far outnumbering the neornithines, but the entire group all went extinct at the K-T Boundary mass extinction, along with the dinosaurs. It's not clear why they died out but their sister clade survived this extinction event and went on to become modern birds. A lack of parental care could have been a contributory factor and this particular species' relatively naked chicks were probably ill-equipped to survive the years of perpetual darkness and winter that followed the devastating meteor strike at the end of the Cretaceous era.

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