Archaeopteryx: The World’s First Bird (Probably)

 

Archaeopteryx represents a pivotal moment in the evolution of birds, which have come to inhabit every corner of the earth.  This is a species which conveys the transitional period from therapod dinosaurs to early birds.  Archaeopteryx fully maintains many of the characteristics of its running dinosaur relatives, such as sharp teeth and a long bony tail, while simultaneously introducing numerous features common to nearly all birds today.   Although Archaeopteryx gives us  a snapshot of the divergence of birds from dinosaurs, it manages to raise nearly as many questions about the evolution of avian flight as it answers. 

One issue with the dinosaur origins of birds has been brain size and function.  The fossil record suggests that dinosaurs had particularly small brains compared to their body size.  In fact, the film Jurassic Park was really the first time anyone portrayed dinosaurs as cunning or clever.  This posed an issue for flight, because flight requires heightened motor control and other higher order neurological processes, which terrestrial based life does not have to perform.  To adress this issue, in 2004, Dominguez Alonso used CT scans from the brain casings of various Archaeopteryx to model its brain.  Alonso’s results suggest that Archaeopteryx had a far larger brain than most dinosaurs, making its brain comprable to pterasaurs.  The models indicate that about 33% of the brain was dedicated to sight, and the areas responsible for muscular coordination and hearing were also well developed.   All these data would seem to suggest that archaeopteryx would have the neurological capacity for flight.

For a number of years, Archaeopteryx had lent little to no conclusive evidence to crediting either the terrestrial or arboreal origins of flight.  Evolutionary biologists have been split for decades about whether ther first flighers had a running start from the ground or some help from gravity by gliding from trees.   In 2010 Robert Nudds and Gareth Dyke of the University of Manchester published their results on the possible aerodynamics of Archaeopteryx.  The analysis of the imprints of feathers from the fossil record seems to indicate that Archaeopteryx must not have been a very good flapping flyer.  They had a significantly different feather structure than modern birds.  Nudds and Dyke conclude that the only way Archaeopteryx could have flapped its wings would be if the rachises of their winds were solid rather than holllow, like every other flying bird on the face of the earth today.   This seems to indicate that flight originated from the trees down and that flapping flight origninated in some divergent branch of the evolutionary tree of Archaeopteryx.

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One Comment

Lorena Barba posted on December 13, 2011 at 8:46 pm

what, no pictures? :-(
I guess I’m spoiled now.