At page 302 of Steve Brusatte’s The Rise and Fall of the Dinosaurs he mentions that the rate of evolution for birds was `much faster than their dinosaur ancestors and cousins’.
In a simplistic application of dimensional capacity (discussed in various articles in my RG project, The principle of dimensional capacity), all other things being equal, one would expect that animals evolving in 3 dimensional space would evolve 50% faster than those evolving confined to the Earth’s surface, on the plain. With 50% more dimensions, energy has 50% more ways to be distributed.
Articles that appear to discuss the rate of bird evolution include: (1) Gradual assembly of avian body plan culminated in rapid rates of evolution across the dinosaur-bird transition in Current Biology (2014, Brusatte is one of the authors); (2) Ksepka Evolution a rapid flight towards birds (2014); (3) Sustained miniaturization and anatomical innovation in the dinosaurian ancestors of birds in Science (2014). The 2014 Science article (Lee, Cau, Naish, Dyke) mentions an average rate `four times as fast as the unweighted average branch rate across the entire tree’ (p. 564). I am not sure how to interpret that statement, as there may be qualifiers.
These questions (among others) arise: Does the principle of dimensional capacity play a role in the different rates of evolution? If birds evolve 4 times faster, and if dimensional capacity plays a role, what other additional degrees of freedom affect the rate of evolution of birds?