Comments on: Dinosaurs Among Us http://afarensis.blogsome.com/2005/06/29/dinosaurs-among-us/ Exploring the World Around Us Thu, 21 Aug 2008 01:28:41 +0000 http://wordpress.org/?v=1.5.1-alpha by: Rasmus Wedin http://afarensis.blogsome.com/2005/06/29/dinosaurs-among-us/#comment-141 Sat, 28 Apr 2007 22:14:34 +0100 http://afarensis.blogsome.com/2005/06/29/dinosaurs-among-us/#comment-141 Great article. Good to see modern science is progressing. Very interesting fossiles, I must say. Dinosaurs with feathers? Well I never..... Hope this gets the point across to some of those narrow minded cretionists. Anyway, who needs a fictive book, like the bible, when reality is this awesome. Thanks for the good reading! Great article. Good to see modern science is progressing. Very interesting fossiles, I must say. Dinosaurs with feathers? Well I never…..

Hope this gets the point across to some of those narrow minded cretionists. Anyway, who needs a fictive book, like the bible, when reality is this awesome. Thanks for the good reading!

]]> by: Philip Chalmers http://afarensis.blogsome.com/2005/06/29/dinosaurs-among-us/#comment-56 Wed, 09 Nov 2005 16:40:53 +0000 http://afarensis.blogsome.com/2005/06/29/dinosaurs-among-us/#comment-56 Nice article!Proponents of the alternative birds-from-thecodonts theory argued that birds have a furclula (wishbone) made of 2 fused clavicles (collar bones) while no theropod furcula had been found. But in the last few decades quite a few theropod clavicles and furculas have been found. In fact clavicles fused into furcula is now one of the <a href="http://users.tamuk.edu/kfjab02/dinos/vptheropod.htm" rel="nofollow">synapomorphies (diagnostic features) for tetanurae</a>, the theropod group which includes tyrannosaurs, ornithominids, velociraptors and birds.Determining birds' evolutionary relatioships beyond that point is <a href="http://www.ucmp.berkeley.edu/diapsids/saurischia/maniraptora.html" rel="nofollow">complicated</a> - some researchers even think that velociraptors were flightless birds, since they have bird-like breast-bones and forelimbs joints (their arms would fold as compactly as a bird's wing).For what it's worth, I prefer the ground-up theory of flight becuase I think it's abetter answer to the question "What use is a half-evolved wing". A bird's wing is like a comb, with a fairly thin "back" (the bony parts) and lots of "teeth" (flight feathers). I've seen macaws' wings extended and there are gaps of almost 2 inches (5 cm) between the roots of the flight feathers but these gaps are closed by the vanes for over 80% of the feathers' length. In the early stages of wing evolution these gaps would have been much larger, initially separating the feathers completely - not much use for gliding. So I prefer the roadrunner analogy - a small predatory dinosaur used its arms for balance while pursuing elusive prey, mutations which enlarged the arm feathers improved its balance and high-speed turning ability and therefore were favoured by natural selection and possibly later sexual selection, further enlargements provided lift, etc. Nice article!Proponents of the alternative birds-from-thecodonts theory argued that birds have a furclula (wishbone) made of 2 fused clavicles (collar bones) while no theropod furcula had been found. But in the last few decades quite a few theropod clavicles and furculas have been found. In fact clavicles fused into furcula is now one of the synapomorphies (diagnostic features) for tetanurae, the theropod group which includes tyrannosaurs, ornithominids, velociraptors and birds.Determining birds’ evolutionary relatioships beyond that point is complicated - some researchers even think that velociraptors were flightless birds, since they have bird-like breast-bones and forelimbs joints (their arms would fold as compactly as a bird’s wing).For what it’s worth, I prefer the ground-up theory of flight becuase I think it’s abetter answer to the question “What use is a half-evolved wing”. A bird’s wing is like a comb, with a fairly thin “back” (the bony parts) and lots of “teeth” (flight feathers). I’ve seen macaws’ wings extended and there are gaps of almost 2 inches (5 cm) between the roots of the flight feathers but these gaps are closed by the vanes for over 80% of the feathers’ length. In the early stages of wing evolution these gaps would have been much larger, initially separating the feathers completely - not much use for gliding. So I prefer the roadrunner analogy - a small predatory dinosaur used its arms for balance while pursuing elusive prey, mutations which enlarged the arm feathers improved its balance and high-speed turning ability and therefore were favoured by natural selection and possibly later sexual selection, further enlargements provided lift, etc.

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