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RE: birds have skulls like baby non-avian dinosaurs



Oh, hey, look at that. ANOTHER paper where oviraptorosaur skulls are so bizarre 
they might as well not be in the plot for all that they contribute to it.

(In case anyone is wondering, there's this: 
http://qilong.wordpress.com/2012/07/12/oviraptorids-and-cranial-morphometrics/ 
-- and it looks like I published that post a day too early....)

[If someone would be willing to send me the paper, I would be quite grateful.]

Cheers,

  Jaime A. Headden
  The Bite Stuff (site v2)
  http://qilong.wordpress.com/

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)


"Ever since man first left his cave and met a stranger with a
different language and a new way of looking at things, the human race
has had a dream: to kill him, so we don't have to learn his language or
his new way of looking at things." --- Zapp Brannigan (Beast With a Billion 
Backs)


----------------------------------------
> Date: Thu, 12 Jul 2012 18:12:13 +0000
> From: jaseb@amnh.org
> To: dinosaur@usc.edu
> Subject: birds have skulls like baby non-avian dinosaurs
>
> A new online paper:
>
> http://www.nature.com/nature/journal/v487/n7406/full/nature11146.html
>
> Birds have paedomorphic dinosaur skulls
>
> Bhart-Anjan S. Bhullar, Jesús Marugán-Lobón, Fernando Racimo, Gabe S. Bever, 
> Timothy B. Rowe, Mark A. Norell & Arhat Abzhanov
> AffiliationsContributionsCorresponding authors
> Nature 487, 223–226 (12 July 2012) doi:10.1038/nature11146
> Received 15 November 2011 Accepted 16 April 2012 Published online 27 May 2012
>
> The interplay of evolution and development has been at the heart of 
> evolutionary theory for more than a century1. Heterochrony—change in the 
> timing or rate of developmental events—has been implicated in the evolution 
> of major vertebrate lineages such as mammals2, including humans1. Birds are 
> the most speciose land vertebrates, with more than 10,000 living species3 
> representing a bewildering array of ecologies. Their anatomy is radically 
> different from that of other vertebrates. The unique bird skull houses two 
> highly specialized systems: the sophisticated visual and neuromuscular 
> coordination system4, 5 allows flight coordination and exploitation of 
> diverse visual landscapes, and the astonishing variations of the beak enable 
> a wide range of avian lifestyles. Here we use a geometric morphometric 
> approach integrating developmental, neontological and palaeontological data 
> to show that the heterochronic process of paedomorphosis, by which 
> descendants resemble the juveniles of their ancestors, is responsible for 
> several major evolutionary transitions in the origin of birds. We analysed 
> the variability of a series of landmarks on all known theropod dinosaur skull 
> ontogenies as well as outgroups and birds. The first dimension of variability 
> captured ontogeny, indicating a conserved ontogenetic trajectory. The second 
> dimension accounted for phylogenetic change towards more bird-like dinosaurs. 
> Basally branching eumaniraptorans and avialans clustered with embryos of 
> other archosaurs, indicating paedomorphosis. Our results reveal at least four 
> paedomorphic episodes in the history of
> evelopment beyond the adult state of ancestors) in the beak. Paedomorphic 
> enlargement of the eyes and associated brain regions parallels the 
> enlargement of the nasal cavity and olfactory brain in mammals6. This study 
> can be a model for investigations of heterochrony in evolutionary 
> transitions, illuminating the origin of adaptive features and inspiring 
> studies of developmental mechanisms.