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RE: Jeholornis and enantiornithines had one functioning ovary like modern birds



Not really, if body size reduction is also a factor. basal Avialae are all 
small, very small animals; it is only much later that birds become much larger, 
in "troodont" size ranges or bigger.

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: Mon, 18 Mar 2013 18:36:50 +1100
> From: tijawi@gmail.com
> To: dinosaur@usc.edu
> Subject: Re: Jeholornis and enantiornithines had one functioning ovary like 
> modern birds
>
> > Xiaoting Zheng, Jingmai O’Connor, Fritz Huchzermeyer, Xiaoli Wang, Yan
> > Wang, Min Wang & Zhonghe Zhou (2013)
> > Preservation of ovarian follicles reveals early evolution of avian
> > reproductive behaviour.
> > Nature (advance online publication)
> > doi:10.1038/nature11985
> > http://www.nature.com/nature/journal/vaop/ncurrent/full/nature11985.html
>
>
> "Why living birds lost the right ovary and oviduct is unclear,
> but the most common hypothesis suggests that this was related to the
> need to reduce weight in flight during the reproductive season, the
> female having to carry only a single egg inside rather than two..."
>
>
> Troodontids had two functional oviducts (Varicchio et al., 1997). So
> did oviraptorosaurs (Sato et al., 2005)
>
>
> If the loss of a functional right oviduct is indeed a flight-related
> feature... does this undermine the hypothesis that terrestrial
> deinonychosaurs and oviraptorosaurs were secondarily flightless?
>
>
>
>
>
> Cheers
>
> Tim