RE: Question: Why did birds lose their teeth?

[Jaime Headden <qi_leong@hotmail.com>]

The first response is simple:

Beaks are heavier than teeth.

But the real answer is more complex:

Having teeth means additional associated features, including bone lining the 
sockets and the subdental platform associated with a tooth row on any given 
portion of jaw. In comparison, a beaky rostrum isn't just an airy, modern 
bird's beak: early birds with beaks had the same internal makeup as early birds 
with beaks. An enantiornithine with a beak didn't look very different from one 
with teeth.

But beaks have additional tissues associated with them than rostra without 
teeth, forcing a necessary comparison to the weights of these distinct 
structures. A beak will also cover more space in a skull than a tooth occupies, 
as it wraps around the rostrum and mandible. Following Lautenschlager et al., 
the weight of keratin is higher than the weight of a tooth, but not merely 
because how much is required. Keratin only forming a plate on a limited 
extension of the outside of the jaw has greater weight than a tooth along the 
same section of jaw.

Thus, a beak cannot be due to "weight saving" in a bird. Birds also seem to 
have diversified and even developed the full modern flight system with a full 
set of teeth (e.g., *Ichthyornis*), leading one to wonder how the idea of 
weight saving came about. Minimization of the early bird lineage doesn't 
necessarily correlate to loss of teeth, and multiple losses of teeth occurred 
in enantiornithines as well as standard non-neoavian carinates without 
concordant shifts in body sizes.

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, 10 Mar 2014 15
> From: martin.baeker@tu-bs.de
> To: dinosaur@usc.edu
> Subject: Question: Why did birds lose their teeth?
>
> Dear all,
>
> I once learned that losing teeth was a weight-saving measure and thus
> a flight adaptation. There is this reference stating this as a possibility
> http://www.newscientist.com/article/dn18248-early-birds-may-have-dropped-teeth-to-get-airborne.html#.Ux3HhdsjulM
>
> However, I seem to remember that there was some study showing that
> birds actually do not lose signifcant weight by replacing teeth with
> beaks - if anybody has a reference on this, I'd be grateful.
>
> Thanks a lot,
>
> Martin.
>
> Priv.-Doz. Dr. Martin Bäker
> Institut für Werkstoffe
> Technische Universität Braunschweig
> Langer Kamp 8
> 38106 Braunschweig
> Germany
> Tel.: 00-49-531-391-3065 <=== NEW phone number!
> Fax 00-49-531-391-3058
> e-mail <martin.baeker@tu-bs.de>
> http://www.tu-braunschweig.de/ifw/institut/mitarbeiter/roesler1
> http://www.scienceblogs.de/hier-wohnen-drachen                                
>