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Re: Beaks



Original Message by Philidor
Sunday, 22 December 2002 13:56

> Beaks have been described as having advantages in weight/balance,

Certainly exists. But how big it is, not compared to the monstrous teeth of 
pretty much any mammal but to those of *Sinornis* or *Yanornis*, has never 
been investigated.

> diet,

Obviously depends on the diet.

> and ease of replacement.

Hm. On the one hand, you need lots of calcium and phosphate for teeth. On the 
other, you need lots of protein for a beak... should therefore depend on the 
diet and the geographical location of the animal that evolves a beak or 
doesn't.
        Hey. All wrong. Who says teeth and beaks are mutually exclusive? Why 
shouldn't Ichthyornithidae, Hesperornithiformes and lots of pterosaurs have 
had both -- assuming a beak is homologous to the gums rather than to lips?

> I'd add defense:  better to stab with something sharp
> than to have the musculature and take the strain necessary for a bite.

If that were enough, we'd see a lot more beaks in amniotes, I think.

> Particularly with the bone structure getting lighter for flight.

The jaws of specialised carnivorous birds aren't that light, are they?

> Also, a beak makes selective capture of small items easier, whether animals
> or seeds.

This sounds best. Apparently it's also easier to lose teeth than to evolve 
teeth with a complex shape to crack seeds.

> Like feathers, though, one wonders what provided the raw material for a
> beak to develop.
> Is there any known appurtenance made of beak-like material?

Yes, the egg tooth. There was a paper in Evolutionary Theory some years ago 
that suggested that its absence in placentals and severe reduction in 
marsupials has to do with the absence of beaks in both groups.