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Re: Question: Why did birds lose their teeth?
As you know, cattle egrets often follow agricultural operations such as pasture
mowing -- and they eat whatever is uncovered and small enough to swallow whole,
frequently making multiple attempts, using gravity and headshaking to clear the
gullet in preparation for another attempt. These gullet-clearing operations
would be greatly hampered by teeth, in the absence of powerful jaw muscles to
process these tidbits, usually mice or toads.
And clearing the gullet with a hind foot, while standing on the other foot, is
obviously less effective than using "hands", both mechanically and
mobility-wise -- the thieving tendencies of flock-mates being another factor
opposing successful ingestion.
So the sequence is -- optimization of the wing reduces wing claws (and the
need to climb) -- and the lack of wing claws reduces the desirability of teeth
-- which predicts a pattern of 'first go the claws, then the teeth'.
On Tue, Mar 11, 2014 2:07 AM EDT Dr Ronald Orenstein wrote:
>I would not expect this unless cleaning teeth was the only function of wing
>claws ( and it isn't - viz the Hoatzin). Besides, living birds can use their
>hind claws to reach the bill (they can certainly scratch their heads) so why
>would wing claws be the ones toothed avians would use?
>1825 Shady Creek Court
>Canada L5L 3W2
>> On Mar 11, 2014, at 9:59 AM, don ohmes <email@example.com> wrote:
>> And I add, now that I have accessed a fresh battery --
>> 1) the reconstructions of toothy birds with wing claws that I have seen make
>> it clear that the claws could reach the mouth, and thus could assist in
>> clearing the obstructions inevitable when working with a small,
>> tooth-infested intake tube.
>> 2) it follows, as matter of selective logic, that if the claws disappeared
>> as the wing was optimized aerodynamically, then then the teeth might follow
>> -- flight being enough of an advantage in accessing prey (among other
>> things) to counteract the occasional escape the lack of teeth might enable.
>> 3) so! Does the record show a clear pattern of 'first go the claws, then go
>> the teeth' in toothed birds?
>> On Mon, Mar 10, 2014 9:14 PM EDT don ohmes wrote:
>> Hence the inclusion of the term "small biped" -- there are multiple
>> underlying allometric principles involved.
>> E.G. -- A large fish falls off a given spear more easily than a small fish
>> And a smooth solid food intake port is no guarantee of trouble-free dining
>> -- I observed a cattle egret impale a toad so enthusiastically that it ended
>> up half way to the base of the beak -- had the toad been larger, perhaps the
>> bird's vigorous headshakes could have transferred enough momentum to the
>> toad to overcome friction -- or, had the toad been smaller, the one foot per
>> effort the bird could use to push on the toad might have removed it. As it
>> was, it was in a bit of trouble, pun intended -- it could not open it's
>> beak, and was totally mobbed by it's flock-mates, who wished to steal the
>> prize -- perhaps 50 birds, in all.
>> This concept is easily demonstrated with a steak and a kitchen knife --
>> vigorous shaking might be required to remove a small piece of impaled meat,
>> while a heavier piece can be removed simply by pointing the knife downward.
>> Also, the brute processing power attainable by terrestrial predators is
>> simply not possible for birds, as Pigdon explains in his initial post.
>> Summing, small tubes are more easily clogged than large, and a very small
>> tooth is larger (relatively) to a sparrow's mouth than the daggers of T rex,
>> et al, are to it's massive head...
>>> On Mon, Mar 10, 2014 8:17 PM EDT Mike Habib wrote:
>>> On Mar 10, 2014, at 4:53 PM, Dann Pigdon <firstname.lastname@example.org> wrote:
>>> Many non-volant toothed theropods also had long necks and short forelimbs,
>>> making any sort of
>>> grooming of the mouth via the forelimbs unlikely (tyrannosaurs and
>>> carnotaurus are obvious
>>> In fact, the vast majority of non-avian theropods could not reach their own
>>> mouths with their forelimbs, even those with relatively “robust” forelimbs,
>>> such as allosauroids (nor can they reach any area in front of themselves
>>> that they could see - which makes use in predation potentially cumbersome).
>>> Interestingly enough, among theropods, some living birds are among the
>>> derived taxa that can reach their mouths: with their hind limbs.