RE: Brooding rex? (was Feathers for T. rex)

["Williams, Tim" <TiJaWi@agron.iastate.edu>]

Tom Holtz wrote:

>IF Galloanserae is monophyletic and near the base of Neognathae, the
>larger clutch size in grouse, ducks, pheasants, etc. may be
>symplesiomorphy rather than ecomorphology (or rather eco-behavior).  >That
is, the smaller clutch size of owls, falconiforms (and sea birds >and
hummers and what have you) relative to galliforms and anseriforms >MIGHT be
a synapomorphy of dervied neognaths.

In a similar vein, I've wondered if other traits seen in certain
galloanserine species (such as the uniform distribution of contour feathers
over the body [rather than organization into tracts]; and the presence of
down/plumules between the contour feathers) may be primitive neognath
traits.
 
>Furthermore, I have no idea of the clutch size of tinamous, which might >be
useful to know! 

>From memory, quite large - up to 12-18 eggs.


Ken Kinman wrote:

>    Should probably be more careful what you aim your torpedoes at.

No, I think this particular torpedo was on target.  Any collateral damage
was unintended.

>I'm not saying there are any hard and fast rules.
>     However, raptorial birds like hawks, eagles, and owls, usually have
>clutches of 2-4 eggs.  Many common prey species (like grouse, ducks, 
>pheasants, etc.) have larger clutches more like 5-15 eggs (or more).  I
>see no reason that trends among early coelurosaurs (predators vs. prey)
>would have been much different (but again there would be exceptions to
>such trends).

True, there are no "hard-and-fast" rules.  There are ecological
considerations to account for too - nesting on the ground vs nesting in
trees; availability of food; etc.  

(An interesting fact: For some raptorial birds, the first chick to hatch
actually eats its younger siblings.  An analogous process happens in some
shark species, where an embryo shark will eat its siblings *in utero*.)

The fact is, for dinosaurs (of the non-avian kind), we really don't know
enough to draw *any* inferences regarding cluch size in different theropod
groups.


>P.S.  I actually live close to a farm, and chickens seem to be prolific
>egg layers (not that I am going to base any biological hypotheses on >farm
animals).

Good idea.  Modern battery hens are bred for proficiency in egg production.
Their selection has been decoupled from any natural processes.




Tim

------------------------------------------------------------ 

Timothy J. Williams 

USDA-ARS Researcher 
Agronomy Hall 
Iowa State University 
Ames IA 50014 

Phone: 515 294 9233 
Fax:   515 294 3163 



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