Re: Origin of feathers

["Ralph Miller III" <gbabcock@best.com>]

 John V Jackson <jjackson@interalpha.co.uk>
> -----Original Message-----From: Jonathan <spockjr@email.msn.com>22
> 
> With regard to feathers evolving for brooding - although I have no doubt
> that Oviraptor did have feathers and was brooding those eggs (the
> positioning is absolutely perfect) - the theory does not satisfy the
> "bootstrap test" - would the adaptation have had advantage the moment it
> first appeared, ie as tiny projections above the level of scales.  If of
> course insulation was already there for normal body insulation, the
brooding
> point would be a very small change.

Thomas Hopp and Mark Orson provided the title, _Dinosaur Brooding Behavior
and the Origin of Flight Feathers_, so it was not explicitly stated that
the initial use of the first protofeathers was hypothesized to be brooding.
 The talk concerned the possible selective pressures leading to the
development of (hypothetical) long feather structures on the arms and hands
of oviraptorids.  I believe that the two were picturing some type of
protofeather integument in place prior to its more extravagant development
as an adaptation to the needs of brooding eggs and/or chicks.  Body
feathers could be useful in themselves (as in the hen and ostrich
photographs shown), but the emphasis of this talk was the potential utility
of long wing and tail feathers to cover eggs or chicks.  In the case of
ducks, it was pointed out that a mother can shelter a dozen ducklings at
once with these long flight feathers.  Likewise, an African eagle was shown
to use these feathers to protect its chicks from the heat of the sun.  Were
the long flight feathers removed from these avians, many of their young
could die from exposure to the elements.

Examining the "brooding _Oviraptor_" fossil, Hopp and Orson felt that the
spindly articulated arms and hands would only have been effectual in
protecting its eggs from the elements had they sported long feathers. 
Furthermore, they hypothesized that the very avian position of the arm,
wrist and fingers (folding up as a wing does) suggests that the selective
pressures for effective brooding may have guided not only the development
of flight feathers, including their length and the flattened feather
morphology which enables folding, but also the development of the folding
articulations of the arm and hand.  In their view, these "wing" adaptations
developed first to facilitate brooding somewhere along the dinosaur
lineage, and were later exapted for flying, eventually leading up to the
avian condition we see today.  It was pointed out that _Archaeopteryx_
would appear to have been well-equipped for brooding eggs and young,
whether it flew well or not.

As Larry Martin pointed out in his _Oviraptor_ talk, "brooding" is a matter
of protecting, and does not necessarily refer to incubating.  He stated
that 200 species of living reptiles attend their nests, but this does not
mean that they are warming the eggs with their bodies (although there are
exceptions, i.e. some snakes which generate heat via muscular
contractions).  Martin felt that the eggs were buried and did not require
protection from the elements.  The most telling point here that I could see
is that the eggs are deposited two layers deep; it is not only one ring of
eggs!  So I don't know if the eggs could have benefited from either the
heat of the oviraptorid's body OR the protection of arms, wings,
what-have-you.  Perhaps the oviraptorid would still act as a roof, shading
the soil, or keeping the soil from getting totally drenched, but only if it
is on high ground (to avoid pooling water).   

Regarding the reason the brooding _Oviraptor_ was still attending its nest
when it died, I am inclined to agree with Martin Human's suggestion that --
if Hopp and Orson are correct in their hypothesis -- the _Oviraptor_ may
well have been protecting its eggs from the elements (rain in this case) or
at least staying with the eggs to protect them against egg-stealing animals
when it was overcome by the sand-and-clay slide -- assuming the
sand-and-clay slide hypothesis is correct.  The slide concept may explain
the spectacular articulated remains of brooding _Oviraptor_ parents and
"fighting dinosaurs" in the Gobi.  Although the slide scenario may be the
most plausible explanation yet, it is none-the-less amazing, if true.  Any
mother that dies protecting its young is a "good mother" in my book. 
(Mother's Day is coming up, you know).  

The above hypotheses belong to their respective authors; don't shoot me;
I'm just the messenger.

-- Ralph Miller III     gbabcock@best.com

"What do you think of the ground-up bird idea?"
"I like it; makes a great substitute for hamburger!"