Feathers, huh? I have my doubts

[stargatedalek]

A bit off topic, but wouldn't the amount Ostritch(es?) lose as they age be enough to be considered "substantial"

I wouldn't say so. It's difficult to tell but ostriches are actually a lot more feathered than they look. The head and neck for example is fully covered in short feathers, they simply look like bare flesh from a distance because of their colour. The young's longer feathers obscure the legs but they're bare even in hatchlings. Cassowary do loose feathers on much of their necks (and I think turkeys do to), but that's not something I would consider substantial either (especially since it's purely for display purposes).

[Lanthanotus]

Please note "insulating" does NOT mean heating. It means "preventing heat transfer".
[...]

I am not sure if this reply was dedicated to my post, but as right as you are about the general function of insulation and the scientifically correct statement "we have no idea" (though I'd like to say "we don't know (but have an idea)"), it's just about right to make an educated guess about such things. In my opinion (and from my general knowledge about the ecology of animals of very differnt kind) feather/protofeather/fur/fat insulations have usually evolved to keep the internal heat in - not to keep heat or cold out. I'd really have to seek for an example animal habitating a tropical or moderatly temperatured environment, that bears insulation just for this purpose. Even if Tyrannosaurus (to stay with this example) wasn't endothermic (what it probably was), it would have been gigantothermic by simple physical reasons. If we also suggest that it had to be active for several hours a day (to sniff out cadavers or to hunt for prey or both) and if we look to its enviroment, I deem it highly unlikely that it was covered in a full coat as shown in recent CollectA models.

Secondly no animal known to science looses substantial amounts of integument as it ages, birds grow new integument to replace damaged integument or to aid in new functions they have available to them as they age, but that's still a far cry from loosing it.

[quote ]
[quote ]A bit off topic, but wouldn't the amount Ostritch(es?) lose as they age be enough to be considered "substantial" [/quote]
I wouldn't say so. It's difficult to tell but ostriches are actually a lot more feathered than they look. The head and neck for example is fully covered in short feathers, they simply look like bare flesh from a distance because of their colour. The young's longer feathers obscure the legs but they're bare even in hatchlings. Cassowary do loose feathers on much of their necks (and I think turkeys do to), but that's not something I would consider substantial either (especially since it's purely for display purposes).
[/quote]

I think that is a very interesting question/statement, as answers seem scarce on this and the definition of "substantial" is quite subjective. Given, in general the loss of integument during aging seems to be out of rule, most animals just seem to grow another form of feahters/fur when aging, best seen on any bird chicks. However, there's also mammals babies like this, that loose a considerable ammount of their hair during their childhood - this may be a rudiment as our Lanugo hair though, but such may also be possible for Tyrannosaurus, having babies/hatchlings with feathers as remainder from their phylogenetic evolution where a small ancestor would have been profitted from a full feather coat - just an idea.

Lastly there is no reason that Tyrannosaurus would need the use of it's forelimbs to groom itself, birds don't exactly have the use of their forearms and they manage just fine. Nor does Tyrannosaurus particularly lack locomotion in its neck that could potentially prevent it from grooming itself. And as you said yourself there's no reason they couldn't have groomed socially or perhaps symbiotically with smaller animals as many large carnivores do today.

Indeed, birds also don't use their forearms for grooming (for most parts), but they have generally longer and way more flexible necks, smaller heads and (most likely) way more articalation in their hind limbs when it comes to standing freely on one leg and scratching with the other. Also, they have beaks which are generally easy to clean, unlike a big mouth with serrated teeth of various enormous sizes. Symbiosis or Probiosis is a good point, but there's no case known to me, where another species cleans up another to such a degree, that their own ability to clean/groom would be rendered obsolete. In fact (well, not fact, but scientifical guess), species like Buphagus seem to be of way less profit for their hosts as guessed in the past. Still, animals like bovines also lack the ability to groom a considerable part of their body on their own....

Now what's the conclusion of all this....? "We don't know (but have an idea)"....