[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

RE: Dinosaur Revolution Review

  The majority of skin impressions yes, that does not mean that the majority of 
dinosaur species were *completely* scaly. As far as I know, all the impressions 
of integument for smaller dinosaurs show bristles and/or protofeathers of some 
sort. The exception being psitticosaurus, and even it has quills along its 
tail. Juravenator and Tianyulong both show filamentous integument in roughly 
similar locations. The former is near the base of ceolurasauria and the latter 
near the base of ornithischia; this suggests to me that, in actuality, the 
majority of dinosaur species (being the smaller forms) were partly or mostly 
fuzzy, with the scaly megafauna and the armored forms being the 'exception'. 
The condition we see with modern birds with a complex assortment of feather 
types, and with scales being limited to the feet, may have been atypical for 
dinosaurs as well. I suspect that the basal condition for ornithodirans may 
have been a variable mix of simple filaments, circular dermal scales and 
epidermal scutes. Scutes can also serve a thermoregulatory function, and so may 
have been favored over 'protofeathers' in sauropods and as well as many armored 
groups such as thyreophorans. if the basal condition was, for example, to have 
scales on the belly, legs and underside of the tail, while protofeathers were 
present everywhere else, then I think it is much more probable that the ratio 
of scales to feathers simply shifted in more advanced forms rather than 
insulation evolving independently in several different lineages. Genetic 
changes may have limited this 'flexibility' in birds due perhaps to their long 
history of being almost completely covered with a complex array of feathers. It 
may be roughly analogous to the loss of color vision in mammals with only a few 
lineages (such as primates) regaining it later on. 

Of course I'm aware this is all speculation on my part and it may only be 
resolved with further discoveries.

Simeon Koning  

> Date: Wed, 14 Sep 2011 15:14:33 -0700
> From: pristichampsus@yahoo.com
> To: dinosaur@usc.edu
> Subject: Re: Dinosaur Revolution Review
> Not to get this thing started again, but do keep in mind that the majority of 
> dinosaur skin impressions show that they were scaly. Filamentous integument 
> is the exception, not the rule.
> Jason
> http://reptilis.net
> "I am impressed by the fact that we know less about many modern [reptile] 
> types than we do of many fossil groups." - Alfred S. Romer
> ----- Original Message -----
> > From: Sim Koning <simkoning@msn.com>
> > To: martyniuk@gmail.com; dinosaur@usc.edu
> > Cc:
> > Sent: Wednesday, 14 September 2011 5:33 PM
> > Subject: RE: Dinosaur Revolution Review
> >
> >
> >    I'm hesitant to use mammals as an analogy, as it may be a largely flawed
> > one. I would much rather look at what we see in birds and other dinosaurs. 
> > If we
> > look as species such as Juravenator starki, we see that the parts of the 
> > body
> > that would have frequently come in contact with the ground, or were 
> > otherwise
> > prone to abrasion, retained scales and scutes. Of course another obvious 
> > example
> > would be the feet of many birds. What I suspect is that there may have been
> > somewhat of a balancing act between the insulation provided by fur and the
> > protection afforded by scales and scutes. We see this in some birds today: 
> > snow
> > owls have replaced almost all of the scales on their feet in favor of 
> > feathers
> > because, in this particular case, insulation is more important than
> > 'armor'. Bare skin was probably common in cases in which neither scales
> > nor protofeathers were strongly needed, or in lineages close to aves that 
> > may
> > have largely lost the ability to grow scales on anything except their feet. 
> > Many
> > of the more basal dinosaurs probably retained scales on their legs, the
> > underside of their tail, and their bellies. In some of the more derived 
> > forms
> > (such as thyreophorans) the parts of the body that were normally feathered 
> > were
> > armored with osteoderms, scutes and scales, which would have left no place 
> > for
> > protofeathers. It probably wouldn't have made much sense to fill the gaps
> > with fuzz as it would have created unnec
> Wed, 14 Sep 2011 08:57:01 -0400
> >> From: martyniuk@gmail.com
> >> To: dinosaur@usc.edu
> >> Subject: Re: Dinosaur Revolution Review
> >>
> >> "And I have a hunch that most if not all non armored small dinosaurs
> >> were at least partially fuzzy."
> >>
> >> If this is the case, why assume armored dinosaurs are an exception?
> >> Armored mammals typically don't lack fur, at least around the
> >> periphery of the armor and on the underside of the animal.
> >>
> >> Matt
> >>
> >