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July 8, 2012
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:iconewilloughby:
This is a sample of a diagram on feather evolution I made for the creation/evolution book I'm working on with ~Agahnim, ~keesey and others. The "stages" represented here are highly simplified from reality (the "interlocking" and "non-interlocking" barbule stages are basically combined into one, since it's not really possible to tell them apart in fossils) due to making it as easy to understand as possible to creationists.

The caption, written by Agahnim:

Five stages in the evolution of feathers, based on an analysis of feather evolution in a 1999 paper by Richard Prum. Each of these stages in feather evolution has been found on dinosaur fossils except for stage 3, which is known from cretaceous amber.

Stage 1 - Simple fibers: Hollow unbranched fibers, with no barbs or barbules. Found on Sciurumimus albersdoerferi.

Stage 2 - Bundles of fibers: Groups of unbranched fibers, each attaching to a central point. Found on Sinosauropteryx prima.

Stage 3 - Unbranched barbs: Rows of unbranched barbs attached to a central shaft. Found preserved in amber alongside troodontid teeth.

Stage 4 - Barbs and barbules: Rows of barbs attached to a central shaft, which branch further into barbules. Found on Protarchaeopteryx robusta.

Stage 5 - Fully-developed flight feathers: Barbs and interlocking barbules; asymmetrical shape. Found on Microraptor gui.
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:icondeinowilly:
~Deinowilly Apr 17, 2013  Hobbyist Traditional Artist
It is said that stage 1 is also preserved in Sinosauropteryx prima, what do you reckon?
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:iconewilloughby:
*EWilloughby Apr 17, 2013
It's possible that it preserves stage 1 as well, but I'm not familiar with whatever literature talks about that. Have a link?
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:iconewilloughby:
*EWilloughby Apr 17, 2013
As far as I know, the feathers on Sinosauropteryx were closer to stage 2: little bundles of unbranched fibers attached to a central point. (See: Currie, Philip J.; and Chen, Pei-ji. “Anatomy of Sinosauropteryx prima from Liaoning, northeastern China.” Canadian Journal of Earth Sciences 38 (1) (2001): 705–727.)
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:icondeinowilly:
~Deinowilly Apr 20, 2013  Hobbyist Traditional Artist
Yep, i've read it too. As far as i've read in the literature there are two types of integumentary appendages in S. prima, one kind with tufted distal part, and the other one simple unbranched hair-like seemingly hollow structure. All these is said in: Richard O. Prum & Alan H. Brush. 2002. The evolutionary origin and evolution of feathers.

You can look at the astonishing integument of the crowns and face patches of these extant genera, which are suposed to be morphologically near the stage 1, it's crazy:

[link]

[link]
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:iconewilloughby:
*EWilloughby Apr 20, 2013
Ah yes, that Prum & Brush paper. Well, if you want my own opinion, I'd have to say that I'm not convinced of the existence of stage 1 feathers from looking at the original analyses and the fossil. It is strange that so many other sources have drawn that conclusion, though, so I'll remain somewhat agnostic on the topic.
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:icondeinowilly:
~Deinowilly Apr 23, 2013  Hobbyist Traditional Artist
I see, well I havenīt look at the fossil that comprehensively. I'll tell you in the future.

Does in Sciurimimus descriptions appear to be stage 1 feathers?
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:iconewilloughby:
*EWilloughby Apr 23, 2013
As far as I know, the feathers on Sciurumimus most closely resemble stage 1, yes.
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:icontherealmaestro:
*TheRealMaestro Dec 23, 2012  Hobbyist Traditional Artist
Do all birds have the Stage 5 feathers, or did some lines (like penguins) develop differently formed feathers? Just curious :-)
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:iconewilloughby:
*EWilloughby Dec 30, 2012
It gets a little more complicated with modern bird feathers, because they have all varieties of feathers but modified in certain ways - for example, the "down" of most modern birds looks like Stage 2 above, but they have barbules on each strand, so it's not actually the same type of feather. A lot of flightless birds don't have Stage 5 feathers, though, because they're not asymmetrical.
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:icontherealmaestro:
*TheRealMaestro Dec 30, 2012  Hobbyist Traditional Artist
Thanks :-)

What exactly are the diagnostic features of Aves, then? Is it the combination of feathers and an opposable hallux (big toe)? Are there any non-avian dinosaurs with opposable halluxes (hallices?)?
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