[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
Here is more information on the possibly relationships of some ofthe
integumentary structures. (forgive the redundancies)
A. Feathers are not modified hairs. True they come from the skin
(which BTW is made from proteins called alpha-keratins). But the similarity
ends there. The intermal structure (molecluar),the processing (development)
etc are different. Aside from the elongated geomerty the only things that
they have in common is a high sulfur content (smells when it burns), and arecom
posed of flimaments (but these too are different in structure etc.). All
epidermal structures are designed to be non-soluble and abrasion resistance.
B. There is no hair on birds. Structures such as filoplumes, eyelashes,
bristles, etc are modified feathers. This is supported by protein evidence and
development mechanism. The morphology is simply an example of convergence.
C. Primitive feathers. There is no common agreement on the stuructre of
the most primitive feather. The current thinking is that it was mostly likely
a contour type feather with both pennaceous (vane-like) and plumulaceous
(down-like) parts. The vane is asymmeterical. This geometry and its relation
to flight capacity is currently being debated in the literature. Asymmeteric
primairies are found in all birds capable of flight, including Archy. Primaries
in all recent flightless birds are symmeterical.
BTW a fully formed feather from Solnhofen was reported in 1860 and preceeded
the discovery of the first Archy specimen. It is fully comtempory in morhology.
D. Relationships. This is a bit more difficult, but the best available
evidence would give a 'tree' something like this:
<<<feather-adult down> natal down>, <<beak, claw> scute>, reticulate scale>
note that there are two types of down. The dwon on adults resides under
the contour feathers. Its the stuff that gets plucked to line nests, jackets.
The other is natal down (the stuff chicks are born with. They are similar in
design. but differ slightly in their proteins. They are made by different
genes than are contour & other feathers. That is, each generation in
development have slightly different genes. However, the changes in molt of
adult feathers are morphological, not in protein content.
E. Flight feathers-called primary feathers, are asymmetrical contour feathers