Beginning with the primitive Sinosauropteryx, all theropods (a class of meat-eating bipedal
dinosaurs including Tyrannosaurus rex) may have had feathers.
In some, like T. rex, the hatchlings shed their downy feathers as they grew.
In others, feathers were present throughout adulthood.
Feathers were one of the adaptations leading to flight
in Archaeopteryx and, perhaps, Archaeoraptor. These two species had startling similarities
to both dinosaurs and birds. The November
1999 issue of National Geographic included the statement, "We can now
say that birds are theropods just as confidently
as we say that humans are mammals."
Birds really are feathered dinosaurs.
Defining a feather defines the bird and conversely
a definition of a bird is not complete without
mentioning feathers. In my biology classes
we were told never to use the word "all"
as some exception could probably be found.
Nevertheless, all birds have feathers.
Feathers grow from the base (follicle) and,
as the cells get farther from their source
of nourishment, they die off. As the cells
die, they become filled with a horny substance
called keratin. In scientific lingo, a feather
is simply an elaborate and specialized keratinous
product of the epidermis of a bird. Hollow
tubes of keratin, like hollow tubes of modern
day aluminum, are very lightweight and very
Feathers come in many designs. Some are used
for insulation, some for flight, and some
for protection. Humans have utilized the
insulation characteristic of feathers for
generations and in recent years have tried
to mimic the benefits with manufactured materials.
It still remains difficult to duplicate the
efficiency and warmth of your Grandmother's