Page 13 - Highlights for Children (December 2017)

What?
My blue
Why do some dogs have blue eyes aren’t

eyes instead of brown eyes? blue?

Brendan, Age 6 (by e-mail)

Like human eyes, dog eyes back. (If no pigment is in either
have a pigment called melanin layer, the iris looks pink.) As an BLUE? NOT TRUE!
(MELL-uh-nin) in the iris—the animal develops, genes in its
There is no blue substance in blue eyes
colored part of the eye. The DNA tell its body how much
(or green in green eyes). Blue eyes look
iris has two layers. Brown eyes melanin to turn “on” or “off.”
blue because of the way short light waves
have melanin in the front and This means that animals can
bounce around in the iris. The sky looks
back layers. Lighter eyes have have a range of eye colors. The
blue for a similar reason.
little or no melanin in the front same is true for skin, hair, and
layer and just a little in the fur colors.
By Dougal Dixon • Art by Robert Squier Its epiparietals
(EPP-ee-pah-RYE-ih-tulz),
the spikes above the skull’s
Machairoceratops
muh-KYE-row-SAYR-ah-tops parietal bone, are flat-tipped.
“bent-sword horned face”

When scientists Head shield,
found the partial or frill,
skull, horns, narrows at
and spikes of the top
Machairoceratops,
they could tell Horn
that this was a above each
new ceratopsian eye, pointing
(SAYR-ah-TOP-see- forward
un) species. Its
discovery shows
that strange
horn and spike
arrangements
appeared
early among
ceratopsians.

WHERE: HOW LONG: WHAT IT ATE: WHEN:

Utah 20 feet Plants 77 million years ago
252 201 145 66 Present
Triassic Jurassic Cretaceous Cenozoic

DECEMBER 2017 13