50 mya Beetle Found, Color Preserved; Possible For Other Fossils?

[Richard W Travsky <rtravsky@uwyo.edu>]

http://news.nationalgeographic.com/news/2003/08/0818_030818_beetlefossil.html

Paleontologists are used to drab brown and gray fossils. Sediments that
seep in to cast the shape of ancient organisms in stone, determine the
color. Instead, long-gone beasts and the ancient worlds they inhabited,
spring to life in the depths of these scientists' imaginations.

Now under exceptional circumstances, scientists have uncovered and
explained a 50-million-year-old beetle fossil that still retains the
bright blue metallic hue it sported in life. This beetle and others from
the same site, are very rare examples of fossils that retain any original
color, and are the oldest colored fossils ever found.

The specimen is a "paleontological Rosetta stone" said Andrew Parker, lead
researcher behind the find, and evolutionary biologist at the University
of Oxford in England. The fossil beetle may be the key to analyzing and
predicting the color of other well-preserved invertebrate fossils, fish
scales and even bird and dinosaur feathers, that have not retained any
original coloration, he said.

The beetle specimen was found in 50-million-year-old oil shale deposits
from the Messel Quarry near Frankfurt, Germany. Messel, a World Heritage
site, is unique because its fossils are so well preserved. Bats and
crocodiles for example, not only retain skeletal parts, but outlines of
their entire bodies. The beetles are unusual in that they still contain
the original materialchitinthat formed their exoskeleton in life.

Messel fossil hunters had previously turned up beetles, which retained
bright colors lost on drying, but those researchers had paid little heed
to color before. "Plenty of people are working on color in animals today,
but few have thought of looking at colors in the past," said Parker.

Parker, and physicist colleague David McKenzie of the University of
Sydney, are the first to detail these colored beetles and explain why they
have retained their decoration over so many millennia. The pair describe
the remarkable find in a recent online edition of the journal Biology
Letters. 
...
However there are ways, other than chemical pigmentation, in which
organisms can produce color. One way is using a structure, such as wafer
thin stacks of thin translucent organic material, to interfere with and
reflect light (in a similar way to a prism splitting white light into
colored beams). These films, made of chitin for example, can reflect and
amplify light of one wavelength (or color). This is how most iridescent or
metallic animal colors are produced, such as those striking hues found to
adorn shiny butterfly wings, the feathers of hummingbirds and peacocks,
and an entire rainbow of beetles.

Microscopic analysis revealed that the exoskeleton of the beetle found at
Messel did indeed retain a type of structure known as a multi-layer
reflector in its chitin exoskeleton, thus explaining its color. 
...
This is the first time that a multi-layer reflector has been found in a
fossil, and the find may have wider implications, said Parker. It could
pave the way for predicting the color of other well-preserved fossils that
no longer retain original hues, but still carry the fine shape of
once-translucent, color-producing structures. Computer models could then
be used to predict the wavelength of light, or color, that would have been
reflected back from these structures in life.

To prove that point, Parker and McKenzie prepared a slice of the fossil
and examined it under a powerful electron microscope. They measured the
dimensions of the multi-layer reflector and fed those details into a
computer program. The results were encouraging. Using those measurements
alone, the computer program predicted that a bright blue hue would be
produced. 

That result proves that the method could be accurately used to measure
other exceptionally well-preserved fossils containing similar
color-producing structures. These would most likely be other types of
invertebrate shell, but could include anything from iridescent reptile
skin to iridescent bird feathersand even feathers of dinosaur relatives,
said Parker. Extinct and numerous trilobitesflattened oval-shaped,
lobster-like animalsmight be one obvious contender, he added.

Data on ancient color could tell us about the environment and behavior of
animals. Coloration is important for mating, camouflage, and intimidation,
said Parker.