Later, more chemical changes occur. Additional minerals fill the bony
pores further, and the blood vessels are replaced with minerals called
siliceous siltstone and calcite.
While the minerals of the bones are being replaced, rock starts forming
around the former bone. The time it takes for fossils to form varies
from a few years to thousands of years. During this time, small
bones are usually washed away or crushed by accumulating sediment. That is another reason why SUE is so remarkable—it is the
first T. rex where tiny, delicate ear bones, called stapes, have
been recovered, showing that SUE’s ear structure had bones
similar to ours.
A window to the past
Fossils not only tell us about animals that died millions of
years ago but also how animals change over time, whether
they disappeared from the surface of the Earth following mass
extinctions or whether they migrated from one area to another,
revealing climate changes and providing evidence for continental plate movements.
Fossils may also be able to preserve more original material,
even protein, than previously thought. If so, new information,
such as the presence of certain tissues, could reveal more
about when and how certain traits evolved. This information
could help us better visualize how the world changed over
millions of years.
The Field Museum of Natural History, Chicago, Ill.: https://
[accessed July 2016].
The University of California Museum of Paleontology, Berkeley, The
Tyrant Lizards: The Tyrannosauridae: http://www.ucmp.berkeley.edu/
diapsids/saurischia/ tyrannosauridae.html [accessed July 2016].
Gail Mitchell Emilsson is a science writer and a high school teacher
in New Haven, Conn. Her latest ChemMatters article, “What’s in
Sunscreens,” appeared in the April 2010 issue. Michael Tinnesand is a
science writer and education consultant who lives in Portland, Ore. His
latest ChemMatters article, “ChemDemos Demystified,” appeared
in the February/March 2015 issue.
Nature’s Recycling Processes
Billions of organisms have lived on Earth over the past 4 billion years. Some lived for brief minutes or hours, while
others survived for hundreds of years. But in the end, all living things die, and most leave no trace behind. So what happens to the bodies of organisms after they die? It is all part of
nature’s grand recycling plan and the circle of life.
The answers are derived from the law of conservation of
matter, which states that matter cannot be created or destroyed.
The same goes with the atoms that make up living things.
Atoms come together to make molecules and materials that
make up organisms. So when organisms die, the matter in their
bodies breaks down, or decomposes, and is available for reuse in new ways.
Chemists estimate that one or two atoms that make up your
body, right now, were likely part of a dinosaur’s body 65 million
years ago. Other atoms in your body might have been part of a
lily pad or a giant sequoia tree.
12 ChemMatters | OC TOBER/NOVEMBER 2016 www.acs.org/chemmatters
excavate the fossils
of the dinosaur that
died in what used to
be a river.
Last Ice Age
67 million years ago, a
dinosaur was swept away
in a river current (shown
at the bottom of the river).
The different stages of the evolution of
landforms over millions of years and the
fossilization of a dinosaur