YSM Issue 94.3

FOCUS
Paleontology
Millions of
years ago,
long before
any of us existed, dinosaurs
roamed the Earth. What might
have stood where you are right now?
Maybe a T. rex or a Triceratops?
If you are somewhere in eastern North
America, the dinosaurs that lived near
you long ago might be unique. Chase
Brownstein, a Yale College junior
pursuing the Ecology and Evolutionary
Biology major, recently conducted
research showing that eastern North
American dinosaurs were probably very
different from the famous species of the
American West. His work sheds light
on the possibility of multiple paths to
evolutionary success.
Dinosaur Island
During the Mesozoic Era, when
dinosaurs like the T. rex existed, the
Earth looked very different from how it
does today. Surrounded by oceans and
seaways, eastern North America was
isolated from the rest of the world for
about thirty million years, constituting
an island landmass named Appalachia.
But since the 1800s paleontologists have
largely neglected the study of what kinds
of life once inhabited Appalachia.
When organisms evolve on an
isolated landmass, it’s considered more
likely for them to develop in ways that
differ substantially from their relatives
elsewhere. This has caused researchers
like Brownstein to ask: was this true for
dinosaurs isolated in Appalachia, and if
so, what unique characteristics did they
have? Poor fossil-forming conditions
and other factors, however, have made
this question difficult to answer.
Firstly, Appalachia has smaller
mountain ranges compared to western
North America. This means that the
shorter rivers created by these mountains
don’t flow as far and therefore cannot
accumulate as much sediment as their
longer counterparts in the West. This
Art by Zi Lin
accumulation of sediment is what
creates fossil-forming regions. Shorter
rivers generate fewer of these regions;
thus, fewer fossils formed on Appalachia
to begin with, making it difficult to
know what kinds of dinosaurs lived
there. Additionally, the fossils that
did form had a high chance of being
destroyed later by glaciers. The same
glaciers that carved out the Great Lakes
dug up much of the fossil-containing
sediment in eastern North America.
Finally, it’s difficult to even access the
fossils that did survive the glaciers, as the
eastern coast of North America is much
more densely populated than the West.
Most of the land is privately owned.
“Nobody wants you to make a giant hole
in their backyard,” Brownstein said.
Many of the major fossil discoveries
that are now in museums like the Yale
16 Yale Scientific Magazine October 2021 www.yalescientific.org