Friday May 10, 1996 10:00am Location: Tappahannock, Virginia
Muskrat home built out of marsh grasses and mud
This morning, Sarah
Ellyson (Advanced biology), Marcy Denault (Environmental
science), and I (John Wemple - Science dept) went canoeing up Hoskins
Creek, towards the marsh. After a 2 hour paddle punctuated by
jumping catfish, muskrats powering from bank to bank, and the
tide’s switch, we decided to turn our boat around and ride
the falling tide back to the Rappahannock. There exists a narrow
strip of beach which is kept in shadow by a 25 foot mud bluff.
We stopped on this beach because I had been told that sharks teeth
are prevalent in these parts. The previous week I had found 2
small teeth at Westmoreland state park and was hoping to repeat
that success on a local level.
I am holding the broken knob against the mud wall
still unaware of what lay only inches behind the mud
The same instant that
my foot touched the muddy beach, my eyes cemented on a slight
inconsistency in the smooth gray wall. I immediately
thought, “Fossil”, though my friends and colleagues
remained skeptical. With a surge of energy I grabbed my paddle
and began shaving mud from around the edges. I must have exerted
too much force because a large knob popped out of the hillside.
The piece I now held in my hand had clearly broken
off from something larger. Although the rounded surface of the
knob was smooth, the cross-section, where it had been broken off
by the paddle, was porous, like I remember volcanic pumice stone
to be. I thought it might be the ball from a ball and socket
joint and decided to compare it with other fossil bones I had
back in the St. Margaret’s science lab.
The back of the skull is to the left and the front to
the right
In the lab I decided it
was bone by comparing my sample with those of other fossil and
contemporary bone samples. I returned in a small motor boat
equipped with a knife and gardening shovel. Even now, a month later,
I shiver with a charge of excitement. With the knife I probed
into the dense mud and was surprised to hit solid material at a
wide radius from the central breakage point. I had entered the
dig expecting a femur, or some other long straight bone, but
soon realized it was something massive. After digging obsessively
for nearly 3 hours, my left hand was bloody from pushing on the end
of the shovel, my hair was caked with heavy gray mud, and my knees
ached from kneeling for so long. I had just unearthed a skull,
complete with sharp, pointed, bullet-like teeth. Notice the tip
of a tooth poking out from the mud to reflect its first
sunlight in perhaps 20 million years!
The fossil's discovery was a solitary experience shared only with the tall
Phragmites across the creek. I felt the urge to tell others about the discovery.
Sarah Ellyson(Biology) was walking down the outdoor stairway from her apartment when I returned to St. Margaret's School. Perhaps Sarah
actually heard the word "fossil" in my frenetic summoning, but more
likely she interpreted my flailing arms and screaming as a call of distress.
Regardless, the result was the desired one, she met me at the small strip of
beach to see what was up.
I had brought back a piece of bone the size of a floppy diskette that was
unlike anything I had ever seen before. I struggled to imagine what the
function of oblate pits on this rectangular plate-like structure could be. The
pits, each roughly a centimeter across and half as deep, were only found on one
side. The other side was smooth, lacking noticeable depressions and tinged the
same pallid greenish brown of the surrounding soil.
I envisioned two scenarios in my minds eye. The first scenario was of an
animal that patrolled the warm seas, protected by external armor plates, like
overlapping shingles. But why would the two sides of the armor plate be so
different? If this animal was a swimming vertebrate, to have smooth, low drag
surfaces facing outward would make hydrodynamic sense. This temporarily
explained the smooth side but left the function of the dimpled side unanswered.
Weight reducing structural adaptations are more common among land animals and
especially flying animals; perhaps these deep pits conferred some weight
reducing benefit upon this ancient animal.
Advanced Biology students consider the functions of bone fragments
while I work to remove more material
The second scenario involves a land animal, of a robust frame, which leads a
conspicuous, highly exposed lifestyle. In thinking about present day land
animals which possess protective plating, the armadillo and turtle come to
mind. Each of these animals is relatively slow but has adaptations that prevent
predators from being successful. Perhaps this animal was big, ugly, and slow,
but ornately decorated in a thick, but relatively light coating of rectangular,
dimpled armor plates.
It was Dustin, the seven a half year old son of Rick Kahler, a Kilmarnock
resident and St. Margaret's Physics teacher, who helped me see what my fossil
really was. Dustin had brought with him four or five coloring and picture books
about fossils. In paging through one picture book of fossil vertebrates my eye
was caught by the picture of a crocodile. Next to the crocodile was a plate,
deeply pitted on one side, while smooth on the other. I had spent many hours
scouring the internet for pictures, reading my college biology books for
evolutionary clues, and buying books with erudite verbiage by various
paleontologists. While the information highways were bustling with useful
information, it was in a child's picture book that held the answer. Crocodiles
have flesh covered plate-like structures called scutes, which provide bony
protection from predators.
This scute was once imbedded beside others like it within the
crocodile's outer skin layers.
Over the course of the next month, the remaining pieces of bone were
removed. The process became quite involved as I dug deeper and deeper into the
side of the bluff. I became worried at the risk of a cave in.
Several tons of
wet, dense soil above my head caused me and those persons close to me great
concern. It is not worth dying over a dead animal. But my obsession about
removing an entire animal from 20 million years of mystery, darkness, solitude,
geologic, evolutionary and human history, compelled me to sure up the gaping
hole with large timbers and continue my careful scraping. Fossil fever had
taken control and I am thankful that the dig soon came to an end.
Laden with dense mud, moss, and saplings, the danger of a cave-in was
reduced by timbers.
After 15 to 20 hours of digging with screwdrivers, scrapers, and small
garden shovels, I finally reached a dead end. In disbelief I probed hurriedly
into the saturated soil, prying away fist-sized chunks of earth. I hoped to
feel the touch of bone transmitted through the digging instrument into the tips
of my fingers. But the probe sunk in deep and settled on nothing. I returned
to the lab, cleaned the soil from my tools, fingernails, face, and hair, and
walked home.
The SMS Science Lab provided space for the tools of fossil preparation:
baby powder, SaranWrap, aluminum foil, newspaper, burlap, and plaster of Paris.
A month later I returned to inspect the chunks of dirt which had been drying
slowly in the darkness of a moist basement. 
I unwrapped the plaster of Paris,
the layer of newspaper, the tin foil and Saranwrap, to expose the dry earth.
What was contained within each nugget of dried earth was still a mystery.
It would require 15-20 additional hours of scraping and chipping to reveal the
contents. I once read about a woman who switched her job mid-life from being a
stone sculptor to specializing in fossil exfoliation. She found the work of
exposing fossil matter tremendously satisfying because the final "sculpture"
had been made long ago. Her job was to expose nature's ancient works of art.
Winnifred Delano, originally from Fairport, Va., is the librarian at St.
Margaret's School (update: Winifred Delano retired June 1999). Winifred possesses the qualities of the sculptor who works in reverse, gracefully scraping at the blank layers of earth, but able to envision a secret form behind the dense wall.
Raw blocks of mud slowly reveal their contents before Winnifred Delano's
focused eyes.
The Rappahannock River has seen recessions and advances of the sea level
with the melting and freezing of polar ice caps and glaciers. As climates have
changed, so too have the flora and fauna which occupy the banks and waters of
the rivers. Today the Rappahannock is home to crabs, oysters, rock fish, clams,
and several species of polychaete worms. The next time you are water-skiing,
sailing, or swimming, pause to think back about 20 million years ago, during the
lower Miocene, when a crocodile could have been right around the corner.