Geoscience Reference
In-Depth Information
no museums with mounted skeletons of dinosaurs, nor did it have any rocks of
the right age holding either dinosaur bones or trace fossils. I was a transgendered
AliceinWonderland,albeitwithmoreamiableandslightlysanercompanions.After
studying the rock for a few more minutes, I set it down and walked away, but held
on to its memory.
Later that day, the professor in charge of our geology field camp, Dr. Wayne
Martin (no relation), casually remarked on these anomalous rocks in the fine-
grainedmudstone.“Gastroliths,” heinformeduswithhisdistinctive slowWestVir-
ginian drawl. Geologists regarded these blemishes in the otherwise smooth, fine-
grained Morrison Formation as evidence that dinosaurs were there. Sure, you could
also find dinosaur bones if you looked hard enough, and the Morrison Formation
was rightly celebrated elsewhere in the western U.S. for yielding some of the best-
loved of all dinosaurs:
Apatosaurus
,
Diplodocus
, and
Allosaurus
, to name a few.
But where we were, these large stones were far more common than bones. Despite
nearly two hundred eyes looking at the ground that day, not one person spotted a
dinosaur bone, but we found plenty of these strange rocks.
I remember being intrigued by this vague, indirect evidence of a dinosaurian
presence.Filledwithnaivetyandimpressionableenthusiasm,Icontinuedtowonder
about that black rock from my field camp and gastroliths in general. Was it, along
with similar rocks there in the Morrison Formation, really connected to dinosaurs?
And if so, how? I wanted to believe they were. Yet when I read more about gast-
roliths much later in my graduate studies, doubt began to erode my faith. Indeed,
in a class the year after this field camp, Dr. Martin seemingly contradicted himself,
saying that such rocks should not be called “gastroliths” unless found in the rib-
cageofadinosaur.Itlaterseemedthatmanygeologistsandpaleontologiststoldme,
to paraphrase Freud, “Sometimes a rock is just a rock,” saying that these rounded
stones could be readily explained by non-dinosaurian means, such as rivers, wind,
or ocean waves. This creeping uncertainty was fueled by later trips to the western
U.S., in which I would find similar rocks in Mesozoic strata and ask if these were
