Geoscience Reference
In-Depth Information
Studied again by Karen Chin and five other paleontologists, it was 64 cm (25 in)
long and as much as 17 cm (7 in) wide. Like the coprolite from Saskatchewan,
it contained many pieces of bone and was cemented with apatite. Nevertheless, it
differedintwoimportantways.First,
Tyrannosaurus rex
couldnothavemadeitbe-
cause this dinosaur was not alive until about 10 million years after this fecal mass
peeked out of a cloaca. The Dinosaur Park Formation did, however, have the tyr-
annosaurids
Aublysodon
,
Daspletosaurus
, and
Gorgosaurus
living there, so one of
these theropods could have dropped it.
The second way it differed was even more extraordinary. In this coprolite was
recognizable muscle tissue, some of it preserved in three dimensions. In their ana-
lysis, the paleontologists were astonished to see: striated cell-like structures re-
vealed in thin sections; bundles closely resembling muscle cells and connective tis-
sues in SEM photographs; and high concentrations of carbon in and around these
structures. All of these observations meant the paleontologists were looking at fos-
silized meat, in which minerals had faithfully mimicked the original muscle cells.
Never before had a tyrannosaurid meal been preserved in such intimate detail.
This3-Dsnapshotofitsformerexcrementrequiredveryunusualconditions,suchas
brief gut-residence time (food rushing through, resulting in incomplete digestion),
dumping it as a cohesive mass on a river floodplain just before it flooded, rapid
burial, and anaerobic bacteria in the feces that helped to precipitate minerals in and
aroundthemusclecells.Basedonthedistinctivebrokenbitsofbonethroughoutthe
coprolite, these paleontologists figured these all came from the same animal, such
as a pachycephalosaur.
Just for some biological trivia, these two tyrannosaurid coprolites also tell us
something about the soft-part anatomy of their makers, namely their cloacas. Based
onwidthsofthecoprolites,theirminimumcloacaldiametersmusthavestretchedto
13 to 17 cm (5-7 in) to allow these fecal masses to bid adieu to their gastrointest-
inal tracts. However, the actual diameter was probably greater, considering that the
