The Dinosaurs of Wyoming - Wyoming State Geological Survey ...

THE AMPHIBIOUS DINOSA URIA 87
quirements and its inadequate food-getting mechanisms were
undoubtedly critical factors in the extinction of this type of
the dinosaurs, which did not survive beyond the Lower Cretaceous.
\Vyoming localities furnishing parts of the Brontosaurus
skeleton mounted in the American Museum, are Nine Mile
Crossing of the Little Medicine Bow River, Como Bluffs, and
the Bone Cabin Quarry. Another dinosaur of this group
reaching a length of 87 feet, was also found in Wyoming.
A number of writers, notably Williston, Wieland, and
Brown, have discussed the significance of certain smooth,
rounded pebbles found associated within the ribs of certain
Mesozoic reptiles. These are often of rock which could only
have been secured at a considerable distance from where they
were found. Such pebbles are now called "gizzard stones,"
"stomach stones," or "gastroliths." Wieland in his discussion
of the sauropod dinosaur Barosaurus, says:
" ... various pebbles of a singular smoothness were noted
at only one point close to the main group of dorsals. As the
specimen was incomplete the reasonable explanation that these
were stomach stones, or as later called, dinosaurian gastroliths,
did not then occur to me, their true character being first recognized
in examples from the Big Horn mountains."
It is well known today how certain birds and reptiles swallow
stones to aid in digestion. I noted a similar habit among
the horned toads which feeding on ants had added various
quartz pebbles to its stomach contents. So far the amphibious
dinosaurs are the only ones known to have had this
habit.