From Bozeman, Mont., at the 61st annual meeting of the Society for Vertebrate
Excavations in southeastern Missouri have yielded fossils of ancient aquatic
reptiles, as well as evidence of the impact that scientists suspect killed off the
When miners were digging clay from the bottom of a large pit near Artiola in 1999,
they exposed three layers of sediment, each about a half-meter thick, says Carl E.
Campbell, a freelance paleontologist in St. Louis. The deepest layer contains
traces of seafloor burrows and large numbers of phosphate nodules that include the
fossils of ammonites, the extinct relatives of today's chambered nautilus.
The next layer up is a jumbled mix of broken limestone and fossils that range in
size from microscopic plankton to hand-size shells. This layer also yielded a 6-
centimeter tooth and a vertebra that probably came from a large marine reptile,
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