Camp classrooms have been provided with an ancient fossil -
this is a REAL fossil that dates from millions, yes millions, of years ago. In
California, ammonites have been found in what are now dry, mountain and
foothill regions, and attest to the fact that the Pacific Ocean once covered
most of California.
What is an Ammonite ?
An ammonite is an extinct cephalopod whose fossil is
frequently found in marine rocks of the Devonian to Cretaceous periods (408 to
66.4 million years ago). The coiled shell served as protection and support. A
highly complex suture occurs where internal partitioning walls come in contact
with the outer shell wall.
Ammonites are relatives of squid, octopus and the chambered nautilus. They went
extinct 65 million years ago with the dinosaurs. While they lived they evolved
quickly so that some species only lived for a relatively brief period of
geologic time. Hence they are excellent fossils for dating of rocks. Several
ammonites were found with and surrounding the dinosaur bones.
How are they found ?
Camp Trail Guide Dick Hilton was looking for ammonites when
he made the discovery of the oldest known dinosaur fossil on the west coast of
the United States. The ammonites he sought in Shasta County were found along
with fossil clams, oysters, and occasional shark teeth, and clearly indicate
that areas of northern California were submerged under the sea during the late Mesozoic Era.
Ironically, it was these marine fossils that first lured Hilton to the hills of
western Shasta County, where the dinosaur remains were inadvertently
discovered. All of the other dinosaur fossils known from California have
likewise been discovered in rocks that originated as sediment deposited on the
sea floor west of the Mesozoic shore.
When did they live ? Ammonoids evolved from nautiloids in the early
Devonian period, about 400 million years ago. They were abundant in world
seas for the next 370 million years. They suddenly vanished at the end
of the Cretaceous period. The rapid evolution of Ammonoids and their widespread
distribution make them of great value in the subdivision of late Paleozoic
and Mesozoic time. As a group, they are characterized by the position
of the siphuncle (the tube connecting the chambers of the shell). Because
they are extinct, we know very little about their soft parts and life
habits. It is rare to find the biting jaws, the tongue-like rasping radula
or the ink sacs preserved in living chambers.