Fossils are also found and collected by persons who are interested in
rocks and minerals. The varied remains of plants and animals long since
petrified or replaced by mineral matter have stimulated the curiosity
and become a source of enjoyment to many persons, from those who merely
give a passing glance to the peculiar organic structures in the rocks to
those who make a serious hobby or business of collecting and classifying
the unreplaceable heritage from the ancient rocks. Fossils are
interesting in part because of their variety, for they include petrified
wood, shells like those of oysters, fish teeth, foot-prints, amber,
dinosaur eggs, coal, imprints of fern leaves, of insects, and of fishes,
and the bones of small and gigantic dinosaurs and elephants. In fact, a
fossil is any evidence of life in the geologic past preserved in the
rocks. Missouri rocks furnish fossils ranging in size from
microscopically small fish teeth to the big skeletal remains of the
mastodon, an ancestor of the elephant; but the most common ones are the
structures and shells of ancient clams, corals, brachiopods, crinoids,
and trilobites.
[Illustration: A tooth of a mastodon, about one-half natural size.
(Photo courtesy of Mr. J. R. Morrison, Louisiana, Missouri.)]
[Illustration: Fossils. Upper row, coral on left, trilobite on
right; center row, brachiopods; lower row, coiled cephalapod,
crinoid head, and a bryozoan spiral.]
The accompanying photographs illustrate a few fossils that may be found
within our state, but a thorough, non-technical treatment of Missouri
fossils is available in a companion volume to this booklet, “The Common
Fossils of Missouri” by Prof. A. G. Unklesbay, Missouri Handbook No. 4.
The study of fossils, or paleontology, is a fascinating branch of
geology which extends far beyond the recognition and cataloging of the
specimens. It has been found that certain particular fossils occur in
rocks of the ages which produce petroleum, and the search for that
valuable substance has been directed in many instances by the fossil
content of the rocks. Rocks of different ages carry different fossil
assemblages, and a man skilled in paleontology utilizes the fossils in
dating geologic history like the page numbers in a book of human
history. Further, any student of present-day animals and plants is aided
in his understanding of them if he knows the fossil record of their
ancestors of the long geologic past.