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WHAT ARE FOSSIL PLANTS?
Plants are an entire kingdom of life forms, and are the most essential group of organisms
in our world. Without plants, all other forms of life would cease to exist. Plant fossils,
also, were very important to the evolution of the world as we know it. Fossilized plant
remains are responsible for the world's vast coal deposits and possibly the huge oil
reserves trapped in the Earth's crust. Plant fossils are also important for studying the
theory of Continental Drift. Glossopteris leaves, for example, were unearthed in adjacent
parts of India and Australia, showing that the habitat of this extinct tree was split
apart when the two continents were divided by plate tectonics. Even fossil amber, used as
a gemstone in jewelry, is actually fossilized tree sap! Many fossil plants are very
collectible and also very beautiful. Museums around the world display fossil plants as a
keystone of their Natural History exhibits.
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CATEGORIES
Fossil plants are usually found as individual parts, not complete, articulated
structures. These parts include leaves, fern fronds, cones, bark sections, flowers and
petrified wood.
Leaves are commonly found as fossils, although fully complete specimens are rather rare.
Some fossil leaves had unique shapes and structures - others are the same exact types
that live today. Some modern day leaves that have been found as fossils are: Maples,
Sycamores, Ginkgos, Willows, Poplars, Oaks, as well as many others. Some of these leaves
exhibit disease scarring or insect predation, which is unusual in the fossil record. Most
leaf fossils are 2 to 4 inches in length, although some fossil leaves have been measured
at over 6 feet long. Complete fossil leaves, with venation preserved and petiole (stem)
intact, are prized by investors and collectors alike.
Fossil ferns are possibly the most abundant and recognizable of all fossil plants. Almost
all of the so-called fossil ferns are actually seed ferns. Seed ferns are extinct plants
(gymnosperms) which resembled true ferns, but reproduced by seeds rather than spores.
During the Pennsylvanian Period, billions of fern plants covered the forest floor and
outlying swampy regions. Now fossilized, these ferns formed dense, fossil-rich
layers dozens of feet thick and miles long. It is thought that the vast coal deposits
of Pennsylvania and West Virginia were made up by millions and millions of fern plants
buried in peat bogs and compressed into coal over many millenia. Plates of fossilized
seed fern fronds are commonly displayed in major museums around the world.
Ancient cones and seeds are also occasionally found as fossils. Cones are the
seed-bearing part of most gymnosperms, and almost all conifers. The unusual feature of
the seeds of gymnosperms is that they are borne naked upon the surface of the
sporophylls (cone), rather than within the ovary. Complete cone fossils are unusual in
the fossil record, although some localities produce fossil cones that look as though
they just fell off the tree!
Fossilized tree bark is also very interesting. Early trees usually had very distinct
bark patterns - diamond-shaped, scale-shaped, etc. Occasionally, branches or trunks
of these trees fell to the forest floor and eventually became fossilized. These logs
left their unique bark pattern imprinted forever in the rock. Some of these bark
sections are many feet long, others are hand-sized remains. But many of these ancient
bark patterns are both striking and beautiful.
Flowers are very rarely found as fossils, for obvious reasons. They were extremely
delicate in nature and only bloomed a few weeks each year. Some flower fossils have
their petals and stamens intact, and some even have the original color pattern
preserved! Fossil flowers are prized by collectors - they are one of the most
sought-after types of plant fossils.
Petrified Wood is a very well known fossil plant. Under certain conditions, entire
trees, even entire forests, can become fossilized. In the petrification process, the
solid trunk of a tree is replaced cell by cell by a mineral, usually silica. The
cellular structure of the tree is then an exact replica of the original tree, only
it is now solid rock. The beautiful colors associated with petrified wood come from
the trace elements associated with the mineral that replaced it. Red, yellow, orange,
and green are examples of the vibrant colors than can be found in petrified wood.
Colorful pieces of petrified wood are probably the most displayed type of fossil
plant available.
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FACTOIDS
Plants are, and always have been, the lowest-most member of the food chain. Almost
all plants are able to produce their own food through the process of photosynthesis.
Plants were the earliest known life on Earth, arising billions of years ago. Plants
are also currently the oldest living organisms on Earth - some are thought to be
thousands of years old. Fossil plants are some of the most widely recognized fossils
ever found. Coal, amber, jet, petrified wood, and some forms of crude oil are all
unique forms of fossilized plant material. Even the air we breathe is a result of
millions of years of oxygen production by the Earth's plant kingdom. We owe it all
to them!
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