The image here is a small section from a large mural of
prehistoric Maryland, which is currently being prepared by local artist
Clarence Schumaker. We are planning to unveil the completed artwork at
Dinosaur Park later this year.
Aside from the charming little
frog, the most prominent organism in this image is a cypress tree –
specifically its characteristic “knees.” Today, bald cypress trees are
common in lowland swamps throughout the southeast United States. These
trees are well-adapted to life in waterlogged, swampy soil. In addition
to their rot-resistant wood, the knees (actually woody extensions of the
roots) help to stabilize the tree in soft ground.
We know that
bald cypress trees grew in prehistoric Maryland because we find their
fossils. In fact, the tiny, globular cones (think pinecones) of bald
cypress trees are some of the most common fossils at Dinosaur Park.
During Saturday Open Houses, visitors typically find many cones over the
course of the afternoon. Unlike animal fossils, which can be found
complete and intact, plant fossils are virtually always found in pieces.
Different conditions are needed to fossilize the trunk or the leaves or
the cones of a tree, and it is rare to find all of these parts in one
place. At Dinosaur Park, the very fine clay is well-suited for
preserving cones, or more often, their impressions. This is fortunate,
because cones are easy to identify. Many kinds of wood look the same,
but different conifer trees produce differently shaped cones. In this
case, the tiny, honeycomb-like cones found at the park are
characteristic of bald cypress trees.
Plant fossils are important
because they are reliable indicators of climate and environment. There
is an obvious reason for this: animals move around, but plants can be
trusted to stay put in an area that suits their needs. The environmental
tolerances of modern plants (temperature, annual rainfall, soil acidity
and stability) give paleontologists a good idea of what the ancient
environment was like when we find their fossil relatives. We can also
compare the plant communities in fossil deposits of different ages to
learn how the Earth’s climate has changed over time. At Dinosaur Park,
the plentiful bald cypress cones are one of many lines of evidence that
central Maryland was warm, wet, and swampy in the Early Cretaceous
Period. Swimsuits, anyone?