Annularia
stellata
Division
Pteridophyta, Class Equisetopsida, Order Equisetales, Family Calamitaceae
Geological
Time: Pennsylvanian (~300 m.y.a.)
Size (25.4
mm = 1 inch): Plant fossil is 100 mm long by 55 mm across
Fossil Site:
Dresden Lakes, Francis Creek Shale, Grundy County, Illinois
Code: DLF03
Price: Sold
Description:
The Mazon Creek deposits of the region near Braidwood, Illinois rival
the other famous Lagerstatten of the Burgess Shale, Solnhofen, and
Liaoning for the variety of detailed life preserved. Many exquisitely-preserved
specimens are found in the ironstone nodules that make up the deposits.
The majority of collecting areas are the spoil heaps of abandoned
coal mines. This particular nodule, however, comes from Dresden Lakes
in Grundy County Illinois. Like the better-known Pit 11 site near
Braidwood, Illinois, this location became the site for cooling ponds
for a nuclear power plant. The site is well known for the dark coloration
that while esthetically pleasing is somewhat harder to photograph.
I recently had an opportunity to acquire a collection that was made
in the 1950’s. This fine specimen is a member of the genus Calamites
, a member of the Calamitales which belong to the Sphenophytes. Whorls
of small leaflets are arranged concentrically around a thin stem and
are called Annularia or Asterophyllites. Calamites itself is the name
originally given to a stem section, but now applies to the entire
plant. These were indicative of humid to wet habitats such as along
rivers and lake shores. This is a fine large example which fills is
enclosing nodule with three star-shaped leaf whorls. |
|