The
First Reported Arthropod Trackways from the Pennsylvanian
Llewellyn Formation: Bear Valley Strip Mine, Shamokin, PA
Smith, Casey
J., Simpson,
Edward
L., and Fillmore, David, 2009, The First Reported Arthropod
Trackways from the Pennsylvanian Llewellyn Formation: Bear Valley
Strip Mine, Shamokin, PA [abs]: Geological Society of America
Northeastern Section - 44th Annual Meeting (Portland, Maine 22–24
March 2009).
The Pennsylvania Anthracite region is
noted for producing some of the world's most spectacular paleobotany
specimens; the lesser known are the insect body fossils. The
newly discovered trace fossil from the Llewellyn Formation is the
first reported arthropod trackway. The trackways—Diplichnites
gouldi Type A—were discovered in the lower Pennsylvanian Llewellyn
Formation between the Middle split (No. 8˝) and Top split (No. 9) of
the Mammoth coal zone. Analysis of the invertebrate ichnofauna
revealed undertracks developed on a shale/siltstone to "clean"
subgraywacke. The trackway displays multiple morphologies.
Appendage imprints are sharply defined and are best interpreted as
locomotion traces. The trackways exhibit the required
digit appendage pattern of arthropods including: 1) curvatures
equating to angular changes in locomotion, 2) identifiable internal
and external widths repeated in a symmetrically staggered
alternating pattern, 3) measurable stride distances (repeatable
digit distance), and 4) appendage morphologies of digit
traces—circular, ellipsoidal, elongated, and comma internal
digits—in an oblique V-shaped orientation to the angle of mid-line
symmetry. This new trace fossil suggests the possible
existence of a diverse inchnofossil assemblage that could lead to a
greater insight into the potentially complex ecosystem developed
among the Pennsylvanian coal swamps.