The discovery of erect cormose club mosses (lycopsids) from the Pride Mountain Formation in
northern Alabama establishes at least a Late Mississippian origin for a growth form previously
known only from Middle and Late Pennsylvanian-aged strata. The lycopsids are found in a
monotypic/monospecific assemblage as sandstone casts which are composed of several basal
rooting structures and non-branching, tapering aerial axes. The standing plants are preserved for
a maximum height of 0.45 m, with plant apices not found above the top of the enclosing
orthoquartzitic matrix. Helically arranged, dichotomizing roots that originated from the corm-like
bases are preserved in the underlying silty claystone paleosol. Scars along the stem axes have
indicated that leaves were spirally arranged. Vegetative and reproductive pant parts are also
preserved in the subjacent paleosol. Vegetative leaves were deciduous with diamond-shaped leaf
bases intact. To date, only incomplete leaves have been recovered from the paleosol, but these
fragments indicate that the leaves probably attained a maximum length greater than 5 cm. The
plants are heterosporous, with a reduced number of large megaspores (ranging between 1.0-2.8
mm) found within isolated megasporangia. Microspores have not been isolated, to date, from the
paleosol, nor have microsporangia been found in the assemblage. It is not known if the plant
produced apical cones or if reproductive zones alternated with vegetative zones.
These herbaceous club mosses are interpreted to have grown in a back barrier or offshore bar
setting. This interpretation is based upon the sedimentology of the enclosing and casting
sandstone, in addition to the presence of euryhaline macrofauna preserved beneath the paleosol
and overlying the sandstone-preserving lithology. If our interpretation is correct, this megafloral
assemblage establishes not only the character of Carboniferous marshes, but also provides some
insight into the paleoecological tolerances of isoetalean-like lycopsids.
Citation: Abstract modified from - Geological Society of America, Abstracts with Program, 29(3):5-6, 1997.