AXSMITH, BRIAN J.*, MICHAEL KRINGS, AND THOMAS N. TAYLOR. Department of Biological Sciences, University of South Alabama, Mobile, AL 36688, Department of Ecology and Evolutionary Biology, and Natural History Museum and Biodiversity Research Center, University of Kansas, Lawrence, KS 66045. - A filmy fern from the Upper Triassic of North Carolina.
A new assemblage of pteridophyte remains from the Upper Triassic Pekin
Formation of North Carolina is believed to represent the earliest
unequivoval Mesozoic record of the Hymenophyllaceae (filmy ferns). The
collection includes numerous fronds and frond fragments, one of which
is attached to a rhizome. Individual fronds were bipinnate, delicate,
and up to 20 cm long. Pinnae are alternately arranged and widely
positioned, giving the frond and open appearance. Pinnules are
segmented with each segment characterized by one to several rounded to
elongate lobes, each of which is vascularized by a single vein.
Laminae are represented by inconspicuous, light brown stains on the
matrix that may be suggestive of a membranaceous organization. Most of
the lobes are fertile, and each bears a marginal sorus consisting of 5
- 8 sporangia radially or helically arranged on a short receptacle
that is situated at the base of a shallow, funnel-shaped indusium.
Sporangia appear to be attached by short, thick sporangial stalks, or
may be sessile. Although this fossil lacks the deep tubular or
bivalved indusium like those of the extant representatives of
Trichomanes and Hymenophyllum , the soral morphology is
similar to that of early developmental stages common to both indusial
types. The new specimens are compared with other Mesozoic fossils
attributed to the Hymenophyllaceae.
Key words: filmy fern, Hymenophyllaceae, Mesozoic, North Carolina, Pekin Formation, Triassic