This is Mazon Monday post #170. What's your favorite Mazon Creek fossil? Tell us at email:[email protected].
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Several species of Aphlebia and Rhacophyllum have been identified in the Mazon Creek fossil deposit, though all are considered rare—and some exceptionally so. Their classification is somewhat uncertain, with some specimens grouped with aquatic plants and others with ferns. These genera are known from numerous Pennsylvanian Period fossil sites across both Europe and the United States, including locations in Illinois, Missouri, Indiana, Pennsylvania, and New Hampshire.
Rhacophyllum clarkii was originally described as Hymenophyllites clarkii by Leo Lesquereux in 1866. Noe and Langford called it Aphlebia clarki. It has most recently be reclassified as Rhacophyllum clarkii.
R. clarkii appears on page 135 of Jack Wittry's "A Comprehensive Guide to the Fossil Flora of Mazon Creek".
Rhacophyllum clarkii Lesquereux, 1866
1866. Hymenophyllites clarkii Lesquereux: p. 438, pl. 39, fig. 7
1870. Hymenophyllites clarkii Lesquereux: p. 416, pl. 16, figs. 1, 2
1879-80. Rhacophyllum clarkii Lesquereux: p. 319, pl. 57, fig. 5
1925. Aphlebia; Noé: pl. 28, fig. 1
1958. Aphlebia clarki; Langford: figs. 535, 536, (fig. 535 re-figured here as Fig. 1)
1969. Aphlebia; Darrah: p. 161, pl. 23, fig. 1DESCRIPTION: These fronds are large, divide irregularly, and have a wide and rather flat rachis. The pinnae are inflated, fan-shaped, and divided into obtuse lobes of varying lengths. The veins are buried in the thick lamina. All exposed surfaces have a rough texture, especially the rachises.
REMARKS: Rhacophyllum clarkii is rare and is the second most common Rhacophyllum/Aphlebia species in the Mazon Creek flora.
Specimens
George's Basement
Wittry's "A Comprehensive Guide to the Fossil Flora of Mazon Creek"
The Field Museum of Natural History
ESCONI members
