This is Mazon Monday post #275. What's your favorite Mazon Creek fossil? Tell us at email:[email protected].
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After Lesquereux (1870)
Rhacophyllum molle is a wispy plant, underfined plant species described by Leo Lesquereux in 1870 as Hymenophyllites mollis. Later, he reclassified it as Rhacophyllum molle. He thought it was a type of aquatic plant. He reported to have found them in irregular masses growing on decaying woody matter. All known specimens are from the Mazon Creek area.
Leo Lesquereux's description, posted on George's Basement.
RHACOPHYLLUM MOLLE, Lesqx.
Hymenophyllites mollis, Lesqx., Geol. Rept. of Ill., VI, p. 418, Pl. XVIII, f. 2-6.
Filaments thin, flat, linear, emerging from a common support, parallel at the base, joined in their length by compression, separated on the borders of the tufts in linear obtuse filaments, nerveless.
These plants, found in numerous specimens, cannot be clearly defined. They seem to grow upon fragments of decayed woody matter, and to cover them by numerous closely apressed filaments, which, by compression, form an irregular mass where their borders only are here and there distinct. In the beginning, these filaments are short, two to ten millimeters, one millimeter broad or a little more, linear, obtuse, close and parallel; later, or in a state which seems to be their full growth, they are four to seven centimeters long, more or less flexuous, sometimes disconnected in laciniae, two millimeters broad, irregularly lined either in the middle or along the borders, while at the apex, when distinctly separated, they have the same width and form as the primary one. These medial laciniae; which of ten join again upwards, are not, therefore, separate leaves, but fragments of two or more filaments pressed and glued together.
Habitat—Nodules of Mazon Creek, not rare.
From Jack Wittry's "A Complete Guide to the Fossil Flora of Mazon Creek", it is shown on page 250.
Rhacophyllum molle Lesquereux, 1870
1870. Hymenophyllites mollis Lesquereux: p. 418, pl. 18, figs. 2-6
1880. Rhacophyllum molle Lesquereux: p. 326
1958. Rhacophyllum; Langford: p. 294, figs. 550, 551DESCRIPTION: The lamina consists of thin, flat, linear filaments which are joined by compression and emerge from a common support. They are parallel at the base and united until close to the distal margin where they sep-arate into thin, obtuse filaments.
REMARKS: Rhacophyllum molle is very rare. It is reported to be found as irregular masses growing on decaying woody matter. All known specimens are from the Mazon Creek area.
Specimens
Field Museum PP 27639
