Mazon Monday #268: Pecopteris lanceolata #fossils #paleontology #MazonCreek #MazonMonday #fern #pecopteris #carboniferous #pennsylvanian

This is Mazon Monday post #268.  What's your favorite Mazon Creek fossil?  Tell us at email:[email protected].

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Pecopteris lanceolata is a very rare variety of true fern found only in the Mazon Creek fossil deposit.  It was first described as Alethopteris lanceolata by Leo Lesquereux in 1870.  Later in 1879, Lesquereux reclassified this fern as Pecopteris lanceolata. Lesquereux described many of the Carboniferous plants of North America, doing surveys for the states of Pennsylvania, Kentucky, Arkansas, Indiana, and Illinois.  He emigrated to the US in 1848.  He is known today for his work as a paleobotanist, but also as an exemplary deaf scientist.  His memoirs can be found at the National Academy of Sciences.  Lesquereux wrote "Atlas to the Coal Flora of Pennsylvania and the Carboniferous Formation throughout the United States", a three volume publication that was the standard reference for Carboniferous paleobotany for many years.

Lesquereux in 1864

The species name comes from the word lanceolate, which means "shaped like the head of a lance; of a narrow oval shape tapering to a point at each end".

The description and remarks shown below comes from Jack Wittry's "A Comprehensive Guide to the Fossil Flora of Mazon Creek".  Pecopteris lanceolata can be found on page 120.

Pecopteris lanceolata Lesquereux, 1870

1870. Alethopteris lanceolata Lesquereux: p. 398, pl. 13, figs. 1-3
1879-80. Pecopteris lanceolata Lesquereux: p. 227, pl. 39, figs. 9, 10
1963. Pecopteris sp.; Langford: p. 207, fig. 812, non figs. 813, 814

DESCRIPTION: The ultimate pinna is lanceolate and has a round, smooth, and thin rachis. The pinnules are oblique to the rachis, distant, entire, constricted and rounded at the base to half of their width, slightly sickle-shaped, and rounded at the apex. The lamina is smooth and thick. The midvein is thin and forms a narrow grove which narrows towards the apex. The veins are very thin, oblique to the midvein, and have simple veinlets. Due to their extremely thin nature and the thick lamina, the venation is rarely visible.

REMARKS: Pecopteris lanceolata is very rare and only known from the Mazon Creek area. P. lanceolata has a very similar venation pattern to Diplazites unita, but the two plants do not share any other characteristics and do not appear to be closely related.

Specimens

From Wittry's "A Comprehensive Guide to the Fossil Flora of Mazon Creek"

Field Museum specimen P31034