This is Mazon Monday post #264.  What’s your favorite Mazon Creek fossil?  Tell us at email:esconi.info@gmail.com.

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Crossotheca boulayi is one of the rarer seed ferns in the Mazon Creek fossil biota.  It was first described as Alethopteris hymenophylloides by Leo Lesquereux in 1870.  The name was changed to Crossotheca boulayi by Charles Rene Zeiller (1847-1915).  Zeiller was French paleontologist, geologist, and mining engineer.  He is known particularily for his work on the Carboniferous plants of France and Algeria.  JSTOR has a nice memorial of his life, published in 1916.

Crossotheca boulayi appears on page 156 of Jack Wittry’s “A Comprehesive Guide to the Fossil Flora of Mazon Creek”.

Crossotheca boulayi Zeiller, 1886

1870. Alethopteris hymenophylloides Lesquereux: p. 393, pl. 10, fig. 1, non figs 2-4 = Sphenopteris illinoisensis
1879-80. Pseudopecopteris hymenophylloides Lesquereux: p. 196, pl. 56, fig. 2, non fig. 3 = S. illinoisensis
1886. Sphenopteris (Crossotheca) boulayi Zeiller: p. 115, pl. 4, figs. 4-4c
1924. Crossotheca boulayi Zeiller; Kidston: p. 352, pl. 91, figs. 1-6
1938. Crossotheca boulayi Zeiller; Bell: p. 47, pl. 36, figs. 1-4; pl. 96, fig. 1; pl. 97, fig. 4
1940. Callipteris sp.; Janssen: p. 63, pl. 17, fig. 1
1958. Crossotheca boulayi Zeiller; Langford: p. 184, figs. 321, 322
1962. Crossotheca boulayi Zeiller; Bell: p. 18, pl. 5, figs. 2, 3; pl. 7 figs. 1, 2

DESCRIPTION: The penultimate rachis is smooth and has a wing. The ultimate pinnae rise obliquely at nearly
a 45° angle. They are close, alternate, lanceolate, and decurrent in the wing of the penultimate rachis. At the apex is a small lobe. The pinnules are either entire or undulate. They are oblique, decurrent, rounded at the apex, and free. At the base of larger pinnules, there is a wide footstalk with a sinus on the acroscopic side and a slight, rounded constriction on the basiscopic side. The midvein is heavy and decurrent. The lateral veins arch slightly and are distant. They rise at an acute angle and fork near the middle. In the lower lateral veins, the upper veinlet divides again. Fertile pinnules are oblong and have sporangia forming a fringe along the lateral margin.

REMARKS: Crossotheca boulayi is rare. Sterile foliage most resembles Oligocarpia gutbieri in size and venation, but they can easily be separated. Of the two, only C. boulayi has a winged penultimate rachis and pinnules constricted at the base.

Specimens

Field Museum P31121

Field Museum PP15308

Field Museum PP43483

Crossotheca boulayi, fertile form from George’s Basement

Crossotheca boulayi, sterile form from George’s Basement