This is Mazon Monday post #299.  What’s your favorite Mazon Creek fossil?  Tell us at email:esconi.info@gmail.com.

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Cordaites borassifolius is an extinct genus of early gymnosperms. Cordaites probably grew maybe 100 feet tall in the drier areas of the Carboniferous swamps. They had stilt-like roots, forming forests similar to modern day mangroves. Cordaites is relatively rare in the Mazon Creek biota with only one known species.

Cordaites are believed to be closely related to conifers, although the exact relationship is unclear. They look quite different, but do share some key features, such as secondary wood in their trunks and clustered ovules and pollen in separate cone-like structures. The kauri trees of New Zealand are the only modern conifers that resemble Cordaites.

Cordaites borassifolius was named by Kaspar Maria von Sternberg  (1761 – 1838) in 1821.  Sternberg was a Bohemian theologian, minerologist, geologist, entomologist, and botanist.  He is widely known as the “Father of Paleobotany”.

Jack Wittry discusses Cordaites borassifolius on pages 224 and 225 of his book “A Comprehensive Guide to the Fossil Flora of Mazon Creek”.

Cordaites borassifolius (Sternberg) Unger, 1850

1821. Flabellaria borassifolia Sternberg: p. 32, pl. 18
1879-80. Cordaites borassifolius (Sternberg) Unger; Lesquereux: p. 532, pl. 76, fig. 3
1899. Cordaites communis Lesquereux; White: partial text p. 260, pl. 3, fig. 1; pl. 16, pl. 46
1917. Cordaites borassifolius Sternberg; Seward: p. 233
1925. Cordaites grandifolius Lesquereux; Noé: p. 109, pl. 45, fig. 2
1958. Cordaites borassifolius Sternberg; Langford: p. 121, fig. 222
1969. Cordaites borassifolius; Darrah: p. 185
1970. Cordaites borassifolius Sternberg; Crookall: p. 807, pl. 153, fig. 3; text-fig. 231
1979. Cordaites borassifolius Sternberg; Janssen: p. 72, fig. 54

DESCRIPTION: These are large, strap-like leaves-up to 64 cm long-that are constricted and partially enrolled at their bases, with slightly obtuse apices. The veins are straight and run parallel to the margins, occasionally alternating in prominence from thick to thin for varying distances. All veins become thinner and more dense near-er the apex. The thin veins, or strands, appear and disappear down the leaf and are difficult to trace for any distance. The heavy vein count is about 10 per centimeter. If desiccated before fossilization, Cordaites leaves appear longitudinally folded. When this happens, it gives a much different pattern, with very heavy veins along the folds, separated by a varying number of thinner veins.

REMARKS: Cordaites borassifolius is uncommon and appears to be the only form of cordaite leaf in the Mazon Creek flora.

It has been found through a cuticle study (Simunek, 2007) that cordaites leaves can only be truly separated into biological species by using stomata and epidermal structures. Leaf shape and venation-as used here have little value in separating biological (natural) species. For now, the names are based on features that may not separate true biological species.

Specimens

Field Museum PP 55152-A (shown in Wittry’s “A Comprehensive Guide to the Fossil Flora of Mazon Creek”)

Field Museum PP 28044 (shown in Wittry’s “A Comprehensive Guide to the Fossil Flora of Mazon Creek”)

From George’s Basement