This is Mazon Monday post #245.  What’s your favorite Mazon Creek fossil?  Tell us at email:esconi.info@gmail.com.

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Annularia annulariaefolius represents foliage from a shrub-like sphenophyte.  It was described as Lycopodites annulariaefolius in 1870 by Leo Lesquereux.  Lesquereux was a swiss bryologist, who lived from 1806 until 1889.  In 1970, he wrote “Report on the Fossil Plants of Illinois” in which he is credited with naming the Mazon Creek deposit by referring to the Mazon River as Mazon Creek.

“At Mazon Creek, the meanders of the stream have dug a broad bed through the bank of shale, and the water, washing for centuries, has uncovered great numbers of concretions and scattered them for miles from their point of origin.”

Annularia annulariaefolius is now associated with Annularia due to differences in form with Lycopodites.  Jack Wittry includes it on page 57 of his book “A Comprehensive Guide to the Fossil Flora of Mazon Creek”.

Annularia annulariaefolius (Lesquereux) Wittry, comb. nov.

1870. Lycopodites annulariaefolius Lesquereux: p. 426, pl. 21, fig. 5
1870. Annularia longifolia? Brongniart; Lesquereux: p. 422, pl. 21, figs. 1, 2
1880. Annularia calamitoides Schimper; Lesquereux: p. 48
1940. Lycopodites annulariaefolius Lesquereux; Janssen: p. 19 (partial), pl. 11, fig. 4 (holotype)

Basionym; Lycopodites annulariaefolius Lesquereux, 1870. III. Geol. Surv., Vol. 4, Report on the Fossil Plants of Illinois. p. 426, pl. 21, fig. 5. Lesquereux’s holotype is housed in The Illinois State Museum, cataloge number ISM 1163.

DESCRIPTION: The stems are smooth and range in width from 0.5 to 1.5 cm. From the nodes grew two opposite branches along with long, erect leaves (see Fig. 2) adpressed along the stem. The leaves of the branches are decurent, lax, generally curved outward from the base, then become straight and more upwardly pointed from the middle. Leaves are widest near the middle, acuminate or obtusely pointed at the apex, and have a well-marked midvein. Stems and branches are crowned with many tightly packed, thin leaves (see Figs. 1, 4). The leaves often can appear as nothing more than a midvein.

REMARKS: Annularia annulariaefolius is common and only reported from the Mazon Creek area. Most examples of this species are crushed, with flaccid, broken, and missing leaves. A. annulariaefolius has leaves and branches borne from nodes. The cones lack the spiral pattern found in all lycophytes. These features necessitate its removal from Lycopodites. All of the observed features of this species are best accommodated in Annularia.

Specimens

From Wittry’s “A Comprehensive Guide to the Fossil Flora of Mazon Creek”

FMNH PP 26314

FMNH PP 59050

FMNH PP 42218

ESCONI member Andrew Jansen (Fossil Friday #105).