This is Mazon Monday post #181. What's your favorite Mazon Creek fossil? Tell us at email:[email protected].
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Mariopteris nervosa is the most common species of Mariopteris found in the Mazon Creek fossil biota. It was named by Adolphe-Theodore Brongniart in 1879. He was a French botanist, who is widely considered the father of Paleobotany. He lived from 1801 until 1876. Some of his works were published posthumously in the early 1880's. He was a prolific writer of books and memoirs and is most known for Histoire des végétaux fossiles ("History of fossil plants").
M. nervosa can be found on page 160 of Jack Wittry's "A Comprehensive Guide to the Fossil Flora of Mazon Creek".
Mariopteris nervosa (Brongniart) Zeiller, 1879
1834. Pecopteris nervosa Brongniart: p. 297, pl. 95, fig. 1; pl. 94 = Mariopteris nervosa var. oblongata
1879-80. Pseudopecopteris nervosa Brongniart; Lesquereux: p. 197, pl. 34, figs. 1-3
1925. Mariopteris nervosa Brongniart; Kidston: p. 601, pl. 138, figs. 3, 4; pl. 140, fig. 1; pl. 143, figs. 1, 2; pl. 144, figs. 4-6
1925. Mariopteris muricata var. nervosa (non Brongniart); Noé: pl. 16, figs. 1, 5 (fig. 1 re-figured here as Fig. 2)
1925. Mariopteris muricata Brongniart; Noé: pl. 16, figs. 2, 3
1958. Mariopteris nervosa Brongniart; Langford: p. 257, figs. 466-468
1972. Mariopteris nervosa (Brongniart) Zeiller; Boersma: p. 94, pl. 9, figs. 20, 21
1979. Mariopteris nervosa Brongniart; Janssen: p. 122, fig. 100
1979. Mariopteris muricata; Janssen: (non text) fig. 101DESCRIPTION: The ultimate pinnae are linear-lanceolate, alternate, and oblique to their rachises. They appear slightly asymmetrical, with the pinnules on the lower side being slightly larger. The pinnules are oblique, confluent at the base, and subtriangular. The sides are convex or straight, and decurrent at the base. Pinnules are rounded at the apex when mature. They become more acute in the small, distal pinnules. The lower basal pinnule displays a prominent lobe on the basiscopic side; most pinnules are entire. The midvein is straight in the lower pinnules. Toward the pinna apex, the midvein becomes progressively more decurrent. The lateral veins are straight, generally immersed and hidden, occasionally inflated, acute to the midvein, and fork once near the base, with the lower-positioned ones often forking again.
REMARKS: Mariopteris nervosa is rare, although the most common Mariopteris in the Mazon Creek flora. The name implies that the veins should appear inflated. This is seldom the case, though they always appear clearly visible.
The "ESCONI Keys to Mazon Creek Plants" has a page describing Mariopteris nervosa and Mariopteris muricata, which was classified as a separate species at the time.
MARIOPTERIS
The fronds are lateral and spirally arranged on a naked primary rachis. The pinnules are large and triangular in form and are prominent, robust, unflattened and leathery. The midvein and veins branching from it are well marked, not systematically as in Pecopteris nor close as in Alethopteris. The base of the pinnule is directly and broadly attached to the rachis. An important characteristic is one or more veins entering the lower base, independent of and below the midvein, direct from the rachis.
Mariopteris nervosa
The rachis is marked with fine parallel lines running its length. The pinnules are triangular to ovate, with smooth margins. The pinnules are oblique to and alternating on the rachis. They are large, 1.5 times as long as wide, and appear leathery and thick. The midvein is prominent, and lateral veins curve out from the midvein and fork, curving back toward the margin. The basal pinnule is often bi- or trilobed.
Mariopteris muricata
M. muricata is similar to M. nervosa. The dentate margins of the pinnules are the primary difference. The venation is less pronounced but also similar. On the lower half of the pinnule, below the midvein, the veins may arise directly from the rachis. The general shape of the pinnule is more triangular than M. nervosa. The pinnules are alternate on the rachis.
Specimens
"A Comprehensive Guide to the Fossil Flora of Mazon Creek"
