This is Mazon Monday post #108. What's your favorite Mazon Creek fossil? Tell us at email:[email protected].
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In general, Mariopteris, a seed fern, is fairly rare across all the Mazon Creek terrestrial localities. Mariopteris tends to have ornate pinnules compared to other species of seed feed like Alethopteris, Neuropteris, and Odontopteris. The species we are looking at today, Mariopteris decipiens, was described by Leo Lesquereux in 1858 as Sphenopteris decipiens. In 1883, Charles David White redescribed it as Mariopteris decipiens. White (1862 - 1935) joined the USGS in 1889 and rose all the way to chief geologist. In 1903, he became the associate curator of paleobotany at the Smithsonian Institution. He is known for his thorough study of the Glossopteris Flora, which is the main component of coal deposits in Brazil.
The following description appears in "A Comprehensive Guide to the Fossil Flora of Mazon Creek" by Jack Wittry on page 165.
Mariopteris decipiens (Lesquereux) White, 1883
1858. Sphenopteris decipiens Lesquereux: p. 862, pl. 18, fig. 2
1879-80. Pseudopecopteris decipiens Lesquereux: p. 648, pl. 52, fig. 9, non fig. 10 = Eusphenopteris neuropteroides
1883. Mariopteris decipiens Lesquereux; White: p. 47, pl. 1, figs 5-8; pl. 2, figs. 1-3EMENDED DESCRIPTION: The ultimate pinna has a narrowly winged rachis and terminates with a large pinnule. The pinnules are distant, oblique, alternate, coriaceous, decurrent, linear, and terminate in wide, blunt lobes. They are divided into three to six pairs of decurrent, deep, and obovate lobes, which are typically longer than wide and touch until near their middle. The veins are thin, distant, oblique, and decurrent. The veins entering the lobe do not branch from a midvein. They are all borne low on the base from a decurring vein which runs nearly parallel to the midvein. Veins fork once or twice, are weakly arched, and can remain nearly parallel depending on lobe position. Veins may appear partially immersed in the thick lamina.
REMARKS: Mariopteris decipiens is very rare and most commonly found as fragments. When Lesquereux re described Pseudopecopteris (Mariopteris) decipiens (1880), he had only two small fragments to study. He commented at that time, "the fragments may represent two species or both pertain as branches of diminutive size to Pseudopecopteris speciosa." His two type examples were identified as Figs. 9 and 10 on plate 52. They differed in the length, shape of pinnae, and lobes; only their venation united the two. The features seen in his figure 10 are not unique, but closely conform to those of Eusphenopteris neuropteroides, and should be discarded as a type for Mariopteris decipiens. Since that time, several more examples which conform to Fig. 9 have been found for study and their unique combination of features is now better understood. It does not appear from the better examples that, as Lesquereux suggested, Pseudopecopteris (Mariopteris) decipiens and Pseudopecopteris speciosa might be conspecific. The latter has lobes with midveins, a feature lacking in the former, and they have differing lobe shapes.
Specimens
From George Langford
From Wittry
From an ESCONI member, from Chowder Flats.
