This is Mazon Monday post #206. What's your favorite Mazon Creek fossil? Tell us at email:[email protected].
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We are looking at another rare Mazon Creek plant fossil, Pseudomariopteris cordato-ovata, which is thought to have grown vine-like. It belongs to the callistophytalean pteridosperms, a group of small, scrambling to climbing forms (Krings and Kerp, 2000). Complete pinnae have been found and some of those had grasping hooks.
P. cordato-ovata was described in 1869 by Christian Ernst Weiss (1833-1890), who was a German geologist, paleontologist, mineralogist, and botanist. He named it Neuropteris cordato-ovata. The name was changed to Pseudomariopteris cordato-ovata by Leo Lesqeureux in 1879. This species is considered problematic by many researchers.
P. cordato-ovata appears on page 172 of Jack Wittry's "A Comprehensive Guide to the Fossil Flora of Mazon Creek".
Pseudomariopteris cordato-ovata (Weiss) Krings & Kerp, 2000
1869. Neuropteris cordato-ovata Weiss: p. 28, pl. 1
1879-80. Pseudopecopteris cordato-ovata (Weiss); Lesquereux: p. 205, pl. 37, figs. 4, 5
1938. Mariopteris? ribeyroni Zeiller; Bell: p. 52, pl. 44, figs. 1-8
1958. Mariopteris cordato-ovata (Weiss) Zeiller; Langford: p. 262, fig. 477
1969. Mariopteris cordato-ovata (Weiss) Zeiller; Darrah: p. 123, pl. 63, fig. 2
1978. Pseudomariopteris cordato-ovata; Gillespie et al.: p. 108, pl. 49, fig. 4
DESCRIPTION: The ultimate pinna is linear with a straight rachis that sometimes displays a very narrow wing uniting the pinnules. The pinnules rise at a near-right angle and are ovate. On the acroscopic side, there is a cleft and on the basiscopic side, there is a rounded constriction. The pinnules are often strongly vaulted. The venation consists of a decurrent midvein that terminates about two- thirds up the pinnule. The lateral veins rise obliquely, arch slightly toward the margin, and usually fork twice. Occasionally, upper veinlets divide again. Some veins appear to enter directly from the rachis into the pinnule on the basiscopic side only. Veins are immersed in the thick lamina and indicated by creases.
REMARKS: Pseudomariopteris cordato-ovata is very rare and, when found, is often just represented by fragments of pinnae. It is thought to have grown vine-like in life, as complete pinnae have been found with grasping hooks at their ends.
Specimens
Field Museum specimens in Wittry's "A Comprehensive Guide to the Fossil Flora of Mazon Creek"
George's Basement has a photo as Mariopteris cordato-ovate.
From the Herrin Fossil Flora - Andrew Young
