This is Mazon Monday post #85. What's your favorite Mazon Creek fossil? Tell us at email:[email protected].
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Our species spotlight for this week is Neuropteris ovata. N. ovata was described by Friedrich Hoffmann (1797-1836) in 1826. Hoffmann was a Professor of Geology at the University of Berlin. He is esspecially known for his work on the volcanoes of Italy. Unfortunately, there doesn't seem to be much other information about him. This paper is the description of N. ovata.
Hoffmann, F. 1826. Untersuchungen über die Pänzen-Reste des Kohlengebirges von Ibbenbühren und von Piesberg bei Osnabrück. Archiv für Bergbau und Hüttenwesen 13: 266-282.
N. ovata is a seed fern, belonging to a group called Medullosales which is an extinct order of plants referred to as the pteridosperms. It is commonly found in terrestrial Mazon Creek deposits. Seed ferms are common across most late Carboniferous localities. The Mazon Creek biota has a number of seed fern species, including Neuropteris, Alethopteris, Cyclopteris, Macroneuropteris, Odontopteris, and Laveineopteris among others. They were medium sized plants. At that time, they formed part of the forest understory. Their closest living relatives are the Cycads.
The book "A Comprehensive Guide of the Fossil Flora of Mazon Creek" by Jack Wittry has a list of names. Besides Mixoneura ovata, it has pretty much always been referred to as Neuropteris ovata, however there has been a fair bit of controversy as to where it should be classified with a few other species of Neuropteris being assigned as subspecies of N. ovata.
1826. Neuropteris ovata Hoffman: p. 158, pl. i b, figs. 5-7, non 8
1866. Neuropteris loschii (non Brongniart); Lesquereux: p. 428,
1879-80. Neuropteris loschii (non Brongniart); Lesquereux: p. 98, pl. 11, figs. 1-4
1925. Neuropteris ovata; Noé: p. 14, pl. 21, fig. 4
1958. Mixoneura ovata Hoffman; Langford, p. 218, figs. 382, 383
1959. Neuropteris ovata Hoffman forma typica; Crookall: p. 153, pl. 43, figs. 1-5
1969. Neuropteris ovata Hoffman forma typica; Darrah: p. 105, pl. 9, fig. 2; pl. 10, figs. 1, (?)2
1979. Mixoneura ovata Hoffman; Janssen: p. 157, fig. 150
The "ESCONI Keys to Mazon Creek Plants" was written in 1990, before N. ovata was split from N. vermicularis. Speaking to the difficultly in classifying N.ovata, the book calls it "the most variable plant in the fossil record of the Mazon Creek area.
Neuropteris ovata
This is the most variable plant in the fossil record of the Mazon Creek area. The following species are now assigned to N. ovata, and their former names are no longer accepted: N. flexuosa, N. plicata, N. vermicularis, N. gigantea, N. heterophylla, N. obliqua, N. loschi, and Mixoneura jenneyi.
Forms
- N. ovata typica has a large tripinnate frond. The pinnules are twice as long as wide, approximately 4-10 by 8-20 mm. The base is attached without a stalk or with a very short stalk and more or less cordate. The pinnules are ovate with rounded apex. The primary pinnule is small, odontopteroid, and asymmetrical. The midvein is indistinct and often appears to be missing because of branching near the base. The fine numerous veins number 50 or more per centimeter at the margin.
Cyclopterid pinnules, when present on the rachis, have fringed margins.- N. ovata flexuosa is characterized by rela tively large pinnules. The upper basal margin is round while the lower basal margin is auricled. The venation is fairly fine but commonly distant. The midvein is sometimes absent; if present, it is a little more prominent than the lateral veins and sometimes persisting to near the apex. The lateral veins are arched and dichotomous, usually dividing four times. Commonly, there are 40 veinlets per centimeter of margin length. The primary pinnule is relatively larger and broader than in N. ovata typica. This species is rare in the Mazon Creek area.
- N. ovata vermicularis is similar to N. ovata flexuosa but with a larger and more symmetrical primary pinnule. The secondary pinnules taper to a rounded apex, and fre quently have a constricted base. The pinnules are large, up to 70 mm long and 25 mm wide, and are ovate. The venation is coarse and not as fine as in N. ovata flexuosa.
But Wittry, in the description and remarks seems to have found them a home.
DESCRIPTION: The ultimate pinna gently tapers, becoming more linear when large. The rachis is straight and longitudinally striate. The pinnules are sessile or attached by a very short petiole, ovate or oblong, and twice as long as they are wide. The pinnules are rounded at the apex. At their bases, the basiscopic side has a small, pro zounced auricle and the acroscopic side is rounded. The terminal pinnule is asymmetric, obtuse at the apex, small, and oval. The midvein is distinctly marked by a depression in larger pinnules, abruptly disappears before the middle, and is accompanied by subsidiary veins (mixoneuran-like) entering the pinnule on both sides. In smaller pinnules, the midvein is replaced by several thin veins that enter directly from the rachis through a wide petiole. Lateral veins are well marked, thin, and close, meeting the margin with 45 to 50 veins per centimeter.
REMARKS: Neuropteris ovata is common. In 1959, Crookall placed Neuropteris flexuosa into N. ovata as a form. Darrah later added Neuropteris vermicularis to N. ovata as a form. Both N. ovata and N. flexuosa have now been shown to be separate species by cuticle studies. For this reason, the forma designations have been dropped from the names N. ovata and N. flexuosa. Also see Neuropteris fimbriata.
Specimens
From George Langford
Chowder Flats
Dresden 1963
Field Museum specimen - PP 58451
Field Museum - Field Museum of Natural History P 31415
