This is Mazon Monday post #91. What's your favorite Mazon Creek fossil? Tell us at email:[email protected].
-----------------------------------------------------
Today, we have a seed fern species called Macroneuopteris macrophylla. It was named Neuropteris macrophylla in 1831 by Alexander Brongniart, a French chemist, mineralogist, geologist, paleontologist, and zoologist. It was mistakenly renamed as Neuropteris clarksoni by Leo Lesquereux in 1879. It seems that Lesquereux just missed the older name. N. clarksoni was carried forward by both Adolf Noe and George Langford. With the name fixed by Robert Cookall in 1959. Epidermal research led by Christopher Cleal in 1990 reclassified Neuropteris species into four genera, Neuropteris, Macroneuropteris, Neurocallipteris, and Laveineopteris.
These seed ferns are often mistaken for Macroneuropteris scheuchzeri. We looked at M. scheuchzeri back in Mazon Monday #39. There are a few differences between the two species, some more obvious than others. The hints listed below come from the ESCONI "Keys to Identify Pennsylvanian Fossil Plants of the Mazon Creek Area". At that time, M. macrophylla was still referred to as N. clarksoni.
- M. macrophylla has no orbicular pinnules.
- M. macrophylla has more coarse venation with sharply defined ridges.
- The shape of M. macrophylla pinnules are nearly triangular.
- M. macrophylla has no surface hairs.
Neuropteris scheuchzeri
The frond is very large. The large primary pinnules are spatulate. The secondary pinnules vary, depending on their position on the frond. The most common is a large elongate pinnule with a constricted base, tapering to a more or less rounded pointed apex. Fine sharp midvein extends nearly to the apex. There may be hairs scattered upon the surface, appearing as scratches across the veins. Two ovate basal pinnules are occasionally present.
The lateral veins and veinlets are fine, arching to the margin, and close. The veins fork usu ally four times, sometimes three or five times. The veinlets number about 40 per centimeter, with a range of 38 to 44.
Neuropteris clarksoni
N. clarksoni is similar in size to N. scheuchzeri, however, the venation is more coarse with sharply defined ridges and valleys with a rasp like appearance. The pinnule is nearly triangular and there are no surface hairs.
M. macrophylla appears in "A Comprehensive Guide to the Fossil Flora of Mazon Creek" by Jack Wittry.
1831. Neuropteris macrophylla Brongniart: p. 235, pl. 65, fig. 1
1879-80. Neuropteris clarksoni Lesquereux: p. 94, pl. 9, figs. 1-6
1925. Neuropteris clarksoni Lesquereux; Noé: p. 14, pl. 20, fig. 2; pl. 21, fig. 1
1958. Neuropteris clarksoni Lesquereux; Langford: p. 197, figs. 340-342
1959. Neuropteris macrophylla Brongniart; Crookall: p. 176, pl. 38, fig. 4; pl. 39, fig. 1; pl. 40, figs. 1-3; pl. 42, figs. 1, 3
1979. Neuropteris clarksoni Lesquereux; Janssen: p. 149, fig. 138
1990. Macroneuropteris macrophylla Brongniart; Cleal: p. 488DESCRIPTION: The rachis is thin and longitudinally striate. The pinnules are attached subopposite, oblique, and often partially cover the rachis with their bases. Their sizes and shapes are highly variable-some may be lanceolate-acute with a large auricle (see Fig. 2), while others are oblong-obtuse and cordate at the base (see Fig. 1) The terminal pinnule is rhombic in shape. The midvein enters the pinnule off-center toward the acroscopic sice it is strongly marked at the base, but gradually disappears toward the middle. The lateral veins are strong, arched, and fork generally four times, with 35 veins per centimeter at the margin.
REMARKS: Macroneuropteris macrophylla is common. This taxon is most easily confused with M. scheuchzeri. However, the latter's characteristics of a symmetrical pinnule base; coarse, scattered "hairs"; and small, orbicular pinnules at the base separate the two. The name Neuropteris clarksoni, often used in North America, was never accepted in Europe. It appears that Lesquereux simply missed the fact that Brongniart had described this form some 50 years earlier, thus making Lesquereux's Neuropteris clarksoni a junior synonym of N. macrophylla.
Specimens
From Langford.
From Wittry
From an ESCONI member
