This is Mazon Monday post #318.  What’s your favorite Mazon Creek fossil?  Tell us at email:esconi.info@gmail.com.

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Eusphenopteris neuropteroides is an extinct seed fern species that is relatively uncommon, though it is primarily known from the terrestrial deposits of Mazon Creek. It was originally described as Pseudopecopteris anceps by Leo Lesquereux, but its classification has shifted over time as its relationships to other taxa became better understood. Over the years, it has been reassigned among several genera, including Sphenopteris and Mariopteris, before being placed in its current genus.

George Langford knew it as Mariopteris anthrapolis, a species he newly erected in his book “The Wilmington Coal Flora From a Pennsylvanian Deposit in Will County, Illinois”. He wrote this on page 268 to justify his identification.

1-4. Mariopteris anthrapolis. new species.

Frond with pinnae attached to a slender rachis; pinnae wide for the length and terminating in a rounded apex; pinnules ovate, basal attachment broad, veination distinct, midvein absent in pinnatifid state, present in matured state; veins forking about three times, with decurrent veins apparently entering base of pinnule independently on the lower side.

Specimens like the ones illustrated are fairly common in the Wilmington area. The pinnules are thick and leathery. One or more veins appear to enter base of pinnule independently on the lower side as seen on the positive impression. However, in well-preserved specimens, the so-called independent veins originate from a single decurrent vein within the rachis. This character is not found in Sphenopteris, for which it may be mistaken.

Figs. 1, 2 and 3 are taken from a series of specimens to illustrate what is here considered as a composite frond. It begins at the base with Fig. 1. The lowest pinna on the right side has a comparitively large lower basal pinnule more matured than the others which are more or less united without midvein. Fig. 2 is taken as higher up on the frond, and Fig. 3 still higher up at near the apex. On the left side of Fig. 3 are three pinnules; the lowermost pinnatifid, the one above it non-pinnatifid and matured; the top pinnule also non-pinnatifid but less matured. The middle pinnule is here considered typical of the species. It is triangular with veins apparently entering the lower side of base independently when seen on the positive impression. However the negative im-pression discloses these independent veins derived from the midvein which is decurrent and branching off from the rachis at an acute angle.

This species is discussed at considerable length because the basal veination here considered an important character of Mariopteris is not so generally regarded, and further because specimens of it are rather common and will be found in many collections from the Wilmington locality. This species resembles Pseudopecopteris anceps and Sphenopteris neuropteroides, but these have Sphenopteroid veination which does not disclose veins apparently entering base of pinnule independently on the lower side.

William Culp Darrah knew it as Mariopteris thompsonii, named for Fred Thomspson, an early prolific collector in the middle 20th century.

Jack Wittry writes of Eusphenopteris neuropteroides on page 158 in his “A Comprehensive Guide to the Fossil Flora of Mazon Creek”.

Eusphenopteris neuropteroides (Boulay) Novik, 1947

1879-80. Pseudopecopteris anceps Lesquereux: p. 207, pl. 38, figs. 1-4
1923. Sphenopteris neuropteroides Boulay; Kidston: p. 52, pl. 12, figs. 3-5
1938. Sphenopteris neuropteroides Boulay, Bell: p. 23, pl. 5, fig. 4; pl. 6; pl. 7; pl. 8 fig. 1
1958. Mariopteris anthrapolis Langford: p. 268, figs. 488-493, (fig. 488 re-figured here as Fig. 3)
1969. Sphenopteris neuropteroides (Boulay) Zeiller, Darrah: p. 158
1969. Mariopteris thompsonii Darrah: p. 123, pl. 25, fig. 1
1975. Eusphenopteris neuropteroides (Boulay) Novik; Van Amerom: p. 54, pl. 28, figs. 1-3; pl. 30, figs. 1-10;
1978. Eusphenopteris neuropteroides; Gillespie et al.: p. 110, pl. 52, figs. 2, 3
1982. Eusphenopteris neuropteroides (Boulay) Novik; Oleksyshyn: p. 58, figs. 13B-F

DESCRIPTION: The ultimate pinnae are alternate, lanceolate, and terminate in blunt, half-round pinnules. The rachises of the ultimate pinnae have narrow furrows. The pinnules are entire or trilobed, coriaceous, generally decurrent, and attached by a wide base. They tend to have a square or rectangular look. The midvein in all but those in some base pinnules is decurrent. The midvein and lateral veins are thin and of the same thickness. The lower lateral veins of the pinnule rise from the base of the midvein as it runs parallel to the rachis, then gradually arch away from it and fork twice. The venation of the uppermost pinnules is fan-like and appears to lack a midvein. The lowermost (proximal) pair of pinnules often looks different than the rest. They are generally slightly larger, more constricted at the base, and often variously lobed. The shape and size of all the pinnae, pinnules, and venation are highly variable.

REMARKS: Eusphenopteris neuropteroides is rare. Some North American and European specimens of E. neuropteroides get a peculiar type of leaf damage (see Figs. 6, 7) which seldom occurs on other species. It looks like random and small, circular holes between, but never into, the veins. It was originally thought to be caused by a fungus and given the scientific name Excipulites callipteridis. This type of damage is now known to be caused by the feeding of a piercing-and-sucking insect.

Specimens

Field Museum PP 58293, K 11-2885 (Konecny), collected from Greer School (Pit 1) on May 8th, 1965.

Field Museum PP 58282, K11-1460 (Konecny) Collected from the Coal City Club (Pit 6).

From Langford “The Wilmington Coal Flora From a Pennsylvanian Deposit in Will County, Illinois”, figure 1 on page 269.