A long-leaved specimen of Lepidodendron

ROBERT M. KOSANKE U.S. Geological Survey, Box 25046, Denver Federal Center, Denver, Colorado 80225

ABSTRACT DESCRIPTION OF THE FOSSIL

Lepidodendron obovatum Sternberg var. grandifolium var. nov. The fossil specimen, Illinois State Geological Survey Paleobotan- is described from a single, unusual specimen collected from the roof ical Collection B-1817, is shown in Figure 1 and is on permanent shale of the Beckley coal (Lower Pennsylvanian) of West Virginia. display at the Illinois State Geological Survey. I here propose the L. obovatum Sternberg var. grandifolium var. nov. is an un- varietal name Lepidodendron obovatum Sternberg var. grand- branched stem with attached leaves and with pyramidal leaf cush- ifolium var. nov. for this specimen. The naming of a new variety ions. The leaves are long, attaining a length of more than 78 cm; requires that the type be redesignated as L. obovatum Sternberg they are sessile, entire, and thought to be sharply pointed. Leaves of var. obovatum. The new variety described in this paper is an un- such length are not generally associated with Lepidodendron, but branched stem 1.03 m long and 10 cm in diameter at the base, tap- with Sigillaria. The description of this new variety of Lepidoden- ering to 5 cm in diameter at the top of the stem. The stem has typi- dron helps to confirm the idea that there is little difference between cal pyramidal leaf cushions arranged in a high spiral, as shown in the foliage of Lepidodendron and Sigillaria. The unbranched con- Figures 1 and 4. The leaf cushions are reasonably well preserved, dition of the new variety herein described is thought to represent a and Figure 2 illustrates the discernible features. The vascular scar, young axis prior to the first dichotomy. which is preserved on many of the cushions, tends to be slightly concave. The parichni scars are somewhat elliptical and are present INTRODUCTION on either side of the vascular scar. The elongate aerating tissue scars appear below the parichni scars on the lower keel. The outline of The specimen described in this paper was presented to the Illinois the leaf scar is convex above and slightly V-shaped below. The State Geological Survey in about 1946 by D. W. Buchanan and ligule pit scar is very small and located well above the leaf scar on John E. Jones, who were then President and Safety Engineer, re- the median line of the upper keel. The leaf cushion illustrated in spectively, of Old Ben Coal Corporation. The specimen was found Figure 2 is 38 mm long and 14 mm broad. The leaf scar is nearly 6 by Jones in the roof shale directly above the Beckley coal in the mm long and 1 mm broad. Raleigh-Wyoming Mining Company No. 2 Mine at Glen Rodgers, The leaves of Lepidodendron obovatum var. grandifolium are West Virginia. The Beckley coal occurs above the Fire Creek and very long, perhaps reaching a metre in length. The longest leaf was below the Little Raleigh coals. The stratigraphic position of the incomplete and measured 78.4 cm from the stem to the broken fossil described is from the lower part of the New River Formation edge of the specimen. The upper surface of the stem is devoid of in West Virginia. This is well below the Sewell coal, which formed attached foliage, but some attached foliage is preserved along the Wanless' (1939, PI. 9) basic line of correlation. The stratigraphic sides of the stem, as seen in Figure 1. The leaves are sessile, entire, position of the Beckley coal would be approximately in the and elongate-linear in shape. A single leaf is about 6 mm wide at Westphalian A in terms of European chronostratigraphy. the base, just above the point of attachment, and slightly less than 3 Jones provided me with notes relating to the location, appear- mm broad 76.2 cm from the basal attachment. The leaf apices are ance of the specimen in situ, and associated plants preserved in the assumed to be sharply pointed. same stratum. Some of these are important to the topic at hand, The leaves are preserved as extremely thin carbonaceous films or and I summarize them here. The stem of Lepidodendron obovatum as impressions on the dark shale matrix, as shown in Figure 3. Thin Sternberg var. grandifolium var. nov. in situ was 3.65 m long and sections and nitrocellulose transfers have failed to provide infor- ~ 15 cm wide at the base, tapering to 5 cm wide at the apical end. mation relative to the stomatal condition. However, some evidence The basal portion of the stem was intersected, at almost a right of the presence of two parallel rows of stomates, the normal condi- angle, by another stem of Lepidodendron which was ~46 cm in tion in arborescent lycopods, is suggested by the presence of two diameter. It was more than a year after the discovery of the speci- small raised ridges on some of the leaves, one one either side of the men before the roof shale loosened enough to allow its removal. mid-vein. These ridges, when they are present, appear represented The specimen was so heavy that it had to be trimmed in order to in both the shale impressions and on the carbonaceous films. They carry it to the nearest underground transportation for removal to are thought to represent the sunken stomatal furrows on the aba- the hoisting shaft. During the trimming process, a portion of one xial surface of the leaf. In some instances, these are filled with the side of the fossil was broken. The specimen as removed from the shale matrix. The leaves were compressed, by the weight of overly- mine was slightly more than 1 m in length (Fig. 1). ing sediments, to a very thin film less than the thickness of the sun-

Geological Society of America Bulletin, Part I, v. 90, p. 431-434, 5 figs., May 1979, Doc. no. 90505.

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ken stomatal furrows, which were filled with the shale matrix. The cushions of these two species can resemble each other, especially at shale in the stomatal furrows was compressed less than the leaves, certain growth stages. resulting in the raised ridges on either side of the mid-vein (Fig. 3). The general growth habit of Lepidodendron was discussed by It would appear that the foliage of Lepidodendron obovatum var. Arnold (1947). Large trees of Lepidodendron have been reported in grandiofolium had deeply sunken stomatal furrows somewhat simi- which the trunk attained a length of 35 m with an additional 6 to 7 lar to several types listed by Graham (1935). m for the crown of the tree. In typical specimens of Lepidodendron, the trunk branched, resulting in an unequal dichotomy, with the REMARKS larger of the two branches continuing on as the main axis. The smaller branch became a side branch, and the ultimate branches The foliage of Lepidodendron has in the past been thought to be bore awl-shaped leaves. relatively short, and the detached leaves of Lepidodendron, One could postulate that the specimen herein described repre- whether preserved as a petrification or a compression, were sents a young shoot prior to the dichotomy of the axis. The appear- classified under Lepidophyllum. Snigirevskaya (1958) reported that ance of Lepidodendron under such conditions would be similar to Lepidophyllum Brongniart was preoccupied and proposed that proposed by Phillips and others (1976, Fig. 5). Jones, the col- Lepidophylloides as a replacement. lector of the specimen, supplied information about the fossil as it The leaves of Lepidodendron obovatum var. grandifolium are appeared in situ. The possibility that the specimen was attached to comparable in size to those of Sigillaria lepidodendrifolia which a larger Lepidodendron stem, with which it intersected at about were 1 m in length (Fig. 5 here reproduced from Grand 'Eury, 90°, is discounted, because of the angle of attachment, and further 1877). Graham (1935. p. 607) stated, "There does not appear to be because it would occur relatively low on the stem it intersected. The any fundamental difference between the leaves of Sigillaria and evidence would support the idea that the specimen herein described those of Lepidodendron. All leaves with a double xylem strand are is an apical portion of a main axis prior to a dichotomy of the axis. attributed to Sigillaria, but this character is not constant for that Nemejc (1947, p. 52) in his discussion of L. obovatum reported, genus." It is apparent that certain identification of the detached "The leaves on younger or slender shoots are only 5 cm long and compressed foliage of Sigillariophyllum, the generic name applied straight; on older branches they are longer, till about 2.5 dm and it to detached foliage of Sigillaria, and Lepidophylloides, where the seems they were persistent." This information would appear to be structure of the xylem elements is unknown, is made less promising at variance with the idea presented by Phillips and others (1976) with the description of Lepidodendron obovatum var. grand- that the young leafy shoots of Lepidodendron displayed a growth ifolium. This is because it so closely parallels that of Sigillaria form similar to that of L. obovatum var. grandifolium. lepidodendrifolia in size. Kosanke (1948, p. 1333) gave a prelimi- It is a reasonable assumption that the specimen described in this nary report on the long-leaved Lepidodendron described in this report is a young axis prior to the first dichotomy, as illustrated by paper and called attention to the fact that these leaves were similar Phillips and others (1976, Fig. 5), but some doubt continues as to in size to those of Sigillaria lepidodendrifolia. whether it is conspecific with Lepidodendron obovatum. Because The leaf cushions of Lepidodendron obovatum var. grandifolium of the apparent differences, I have decided to treat this unusual have been compared with published descriptions of the species of specimen as a new variety. the genus and with available specimens at hand. These leaf cush- ions compare with some of the published illustrations of L. DIAGNOSIS aculeatum in size and shape, as they are about three times as long as their greatest width. They do not have the S-shape which Nemejc The type specimen of Lepidodendron obovatum var. grand- (1947, p. 52) considered characteristic of L. aculeatum. The posi- ifolium var. nov. is an unbranched stem 1.03 m long, bearing at- tion of the leaf scar as well as the shape resembles that of L. tached leaves. The stem is marked by closely spaced pyramidal leaf obovatum, a point called to my attention by the late Chester Ar- cushions 28 to 39 mm long, arranged in a high spiral. The small nold (1949, written commun.). It is obvious that some uncertainty ligule pit scar is located on the median line of the upper keel well exists in the differentiation of these two species. Nemejc (1947, above the leaf scar, which in outline is convex above and V-shaped p. 52) reported that the leaf scars of L. obovatum are "relatively below. The vascular scar tends to be somewhat concave with low and broad." This, Nemejc reported, was the primary difference elliptical-shaped parichni scars on either side of the vascular scar. between L. obovatum and L. aculeatum. It is obvious that the leaf The elongate aerating tissue scars are below the parichni scars on

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Figure 1. The type specimen of Lepidodendron obovatum mat. grandifolium var. nov., Illinois State Geological Survey Paleobotanical Collection number B-1817. Note the attached foliage and arrangement of the leaf cushions in a high spiral. Figure 2. Drawing of one leaf cushion shown about twice natural size. (A) The median line of the upper keel; (B) the small ligule pit scar; (C) the leaf scar; (D) a parichnos scar; (E) the vascular scar; (F) aerating tissue scar; (G) transverse wrinkles on the lower keel; (H) median line of the lower keel. Figure 3. Leaves with parallel ridges on either side of the mid-vein, suggesting the presence of sunken stomatal furrows. This photo- graph is shown at approximately natural size. Figure 4. Leaf cushions showing spiral arrangement and position of the leaf scar. This photograph shows the leaf cushions at about Xl.3. Figure 5. Copy of a portion of a plate from Grand'Eury (1877), representing (A) Sigillaria lepidodendrifolia in the center, (B) S. elegans to the left, and (C) S. brardii to the right.

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the lower keel. Transverse wrinkles are present on the median line Graham, Roy, 1935, An ana tomical study of the leaves of the Carbonifer- of the lower keel. The leaves are known to be at least 78.4 cm long. ous arborescent lycopods: Annals Botany, v. 49, p. 587—608. Grand'Eury, C., 1877, Mémoire sur la Flore Carbonifère du Départment de They are entire and elongate-linear in shape, with evidence of two la Loire et du Centre de La France: Paris, Mémoirs a l'Académie des deeply sunken furrows. Sciences de l'Institut National de France, v. 24, no. 1, p. 156. Kosanke, Robert M., 1948, Unusual specimen of Lepidodendron [abs.]: ACKNOWLEDGMENTS Geological Society of America Bulletin, v. 59, no. 12, pt. 2, p. 1333. Nemejc, F., 1947, The Lepidodendraceae of the coaldistricts of Central Bohemia: Sbornîk Nârodniho Musea v Praze, v. III. B, no. 2, p. 45- I am most grateful to D. W. Buchanan and John E. Jones of Old 87. Ben Coal Corporation for the collection and gift of the specimen to Phillips, Tom L., Avcin, Matthew J., and Berggren, Dwain, 1976, Fossil the Illinois State Geological Survey. Appreciation is extended to peat of the Illinois Basin, A guide to the study of coal balls of Pennsyl- Henry N. Andrews, Jr., Hermann W. Pfefferkorn, and Survey col- vanian age: Illinois Geological Survey Educational Series 11, 31 p. Snigirevskaya, Natalie S., 1958, An anatomical study of the leaves (phyl- leagues who reviewed the manuscript or offered suggestions. loids) of some lycopsids in the Donets basin coal balls: Academy of Lastly, I am indebted to Chester A. Arnold and James M. Schopf, Scicnes USSR, Botany Journal, v. 43, no. 1, p. 106-112. both of whom are now deceased, for their suggestions and encour- Wanless, Harold R., 1939, Pennsylvanian correlations in the Eastern In- agement. terior and Appalachian coal fields: Geological Society of America Special Paper 17, 130 p. REFERENCES CITED MANUSCRIPT RECEIVED BY THE SOCIETY SEPTEMBER 29, 1978 Arnold, Chester A., 1947, An introduction to paleobotany: New York and REVISED MANUSCRIPT RECEIVED DECEMBER 18, 1978 London, McGraw-Hill Book Co., Inc., 433 p. MANUSCRIPT ACCEPTED DECEMBER 28, 1978

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