LITOSTROMA, A NEW GENUS OF PROBLEMATICAL ALGAE FROM THE PENNSYLVANIAN OF OKLAHOMA

MAMAY, SERGIUS H. (U. S. Geological Survey, Washington, D. C.) Litostroma, a new genus of problematical algae from the Pennsylvanian of Oklahoma. Amer. Jour. Bot. 46(4): 283-292. Illus. 1959.-Litostroma oklahomense, gen. et sp. nov. is described on the basis of fossil plant material found in a Pennsylvanian marine limestone from the vicinity of McAlester, Oklahoma. Litostroma is a simple plant consisting of a small, irregularly shaped thallus 1 cell thick. Some thalli have small perforations and filament-like marginal outgrowths. The reproductive organs are not known. A marine fauna is intimately associated with Litostroma, and includes epiphytic Foraminifera preserved in actual growth positions on surfaces of the plants. The evidence indicates a marine habitat for Litostroma and, accordingly, algal affinity. Without information bearing on its reproductive organs or pigmentation, however, Litostroma cannot with assurance be assigned to any known group of algae. It possibly represents a group of green, brown, or even red algae. AN INVESTIGATION of marine faunas associated with land plants in American coal balls led to examination of samples of a fossiliferous marine limestone associated with coal balls from Oklahoma. The limestone contained some curious thallose plant remains, the unusual structure and excellent preservation of which warrant detailed description and an attempt at interpretation. The material was collected in 1939 by C. B. Read, U. S. Geological Survey, at a slope mine owned by Joseph Lemont, near McAlester, Oklahoma. The productive seam, the Secor coal, lies in the Boggy shale of lower Des Moines age (Hendricks, 1937). Hendricks mentions no limestone above the Secor coal, but during my visit to the locality in 1955 Mr. Lemont informed me that the limestone overlay the coal directly, at the site of the coal ball occurrence. The limestone was likely of very local development. The exposure has since been filled and is no longer accessible. MATERIAL AND TECHNIQUES.-The plants were richly concentrated in an ovoid chunk of nodular limestone, 8 cm. in greatest dimension; they also occurred sparingly in a few other nodules in the collection. Since it was evident that the thalli contained in the several nodules were identical, only the contents of the richest specimen (U.S.G.S. 8764-9) were investigated in detail. Saw cuts of the nodule revealed a diverse assemblage of marine animal remains associated with the plant material. Most of the rock matrix is dark 1Received for publication September 18, 1958. Publication authorized by the Director, U.S. Geological Survey. I wish to express my appreciation to Dr. W. C. Steere, New York Botanical Garden, and to Dr. Rufus H. Thompson, University of Kansas, for their interest and advice in this investigation. Thanks are also due to Mr. L. G. Henbest, U.S. Geological Survey, for the photographs shown as fig. 29-31 and his paleozoological and paleoecological contribution to this paper, and to Mr. N. W. Shupe, U.S. Geological Survey, for the remainder of the photographic illustrations. brown, but there also are roughly cylindrical, intertwined areas of light gray color. The distinct color and sharp contacts of these light areas with the surrounding matrix suggest that they are filled animal burrows, made while the limestone was still a calcareous mud. A faint lamination of the dark part of the matrix is visible on smoothed surfaces, roughly parallel to the plane defined by the long axes of the nodule. This is due to a concentration of small, bedded plant thalli. In section, the plants appear as numerous chainlike groups of cells (fig. 3, 4), the chains lying parallel to each other. In places, groups of several are bent and contorted (fig. 1) but they are mostly flat and parallel, imparting the laminated appearance to the matrix. Etching the rock surface with weak formic acid showed the plants to be well preserved and undistorted by compaction; it also showed that they were not actually simple cellular chains 'but small, flat platelets a single cell thick. Sectional views showed no diagnostic features, so a chip of the rock was broken off and slowly dissolved in weak formic acid with the hope of isolating specimens whose surface features could be observed. The resultant sludge contained literally hundreds of fragmentary thalli. The process was repeated with additional samples. Tap water was then added to the sludge and decanted after settling of the organic matter; this was repeated until all acid had been removed, and all specimens except those selected for permanent mounts were placed in 30% ethyl alcohol for storage. Attempts to dry specimens were unsuccessful, as the cell walls collapsed with desiccation. This rendered the preparation of permanent mounts difficult, and the delicacy of the thalli necessitated caution in both chemical and mechanical treatment. The following technique produced excellent results. The aqueous residue was scanned in a dish under a binocular microscope. When a suitable specimen