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Contributions to Our Knowledge of American Carboniferous Floras. VII. Some Pteridosperm Stems from Iowa

1945; Missouri Botanical Garden; Volume: 32; Issue: 3 Linguagem: Inglês

10.2307/2394379

2162-4372

Henry N. Andrews,

Plant and animal studies

The occurrence of richly fossiliferous coal balls in the Upper Pennsylvanian rocks of Iowa has been reported by Darrah in 1939 and 1941.In the latter paper he gives a list of the species observed as well as a brief discussion of the dominant floral elements.The distribution and occasional abundance of these petrifactions in Iowa is now sufficiently well known so as to render a detailed review unnecessary, but certain introductory remarks are in order relative to the general floristics, as compared with the Illinois coal balls.In September, 1944, Mr. Frederick O. Thompson of Des Moines very generously turned over to the writer, for study and preservation in the Henry Shaw School of Botany, a selected portion of his remaining coal-ball specimens.All of this material was collected from the highly prolific, although now abandoned, Urbandale mine located on the north side of U. S. Highway No. 6, 1.2 miles west of the city limits (63rd Street) of Des Moines.The coal seam from which the petrifactions were obtained lies 185 feet below the surface, the elevation of the latter being 805 feet.It is regretted that a more precise stratigraphical position, other than "the Des Moines Series," cannot be given at this time.The author has been informed that a detailed study of the stratigraphy of this region will be published shortly, and it is hoped that this information may be given in the next number of our "Contributions" which will deal with seeds from the Urbandale coal balls.Our collection consists of approximately 110 cut slabs which vary from 3 to 20 cm. in diameter.It is admittedly small as coal ball collections are accounted, yet rich in the number of seeds, leaves, pteridosperm stems, fertile fern-like foliage, and other plant parts, many of which are either striking novelties or very imperfectly known.During the three years prior to the war the paleobotanical work in this laboratory was devoted very largely to a study of fossil plants from certain southern Illinois mines. 1 Although the progress made in that region constitutes but little more than a bare introduction to the field work lying ahead, it does seem clear that the Carboniferous flora that occupied much of southern Illinois was dominantly pteridophytic.Certainly the Herrin coal from the great Pyramid strip mine south of Pinckneyville was formed to a very considerable extent from the remains of Lcpidodcndron (Pannell, '42), and the roof shales above the same coal in the 1 See parts I-VI of this "Contributions" series, in Ann.