An unexpected exposure: Pleuromeia
One of the stranger items in the annals of fossil plant discoveries is that of the Triassic lycopod, Pleuromeia. During the repair of Magdeburg Cathedral in the 1830s, a block of Bunter Sandstone (Lower Triassic) fell down onto the pavement, and split open. A short section of the stem of Pleuromeia sternbergi was revealed, and was later described by Count George Munster (Beitragen zur Petrefacten-Kunde, 1839). He, incidentally, described it, very reasonably, as a species of Sigillaria, and it was Corda who later made it the basis of a new genus, Pleuromeia. (Corda actually spelt it Pleuromeya). It was later realised that the sandstone had come from a quarry near Bernburg (Saale) where subsequently, numerous specimens of Pleuromeia, including fertile material, were found. Pleuromeia has since been described from other Middle and Lower Bunter exposures elsewhere in Germany, France and Spain. Similar species have been reported from the Trias of Russia from several localities, including Vladivostok and Rubinsk, and from Australia, South America and Japan. Among other interesting features of the genus, which link it with Isoetes, is the fact of its having trilete megaspores and monolete microspores.
For a good account of Pleuromeia (in English) see Taylor and Taylor (1993) 'Biology and Evolution of Fossil Plants' (Published by Prentice Hall), where they illustrate material of that genus from Russia, China and Australia, and explain the significance of the genus in both its structure and age, considering it to be intermediate between the Carboniferous arborescent lycopods and the living genus Isoetes.
Pleuromeia - Image by Ronny RoesslerThe best (and only !) account of the original discovery that is readily accessible (and the source of our note) is in Karl Magdefrau's Palaobiologie der Pflanzen, Chapter 10, Die Pflanzenwelt des deutschen Buntsandsteins (Published by Fischer Verlag, 4th. ed.
There are a number of interesting sides to this story. Perhaps the most important for all of us is to look out for fossil plants occurring in building stones - not only those falling off cathedrals, but in many other settings!
Bill Chaloner & Geoff Creber Royal Holloway, University of London.
Images provided by Ronny Roessler