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Dear all, It was difficult, very difficult to wait with posting, since I am very, very excited about this fossil find. However, I also wanted the Dutch magazine version to come out first. Well, it finally did this Tuesday, so here is some info in English, along with a couple of the figures. During a visit to the Piesberg near Osnabrück (Germany) in 2010, I found a stem fragment of Calamites decorated with strange, elongate-oval structures [Fig. 1]. While those features were unusual and quite remarkable, it proved difficult to find information about them and the fossil consequently went into my collection as unidentified. Last January, however, I stumbled upon a research paper that could shed light on the matter. The elongate-oval structures turn out to be one of the oldest-known examples of endophytic oviposition, i.e. egg-laying inside plant tissue, by insects. Fig. 1. The fossil specimen is atypical in several respects [Fig. 2]. The stem fragment doesn’t show the longitudinal ribs one usually sees on the internodes of Calamites. This is because we are looking at a preservation of the epidermis (outer layer of the stem), not at a cast of the central pith, which are more commonly found. Fossils of the epidermis (sometimes referred to as Calamophyllites) typically have internodes with a smooth surface (though it may be lightly striated or wrinkled), leaving few diagnostic features. Nonetheless, due to the presence of a characteristic nodal line with large, circular branch-scars [Fig. 2, shown on schematic in green], the fossil fragment can be identified as Calamites (subgenus Calamitina) with reasonable confidence. Below the nodal line with branch-scars, about eight elongate-oval structures can be observed [Fig. 1]. They are all orientated roughly parallel to the axis of the calamite stem and vary in length from 6 to 16 mm. A foreign nature with respect to the plant tissue is suggested by the gümbelite film in which the epidermis is preserved (gümbelite is a hydromuscovite and responsible for the well-known silver-grey colour of the fossils from the Piesberg). Note how this thin film of mineralization does not extend across several of the elongate-oval structures, which may indicate that the plant tissue there is either missing or damaged. Their exact origin, however, remained a mystery to me. Until recently. Fig. 2. While looking for information on some Carboniferous localities in France, I happened upon the research article ‘Earliest Evidence of Insect Endophytic Oviposition’ by Olivier Béthoux et al. (2004). The paper describes insect egg-laying structures, called oviposition-scars, found on two stem fragments of Calamites cistii from the Upper Carboniferous (Stephanian B/C) of Graissessac, Southern France. These scars are elongate-oval structures, orientated parallel to the axis of the stem, occurring on a preservation of calamite epidermis [see their Figures 1 and 2]. Careful preparation of three of these scars yielded small spherical cavities, which the researchers interpreted as imprints of the eggs themselves [see their Figure 2b]. The oviposition-scars from Graissessac vary in length from 5 to 38 mm and are surrounded by a thin film of organic material [see their Figure 2c]. Given the strong resemblance with the Piesberg-material, it didn’t take long to make the link with the mystery markings I found years earlier. Now, after confirmation by email from Olivier Béthoux and in person from Han van Konijnenburg-van Cittert, I can with reasonable certainty say that some sort of Carboniferous insect has laid its eggs in the calamite stem I found in the Piesberg quarry. This type of trace fossils is quite rare, so I am very happy I brought this one home. As a nice bonus this specimen comes from the Westphalian D, and is thus somewhat older (about 4 million years) than the published material from Graissessac (Stephanian BC), which is still cited as the oldest occurrence in recent literature. So you can really say this specimen from the Piesberg is one of the oldest examples around! Hope this was as fun and informative as this fossil has been for me, Tim