Late Cretaceous nautilid juveniles of Cymatoceras reussi and Eutrephoceras aff. sublaevigatum – scarce fossils under risk of pyrite degradation
Frank Jiří, Sklenář Jan, Ekrt Boris
The syntype collection of “Nautilus reussi” has been subject to a detailed revision resulting in confirmation of at least provisional validity of the species represented by a single juvenile specimen. This species, restricted now to the Late Coniacian, is inserted into the genus Cymatoceras Hyatt, 1884. The rest of the collection differs from the original description and is left separately as Eutrephoceras aff. sublaevigatum, being considered juveniles of the species. The lithology, geographic and stratigraphic position of the type locality of Cymatoceras reussi (FRITSCH IN FRITSCH ET SCHLÖNBACH, 1872) as well as the other sites are discussed here. The valuable material is endangered due to pyrite degradation as relics of this unstable sulphide are still at present hidden in the secondary limonitic material. The degradation products cause volumetric expansion resulting in formation of crevices and loss of integrity. Some of them are corrosive and destroy labels and other attached documentation. Discussion of procedures which could be employed to prevent this valuable material from being lost are one of the objectives of the present study.