A new species of Thecotheus from Croatia with a key to the known species with apiculate spores

During systematic research on fimicolous fungi in the Sjeverni Velebit National Park, a new species was revealed. It is described here as Thecotheus platyapiculatus. Taxonomic characters are studied in detail on both living and dead material. Ascospore germination was tested on dung agar and dung oatmeal agar. The most important differential characters of the new species related to apiculi, spore symmetry and ascal strangulation are discussed and compared to the most similar T. keithii. Semi-resistant vacuolar bodies are described as new type of cell inclusions. Guidelines to the standardised procedure of treating Thecotheus collections in order to efficiently characterise and differentiate the species are recommended. The ecology of T. platyapiculatus as well as the importance of traditional way of stock breeding for preserving the fimicolous species is discussed. A worldwide identification key to the apiculate species in the genus Thecotheus is provided. A list of 19 additional fimicolous species found on the horse dung during this study is also given. All ascomycetous species but Peziza vesiculosa are reported as new to Croatian mycobiota.