O. crassicornis was first described from the Ionian island of Lefkada, as a form of O. cornuta by Renz in 1928 and promoted to full species status in 2004 by Devillers and Devillers-Terschuren. Its name means "thick horned" and is a reference to the well developed protuberences of the species.
It's a member of the large O. oestrifera group which has been the recipient of much study and attention over the last two decades but none of which has satisfactorily clarified significant taxonomic questions, particularly as they relate to the group in the eastern Mediterranean. The distribution and very existence of O. crassicornis has been called into question over recent years. The description that follows reflects one of the views, that it is a valid species with a range encompassing the southern Ionian islands and adjacent areas of the Greek mainland and northern Peloponnese.
Distinguishing this species from O. cerastes is a job for the experts and in the absence of pollinator identification the plants depicted here have been selected with reference to the parameters of their known distribution. The photographs all come from the island of Cephalonia where only O. stavri and O. cephaloniensis present challenges to identification though both are extremely rare and relatively easy to differentiate. It is worth mentioning however that O. crassicornis grows alongside both these taxons in some sites. O, crassicornis exhibits a slightly larger flower than any of the previously mentioned species and is also a more robust plant with a basal rosette of silvery green leaves.
The pictures date from the first week of April.
