Digestive structures in Middle Ordovician trilobite Prionocheilus Rouault 1847, from the Barrandian area of Czech Republic.

Remains of a digestive system from a slightly damaged articulated specimen of the comparatively rare bathycheilid trilobite Prionocheilus vokovicensis (Snajdr, 1956) are described for the first time. The specimen comes from the Middle Ordovician Sarka Formation of the Prague Basin and contains the midgut region of the digestive system preserved through the axial region of glabella and six anterior thoracic segments. The anterior-most part of the digestive system is unknown as the anterior glabellar lobes are not preserved in the studied specimen. In the cephalic shield, the remains of two pairs of gut diverticulae are seen in the posterior region of the glabella. Remains of five pairs of small cavities developed in the axis of the first six thoracic segments represent the remains of thoracic gut diverticulae. The discussed specimen possess the first undoubted remain of digestive structures established within the family Bathycheilidae (PŘibyl, 1953).