Fossilised guts in trilobites from the Upper Ordovician Letná Formation (Prague Basin, Czech Republic)
Abstract
The preservation of digestive structures of trilobites is extremely rare. Here we describe two new examples of trilobites from the Upper Ordovician Letná Formation (Prague Basin, Czech Republic), which display remains of the digestive system.
The first specimen, assigned to Selenopeltis buchi (Barrande, 1846), exhibits cavities under the posterior part of the glabella and the axis of most thoracic segments. These cavities are interpreted as remains of metamerically paired digestive caeca and constitute the first example of preserved digestive structures in the order Odontopleurida.
The second specimen belongs to Birmanites ingens (Barrande, 1852) and displays a tube-like structure, filled with a finely-grained material, that runs under the axial lobe of the entire trunk. We interpret this structure as a gut infilling similar to that repeatedly observed in the Moroccan Basilicus calzadai.
These specimens confirm that the depositional environment of the Letná Formation was locally favourable to soft-tissue preservation. They also further document the presence of two different types of digestive systems in trilobites.
The possibility that different processes might have been involved in the preservation of different parts of the trilobite gut is discussed, and several criteria to differentiate genuine gut remains from scavenger burrows are proposed.