Preservation of the digestive structures in Harpides (Trilobita) from the Lower Ordovician of the Barrandian area (Czech Republic)

摘要

Remains of the digestive system are described in the holotype of the rare harpidid trilobite Harpides grimmi Barrande, 1852 collected from the Lower Ordovician Mílina Formation of the Prague Basin. The intestine (post-stomach alimentary canal) starts just behind the glabellar posterior margin and extends through the narrow axial region in all nineteen thoracic segments of this exceptionally preserved specimen. The anterior-most part of the digestive system is masked by the in situ hypostome preserved under the missing glabella. Similarly, also the posterior-most part of the post-stomach alimentary canal is absent, as the pygidium is not preserved. This specimen constitutes the first example of preserved digestive structures in the family Harpididae. Earlier finds of digestive system in Ordovician trilobites are briefly assessed.