Below, you see a list with possible ichnogenera for an unlined (sub)horizontal, unbranched burrow with a cylindrical cross section or a ridge-like appearance and active filling. Click on them to get detailed descriptions of the ichnogenus and a list of its ichnospecies. (Please allow for pop-up windows):

• Alcyonidiopsis (Usually unbranched, but may be branched)
• Arthrophycus (Usually branched, but may be unbranched)
• Bichordites
• Bolonia
• Climactichnites (May also occur as surface trace (track, trail, impression, etc.; ichnogenus includes ornamented ichnospecies)
• Edaphichnium
• Entradichnus (Taxonomical status unclear, use not recommended)
• Fucusopsis (Usually unbranched, but may be branched; ichnogenus includes ornamented ichnospecies; taxonomical status unclear, use not recommended)
• Halopoa  (Usually unbranched, but may be branched; ichnogenus includes ornamented ichnospecies)
• Microspherichnus
• Naktodemasis
• Parataenidium
• Planolites (Usually unbranched, but may be branched)
• Scalarituba (Taxonomical status unclear, use not recommended)
• Scolecocoprus
• Scolicia
• Taenidium