An example of 'deep' tier level Teichichnus with vertical entrance shafts, from the Carboniferous of Ireland

The occurrence of vertical entrance shafts linked to Teichichnus, of up to 360 mm depth, are noted from the Lower Carboniferous of northwest Ireland. Examination of the spreite bearing part of these burrow systems indicates that T. rectus Seilacher 1955 and T. ovillus Legg 1985 form part of a morphological continuum, in which T. ovillus is considered a junior subjective synonym of T. rectus. The vertical entrances to the Teichichnus burrows appear similar to large Skolithos, and can be mistaken as such where exposure is poor, which indicates the need for detailed field observations if misleading taxonomic, ethological, or environmental interpretations are to be avoided. The latter problem may be particularly exasperated when working with the restricted surface areas associated with cores. In contrast to their Lower Paleozoic precursors, which occurred within shallow level tiers, these Carboniferous Teichichnus were positioned within a 'deep' level tier.