Heimdalliais recorded for the first time from the Carboniferous, and the new ichnospeciesHeimdallia mullaghmoriis erected for material from the Lower Carboniferous of northwest Ireland. The latter ichnospecies is the first recorded branched representative ofHeimdallia.Examination of well‐exposed examples ofH. mullaghmoriindicates the need to emend the diagnosis ofHeimdallia, to allow for the concept of a horizontal basal tube, overlain by a vertical spreite‐like structure comprising inclined sediment packets, with the latter marking the former positions of upwardly inclined sections of distal tube.H. mullaghmoriresemblesPhycodes circinatus, as well asTeichichnus, but can nevertheless be distinguished on the basis of the discordant relationship between the inclined packets of sediment, that form the ‘spreite’, and its basal tube.H. mullaghmoriis at present only recorded from the Mullaghmore Sandstone Formation, within shallow‐water deltaic siliciclastic facies, where it occurs in parallel‐laminated and hummocky cross‐stratified sandstones; representing tempestite and storm reworked facies. The range ofHeimdallia (H. chatwiniandH. mullaghmori)can now be extended from the Lower Ordovician to Lower Carboniferous.