Heimdallia from the Lower Carboniferous of Ireland: H. mullaghmori a new ichnospecies, and re‐evaluation of the three‐dimensional format of the ichnogenus

Heimdallia is recorded for the first time from the Carboniferous, and the new ichnospecies Heimdallia mullaghmori is erected for material from the Lower Carboniferous of northwest Ireland. The latter ichnospecies is the first recorded branched representative of Heimdallia. Examination of well‐exposed examples of H. mullaghmori indicates the need to emend the diagnosis of Heimdallia, 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. mullaghmori resembles Phycodes circinatus, as well as Teichichnus, 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. mullaghmori is 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 of Heimdallia (H. chatwini and H. mullaghmori) can now be extended from the Lower Ordovician to Lower Carboniferous.