Todd and Palmer (2002) have commented on their perceived distinction between those “small round holes in shells” Oichnus Bromley 1981, and Tremichnus Brett 1985. They took particular issue with the recent paper of Nielsen and Nielsen (2001), who made brief comments on the similarities of these borings and considered them synonymous. In so doing they were following the more detailed comparison of these ichnogenera by Pickerill and Donovan (1998), and with whose nomenclatural philosophy and recommendations they apparently disagreed. In discussing Nielsen and Nielsen (2001), Todd and Palmer (2002) failed to fully review the reasons for synonymizing these ichnotaxa, as discussed at more length by Pickerill and Donovan (1998). We therefore take this opportunity to outline the ichnotaxonomic philosophy upon which this decision was based as a preamble to replying to Todd and Palmer’s (2002) assessment of the validity of Oichnus and Tremichnus.