Tommotiids are Cambrian (Terreneuvian) shelly fossils of uncertain affinity.

Unlike most of the small shelly fauna, tommotiids are mineralised with calcium phosphate rather than calcium carbonate. Tommotiids have a wide range of sclerite shapes and internal structures, and may in fact represent a polyphyletic set of lineages, having independently developed phosphatic scleritomes rather than inheriting them from a common ancestor. Others consider them to be a sister group to the brachiopods. Indeed, Micrina and Paterimitra possess bivalved shells in their larval phases, which preserve characters that would position them in the Linguliformea and Rhynchonelliformea stem lineages respectively. This would indicate that the brachiopod shell represents the retention of a larval character.