Lotagnostus is a genus of very small trilobites in the order Agnostida, which lived on the outer continental shelves worldwide, during the late Upper Cambrian.

[3] The first appearance datum (FAD) of Lotagnostus americanus has been proposed to define the lower limit of Cambrian Stage 10.

[4] This proposition is based on the interpretation that L. americanus is a polymorph species with a global distribution, a concept that included L. obscurus, and Agnostus trisectus, the type of Lotagnostus.

[3] Lotagnostus is also present in Siberia (Ogon'or Formation along the Khos-Negele River), but its assignment to a particular species is difficult.

Like all Agnostida, Lotagnostus is diminutive, with the headshield (or cephalon) and tailshield (or pygidium) of approximately the same size (or isopygous) and outline.

The surrounding axial furrow is directed outward, then strongly bends backward and then curves regularly ever more inward.