Cambrian molluscs of North America

Yochelcionella is an extinct genus of basal molluscs which lived during the Tommotian epoch, the first epoch of the Cambrian period. This genus is often reconstructed to resemble snails.

Plectronoceras is the earliest known shelled cephalopod, dating to the Late Cambrian. None of the fossils are complete, and none show the apex or aperture of the shell. Approximately half of its shell was filled with septa; 7 were recorded in a shell. Its shell contains transverse septa separated by about half a millimetre, with a siphuncle on its concave side. Its morphology matches closely to that hypothesised for the last common ancestor of all cephalopods.