and see text for species [1] Pentagnostus is a genus of trilobites restricted to the Middle Cambrian.

Its remains have been found in Siberia, Australia, North America, Scandinavia, and Kazakhstan.

[1] The probable ancestor of Pentagnostus is Archaeagnostus.

Two subgenera can be distinguished.

The nominate subgenus occurred first and developed into the later subgenus Pentagnostus (Meragnostus) and the family Ptychagnostidae.