See text Ptychagnostidae is a family of agnostid trilobites from the 5th Stage to the Paibian Age of the Cambrian (506.5 to 497 million years ago).

Like all agnostids, ptychagnostids have cephalons and pygidia that are more or less uniform in size and shape (isopygous).

[1] The earliest member of the family is Ptychagnostus praecurrens from the Burgess Shale fauna.

[3] Ptychagnostidae is classified under the superfamily Agnostoidea of the suborder Agnostina, order Agnostida.

The family was first established by the Japanese paleontologist Teiichi Kobayashi in 1939.