Ptychagnostidae
| Ptychagnostidae Temporal range:  | |
|---|---|
| Ptychagnostus gibbus | |
| Ptychagnostus cuyanus | |
| Scientific classification | |
| Domain: | Eukaryota | 
| Kingdom: | Animalia | 
| Phylum: | Arthropoda | 
| Class: | †Trilobita (?) | 
| Order: | †Agnostida | 
| Suborder: | †Agnostina | 
| Superfamily: | †Agnostoidea | 
| Family: | †Ptychagnostidae Kobayashi, 1939 | 
| Type genus | |
| Ptychagnostus Jaekel, 1909 | |
| Genera | |
| 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). The family includes several important index fossils.