|Basic info||Taxonomic history||Classification||Relationships|
|Morphology||Ecology and taphonomy||Age range and collections|
Trilobita - Agnostida - Ptychagnostidae
It was reranked as Acidusus by Sepkoski (2002) and Weidner and Nielsen (2014).
It was assigned to Ptychagnostus by Opik (1979); to Agnostida by Sepkoski (2002); and to Ptychagnostidae by Weidner and Nielsen (2014).
If no rank is listed, the taxon is considered an unranked clade in modern classifications. Ranks may be repeated or presented in the wrong order because authors working on different parts of the classification may disagree about how to rank taxa.