Ptychagnostus
Ptychagnostus is a genus of trilobites in the order Agnostida that lived during the Cambrian period. Their remains are rarely found in empty tubes of the polychaete worm Selkirkia. The genus probably ranged throughout the water column. It has two glabellar lobes, and three pygidial lobes.
Type species
Agnostus punctuosus Angelin, 1851 from the Ptychagnostus punctuosus zone of the Alum Shale, Sweden. Official ruling on the conservation of accepted usage of A. punctuosus as the type species was given by the International Commission on Zoological Nomenclature, 1993.Remarks
Ptychagnostus affinis was once considered a subspecies of Ptychagnostus punctuosus.Laurie grouped punctuosus and affinis within Ptychagnostus, but preferred to place the closely related atavus within Acidusus.Species
- Ptychagnostus punctuosus.
- Ptychagnostus affinis
- Ptychagnostus aculeatus
- Ptychagnostus akanthodes
- Ptychagnostus atavus
- Ptychagnostus cassis
- Ptychagnostus ciceroides
- Ptychagnostus cuyanus
- Ptychagnostus germanus
- Ptychagnostus gibbus
- Ptychagnostus hybridus
- Ptychagnostus intermedius
- Ptychagnostus michaeli
- Ptychagnostus praecurrens
- ''Ptychagnostus seminula''