>>57696340>>57696363Anorith/Armaldo are probably the oldest fossilmons, as they're based on Anomalocaris specifically, which is from the Cambrian period ~500 mya.
Kabuto/Kabutops appear to be a mix of trilobite and horseshoe crab. Trilobites lived from the Cambrian to the Permian, but horseshoe crabs are still around.
Omanyte/Omastar are based on Ammonites which I would associate more with the Mesozoic, and I'm not sure what specific organism Lileep/Cradily are based on.