Nope, Omanyte/Omastar are based on Allonautili.
Allonautili are extremely different from Nautili.
Allonautili are extinct (hence one of the biggest reasons Omanyte/Omastar is based off of them) and considered to be the predecessor to Nautili, however over time (through microevolution) Nautili have acquired many morphological differences. The biggest one being the chambered shell.
Allonautili are extremely different from Nautili.
Allonautili are extinct (hence one of the biggest reasons Omanyte/Omastar is based off of them) and considered to be the predecessor to Nautili, however over time (through microevolution) Nautili have acquired many morphological differences. The biggest one being the chambered shell.