What is the Difference Between Ammonite and Nautilus?

Ammonites and nautiluses are both marine mollusks with spiral shells, but they belong to different subclasses of the class Cephalopoda and have several differences. Key differences between ammonites and nautiluses include:

1. Extinction: Ammonites are extinct marine mollusks, while nautiluses are extant marine mollusks.
2. Chambers: Ammonites had 26 chambers, while modern nautiluses have 30. The sutures (walls separating the chambers) in ammonites undulate, giving the shell a "ribbed" appearance, while the sutures in nautiluses are uniformly curved.
3. Siphuncle: The siphuncle (a tube that runs along the shell) is positioned differently in ammonites and nautiluses. In ammonites, the siphuncle runs along the outer edge of the shell, while in nautiluses, it runs along the inner edge.
4. Septa: Nautiluses have simple septa (partitions within the shell chambers), while ammonites have complex septa.
5. Defense: Ammonites had the ability to suck their bodies into their shells for protection and used a flap called the aptychus to close the head of their shells. Nautiluses cannot retract into their shells and use a leathery hood atop their heads for protection.
6. Camouflage: Modern nautiluses use dark colors atop their shells and light colors on the bottom for camouflage, but the colors of ammonites are unknown since they only exist as fossils.

These differences highlight the distinct evolutionary paths and characteristics of ammonites and nautiluses, despite their similarities in appearance.

Comparative Table: Ammonite vs Nautilus

Ammonites and nautiluses are both marine mollusks with spiral chambered shells, but they have some differences in their anatomy and evolutionary history. Here is a table summarizing the differences between ammonites and nautiluses:

Ammonites are extinct marine mollusks and predecessors of nautiluses, with a different number of chambers, suture patterns, and defensive behaviors. Nautiluses are living marine mollusks with a smooth shell appearance, simple septa, and the ability to retract into their shells for protection.