Kikushi, a collective term for cephalopods and ammonites in the phylum Mollusca, is a group of extinct marine organisms. Kikushi lived from the early Devonian to the late Cretaceous period, and its shell is often preserved in the form of fossils in the strata. The outer shell of ammonite is a single petal, consisting of three parts: the fetal shell, the gas shell, and the living room. It usually spirals around the fetal shell along a plane, with each revolution forming a spiral ring. Adult ammonite shells generally have 5 to 9 spiral rings, symmetrical on both sides, and can be straight, curved, or even irregular.

Kikushi, a collective term for cephalopods and ammonites in the phylum Mollusca, is a group of extinct marine organisms. Kikushi lived from the early Devonian to the late Cretaceous period, and its shell is often preserved in the form of fossils in the strata. The outer shell of ammonite is a single petal, consisting of three parts: the fetal shell, the gas shell, and the living room. It usually spirals around the fetal shell along a plane, with each revolution forming a spiral ring. Adult ammonite shells generally have 5 to 9 spiral rings, symmetrical on both sides, and can be straight, curved, or even irregular.

It is an ancient marine mollusk belonging to the order Nautilus in the cephalopod class. Known for its spiral shaped shell, which is not only beautiful but also has a unique structure, it is a miracle in nature. The shell is composed of multiple chambers, each connected by a structure called a "partition". By adjusting the gas and water inside the chamber to control buoyancy, one can freely swim in the ocean. They mainly live in tropical and subtropical coral reef areas and are nocturnal animals. They usually hide under the sand or rocks on the seabed during the day and come out to forage at night. Food mainly includes small fish, crustaceans, and other small marine organisms.

Nautilus is a general term for marine mollusks in the family Nautidae, belonging to the order Cephalopoda. There are 2 genera and 6 species, with curled pearl like shells that can grow up to 26 centimeters in size, but adult parrots generally do not exceed 20 centimeters. Usually only 16 centimeters. The shell is composed of many chambers, and the outer shell is located inside the shell. There is a diaphragm separating each chamber; Two pairs of gills; 63-94 wrists, but without suction cups. The shell is thin and light, coiled in a spiral shape, with a white or milky white surface. The growth lines radiate from the navel of the shell, smooth and fine, mostly reddish brown in color. The entire spiral shell is smooth like a disc, resembling a parrot's beak, hence the name "Nautilus".

Nautiloidea: A general term for marine mollusks in the family Nautilidae, belonging to the order Cephalopoda. There are 2 genera and 6 species with curled pearl like shells. The parrot snail has undergone hundreds of millions of years of evolution on Earth, but its appearance, habits, and other changes are minimal. It is known as a "living fossil" in the ocean and has high value in studying biological evolution and paleontology. It also holds a place in biomimetic science. In 1954, the United States developed the world's first nuclear submarine, the Nautilus, which was launched in Groton, USA.