The sea turtle is found in some medieval encyclopedias. It is said to have a mouth that is stronger than that of any other animal, able to break stones and crush sticks. While it lives in the ocean, it sometimes comes out onto land to eat grass. It cannot stay out of water long because the sun will dry out its flesh.

The sea turtle was also called the "sea soldier" (zityron) because its shell resembles the armor of a medieval soldier. Some sources include both the sea turtle and the sea soldier, usually with similar descriptions.

Both the sea-turtle and the tortoise are called tortuca.

The shells of the sea-turtles of the Indian sea are large enough for people to make shelters out of them, and to use them for boats to sail the Red Sea.

These elements suggest that the zytiron could have some relationship with a sea turtle of cold seas, for example the leatherback turtle (Dermochelys coriacea), which can withstand very low temperatures, and thus migrate to the outskirts of the polar circle. It is a large turtle, without scales, wearing on its bluish and smooth carapace long hulls, which can give the appearance of a cuirass, evoking medieval military equipment. Its back has the shape of a shield, forming a point at the back. All these elements give it the appearance of a soldier of the sea. - [Buquet, page 7]