Amargasaurus
Amargasaurus is a small sauropod from Argentina that lived in the Early Cretaceous period 130-125 million years ago. This dinosaur had a very interesting feature: a row of spines up to 65 cm in length each, located on the back and neck. They could form a spiky mane or be covered with skin, creating a structure like a double sail.
Whatever form they took, it was a very unusual adaptation, and probably played a role in the animal's social life or was used for defense - a valuable asset for an animal that was almost half the length of its relatives.
