Please identify all overlaps of the following two texts and name them precisely. Provide just the common information that is shared by both texts. Ignore the information which is only mentioned once.

Text one: Dolphins are a group of highly intelligent marine mammals that belong to the family Delphinidae. They are characterized by their streamlined bodies, long snouts, and dorsal fins. Dolphins are found in all the world's oceans and are known for their playful behavior and intelligence. They are known to use complex communication systems and work cooperatively in groups to hunt for food. Dolphins have been observed using tools, learning, and exhibiting self-awareness.

Text two: A dolphin is a marine mammal that is closely related to whales and porpoises. It is characterized by its streamlined body, which is adapted for fast swimming, and its large, curved teeth. Dolphins are known for their intelligence, social behavior, and playful nature. There are approximately 40 species of dolphins that are found in oceans and seas throughout the world, ranging in size from the pygmy dolphin, which is only about 6 feet (1.8 meters) long, to the killer whale, which can reach lengths of up to 32 feet (9.8 meters). Dolphins are popular in aquariums and are often kept in captivity, but they are also protected by conservation laws in many countries.