Cetology (from Greek , kētos, "whale"; and , -logia) or whalelore (also known as whaleology) is the branch of marine mammal science that studies the approximately eighty species of whales, dolphins, and porpoises in the scientific order Cetacea. Cetologists, or those who practice cetology, seek to understand and explain cetacean evolution, distribution, morphology, behavior, community dynamics, and other topics. History Observations about Cetacea have been recorded since at least classical times. Ancient Greek fishermen created an artificial notch on the dorsal fin of dolphins entangled in nets so that they could tell them apart years later. Approximately 2,300 years ago, Aristotle carefully took notes on cetaceans while traveling on boats with fishermen in the Aegean Sea. In his book Historia animalium (History of Animals), Aristotle was careful enough to distinguish between the baleen whales and toothed whales, a taxonomical separation still used today. He also described the sperm whale and the common dolphin, stating that they can live for at least twenty-five or thirty years. His achievement was remarkable for its time, because even today it is very difficult to estimate the life-span of advanced marine animals. After Aristotle's death, much of the knowledge he had gained about cetaceans was lost, only to be re-discovered during the Renaissance. Many of the medieval texts on cetaceans come mainly from Scandinavia and Iceland, most came about the mid-13th century. One of the better known is Speculum Regale. This text describes various species that lived around the island of Iceland. It mentions orcs that had dog-like teeth and would demonstrate the same kind of aggression towards other cetaceans as wild dogs would to other terrestrial animals. The text even illustrated the hunting technique of orcs, which are now called orcas. The Speculum Regale describes other cetaceans, including the sperm whale and narwhal. Many times they were seen as terrible monsters, such as killers of men, and destroyers of ships. They even bore odd names such as "pig whale", "horse whale", and "red whale". But not all creatures described were said to be fierce. Some were seen to be good, such as whales that drove shoals of herring towards the shore. This was seen as very helpful to fisherman. Many of the early studies were based on dead specimens and myth. The little information that was gathered was usually length, and a rough outer body anatomy. Because these animals live in water their entire