The order Carnivora comprises a very distinctive group of animals numbering 274 living species. The members belonging to this order are called carnivores and have a worldwide distribution. The term "carnivore" broadly applies to any flesh eating animal. Although carnivores are principally meat eaters, some members in this group (e.g. pandas) feed mostly on vegetable matter. Most carnivores are ground living mammals, though aquatic (e.g. sea otter) and arboreal (e.g. palm civet) members are also found. Their size ranges from the smallest weasel to the largest polar bear. The most important anatomical character by which carnivores can be distinguished from other mammals is their shearing cheek teeth or carnassials. The fourth upper premolar and first lower molar are collectively known as carnassials teeth. They are fit together perfectly to provide a shearing surface to cut meat. Incisor and canine teeth are used for seizing, holding and biting of prey.