The maxillary fourth premolar is the upper carnassial tooth (meat cutter) which, along with the mandibular first molar (the lower carnassial) acts as a pair of scissors to cut meat from prey. Molars are teeth which have flattened occlusal tables and contact each other in order to grind food. The modification arose separately in several groups of carnivorous mammals. Humans lack carnassial teeth. (see: Wikipedia).