Tooth 29036 (Pan paniscus) – one of the problematic teeth illustrating how occlusal morphology can make it difficult to define cusps, which may lead to interobserver error. In this case, the strong crista obliqua connecting the distobuccal and mesiolingual cusps (metacone and protocone) and mesial trigone accessory crests obscure primary fissures. Orientation: M, mesial; D, distal; B, buccal; L, lingual.