全棱兽（Pantolambda），又名五棱兽或皆齿兽，是已灭绝的古新世全齿目动物。虽然全棱兽的整体外观像猫科，但牠是吃植物及有像蹄的脚掌。牠的脚上有五趾，趾上有爪。牠的牙齿呈半月齿结构，即牠的齿冠呈新月的形状。全棱兽的体型约有绵羊的大小。由于全棱兽较重，故可以肯定牠们不是栖息在树上的。

已知全棱兽共有三个物种，牠们的化石是在美国新墨西哥州、怀俄明州及蒙大拿州发现。

Pantolambda is an extinct genus of Paleocene pantodont mammal. Pantolambda lived during the middle Paleocene, and has been found both in Asia and North America.

Cretaceous mammals, which had to compete with dinosaurs, were generally small insect eaters. Pantolambda was one of the first mammals to expand into the large-animal niches left vacant by the extinction of the dinosaurs. Pantolambda and other early pantodonts would quickly evolve into heavy animals such as Barylambda and Coryphodon. These were the first large browsers, pioneering styles of life later followed by many unrelated groups of mammals: rhinos, tapirs, hippos, ground sloths, and elephants. Pantodonts such as Pantolambda were definitely not tree dwellers.