Some abnormalities of the arterial system of adult individuals can be interpreted as retentions of a state that normally occurs only during early embryology. The teratogen thalidomide primarily affects the anlagen of the blood vessels and only secondarily the development of the complete limb. To understand the normal development of limbs as well as limb malformations the morphogenesis of their blood vessels must be considered. Describing the embryonic development of the arteries of a primitive mammal, this text focuses on the tree-shrew Tupaia belangeri to explain the variability among other mammals on the basis of a common developmental pattern. It establishes criteria for the comparison of data published in the literature.