Penis
Domestic cats have barbed penises, with about 120–150 one millimeter long backwards-pointing spines. Upon withdrawal of the penis, the spines rake the walls of the female's vagina, which is a trigger for ovulation. Lions also have barbed penises. Male felids urinate backwards by curving the tip of the glans penis backward. When male cheetahs urine-mark their territories, they stand one meter away from a tree or rock surface with the tail raised, pointing the penis either horizontally backward or 60° upward.
Brain size
When the mammalian brain increases in size, not all parts increase at the same rate. In particular, the larger the brain of a species, the greater the fraction taken up by the cortex. Thus, in the species with the largest brains, most of their volume is filled with cortex: this applies not only to humans, but also to animals such as dolphins, whales or elephants.