"Two penises"

A funny recommendation from Tyler Cowen: Robert Trivers' Wild Life: Advevntures of an Evolutionary Biologist. Trivers is an extremely distinguished and influential figure, but it is quite an eccentric book (it becomes immediately clear why it wasn't published by a more mainstream press). I was captivated by this bit in particular:

It is a little known fact outside of Herpetology that all lizard and snake males have two penises, one on the left side and one on the right. A given penis is used preferentially depending on whether the male winds around to the right or the left of the female. (If you are a mammal and have a penis, look down at its underside and see if you do not see a line running up it that shows where the two hemi-penes fused during early development.) Initially in evolution, all genital organs tended to be bi-laterally symmetrical. Testicles and ovaries retained this symmetry, but reductions to one also occurred, as in the case of the penis and the scrotum.

In any case, it is easy to reveal the trait in Anolis males. You hold him upside down and manipulate the penis on either side to cause it to extrude. When both are extruded they look like two bananas peeled outwards.

I used to amuse myself by showing this feature off to Jamaican men, knowing that having two penises would arouse excitement, as well as admiration. "One for the yard, one for the road," was a common excited response.