Tuatara Gallery photo with the late Rico Walder
The rare New Zealand Tuatara (Sphenodon punctatus) doesn't have a penis but it may go a long way to help scientists understand phallic evolution.

Researchers at the University of Florida in Gainesville found that the tuatara develop tiny nubbins as an embryo but the development of these nubbins stalls and they never form into a proper penis. Nubbins represent an early trace of the phallic development process. This initial growth suggests the phallus developed only once throughout the evolution of mammals and reptiles, according to the UF researchers.

Their research indicates that the tuataras lost a phallus, indicating that the basic penis evolved only once.

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