In addition, there were active debates on the usage of the term "penis" for a female intromittent organ (Newitz 2014; Yong 2014). Of course, the female penis is not homologous to the male one, and it may be natural to use a different term (gynosome) for a different structure. However, the male penises evolved many times independently and thus are also not homologous between different groups of animals (e.g., the human penis is not homologous with that of turtles: Kelly 2004). Non-homologous structures have long been termed as penis without any doubt because they share some key features in common: they are exclusively owned by males, inserted into females, and are used for sperm transfer. Although owned by the opposite sex, the "female penis" shows a lot of analogous features with the male one, e.g., it is an erectile intromittent organ used for sperm transfer, and has spines to anchor to the opposite sex. Therefore, we consider that adopting the term "penis" also to the female structure can be justified. It may even be possible to extend the definition of penis as "an intromittent organ used for sperm transfer", without considering the sex of possessor.