— “scientists used pictures of the reptile embryos to recreate their 3d structure. the team discovered that, even though the tuatara has no external phallus, it grows the beginnings of one during development. at some point this “genital swelling” recedes and the reptiles are born sans phallus”

read article : the penis only evolved once, suggests study of reptile embryos

read more : resurrecting embryos of the tuatara, sphenodon punctatus, to resolve vertebrate phallus evolution