Vertebrate Penis Only Evolved Once

Resurrecting embryos of the tuatara, Sphenodon punctatus, to resolve vertebrate phallus evolution. 2015. Biology Letters

image

New research on 100-year old data indicates that the vertebrate penis only evolved once.

Using a 3D model generated from slides of thin-sectioned tuatara - a rhynchocephalian reptile that shares a common ancestor with living squamates (lizards & snakes; see cladogram below) - embryos, the team found genital swellings, a precursor to penis development in many vertebrates. In the tuatara, the developments do not mature, like many modern bird species, they cease developing, thus adults have no penis. But the swellings clearly show the possibility, which the team suggests, offers a strong argument to the case of the penis developing from a common ancestor.

Cladogram showing relationships of extant members of the Sauria.1. Tuatara, 2. Lizards, 3. Snakes, 4. Crocodiles, 5. Birds (& dinosaurs). From here

Yes, DC Comics has a 'superhero' from New Zealand called 'The Tuatara'!

Some dodgy evolutionary biology from writer, E. Nelson Bridwell

Read more at Phys Org. And thanks to MonsterRobot!