The Argentine blue-bill or lake duck has the longest penis, relatively speaking, of any vertebrae. Though the species has an average penis length of 8 inches, the longest recorded unfurled to 17 inches (pictured).

The Argentine blue-bill or lake duck has the longest penis, relatively speaking, of any vertebrae. Though the species has an average penis length of 8 inches, the longest recorded unfurled to 17 inches (pictured).