Table S1: Length of endocasts and penis tips in four species of marine mammals. from Genital interactions during simulated copulation among marine mammals

Penis lengths were collected after inflation but prior to formalin-fixation. Penises were measured from the cranial point of fusion of the sheath to the shaft through to the cranial (distal) tip of the penis. Endocast and penis length measurements were collected in ventral, dorsal, left lateral, and right lateral orientations. The longest length is presented due to asymmetries in shape.