As their name implies, megamouths have a large mouth with small teeth, and a broad, rounded snout, causing observers to occasionally mistake megamouth for a young orca. The protruding inside of the upper lip is a brilliant silvery-white, which is very visible when the mouth is open. This lip was initially thought to be possibly embedded by luminous photophores when the first shark were examined in the early 1980s, which may act as a lure for plankton, while the team examining the second shark in the mid-1980s instead proposed that the lower lip might glow with the white band used as a reflector of sorts, but neither theory has been proven. In 2020, a study concluded that this species of shark does not in fact produce any light; the white band was found to merely be highly reflective of light. This white band is present in both sexes and could be either a feeding mechanism or possibly be used as a means of identifying other individuals of megamouth sharks. Their mouths can reach up to wide. Megamouth sharks have up to 50 rows of teeth in their upper-jaw and up to 75 rows of teeth in their lower-jaw.