WHAT DOES YOUR GOLDFISH HAVE IN COMMON WITH THE ALIEN?

There were a few white "scales" laying on the bottom of my ranchu pond today. After I picked and examined them, these "scales" appeared to be pharyngeal teeth shed by one of my ranchu. Goldfish possess four teeth on each of the two pharyngeal arches and use them to breakdown food. Unlike mammals, goldfish are able to replace each tooth many times throughout their life.

A set of pharyngeal teeth of one of my ranchu

For those who did not know that goldfish do have teeth, here is some more information. Technically goldfish belongs to a group of toothless fish, or fish with no jaw teeth. Instead they developed so called pharyngeal teeth attached to the pharyngeal arches located in their throat.

Pharyngeal teeth location in goldfish marked in red, an open source image

As strange as it may sound, teeth predate jaws in their evolutionary development and first appeared in the pharynx of prehistoric jawless fish and possibly marine worms. Today pharyngeal teeth can be found in some toothless fish species, and as a second jaw set in addition to the developed jaw bone with teeth, in such fish as moray eels.

An open source image

This could have been the inspiration in creating an alien character for the classic horror film "Alien" and its sequels. That small set of jaws that would come out of the alien's mouth could be identified as the secondary pharyngeal jaws.

Poster for "Alien 5" movie, an open source image