© Rob Kolakowski
via: stfrancisjigger.com
Habitat: North and Central America
Status: No Conservation Concerns

This seemingly ordinary looking fish is a Freshwater Drum (Aplodinotus grunniens) though you may know it as shepherd’s pie, “perch,” silver bass, gray bass, Gasper goo, Gaspergou, gou, grunt, grunter, grinder, wuss fish, and croaker, and is commonly known as sheephead or sheepshead in parts of Canada. Any of those ring a bell? 

This fish typically weighs in around 5-15 pounds, though the largest ever caught tipped the scales at 54lbs 8 oz.  It is a member of the family Sciaenidae, and is the only member of the group that inhabits freshwater for its entire life. Some people call them ‘grunters’ because of the grunting sound the mature males make. No one is really sure why they grunt, but most assume it’s linked to breeding. What caught my eye about these ‘normal’ looking fish was the set of teeth they had. After looking at the photos above you might be thinking “… I don’t see any teeth… crazy woman.” But don’t doubt me, for they are hidden away in the back of the fish’s throat. Check these out: 
via: sciencebuzz.org

These pharyngeal “throat” teeth are located on the last gill arch at the posterior region of a fish’s head. They are visible only upon lifting off the gill cover (operculum) and exposing the gills beneath. The arrangement and number of these teeth are specific for certain families and species of fish. 
 © Goody
The teeth are used to crush the tough shells of mussels; one of the Freshwater Drum’s favorite foods.  I don’t know about you but I would have never expected to find such a cluster of teeth packed so tightly into a fish’s mouth. Weird stuff.