The fish with a knife on its face

Unexpectedly, Smith discovered that his pet essentially possessed a switchblade on its face. The weapon is known as a lachrymal saber: “lachrymal” meaning “concerned with tears” and referring to the armament’s placement on each cheek below the eye. And saber, well, it pretty much speaks for itself.

The weapon is usually tucked alongside their face, but when danger looms a series of muscles and ligaments whip the wicked blade into action. The lachrymal saber can ratchet to different angles depending on the situation, in addition to locking all the way in or out. This switchblade is likely defensive — in pictures of stonefish in the mouths of predators, the lachrymal saber is always locked out, Smith said. “As far as I can tell, the saber itself or its surrounding tissue are not venomous,” he added.

http://blogs.discovermagazine.com/d-brief/2018/04/13/stonefish-switchblade-lachrymal-saber/