The Chimaera pup is a juvenile Chimaera fish introduced to Hogwarts students by Headmaster Kobus Hendrik in Care of Magical Creatures class during Term 8. Additional information can be found in What Lies Beneath by P.H. Athoms.
According to Hendrik, the creature was found by Muggles who did not realize what they had found. Although he rushed to take possession of it, the creature did not survive. Adult Chimaera fish are seldom seen by Muggles due to the fact that they make their home at extreme ocean depths.
The young Chimaera fish (or pup) has developed a unique survival technique - it is able to make itself invisible when in danger. When visible, the creature has a long snout-like appendage with hardened cartilage 'teeth' along the length. These are used for foraging on the sea floor and are replaced as the Chimaera fish matures. An adult Chimaera fish loses the protuberance, having a jaw full of razor sharp teeth instead.
Both Chimaera pups and adult fish have the long, slim tail and immense black eyes. These eyes are nearly all pupil due to the lack of light at the ocean depths the Chimaera fish calls home.
Not to be confused with the Muggle chimaera fish, this creature is far more deadly than its counterpart. The dorsal spine contains a potent neurotoxin that causes the nervous system of the attacker, or prey, to shut down.