A Leucrotta is a large moose-like creature with a gigantic mouth.
Roman author Pliny the Elder first wrote about the Leucrotta or Crocotta in his Natural History, describing the beast as "the swiftest of all beasts, about the size of an ass, with a stag's haunches, a lion's neck, tail and breast, badger's head, cloven hoof, mouth opening right back to the ears, and ridges of bone in place of rows of teeth—this animal is reported to imitate the voices of human beings." Many believe Pliny might have been referring to a species of hyena, which has a large mouth and the ability to mimic human sounds, ncluding a famous cackling laugh.
Medieval Bestiaries refer to the Leucrotta as a wolf-dog or lion-hyena hybrid native to India.
The Leucrotta was listed in the first Monster Manual for the game Dungeons and Dragons. Said to dwell on the outskirts of civilization, the beast was the symbol of Chaotic Evil because of its ability to mimic a woman or child in distress and therefore lure heroes to their deaths.
From the Web
Entertainment Weekly, "Fantastic Beasts sequel reveals adorable baby Nifflers," 9 August 2018
Leucrotta on Harry Potter Wiki