This is the Giant Anaconda. I created this cryptid creature / monster art for Fairytales and Myths.
The giant anaconda (Sucuriju Gigante or Megaconda) is a cryptid similar to but said to be much larger than the regular anaconda (genus Eunectes). Early 20th-century European explorers in the Amazon River Basin first learned about supposed giant anacondas from native accounts of fearsome super-sized boas living in the dense jungles.
Check out the Giant Anaconda page for more details.