teratology now means a study of deformity, in the olden days it referred to monsters

writhing sea monsters of the deep… whales were monstrous

hell lay inside their mouths (jonah’s experience)

they were often depicted with horns and scales.

Isidore of Seville [7th century CE] (Etymologies, Book 12, 6:6): Whales (ballenae) conceive through coition with the sea-mouse. (Book 12, 6:7-8): Whales are immense beasts, with bodies equal to mountains. They have their name from emitting water, for the Greek ballein means emit; they raise waves higher than those of any other sea beast. They are called monsters (cete) because of their horribleness. The whale that swallowed Jonah was of such size that its belly resembled hell; as Jonah says (Jonah 2:2): “He heard me from the belly of hell.” – medieval bestiary