Sources : Molosus

Thomas of Cantimpré [circa 1200-1272 CE] (Liber de natura rerum, Quadrupeds 4.70): The molossus is a very large beast, which is found in many parts of the world. it pursues savage enemies as if created for this purpose. it has a big and huge smile, with strong and prominent teeth, with which it boldly wages wars with its adversaries. With strong men it is terrible and horrible, and boldly treads upon those whom it meets, yet it is wonderfully terrified by the innocence of children and their smallness, and flees from their blows, and in this dignified innocence its magnificence is confirmed. And no wonder, because the cruelty of beasts was not created to destroy innocence, but to punish the guilt and malice of men. - [Badke translation/paraphrase]

Albertus Magnus, De animalibus, 73 [circa 1200-1280 CE]: The molossus is a very large beast, found in many places. it has a large and strong grin, strong and prominent teeth: and therefore it fights harshly: which, although it is terrible and aggressive to all, yet it fears the beatings of children, and flees from them. - [Badke translation/paraphrase]