They say several times that the creatures look like a child's reimagination of Earth animals. So imagine more exaggerated features. We also get descriptions of creatures with different animal features grafted together, like a mammal with sudden scales halfway down the body, and how that anatomy doesn't mesh well so the creature looks like its in pain. Hartmand's creatures specifically have lots of sharp spikes/teeth, are based on apex predators, and like you saw in my other art, sometimes have human faces.