Until I saw that it's legs were crossed, the blue one made me think of a naga. First two remind me of cobras or maybe a fish(respectively) with their head appendages. 3rd One makes me think of a T-Rex more than anything. Maybe throw a croc and Komodo dragon in the mix, and a hulking plant eater dinosaur for the thick body and limb mass.... I dunno what to think about the last one. The concept of them being diverse (but related) creatures in a group of four reminds me of extreme dinosaurs.