Cimolestes was a tree climbing rat sized mammal and it has been drawn as such many times. It has also been drawn to look something like a shrew and even an opossum. Regardless, it is a small mammal with a rodent-like body plan. Adept at clambering up trees and chasing down insects, Cimolestes was an iconic mammal of the Mesozoic. The iconic image of a very small mammal racing around underfoot of dinosaurs is perfectly filled by Cimolestes, however it is usually drawn in the trees, like this image. Its agile little body was slender, but the fluffy images that make it look more like an opossum (not this one) could be said to just be the result of its fur being puffed up. This less furry version looks a little sly, but may be a little more accurate.