The biggest mammal-like reptile was probably a large herbivore found from South Africa, like Moschops . Most of the trees and plants around today, the flowering plants, were not around during the times that mammal-like reptiles lived. South Africa has so far found the most mammal-like reptiles, but Russia is a close second. The period that the mammal-like reptiles were most common is the Permian, from about 280 million years ago to 250 million years ago. We can tell more about how mammal-like reptiles lived by the shape of their bones and the length of them.
Long bones are usually from fast runners, while short bones are usually from slow movers.
We can tell the skin of some extinct animals if we find impressions on rock of their skins. We have not yet found any skin impressions for mammal-like reptiles so we are not sure what their skin looked like. Modern mammals have fur or hair, modern reptiles have scales. The mammal-like reptiles were around for about 120 million years, while the dinosaurs were around for 180 million years. The climate began to get warmer, which favoured the dinosaurs while not being as good for the mammal-like reptiles.