Their ancestors appeared around the same time as the first small mammals, and they were probably able to survive because they were evolving— and growing—at the same time as their mammalian predators.
Nenek moyang mereka muncul pada waktu yang sama seperti mamalia kecil pertama, dan mereka mungkin hidup karena mereka berevolusi -- dan bertumbuh--pada waktu yang sama seperti pemangsa mamalia mereka.