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.
Sus antepasados ​​aparecieron  al mismo tiempo. que los primeros pequeños mamíferos, y probablemente fueron capaces de sobrevivir porque estaban evolucionando y creciendo, al mismo tiempo que sus depredadores mamíferos.