On the Jurassic coast, British scientists have discovered two teeth that are 145 million years old and belong to animals like rats. They were called Durlstotherium and Durlstodon and were referred to as eutheria (higher animals). The same species of mammals, to which most animals in our modern world, including humans, belong.
Scientists are used to dividing mammals into three types. These are marsupials, of which the kangaroo is a prominent representative - they carry their offspring in a special bag. Oviparous, which are not birds or reptiles, but lay eggs - such as the platypus. And placentals, they are eutheria, for which it is common to give birth to live babies at once. Each species once had an ancestor, and for eutherians, they can now become an over-ancient rat.
Such confidence is given to scientists by the structure of the teeth, too complex for typical representatives of the era when dinosaurs still roamed the Earth. They are much more similar to the teeth of animals of the Cretaceous period, and this is a completely different time frame, only 60 million years ago. Such advanced teeth can bite, gnaw, pierce, and specifically these two samples are badly worn out - their owner ate a lot and managed to live a long life.
It is clear that the human ancestor of these rats can be called with a stretch, since they became the progenitors of all placental mammals. But the very fact of the existence of such creatures simultaneously with predatory dinosaurs excites the minds of paleontologists. It's time to dig further - in the literal sense of this expression.