The discovery of an early silesaur in Tanzania may push back the date when dinosaurs developed, though not their period of dominance. Silesaurs formed one of a number of competing but related reptilian groups, of which the dinosaurs proved the most successful. The Telegraph article is slightly scary in its treatment of dogs, though. Here is the initial description, though I miss out the illustrated nonsense:
Palaeontologists have found a four-legged ancestor of the prehistoric creatures that hails from 250 million years ago – 10 million years earlier than first thought.
The large dog sized creature, which ate meat and vegetation, is thought to be a similar relation to dinosaurs as chimps are to humans.
However, it is not really a dog now:
Each individual stood about 1.5 to 3 feet tall at the hips and were 3 to 10 feet long. They weighed about 22 to 66lbs.
So
the article's terms of reference: dinosaurs (it isn't one) and dogs
(it doesn't resemble one) are fairly poor. It is neither a dinosaur nor a dog.