The discovery and identification of Raptorex kriegsteini, a minute Tyrannosaur (note: this is different than Tyrannosaurus rex which is the best known species of Tyrannosaur) throws some wonderful new insight into the evolution of one of the best known dinosaurs of all time. You can read all about it in this New York Times article. What is most amazing is that this eight to nine foot long animal had so many similar features to its huge descendant, including the well known little two fingered arms. Raptorex came quite some long time before T. Rex walked the Earth, some 35 million years ago according to the article, but it demonstrates to paleontologists that a lot of the features which attributed to the King of the Dinosaurs’ success as an apex predator were already present long before. Likely it was the success of these features (things like powerful sense of smell, strong legs for fast speed, etc.) which allowed Raptorex to have a lineage of progressively dominant predators.
This is wonderful stuff which adds to the allure and interest of one of the world’s favorite dinosaurs.
Here is another article about raptorex. It if from Io9 whihc generally seems to focus a bit more on science fiction than scinece fact (though it does nerd out on some good dinosaurs and space discoveris every once and awhile). The article doesn’t really say anything new beyond what was said in the New York Times one, but it does offer a good number of images, including a couple that offer nice size comparison between Tyrannosaurus rex and Raptorex.