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Earliest Primate Placed With Dinosaurs
Quirk writes "National Geographic has a piece suggesting the earliest primates were contemporaries of dinosaurs. The article is an endorsement for the evolutionary dating system using molecular-clock studies. The earliest primates according to the current fossil record suggests a common ancestor about 55 million years ago after the great dinosaur die-off. Relying on biology and mathematics the new study suggests a small, nocturnal creature of the tropical forests was the earliest primate. The research viewed fewer differences in genetic codes as an indicator that the more recently two species parted evolutionary company, and, math equations were used to flesh out the tree and to predict when and for how long species may have lived. So, really, a Rachel Welch lookalike in a skimpy fur bikini may have actually fled a rampaging T-Rex."
The mammal-like reptiles had a skull structure very much like modern mammals and lived not only with the dinosaurs, but hundreds of millions of years before them. These creatures are considered the ancestors of all modern mammals and they would probably have had a facial structure similar to modern mammals given that they had a ridge of bone above the eye sockets where the jaw muscles from their jaw --similar in shape and function to a mammalian jaw, as opposed to a reptilian jaw-- connected to the skull.
It sounds like the technique they used was Mitochondrial DNA Concordance
Mitochondrial DNA is different from nuclear DNA. With the help of mathematics, can be used to determine degrees of relatedness between species, and when two species diverged from their common ancestor. My Human Evolution professor explained this technique in class just yesterday. It was used as evidence that Neanderthals contributed no DNA to the Homo Sapien gene pool.
Incidentally, talkorgins.org is a great site for this kinda stuff.