As long as we are talking about new/unknown and fascinating dinosaur sites in the U.S., I might as well bring up the new Arlington Archosaur Site in Arlington, Texas. This site has garnered a bit of attention in the last few days, and is rather interesting to quite a few people, myself included.
One reason the Arlington Archosaur Site has been given so much attention is because it is in Arlington, Texas. Arlinton is smack dab in the middle of the Dallas-Fort Worth Metroplex, a huge urban area. Most of the time, cities tend to be built on sites that do not contain dinosaur fossils, but Dallas and Fort Worth are exceptions. Like twin magnets, these cities seem to just draw dinosaur fossils to them, resulting in many fantastic dinosaur finds. There have even been dinosaurs found in the DFW airport!
The Arlington Archosaur Site itself is situated in the Woodbine Formation, a strata of rocks dating back to aproximately the Early Cretaceous period, 95 million years ago. Specifically, the site is Cenomanian in age, a period dating back towards the end of the Early Cretaceous. During the Cenomanian, a great inland sea cut North America, and Texas, right down the middle. The Dallas-Fort Worth coast was probably swamps and wetlands, much like the Everglades or the coast of Alabama or Mississippi today.
As the site name would suggest, numerous archosaurs have been found here at this site. One of these is Woodbinesuchus, a thin-snouted crocodile which probably resembled today's gharial. Like the modern gharial, the thin snout of Woodbinesuchus suggests that it was primarily a fish-eater, using its long snout and needle-like teeth to catch fish in the water.
The main dinosaur of the Arlington Archosaur Site is Protohadros. Protohadros is a primitive hadrosaur (or, as contested by some, an advanced hadrosaur-like iguanodontian) known from a skull found in Flower Mound, Texas, also in the Woodbine formation. Technically, we are not totally sure if the hadrosaur here is Protohadros, as the only other Protohadros specimen is known from the skull, which this specimen is lacking, but the general anatomy and the fact that no other hadrosaurs are known from the Woodbine formation suggest that it is Protohadros. Even better, the atlas vertebra of this animal has been found, which is a good indicator that the skull is also in the ground, merely awaiting excavation.
In addition to Protohadros, there have been several fossils of a theropod dinosaur found at the site. However, unlike Protohadros, these fossils are as of yet unable to be identified down to the generic level, or any further than "theropod". Theropods are unknown from the Woodbine formation, so hopefully more material of this animal will be found so science will be able to figure out what this animal is.
Only one question remainds. The site is called the Arlington Archosaur Site, but there have been turtles found there. So...that would make it the Arlington Aminote Site? But then there's that new species of lungfish....