All three articles are about discoveries from a Virginia fossil site called the Fisher/Sullivan site which is located in the Nanjemoy formation. The Nanjemoy formation is the accumulation of sand and mud on the bottom of the Atlantic Ocean 53 million years ago.
The Earth was so warm there were no polar ice caps and the Atlantic came up to the fall line (or roughly I-95). The site is about 5 miles east of the fall line, so it would have been off shore. Mostly, you find marine animals, but occasionally you find terrestrial animals, birds or fresh water animals as is the case with two of these discoveries.