This is a 9 May 2013 video from Wyoming, USA. Triceratops fossils had already been found there. Since then, even more have been found.
Translated from Vroege Vogels TV in the Netherlands:
Triceratops did not live on its own
Tuesday, September 8th, 2015 19:07
The excavation by a Naturalis team of five Triceratops skeletons in one location means that the theory about solitary Triceratops should be reviewed. This is the conclusion of paleontologist Peter Larson of the Black Hills Institute. “This changes everything. We have always believed that Triceratops lived alone and not in herds or families. Until this excavation,” says Larson on Vroege Vogels TV on Tuesday September 8th 19:20. After the excavations, the bones will be brought to Naturalis in Leiden for further research.
Peter Larson is present at the excavations by Anne Schulp of Naturalis with his expedition team in Wyoming. Here a number of young and adult specimens have been found. That there are so many of them together makes the discovery unique. The bones are very well preserved. This will ensure that the skeletons will be properly mounted. Concerning Triceratops skeletons, so far worldwide only two individuals had been found which were complete for more than half. Only when the entire excavation will be finished, it will be possible to say exactly how complete the skeletons are. Triceratops lived over 66 million years ago and is a herbivorous dinosaur.
Naturalis will bring the skeletons to Leiden for further research. 2018 will see the Triceratops skeletons in the new permanent exhibition which will include the previously found T. rex.
Why are dinosaurs extinct? You asked Google – here’s the answer, by Brian Switek: here.