http://www.sciencedaily.com/releases/2009/03/090324081431.htm
Triceratops Was A Social Animal, Group Of Dinosaur Fossils Suggests ScienceDaily (Mar. 24, 2009) -
Until now, Triceratops was thought to be unusual among its ceratopsid
relatives. While many ceratopsids-a common group of herbivorous dinosaurs
that lived toward the end of the Cretaceous-have been found in enormous
bonebed deposits of multiple individuals, all known Triceratops (over 50 in
total) fossils have been solitary individuals.
...
In 2005, Brusatte and colleagues found and excavated a site that contained
multiple Triceratops juveniles in 66-million-year-old rocks in southeastern
Montana. The geological evidence ...
...