sentences:  At the end of the later Maastrichtian stage, tyrannosaurines like "Tyrannosaurus rex", hadrosaurines like "Edmontosaurus" and chasmosaurines like "Triceratops" were widespread throughout western North America, while lambeosaurines were rare and albertosaurines and centrosaurines had gone extinct.Gregory Erickson and colleagues have studied the growth and life history of tyrannosaurids using bone histology, which can determine the age of a specimen when it died.A growth curve can be developed when the ages of various individuals are plotted against their sizes on a graph.