Identity plates

IN MANY living species, the sexes look different from one another. Presumably that was true in the past, too, but knowing for certain is hard because pigments and soft tissues that might be sexually dimorphic are rarely preserved in fossils. Among dinosaurs in particular, even the durable fighting parts more usually sported by males than females have proved a disappointment to those seeking dimorphism. Famously horned dinosaurs such as Triceratops show no convincing evidence of such differences....