But the plural of "species" is "species". When you are talking about one species, you say "species". When you are talking about multiple species, like all the

But the plural of "species" is "species". When you are talking about one species, you say "species". When you are talking about multiple species, like all the species of dinosaurs, you say "species". "Dinosaurs were the dominant species" is correct, talking about multiple species. "Humans are the dominant species" is correct, talking about one species.