Allosauruses, plural, Allos. Giganotosauruses, Gigas. Tyrannosauruses Rex, Rexes. Why do I keep seeing this Allo’s or Rex’s or Giga’s bullshit? Many Giga’s? The APOSTROPHE (‘) means that we are talking about a belonging! There is lots of Gigas. The Giga’s teeth. Plural or possessive.