I have good news and bad news - the bad news is today is not the day you get a general estimate of the mass of Spinosaurus. I know, I know, and I'm sorry. Here's the good news - in preparation for a deeper look at the challenges of estimating the mass of Spinosaurus, I've produced far more rigorous mass estimates of Tyrannosaurus and Giganotosaurus from GDI, and I got some surprising results.  Jump below the fold to see who is bigger (and why I think this is so).