Speed over 100m is based on the animal, vehicle or person's top speed and does not take into account acceleration or the ability to maintain the speed over the given distance. This is why, for example, Usain Bolt’s time is slightly lower than his actual 100m record. This is done to allow comparisons between things that don’t have a recorded time over 100m, but do have a recorded or estimated top speed.
The sources of the speeds are given below. Yes, it's possible that we've missed a faster time for one thing or another - this graphic is to give a general indication of relative speed differences. It's also worth keeping in mind that speeds for extinct dinosaurs differ dependent on the methods used.
This is an updated version of a graphic originally published in 2014.