The person who gets to name a new type of dinosaur or any other kind of animal or plant is the first person to write a description of the new specimen, showing how it is different from others like it. There is a set of rules for how the description is to be written, and how the names are to be composed. For example, there has to be a drawing or photograph of the new dinosaur, and the name has to have two parts. The second part is the trivial or specific name the rex in Tyrannosaurus rex. One of the generic names I've made, inspired by my wife, was Excalibosaurus for an ichthyosaur.
Ichthyosaurs are reptiles that lived in the sea at the time dinosaurs roamed the land.
The name Excalibosaurus means Excalibur reptile, taken from the name of King Arthur's sword. This is because this particular ichthyosaur had a long bill, like a swordfish, and was found embedded in the rock not far from King Arthur's legendary home of Camelot. When skeletons are being dug up a great deal of care is taken to label their field jackets so that the bones of one specimen do not get mixed up with those of another. If this did happen, and if the two dinosaurs were of similar size, it could be very difficult to know which bones fitted with which skeleton. Paleontologists need to have a good knowledge of animals and plants that are alive today.