This subject comes up fairly often, so I'm putting my mini-essay here as an easy reference. Feel free to share, or copy and paste with attribution, as you see fit. Comments, suggestions, and corrections are welcome. 🦖 🧪 🚀 ✍️

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Michael Crichton's main reference when writing #JurassicPark was Gregory Paul's Predatory #Dinosaurs of the World. That's how we ended up with human size "velociraptors," later retconned to the considerably larger #Utahraptor. Although the poor creatures still have broken wrists and a severe case of mange.

Paul is a notorious #lumper, who likes shoving distantly related organisms into the same #taxonomic category. (The opposite of lumpers are #splitters, who try to put every specimen into as distinct a category as possible.) But even he never claimed they were the same species. Rather, he put them into the same genus, making #Deinonychus into another species of #Velociraptor, i.e. V. antirrhopus instead of D. antirrhopus.

This isn't entirely a crazy idea. Lots of modern genera have species with similar body plans but enormous size differences. Consider #Panthera, the big cats, which contains species from P. uncia, the #snowleopard, to P. tigris, the #tiger—even though tigers are generally about five times the mass of snow leopards, similar to the ratio between D. antirrhopus and V. mongoliensis.

However, there are enough other differences between Deinonychus and Velociraptor that even Paul has long since admitted this was a mistake. No #paleontologist now doubts they each belong in their own genus. Unfortunately, since Jurassic Park has so thoroughly cemented the idea of the big V, I doubt it will ever go away.