An asker (who asked to remain anonymous) wanted a good explanation for why birds are considered dinosaurs. As I was tediously typing my usual answer on my tablet, it occurred to me that it would probably be a good idea to make a sort of masterpost addressing the various arguments people who accept evolution but aren’t familiar with cladistics tend to use when claiming birds aren’t dinosaurs. I want to be as thorough as possible so suggestions would be helpful.
We switched to a new classification system that requires groups to be monophyletic and abandoned ranks like Class and Order. Not really any particular scientific reason as much as a bookkeeping one. As much as proponents of birds=dinosaurs (including myself of course) hate to admit it, the difference between “birds evolved from dinosaurs” and “birds are dinosaurs” is mostly semantic. The one bonus is it allows you to see the lineage as a continuous acquisition of shared features, which is true either way, just with an arbitrary cutoff in the. “Evolved from” version.
Then the deadliest dinosaur is officially Amphicoelias!
Velociraptor sans Primaries
It’s become almost an article of faith within the paleo fandom that Velociraptors would have primary feathers sticking out of their second finger, a la modern-day birds, and therefore any artwork omitting these and leaving the hands exposed is paleontologically inaccurate. However, I’ve never actually heard of any direct evidence that Velociraptor or any other large terrestrial dromaeosaurid actually had primaries (as opposed to secondaries sticking from the forearm, which is what the quill knob data reflects). Until that evidence surfaces, I am not sure we can really criticize artists for omitting the primaries, as if the animals couldn’t lose them secondarily throughout their evolution for whatever reason. Besides, it’s not like Velociraptor would have really needed primaries since it was probably a flightless animal.
I will concede that I have an artistic motivation for cutting out the primaries here. I always felt primaries got in the way of a good view of the raptors’ frontal talons, which is a shame because those are probably their most feared weapons after the famous hind-foot sickle claws.
"Besides, it’s not like Velociraptor would have really needed primaries since it was probably a flightless animal."
Even big, flightless modern birds like the ostrich retain their primaries.
You also have to consider that primaries are useful for more than just flight.
Obviously flightless animal, a related but more basal maniraptoran than dromaeosaurs, with exquisitely preserved primaries attached to the second digit. Unfortunately, so far all known larger dromaeosaurids are known from formations where actual preservation of integument is unlikely to functionally impossible.
In the absence of definite fossil information for any given genera, phylogenetic bracketing is the only actual information we have to work with. I therefore think it’s reasonable to require positive evidence that Velociraptor did not have primaries in order to consider oneself “equally accurate” when reconstructing it that way.
The wing claws of many feathered dinosaurs were probably not visible in life due to the feathers, just as they’re not visible in many modern clawed birds. They may have poked out if the wing a bit in big clawed species, but if Velociraptor were alive today I doubt it would be known for its hand claws.