This is still not something we can answer with certainty. For a couple of years there, paleontology thought that psittacosaurus had feathers on its tail - and as a ceratopsian, on the complete other side of the dinosaur ‘tree’, that would suggest the base form for dinosaurs must have feathers and any that didn’t have them lost them at some point in their lineage (and thus could potentially regain them if the DNA was deactivated rather than lost). Now the feathers are disputed again, as “something else” - spines of some sort unrelated to feathers.
No doubt lots of dinosaurs were scaly, but I don’t think anyone would say with certainty that feathers were limited to late theropods.
I’ve also heard some contention over the ground up evolutionary theory for birds. Mainly that you don’t evolve flight from jumping up, but rather from jumping tree to tree and gliding. I’m certainly not an expert in this but as a layman it does make sense to me, if you jump to escape a predator on the ground you inevitably come back down, but if you can make it to the next tree and your predator can’t, that would indeed be a significant enough advantage to be passed down to your children. Seems easier to convert lizardy gliders like on the yi qi to wings too, rather than lizardy arms to wings.
This is still not something we can answer with certainty. For a couple of years there, paleontology thought that psittacosaurus had feathers on its tail - and as a ceratopsian, on the complete other side of the dinosaur ‘tree’, that would suggest the base form for dinosaurs must have feathers and any that didn’t have them lost them at some point in their lineage (and thus could potentially regain them if the DNA was deactivated rather than lost). Now the feathers are disputed again, as “something else” - spines of some sort unrelated to feathers.
No doubt lots of dinosaurs were scaly, but I don’t think anyone would say with certainty that feathers were limited to late theropods.
I’ve also heard some contention over the ground up evolutionary theory for birds. Mainly that you don’t evolve flight from jumping up, but rather from jumping tree to tree and gliding. I’m certainly not an expert in this but as a layman it does make sense to me, if you jump to escape a predator on the ground you inevitably come back down, but if you can make it to the next tree and your predator can’t, that would indeed be a significant enough advantage to be passed down to your children. Seems easier to convert lizardy gliders like on the yi qi to wings too, rather than lizardy arms to wings.