Feathered Dromeosaurs: Bakker's Theory Proved Right

Robert Bakker's The Dinosaur Heresies, a book I got as a teen one Christmas, was  one I still might not have taken the best care of, because of the smudges seen here. This was one of my favorite books, once again.The concept of hot-blooded active dinosaurs, which had been been going on since the seventies, was at last coming into vogue. 

John Ostrum's discovery of Deinonychus was what got the ball rolling, but it was Robert Bakker who took to it so enthusiastically. I remember so many books from my childhood that still taught a very unflattering portrait of dinosaurs. You know all that--that they were cold blooded, tiny brained, clumsy, had brains in their rear-ends, all of it. Even comics, like I talk about so often did this; the old fifties Tor issues, reprinted in the seventies, talked about the superiority of man, how he survived, while the "the mighty titans of prehistoric times" died out". Never that dinosaurs never existed at the time of man--but that was for dramatic purposes. 

Deinonychus, pictured above as depicted by Bakker for his book, also sported feathered. Now I'd seen this dinosaur depicted in comics and at least once on TV, and a few books, and it was always depicted as naked and scaly. Toe and Warlord both fought featherless deinonychi. And even when the first Jurassic Park movie appeared a few years after Dinosaur Heresies, they were depicted thusly, though by the time of the third movie, the male "raptors", appearing on screen for the first time, sported feathered quills on their heads. Somehow, only females were shown in following "Jurassic World" films, and they were featherless for the sake of consistency. For the few who don't know, the JP raptors are anatomically Deinonychus, true velociraptors having slightly up-turned jaws, and being not much larger than a turkey. 

The name "Velociraptor" became a mainstay after that, and I finally knew to pronounce that name with a "s" sound for the "c"; I'd been pronouncing it as a "k" since I'd never heard the name said out loud. 

Bakker's theory of Deinonychus, "so avian were these dinosaurs that it is quite probable that they had already evolved feathers for insulating their bodies" was a theory I took with a grain of salt. No imprints had been found, and the structure of a feather is so intricate that it suggests it had first been designed for flight, not merely for insulation. Would it not have been more likely that they evolved fur-like structures for insulation, like pterosaurs did, assuming they were endotherms? Even though Ostrom first proposed that small theropods like Deinonychus were endothermic, he was later somewhat at odds with Bakker concerning the larger dinosaurs. This including sauropods, whom Ostrom suggested may well have been ectothermic, but might have lived like warm-bloods given that they could retain heat with their gigantic size. 

Fossilized skin from the neck of a Tyrannosaurus rex. ©2004 Black Hills Institute of Geological Research, Inc., Hill City, SD     

Ostrom also suggested the same for large predators like tyrannosaurs, but here he seems to have been wrong; most if not all theropods are now believed to be not only endotherms, but having to possesed at a few feathers. Of course, some dinosaur skin simples have been found with scaly imprints, including one believed to be t-rex. If the larger theropods possessed feathers, it was probably as infants, or species that lived near to the poles, such as Yutyrannus, which is often depicted in white, hair-like feathers. If this is true, it would verify the existence of "snow-dinosaurs" that my father once invented for fun!

It could well be true. Only no dromeosaur (the theropod family now commonly called raptors), has been found with feathered imprints, even though plenty of the smaller theropod species have. However, quill-knobs were finally discovered along the arm bones of Velociraptor, indicates that some, and perhaps all dromeosaurs had feathers and smallish wings.

https://www.amnh.org/research/science-news/2007/velociraptor-had-feathers

Quill knobs on a velociraptor arm bone

 A paper by paleontologists William and Kristen Parsons, found here:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4398413/

suggests that younger Deinonychus may have been capable of flight, based on their bone structure.  

If so, it must have been derived from flying or gliding ancestors. This ability in hatchlings is a powerful indicator of this. A flying theropod, evolving to hunt large, earth-bound prey, perhaps in packs, isn't so far-fetched. 

This suggests perhaps that dromeosaurs might well have evolved from smaller theropods that very nearly would qualify as true birds. In other words, something of what I (as a non-scientist) call the family that includes Microraptor and Anchiornis "dino-birds."

Did some dinosaurs evolve from birds, or at least near-birds, rather than the other way round? It seems likely. Evolution takes all manner of divergent pathways as species branch out to fill various niches. 

In short, these days Bakker appears to have been right all along on this one, while his theory that I agreed with, about live-birthing sauropods, seems pure speculative fiction. 

But why did such an intricate structure as a feather develop for insulation first, though sometimes they revert to a hair-like covering for insulation. The same may have been the case for dinosaurs which were basically flightless, save for those on the wings. The fact Bakker's theory has now been virtually varified may provide a clue--the answer may be: feathers DID develop for flight first, then became vestigil. 

And I've read theories that Archeopteryx was also generally flightless, but used its feathered wings as a shield to catch insects. But frankly, I still don't buy that. Wings are for flight. 

Bakker's illustration of the deinonychi, one leaping, the other on his back, seems to have been inspired by this rather famous depiction of  Dryptosaurus (then called Laelaps) by Charles R. Knight, that shows them engaged in a battle like the modern depictions of "raptors." Knight, even more than Bakker, must have been way ahead of his time.