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The Dromaeosauridae Thread- Anything "raptor" related

  • 16-05-2012 4:46pm
    Moderators, Science, Health & Environment Moderators Posts: 5,279 mod Adam Khor

    The name means "coyote" after a similar-sized predator that inhabits today the same regions. It was found in Utah and found to be related to Utahraptor, a contemporary. Because of it I immediatly thought, what if it's just a juvenile Utahraptor? But the article mentions that its bones seem like those of a fully grown adult.


    For some weird reason the paper talks about giant raptors like Utahraptor and Achillobator, but they say that dromaeosaur size ranged from mockingbird to emu. (Aren´t emus very small compared to Utahraptor? :confused:)

    Also, it seems that the caudotheca of dromaeosaurs became reduced when they became larger, to allow greater tail flexibility and better maneuverability while running and turning at high speed.



  • Gotta love the scared cat in the size chart.

  • Apparently they found 2 other kinds of raptor in the region too...

  • Galvasean wrote: »
    Apparently they found 2 other kinds of raptor in the region too...

    Just fragments. That's why I didn´t mention them :S Such measly remains frustrate me.

  • It is apparently a new species of the already known genus Saurornitholestes.


  • In case you missed it. It is called Dakotaraptor and was comparable in size to Utahraptor, but it had more Deinonychus-like proportions (meaning it was a faster, more agile animal) and coexisted with T. rex. This also proves that the idea of T. rex completely monopolizing the medium to large predator niche is incorrect- Dakotaraptor fills the gap very nicely.


    Dakotaraptor claw (right) compared to Utahraptor's


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  • Was Dakotaraptor a winged Deinonychus? Vestigial wings or display?

  • Fathom wrote: »
    Was Dakotaraptor a winged Deinonychus? Vestigial wings or display?

    Deinonychus most likely had wings too; there was a recent study which suggests the very young ones could even flap their wings and fly (even if they probably weren´t very skilled). Enough to keep out of reach of the big adults, maybe.

    Who knows? Maybe young Dakotaraptor were volant or semi-volant as well.

  • Deinonychus had rounded snout. Did Dakotaraptor?

  • Dakotaraptor' skull was not found (even though teeth are apparently known from earlier discoveries). However, if it was indeed a big game hunter, and its size and body proportions seem to indicate so, then chances are high it had Deinonychus or Dromaeosaurus-like jaws to deal with struggling prey, rather than long and slender like Velociraptor or Austroraptor. It's just guessing for the moment.

  • Hello all,

    I am convinced that neither Dakotaraptor nor Deinonychus could fly, or even glide; indeed, probably the great majority of the so-called "feathered dinosaurs", paravians, theropod avialae etc. could not do so. Their anatomical structure (underdeveloped sternum, relatively short arms, weak wings) plus their body weight would not have allowed this. At best, Dakotaraptor and company might have been able to flap around a bit like chickens.

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  • I don´t think anyone would suggest that a 50-100 kg Deinonychus or a 300-400 kg Dakotaraptor was flight-capable, but I think the small juveniles would be a different story.

    There was this recent study about a juvenile Deinonychus which suggests their arm structure was fit for flight. They estimate the weight of the 1.3 meter long raptor as being less than 9 kg, which is within the range of flying birds today.

    I admit that looking at the known elements of the skeleton as pictured, it does seem like a lot of assumptions based on very little evidence, but I wouldn´t be surprised if it was true. After all, dromies as a whole do seem to have evolved from flying or gliding ancestors, and there's no evidence at all that they cared for their young. So it would make sense for the young to be neotenic so to speak, and retain the flight capability to increase their chances of survival while small and vulnerable. This wouldn´t be unlike the modern megapode which does incubate and care for its eggs but then abandons the newborn chick, which is however able to fly (better than the adults actually) and fending for itself practically from the moment its born. There's also a few birds that are flightless as adults but not as chicks. I doubt any of them were good fliers but you really don´t have to if you spend most of your time up in trees- many birds that live in dense forests are actually poor fliers- all they need is to be able to fly up and down trees, and from one branch to another.
    Think peafowl, or cracids.

    The fact that some of the most recent dromaeosaurs known such as Velociraptor and Dakotaraptor itself do seem to have arm feather quill knobs suggests these feathers were still important at some point of their lives.

  • Hello Adam,

    What you say is possible...Surely a great number of theropod species bore plumage on their bodies, and some had what we might call real wings, not just feathery arms.

    I think that we need to determine if their nestlings hatched naked, feathered, or just downy like ducklings and chicks. In the latter case, they would not have been capable of flight in their infancy.

    Effective aerodynamic flight in avialae requires a sturdy extended sternum plus keel, which enables the creature to achieve sustained wing strength and airborne thrust. Feathered theropods, with few exceptions, did not have this anatomical feature. As you suggest, perhaps those paravian theropod juveniles which were equipped with proto-wings and feathers might have been able to glide briefly from tree to tree; in spite of their light bodies, I do not think that they could have maintained a flight impetus.

    An extremely interesting case is that of Changyuraptor, a dromaeosaurid theropod from the Early Cretaceous which has been extensively studied since 2012. This amazing "four-winged" paravian, discovered in Liaoning Province, China (a genuine treasure-trove of feathered dinosaurs), with its lavish, well-developed plumage and exceptionally streamlined shape, may indeed be one of the few theropods which achieved true flight. I have not seen photos of its skeleton, however, and thus have not been able to determine what its sternum was like. Could you please help me to find some scientific reports about Changyuraptor which provide photos of the fossil and anatomical details?

  • I don´t know if the paper is open access (I only found previews) but here's the original Changyuraptor skeleton:


    As for comparing adults and hatchlings, the problem is paleontologists often cannot tell for sure if the creature they found is indeed a new species, or just a young specimen of an already known one. In fact, I suspect this is the case with some of the numerous feathered dinos found in China in recent years. Take the recently described Zhenyuanlong, for example:


    To my (admittedly untrained) eyes, it looks like it could easily be a fully grown Sinornithosaurus specimen:


    Sinornithosaurus was 90-100 cms long whereas "Zhenyuanlong" was 2 meters; Sinornithosaurus has more slender limbs and jaws, and longer grasping arms, but overall they were very similar and are considered to be closely related. Sinornithosaurus has been suggested as a gliding and climbing animal that spent much of its time up in trees, whereas "Zhenyuanlong "was evidently a ground based creature.

    And then there's the famous NGMC 91 fossil nicknamed "Dave" which has been tentatively assigned to genus Sinornithosaurus and could very easily be an even younger specimen:



    It might be possible that what they have here is part of the growth sequence of the same animal...

  • Thank you so much, Adam, for your very interesting reply to my post and for the splendid photos. I'm going to print these out and study them with care; the details are wonderful.

    Well, from what I can see in the illustration, Changyuraptor's sternum does not seem to be particularly developed; but, as it appears to be partially crushed and distorted, it's not so easy to tell. Unfortunately, only this single skeleton is known. I think I'll write to the discoverers of this theropod; possibly they could send me a plaster cast and some technical anatomical information. Anatomy is my weak point...What do you think, personally? Could Changyurapror have flown? Was this avialid on the direct evolutionary line toward birds, or just a sideline?

    During the Jurassic and Cretaceous, there were so many "feathered dinosaurs" and almost-birds, that keeping track of them becomes bewildering. Even Dr Xu Xing, China's top expert in palaeo-ornithology, has lost count of the species he's discovered! Many of these theropods bore a strong family resemblance, to the point where it can indeed be difficult to distinguish between them. Within each species, there may have been several sub-species. And this only complicates classification...;)

  • Linnaeus wrote: »
    Could Changyuraptor have flown?

    I don´t think these "four winged" microraptorans could actually fly. I do think they were probably decent gliders, tho; there was a study that tested Microraptor's flight capabilities. It found that it glided best when its legs were directed downwards, rather than sprawled to the sides as in the first reconstructions.


    Looks to me like Microraptor would spend a great part of its time up in the trees, but would regularly glide down to the forest floor to hunt; this explains why fish and non-climbing mammal remains were found in its gut. It probably did this during the time when other, larger ground-dwelling predators were resting. Then, after it had its fill, it would climb back to the safety of trees (it was definitely well adapted to climbing). It would probably also glide and jump from one tree branch to another all the time.
    Changyuraptor is in many ways a larger version of Microraptor so it may have been the same in this regard. This is of course speculation on my part based on what little we know about Microraptor.
    Linnaeus wrote: »
    Was this avialid on the direct evolutionary line toward birds, or just a sideline?

    I think fossils from pretty advanced-looking birds have been found dating from about the same time as Microraptor and co, so I don´t think these guys were bird ancestors at all.

  • Discussion of interest Adam Khor & Linnaeus. Summary. Young light Dakotaraptor perhaps glided. Survival advantage. Adults & young didn't fly. Lacked anatomical structure. Proto-wings.

  • Thanks Adam, I'm grateful for the information you posted concerning Changyuraptor's gliding ability, habitat and habits. Taking this into consideration, it seems that the microraptors had a varied diet, and were skilled hunters/anglers. As fish formed part of their diet, at least in the case of Changyuraptor, we can assume that they agilely snatched up fresh-water fish that swam close to the surface. The microraptors, which probably had keen nocturnal vision and sharp senses in general, might have hunted in the evening or at night. Due to their small size, they would certainly have avoided larger predators, unless they hunted in packs as many raptor species apparently did.

    I wonder, do we have any evidence that these microraptors were omnivorous?
    As they became increasingly birdlike, I suspect that the theropods developed a liking for fruit and seeds.

  • Sorry, it was Microraptor that ate fish; I'm not sure if the Changyuraptor fossil reveals any remains of food in the digestive track. I need to check this...Please excuse the inadvertent error.

  • Even hypercarnivorous animals eat fruit once in a while- tigers love durian, lions love watermelon (although this may have more to do with the water content than the taste itself), and even crocodilians have been seen eating fruit at times. I wouldn´t be surprised if carnivorous dinos too (especially small ones) changed their menu once in a while.

  • Hello again Adam,

    Some observations on the chronology of Microraptor, Changyuraptor and Iberomesornis (this latter is, in my opinion, the first true bird). Microraptor, ostensibly the earliest, dates back to between 130 and 125 MYA. Changyuraptor and Iberomesornis were near contemporaries (ca. 125 MYA). An early but already derived "four-winged" theropod such as Microraptor, living up to 5 million years before Iberomesornis, may possibly have been an ancestor or at least distant cousin of this dawn bird.

    The only skeleton of Iberomesornis which we possess (although a recently discovered fossil of a juvenile feathered avialid may also belong to this species) displays unmistakeable, albeit rather primitive, features which characterize it as a genuine bird. Unfortunately the head is missing...But it seems certain that Iberomesornis would have had a real beak, not a reptilian snout. Iberomesornis, like many other primitive birds, may have had teeth. In order to find out, we eagerly await the discovery of a complete Iberomesornis skeleton.

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  • Hello Adam,

    Some comments on the dating of Microraptor, Changyuraptor, and Iberomesornis (which in my opinion is the first true bird). Microraptor, demonstrably the earliest of the three, dates back to 130-125 MYA. Changyuraptor and Iberomesornis were near contemporaries (ca. 125 MYA). As Microraptor, an early but already derived "four-winged" theropod, lived up to 5 million years before the proto-bird Iberomesornis, it may have been an ancestor or at least a cousin of this avian.

    The only skeleton of Iberomesornis which we possess (although a recently discovered fossil of a juvenile specimen may also belong to this species) reveals unmistakable, albeit somewhat primitive, features which characterize it as a genuine bird. Unfortunately the head is missing; if we also possesed the skull, we would know whether Iberomesornis was toothed, as were many prehistoric birds. Nevertheless, it is practically certain that Iberomesornis would have had a real beak, not a reptilian snout.

  • Iberomesornis may be a bird but it belonged to a different branch of the bird "family tree", the enantiornithes, which went extinct at the end of the Cretaceous leaving no descendants.
    I don´t believe in singling out a fossil species as "the first bird", but in any case, the 130 million year old Archaeornithura found in China is probably more deserving of the title, considering that it is older than Iberomesornis and actually belongs to the same line that gave rise to modern birds. It would also look a lot more familiar than enantiornithes if we saw it nowadays.


  • This is fascinating...You've sent me a photo of a fossil I'm not at all familiar with. I'm going to search for information on this creature.

    As for the enantiornithes: I'm doing special research on them. I've been fortunate to find a beautifully designed pertinent file in Internet: will send the link later. Now, I may be mistaken, but possibly birds of the "modern" type may descend from the enantiornithes after all. We have only one fossil of Iberomesornis. This species may already been in existence as early as 130 MYA or even earlier; we just haven't found fossil evidence yet. New palaeontological discoveries keep pushing back the timeline; many species, including mammalian, have been proven to be far older than we ever suspected. Nevertheless, I would not like to make categorical declarations until material evidence arrives.

  • Although not everything has been revealed about these famous Utahraptor specimens (apparently trapped in quicksand along with an iguanodont), at least they've allowed for a new, more precise reconstruction of their anatomy. It actually looks quite strange.

    The head is huge proportionally to the body, and the tail pretty short. Most intriguingly, it lacks the ossified tendons that made Velociraptor's tail relatively rigid... 

    What do you think?

  • When people complain that Velociraptor was smaller than portrayed in Jurassic Park, but Utahraptor was bigger. :eek:

  • There's now plenty of evidence of big raptors. Not only Utahraptor, Achillobator, Austroraptor and Dakotaraptor, but also footprints from China that show raptors about the size of the ones in Jurassic Park, traveling together (hunting?).

    People just like to complain. :B



  • Great pics!

    Forgive my ignorance, but do they know that the raptors' big claw would be help upright like that?
    As opposed to just being a longer regular claw that could be utilised to great effect when needed?

    Just seems a bit odd to me that they're always depicted as lifted up, but I would have thought holding up one of the toes would be detrimental to stability when moving around.

  • It's an interesting question actually. We know they did for two main reasons, first being the way in which the second toe is articulated, allowing for extreme retraction of the claw not unlike felids today; we just don´t see it in cats because there's lots of other stuff obscuring it (fur, padding, skin folds), and because the toes are shorter and the claws are proportionally much smaller. The big difference is that whereas all toes on a cat's paws have retractable claws (or semiretractable, in the case of the cheetah and a couple other species) , dromaeosaur foot anatomy shows that only the second toe claw could be retracted this way. The basic idea was the same, tho; to keep the claw sharp at all times by avoiding friction against the ground. There is, to my knowledge, only one kind of modern bird that holds its inner claw lifted above the ground to keep it sharp, and it's the South American seriema (closely related to the famous terror birds):

    The raptor version was more extreme, tho (at least in those seemingly adapted for big game hunting, like Deinonychus here). 


    And then you have the many two-toed tracks found around the world, that perfectly fit what you'd expect a deinonychosaur (dromaeosaurids and troodontids) footprint would look like. Walking on two toes was evidently not a handicap for them; in fact, it may have increased their speed. After all ostriches, the fastest bipeds today, have only two toes.

  • Great answer - thanks!
    So from the footprints (where you can see a residual mark from the base of the 1st toe) and the way the South American seriema holds it's toe, it looks more likely that just the end of the toe and the claw itself were lifted up. Some of those dino depictions show the whole 1st toe waving about in the air, which always bothered me!

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  • Well, seeing as the toe does seem able to retract further back, maybe they held it like the seriema when walking, but lifted it when they ran (to keep it out of the way and increase speed), or when they attacked prey/fought each other? Keep in mind that the first (?) and most influential reconstruction of a raptor (Robert Bakker's Deinonychus sketch) has it running at full speed. Pretty much every raptor picture (including those in Jurassic Park) take inspiration from this one.