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The Dromaeosauridae Thread- Anything "raptor" related
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16-05-2012 4:46pm#1The 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?
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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.
http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.00367902
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It is apparently a new species of the already known genus Saurornitholestes.
http://www.cbsnews.com/news/new-dinosaur-species-saurornitholestes-sullivani-keen-sense-of-smell/
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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.
http://blogs.discovermagazine.com/d-brief/2015/11/02/giant-raptor-north-dakota-hell-creek/#.VjlNUNIvcsY
Dakotaraptor claw (right) compared to Utahraptor's
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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...0 -
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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.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.0 -
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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.
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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.
https://mongoliandinosaurs.org/velociraptor-and-utahraptor-how-do-the-cousins-compare-after-new-information-comes-to-light/
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?0 -
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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
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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.
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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.
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