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Check this out if you haven't already. This is just the cutest thing. Dr. Phil Currie kicks off 2016 with a description of a near-complete baby Chasmosaurus!

I remember Chasmosaurus with a lot of nostalgia. It was my favorite horned dinosaur growing up. In fact it was my second favorite dinosaur of any sort for a long time (after Giraffatitan of course, which was then known as "Brachiosaurus brancai"). The different species and horn configurations fascinated me no less than the endless variations in modern antelope horns, from the little nubs on C. belli to the longer studs on C. russelli, to the impressive upturned skewers of C. kaiseni (or Mojoceratops, if the two skulls are truly from the same species). The frill was large but simple, a rectangular shield framed with rows of basic epoccipital studs and a couple of pairs of larger studs at the corners. This genus was the namesake of its own subfamily, the classic "standard model" three-horned dinosaur by which all others were measured, most of which appear like some fancier variation of it. More of the "three-horns" in fact resemble Chasmosaurus than they do Triceratops. But there was never a baby specimen... until now.

Baby-chasmosaurus by Paleo-King


The strangest thing about this adorable dinosaur is how long the hindlimbs are compared to the body, particularly when you scale it up against an adult's proportions. While the arms are missing, there's a possibility that they were not unusually elongated relative to the adult proportions, which begs the question - were baby ceratopsids bipedal? This was after all the basal ceratopsian condition found in Leptoceratops and other protoceratopsids. There's already been some venturing (and illustration) of the theory of habitually bipedal running among baby sauropods, which makes a lot of sense (for the bottom-heavy diplodocids anyway - I don't really see Toni the Brachiosaurus doing too much of this). But there haven't been a lot of juvenile ceratopsid remains complete enough to do a biometric analysis of bipedal running and its feasibility. What do you think?  (BTW the paper is free to download, though being in the control of JVP's new masters Taylor and Francis, it's uncertain how long that will last. Get it while you can!)
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:iconthedinorocker:
thedinorocker Featured By Owner Jan 31, 2016
There is another Chasmosaurus paper Campbell et al.(2016)
Here the abstract:

An analysis of every potentially taxonomically informative chasmosaurine specimen from the Dinosaur Park Formation indicates that Cbelli and Crusselli have indistinguishable ontogenetic histories and overlapping stratigraphic intervals. Neither taxon exhibits autapomorphies, nor a unique set of apomorphies, but they can be separated and diagnosed by a single phylogenetically informative character—the embayment angle formed by the posterior parietal bars relative to the parietal midline. Although relatively deeply embayed specimens (C.russelli) generally have relatively longer postorbital horncores than specimens with more shallow embayments (Cbelli), neither this horncore character nor epiparietal morphology can be used to consistently distinguish every specimen of Cbelli from Crusselli.

After that I think that the 2 species could really be sexual dimorphism as well (considering Mojoceratops/C.kaiseni is found to be a full grown C.russelli aka a full grown male)
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:iconpaleo-king:
Paleo-King Featured By Owner Jan 31, 2016  Professional Traditional Artist
Hmmm... very interesting. Is that finding about C. kaiseni in the same paper, or is it found somewhere else?

I always did have a hunch that this could be dimorphism. The short horns of the average C. belli/C.russelli seem odd unless at least some members of the species had longer horns. However isn't it also true that all three species have different epoccipital configurations at the back of the frill? Also in C. belli, the nasal horn is upturned and in C. russelli it is straight or forward curved (or was it the other way around?).
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:iconpilsator:
pilsator Featured By Owner Feb 1, 2016  Hobbyist Traditional Artist
kaiseni seems to be dead. They do point to some surprising things, such as russelli persisting longer in the Dinosaur Park than expected, they don't recover Vagaceratops as sister to Kosmoceratops, and so on. I was also surprised just how "craniocentric" ceratopsid matrices still are (~6:1, skull:postcrania), but I strongly suspect this mismatch was more extreme before.
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:iconpaleo-king:
Paleo-King Featured By Owner Feb 6, 2016  Professional Traditional Artist
Yes, ceratopsids are very front-heavy indeed, and many old illustrations didn't appreciate just how big-headed they were. Vagaceratops is an odd one.... it does look a lot more like Chasmosaurus than Kosmoceratops, perhaps the odd frill comb is just convergence.
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:iconpilsator:
pilsator Featured By Owner Feb 18, 2016  Hobbyist Traditional Artist
I was talking about the cranial:postcranial character ratio in the data matrix.
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:iconthedinorocker:
thedinorocker Featured By Owner Jan 31, 2016
The paper is on PlosOne so you can read it but the short version is both epoccipital configuration and horns morphology aren t good to distinguish the species, the only statistical relevant issue is the angle of employent of the frill bar.
That said appear the one morphology had more often long horns than other (and this morphology called C.russelli could be the male morphology).
For me only one distinguishing caracter for stratigraphical overlapping and ontogenic indistinguishable species is really weak and I think the sexual dimorphism hypothesis is stronger
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:iconpaleo-king:
Paleo-King Featured By Owner Jan 31, 2016  Professional Traditional Artist
If that's the case then perhaps other ceratopsids are dimorphic too.... Styracosaurus parksi (the AMNH specimen) is probably just a female of S. albertensis.
Since the S. albertensis type specimen (probably male) is very similar but has much longer nose horn, spikes, and bigger hook-shaped jaws.
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:iconthedinorocker:
thedinorocker Featured By Owner Feb 1, 2016
I do not remember a good photo of S.parksi but Surely time overlapping and overall morphology very similar (except for horns size) could indicate a sexual dimorphism
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:icondontknowwhattodraw94:
Dontknowwhattodraw94 Featured By Owner Jan 30, 2016  Hobbyist Traditional Artist
That's quite interesting! Maybe they were only habitually bipedal so they could run faster and walked on all fours the rest of the time?
I see in the paper there are even skin impressions, what an amazing find.
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:iconpaleo-king:
Paleo-King Featured By Owner Jan 30, 2016  Professional Traditional Artist
Yes indeed, skin impressions are always a big deal. Though there are actually several better ones known from ceratopsids already (both centrosaurines and chasmosaurines) so there isn't a lot of new ground to cover there.

Sauropods on the other hand.... despite their being so huge, all we have from their skin impressions is an elbow impression from the near-titanosaur "Pelorosaurus" becklesii (England), a couple of messy brachiosaur handprints that show marks from "spiky" traction scales on the bottom (Spain), and a tiny patch of embryonic titanosaur skin impression from an egg fossil in Auca Mahueco (Argentina), a patch which is literally not much bigger than a postage stamp. Apparently there are no skin impression known from diplodocids, mamenchisaurids, euhelopodids, camarasaurs, and a whole host of other sauropod groups.

I can definitely imagine this baby being bipedal at least for running, if only for the fact the head is small and the arms are unlikely to have been elongated far beyond adult proportions like the hind legs are. Sort of a juvenile throwback to the "crossover bipedalism" found in many protoceratopsids.
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:icondontknowwhattodraw94:
Dontknowwhattodraw94 Featured By Owner Jan 31, 2016  Hobbyist Traditional Artist
Ah, I see.

Don't we also have spikes from the back of a Diploducus and osteoderms from Titanosaurs? (if you count that as skin impressions)
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:icondontknowwhattodraw94:
Dontknowwhattodraw94 Featured By Owner Jan 31, 2016  Hobbyist Traditional Artist
Ah, I see.

Don't we also have spikes from the back of a Diploducus and osteoderms from Titanosaurs? (if you count that as skin impressions)
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:iconpaleo-king:
Paleo-King Featured By Owner Jan 31, 2016  Professional Traditional Artist
Actually we do have some skin impressions (or actually preserved nodules surrounding the osteoderms) from saltasaurine titanosaurs. This isn't the regular skin, but hardened scaled on the back that form a pebbly matrix (lithostrotos) in the region where the big osteoderms are. So for titanosaurs (the most derived ones anyway) we have not just osteoderms but also the small nodules. Thanks for catching that! But it's not the normal skin you would find on their underbelly, limbs, or neck and tail. Osteoderms are also known for more basal types like Malawisaurus and Mendozasaurus, but these are more spike-like and don't come with nodules attached, so they may not have had them. Of course "osteodermata" is a more inclusive titanosaur group than "lithostrotia" in plenty of other ways including morphology of the skeleton. But that's a rather fuzzy topic for another time.

The diplodocid spikes from the morrison are interesting as I hear about them all the time but have never come across actual photos of the things. Yes those seem to be legit, but it's odd how documentation of them seems so hard to come by... especially since a lot of artists ended up revising their diplodocids on the basis of these finds alone.
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:icondontknowwhattodraw94:
Dontknowwhattodraw94 Featured By Owner Jan 31, 2016  Hobbyist Traditional Artist
Oh cool, didn't know we had that much of Titanosaurs. Looking at the description you gave, those animals must've had quite a special appearance with all that armour. 
I can't really imagine what you mean with nodules though (how they look like). Are they sort of bumps surrounding the osteoderms, larger than normal scales?

Yeah, I guess that's true. I've only seen them in this post by Mark Witton: markwitton-com.blogspot.be/201…
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:iconpaleo-king:
Paleo-King Featured By Owner Jan 31, 2016  Professional Traditional Artist
Yes the nodules are basically hardened scales that are a bit larger than normal scales (or taller anyway) and function as secondary armor. This made it very hard for predators, especially the proportionally small-toothed abelisaurs, to bite a saltasaurid.

That said, the saltasaurid osteoderms are a bit different from those of most other armored titanosaurs. They are disk-shaped and in Laplatasaurus they are flat with a small central ridge, this ridge is bigger in Saltasaurus and sometimes has a small central spike.

More primitive armored titanosaurs like the lognkosaurians (i.e. Mendozasaurus) have osteoderms in the shape of fat spikes, rather than disks with a central ridge or small spike. Also they are not known to have the nodule scales. The most heavily armored titanosaur may be Ampelosaurus, which judging by the skull and limbs is probably an antarctosaurid (somewhere between lognkosaurs and saltasaurs in evolutionary terms). Ampelosaurus has both spike-shaped and disk-shaped osteoderms. Possibly nodules too. Also the skull shapes are different in lognkosaurs (at least their basal cousins like Malawisaurus, which has a big nasal crest) versus true "lithostrotians" known for nodules and their diplodocid-mimic skull designs (Antarctosaurids, Saltasaurids, Nemegtosaurids).

Nemegtosaurids like Rapetosaurus appear to retain a few of the more primitive spike-osteoderms despite being lithostrotians, probably a basal holdover from their high-browsing lognkosaur ancestors. I would expect them to have the nodules too. And as mentioned before Ampelosaurus also retained the spikes, despite being a shorter-necked grazer with probably  a more saltasaurid-like lifestyle. Only the Saltasaurids appear to have lost the basal "fat spikes" entirely.
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:icondontknowwhattodraw94:
Dontknowwhattodraw94 Featured By Owner Feb 1, 2016  Hobbyist Traditional Artist
Interesting. How about the giant titanosaurs like Argentinosaurus or Alamosaurus? Would those have then only disks with a possible ridge since they're younger species?

How would their armor be placed? Looking at how large they are, the only option for predators is to bite on quite low places. In reconstructions you always see titanosaurs with their osteoderms mostly located on top of their back and upper part of their torso. Could it be then that large titanosaurs had armour more close to their belly too? I'm just thinking out loud, but it doesn't seem so far stretched. 
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:iconsaurornithoides:
Saurornithoides Featured By Owner Jan 30, 2016
Skin impressions appear to be known in some Diplodocids, Mamenchisaurus youngi, Tehuelchesaurus, and Camarasaurus sp.: www.app.pan.pl/article/item/ap…
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:iconpaleo-king:
Paleo-King Featured By Owner Edited Jan 31, 2016  Professional Traditional Artist
Wow this should be a big deal, if it isn't already :XD:  But where is it? You linked to an article about hadrosaurs, not sauropods.
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:iconsaurornithoides:
Saurornithoides Featured By Owner Jan 31, 2016
There's a table with all known dinosaur skin at the time in the supplementary data
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:iconpaleo-king:
Paleo-King Featured By Owner Jan 31, 2016  Professional Traditional Artist
Thanks. Gotta love that supplementary data! So easy to miss when it's not in the main paper.
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