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A "vanilla" abelisaur by ScottHartman A "vanilla" abelisaur by ScottHartman
I recently overhauled this skeletal:

Aucasaurus is pretty plain by abelisaur standards. It's head isn't quite as derived as Carnotaurus. It's body isn't as strangely proportioned as Majungasaurus. It's so "stock" that in his last book Greg Paul suggested it may be synonymous with Abelisaurus itself.

Yet even a plain-jane abelisaur is plenty weird. It has a hypertrophied cnemial crest, giving it ginormous calve musles. The transverse processes on the tail are swept up and over the neural spines, giving it a "flat-topped" tail that had a lot of junk in its trunk in terms of leg-retracting muscles. And of course it still has those ludicrously small arms, that almost make T. rex arms seem normal in comparison. Yet all of those features are "normal" for abelisaurs.

So I guess Aucasaurus is weird in a very average way.

Edit: Reposed, with minor revisions to the soft tissue anatomy to bring it up to date.
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:iconpedrosalas:
PedroSalas Featured By Owner May 1, 2014  Hobbyist Traditional Artist
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:iconrobosawrus:
robosawrus Featured By Owner Mar 17, 2013
Where do you find skull neck and torso data for the animal? Ive seen photos of mounts but from odd angles. any more recent publication than the jvp one?
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:iconmadhattermuscaria:
MadHatterMuscaria Featured By Owner Mar 13, 2013  Hobbyist General Artist
Realmente respeto mucho su trabajo, me base en el para hacer algunos de mis dibujos, pero creo que el cráneo de este dinosaurio es mas corto, tuve la suerte y la oportunidad de ver el fósil, y junto con un paleontólogo amigo nos dimos cuenta de que el cráneo era bastante corto...
Espero que esta crítica no sea de ninguna forma ofensiva.

Saludos desde Argentina
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:iconscotthartman:
ScottHartman Featured By Owner Mar 14, 2013  Professional Digital Artist
Sin ánimo de ofender tomado - que no es imposible que la cabeza es más corto, ¿por casualidad tiene fotografías que muestran que están mejor que en la descripción original?
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:iconmadhattermuscaria:
MadHatterMuscaria Featured By Owner Mar 14, 2013  Hobbyist General Artist
No tome fotografías, pero voy a tratar de conseguir algo, si consigo se lo hago saber.

Un gusto comunicarme con usted.

Saludos.
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:iconzegh8578:
ZEGH8578 Featured By Owner Mar 13, 2013
Drawing up an abelisaurid, I settled on Aucasaurus. I imagined a lifestyle specialized to snapping up sauropod babies. Sauropods were abundant in South America, and abelisaurs have these long strong necks, long strong run-happy legs. I imagined a lifestyle of sprinting into sauropod flocks, picking up sauropod babies by their necks, and then running off with them. Which became the motif for my image.
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:iconscotthartman:
ScottHartman Featured By Owner Mar 13, 2013  Professional Digital Artist
That would nicely explain their oddities!
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:icongoldendoggodess:
GoldenDogGodess Featured By Owner Mar 13, 2013  Student Filmographer
Wow, thats some teeny-tiny arms!
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:iconscotthartman:
ScottHartman Featured By Owner Mar 13, 2013  Professional Digital Artist
Yeah, it's hard to imagine that he forelimb was used for a whole lot...but then you never know.
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:icontitanorex:
TitanoRex Featured By Owner Mar 23, 2012
I prefer chocolate i mean carnotaurus
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:iconscotthartman:
ScottHartman Featured By Owner Mar 24, 2012  Professional Digital Artist
I see what you did there!
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:icontitanorex:
TitanoRex Featured By Owner Mar 24, 2012
comparing abelisaurs to flavors of ice cream is the best conversation ever
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:iconsupergoji18:
supergoji18 Featured By Owner Sep 18, 2011  Student Traditional Artist
I needed a magnifying glass just to see those arms.
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:iconscotthartman:
ScottHartman Featured By Owner Sep 19, 2011  Professional Digital Artist
Indeed, you practically do in real life when you see the fossil!
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:iconsupergoji18:
supergoji18 Featured By Owner Sep 20, 2011  Student Traditional Artist
i remember that there are 3 or 4 dinosaurs with arms that small in proportion to their body. Carnotaurus, Majungatholus, and this dinosaur. Was there a 4th?
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:iconskull-island-master:
Skull-Island-Master Featured By Owner Mar 7, 2011
that thing was surley a strong predator unlike most other abelisaurs that are rather weak for theropods.
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:iconscotthartman:
ScottHartman Featured By Owner Mar 7, 2011  Professional Digital Artist
Well, I don't know if any abelisaurs are particularly weak in their post-crania. It's their skulls (and especially their lower jaws) that are odd and sometimes bizarrely weak. But clearly abelisaurus was able to sprint quickly for a theropod of its size, and presumably brought it's open mouth down on its prey with a powerful hatchet-chop as suggested by some of the finite element analyses and muscle insertations.
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:iconskull-island-master:
Skull-Island-Master Featured By Owner Mar 7, 2011
ok
and what avbout ligabueino, some say it was juvenile due unfused vertrebas, but couldi tbe possible that it had unfused vertrebas even as adult, that would give him enormus flexibility. The river dolphin also have unfused vertrebas.

or maybe ligabueino was arboreal, an flexible body could be an advantage here. or do you doub that ??
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:iconscotthartman:
ScottHartman Featured By Owner Mar 9, 2011  Professional Digital Artist
As far as I know, all terrestrial amniotes fuse their neural arches as adults, so I think we can safely rule out the possibility that Ligabueino is an adult. Animals with flexible backs (e.g. for climbing trees) do so by altering the vertebral morphology, so you can tell by examining them.

Also, in general be skeptical of claims of arboreal dinosaurs until you reach the flying ones (and even for a while after that).
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:iconskull-island-master:
Skull-Island-Master Featured By Owner Mar 9, 2011
how big could an adult ligabueino be ??
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:iconscotthartman:
ScottHartman Featured By Owner Mar 9, 2011  Professional Digital Artist
Unfortunately your guess is as good as mine at this point. The rate at which neural spine closure happens varies between lineages, so without a growth series of an abelisaur to go off of it's not really possible to tell if you're looking at an animal that is 60% of the way grown or 15%. Given that it's a noasaur I'd presume it didn't get too large (3-4 meter range?) but honestly our sample size for the group is too small to infer that we're seeing a representative sample of its size range.

It's just one of those cases of needing more data :(
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:iconskull-island-master:
Skull-Island-Master Featured By Owner Mar 9, 2011
well i personally hope it didnt grew much then, such a small noasaur would be kinda cute.
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:iconbensen-daniel:
bensen-daniel Featured By Owner Feb 28, 2011
What were the huge cnemial crests for? I can see why having leg-retracting muscles would give more oomph to a runner, but very strong leg-extending muscles? Was this thing unusually heavy or something?
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:iconscotthartman:
ScottHartman Featured By Owner Mar 1, 2011  Professional Digital Artist
Remember that the cnemial crest also is the origin for the third head of the gastrocnemius in dinosaurs (which of course is an ankle extending muscle). I presume that's the reason why it's enlarged.
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:iconbensen-daniel:
bensen-daniel Featured By Owner Mar 1, 2011
To give more power to the push-off with the foot?
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:iconscotthartman:
ScottHartman Featured By Owner Mar 1, 2011  Professional Digital Artist
Yeah, the tail-based retractors only really work on the first 50-60% of the stride, after that the femur is fully retracted, and it's knee closure and (mostly) ankle extension that is powering the stride up until pushoff. Actually, this is what most digitally animated dinosaurs screw up royally, which is why on most animated specials it feels like the dinosaurs have no real mass to them.
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:iconbensen-daniel:
bensen-daniel Featured By Owner Mar 1, 2011
Ah ha. No kidding. Does anyone get it right?
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:iconscotthartman:
ScottHartman Featured By Owner Mar 1, 2011  Professional Digital Artist
Actually, Jurassic Park does that part of the stride pretty well. Unfortunately they also hyperextend the knee in most of their animal, but the push off is pretty good. There are some upcoming works that do it better, but off hand I can't think of a single documentary that really nails dinosaur locomotion in their digital dinos.
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:iconskull-island-master:
Skull-Island-Master Featured By Owner Mar 4, 2011
have you ever heard of Ekrixinatosaurus ?? Was a very cool abelisaur, also very big ( 11 m ) with an bone crushing skull.
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:iconscotthartman:
ScottHartman Featured By Owner Mar 5, 2011  Professional Digital Artist
I have. I have the 2004 Ameghiniana paper that names it, but while the specimen is certainly complete enough to restore, the paper doesn't really documents the bones well enough to do so (and the skeletal reconstruction published in it doesn't look 100% reliable to me).

So I'd need photographs and measurements before I could produce a skeletal. It's a really cool animal, so if anyone from Argentina wants to pop on over to el Museo Universidad Nacional del Comahue and do some data gathering, I'd be happy to do a skeletal reconstruction of Ekrixinatosaurus.

I was in Brazil a few years back (and saw some great specimens) but I haven't gotten anywhere else in South America yet. Which is tragic, as there are some great people, places, and fossils down there, but it's also pretty expensive to take trips like that.
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:iconpilsator:
pilsator Featured By Owner Feb 23, 2011  Hobbyist Traditional Artist
Very cool. Still wondering what stumpy-legged abelisaurs a la Majungasaurus did with such a huge cnemial crest and attachments for a caudofemoralis that large.
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:iconscotthartman:
ScottHartman Featured By Owner Feb 24, 2011  Professional Digital Artist
Well, those long lever arms are actually better for supplying leverage rather than rapid acceleration. If it weren't for their heads I'd think they were taking on large prey and wrestling with it.

Although it'll probably be more obvious once we get say twice as many decent abelisaurs and can map out a robust family tree. After all, some of these features are just plesiomorphic, and we're all sitting here trying to understand each taxon like they are entirely apomorphic, since they are so different from other theropods.
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:iconpilsator:
pilsator Featured By Owner Feb 24, 2011  Hobbyist Traditional Artist
Yeah, it's surprising how different postcranially abelisaurids tend to be.

wrt the wrestling model, I wonder since quite a time if it might truly hold any water regardless the skulls. Especially the very broad snouts of Majungasaurus-like taxa look resistant to torsional forces, so these theropods might have held on to their prey (then again, my example is one of the shortest of all which might not have been able to reach the necks of contemporaneous sauropods). Any idea if abelisaurs might have been able to rear up into a semi-erect posture with a better "grip" to the ground, using their heavy tails as a semi-Paulian prop? Not that the neck or muzzle of a small-ish titanosaur wouldn't fit between the jaws of a larger abelisaur.
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:iconskull-island-master:
Skull-Island-Master Featured By Owner Feb 23, 2011
can i use it as refrence ??
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:iconscotthartman:
ScottHartman Featured By Owner Feb 23, 2011  Professional Digital Artist
Yes, draw away!
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:iconamorousdino:
amorousdino Featured By Owner Feb 23, 2011  Student General Artist
Mother nature must hav been smoking some weird shit when she designed the Abelisaur family....
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:iconashere:
Ashere Featured By Owner Feb 22, 2011  Hobbyist Traditional Artist
It's quite an elegant looking animal. In a weird way, it's like its taken the theropod body plan to the logical extreme: a mouth on legs with a tail. The simplicity of the very, very derived. :)
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:iconscotthartman:
ScottHartman Featured By Owner Feb 22, 2011  Professional Digital Artist
Actually, those were my thoughts pretty much exactly as I finished. It's funny, because when I work on a skeletal there's so much scaling (and double checking) and rendering individual parts (many of which are serially repeated and mind-numbingly boring to draw) that I often really don't get an impression of an animal until just before I finish.

I sort of like that because I feel that I'm less likely to be biased by a sense of aesthetics, but also because when I end up thinking they are elegant looking it ends up being quite the reveal.
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:iconashere:
Ashere Featured By Owner Feb 22, 2011  Hobbyist Traditional Artist
I can imagine. It's almost like re-excavating the animal. And we other artists are insanely grateful to you for the work. :)
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:iconpaleo-king:
Paleo-King Featured By Owner Feb 22, 2011  Professional Traditional Artist
Excellent skeletal! Yeah, Aucasaurus was pretty "normal" for an abelisaur... just like Skorpiovenator.

The most interesting thing about these abelisaurs is how powerfully muscled their legs and tails were. Despite their weird blunt heads and tiny arms, they were very fast for their size, like giant bullets on legs. I wonder what the reason for this was... did they hunt fast prey or were they simply fast hit-and-run scavengers who could eat quickly and outrun bigger opportunists? Or were they professional baby-snatchers, as John Sibbick seems to say with his national Geographic painting of Aucasaurus....
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:iconscotthartman:
ScottHartman Featured By Owner Feb 22, 2011  Professional Digital Artist
"Professional baby snatcher" probably wouldn't be the best pick up line IMO. These medium-sized fast abelisaurs with narrow reinforced skulls and slender mandibles seem to be good at running up and whacking things with their upper tooth row...perhaps they are small-medium sized dinosaur killers?

Whatever it is it must have been successful, as they have a good run of things in the Cretaceous.
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:iconpaleo-king:
Paleo-King Featured By Owner Feb 23, 2011  Professional Traditional Artist
They could be built for slicing into the necks of juvenile sauropods... and yeah it's a terrible pickup line. But pretty much all pickup lines are awful LOL :D

Since they were so successful, I wonder if larger predators like carcharodontosaurids also were.... yet I don't know of any of them surviving to the Campanian or Maastrichtian. Were there any giant predators left in the southern hemisphere by that time, considering that there were still giant herbivores (Puertasaurus, Argyrosaurus, Antarctosaurus)?
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:iconthemacronian:
TheMacronian Featured By Owner Feb 22, 2011  Hobbyist Traditional Artist
Look at T-rex, it was normal. After 15 million years of previous "large" tyrannosaurid domination, (Albertosaurus, Daspletosaurus, Gorogsaurus, Bistahieversor etc.) He was just the larger version.
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:iconafrovenator:
Afrovenator Featured By Owner Feb 21, 2011
Where did you find information about its skull? I know it is there and pretty well-preserved but I haven't seen any pictures of it other than line drawings thus far.

BTW, I love the proportions on this guy, it almost looks elegant among its relatives! :)
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:iconscotthartman:
ScottHartman Featured By Owner Feb 21, 2011  Professional Digital Artist
I have my ways (this reads better if you imagine maniacal laughter emanating from the screen).

I agree, it's quite good looking by abelisaur standards (which is sort of like being the tallest pygmy, but still, I like it).
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:icontheblack-kat:
TheBlack-Kat Featured By Owner Feb 21, 2011  Student Filmographer
I'm a dinophile but I don't know this one. He looks like he hasn't got any elbows, or are his ulna's and radius's so small they look like his wrists (sorry if those aren't the right words but I hope you know what I mean)?
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:iconscotthartman:
ScottHartman Featured By Owner Feb 21, 2011  Professional Digital Artist
You are correct, his ulna and radius are so small they are easy to mistake for wrist bones. But functionally speaking they may as well have no elbow, since the forearm couldn't really move independently anyways.
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:iconemperordinobot:
EmperorDinobot Featured By Owner Feb 21, 2011
this animal was pretty powerful in terms of locomotion. And this is a nicer reconstruction than your previous one.
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:iconscotthartman:
ScottHartman Featured By Owner Feb 21, 2011  Professional Digital Artist
If we could never mention the previous one again we'll all live happier, more productive lives.

Seriously, that was one of my oldest surviving skeletals, and it was in dire need of a rework I'm afraid (the original version was done in the late '90s, and in 2003 all I did was create a rigorous version, I didn't rework the anatomy.../shudder).

You are right, Aucasaurus appears to have been quite a speed guys for a medium-sized abelisaur.
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:iconemperordinobot:
EmperorDinobot Featured By Owner Feb 22, 2011
And as a matter of fact, I took special care doing my Aucasaur and it ended up looking more like this than your old stubby version. So we're living happier, more productive lives already!:la:
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February 21, 2011
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