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Rhedosaurus
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PostSubject: Re: Ask a paleo question   Mon Dec 26, 2016 6:50 pm

I remember reading that Appalachiosaurus was part of the Albertosaur branch of the Tyrannosauroidea superfamily, but after reading David Hone's new book, 'The Tyrannosaur Chronicles' during Christmas. (It was one of my gifts and I love it.) I found out it was no longer the case. What are the reasons and can it still be reclassified as an albertosaur in the future?
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PostSubject: Re: Ask a paleo question   Tue Dec 27, 2016 12:06 am

According to the formal 2005 description of Appalachiosaurus:

"The basal position of Appalachiosaurus is supported by three unambiguous character states: the apex of the dorsolateral ridge of the lacrimal is rostral to the level of the ventral ramus, the lacrimal pneumatic recess is small, and the accessory lacrimal recess is proximal in position." (Carr et al. 2005) From:A NEW GENUS AND SPECIES OF TYRANNOSAUROID FROM THE LATE CRETACEOUS (MIDDLE CAMPANIAN) DEMOPOLIS FORMATION OF ALABAMA

In short, some key features of the skull place it outside of Tyranosauroidea, and more recent analyses that include more Asian Tyrannosaurs continue to find it there. Older analyses were more informal, failed to include asian taxa (which to be fair many of which had not been discovered at the time), and were less informed on the nature of Tyrannosaur growth.

We definitely need more material to gain a better understanding of Appalaciosaurus, but I don't think it is likely that it will be reclassified as an Albertosaur.
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PostSubject: Re: Ask a paleo question   Tue Dec 27, 2016 10:12 am

I know that the holotype was found in Northern Alabama and that some material was also found in SW Georgia, but what other places would be good places to look to find more skeletons?

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PostSubject: Re: Ask a paleo question   Tue Dec 27, 2016 11:02 am

I'm not super familiar with the geology of the eastern US, but it looks like the unit that has yielded Appalachiosaurus outcrops in Mississippi and Tennessee as well. It looks like it is found in Northeastern Mississippi and in a thin band that travels N-S on the West side of Tennessee.
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PostSubject: Re: Ask a paleo question   Tue Dec 27, 2016 1:19 pm

I never heard of Appalachiosaurus remains being found in those states. That said, I'm not surprised that fossils of that dinosaur have been found there. After all, if T. rex had a range from Saskatchewan, Canada down to New Mexico and Texas, then I don't see why Appalachiosaurus had a short range.

I just find it a bit odd that between Appalachiosaurus and at least 2 duck-bills/hadrosaurs being found that it would have launched a massive interest in finding dinosaurs in the South.

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PostSubject: Re: Ask a paleo question   Tue Dec 27, 2016 1:37 pm

Sorry, that was unclear. Appalchiosaurus hasn't been found there, but the rocks that it has been found in outcrop in those states. So there is potential to find more specimens there. But it is harder to do paleontology (or any geology really) in the southeast because it is so forested.
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PostSubject: Re: Ask a paleo question   Tue Dec 27, 2016 3:41 pm

No problems. We all make blunders on sentences and grammar sometimes.

It makes sense that all the forests makes it harder to dig for dinosaurs. Back when my family went for a vacation to Kentucky back in 2004 (which was a disaster since nobody planned anything) I saw a ton of trees in Tennessee and Kentucky. The fact that a lot of the SE is also swampland makes things harder too.

Has any skeletons of Deinosuchus or a similar sized crocodilian been found in the same formations that T. rex and Triceratops have yet?

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PostSubject: Re: Ask a paleo question   Tue Dec 27, 2016 4:25 pm

To the best of my knowledge there has not. Deinoschus remains have been found as far north as Montana, but those are earlier than T.rex (though they are contemporary with Daspletosaurus). I wouldn't necessarily expect to find a similarly large crocodilian in the hell creek, because it seems that Deinosuchus liked estuary type environments and the hell creek might have been too marshy. But the fossil record is full of surprises, and It's possible that large crocodilians were still hanging around in the south during the end of the Cretaceous.
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PostSubject: Re: Ask a paleo question   Tue Dec 27, 2016 4:27 pm

I have some questions about the robust and gracile morphs of T. rex

1. Does it have to do with anything like gender or distribution throughout time
2. What specimens would fit under each category?
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PostSubject: Re: Ask a paleo question   Thu Dec 29, 2016 7:03 am

@tigris115 wrote:
I have some questions about the robust and gracile morphs of T. rex

1. Does it have to do with anything like gender or distribution throughout time
2. What specimens would fit under each category?

1. Gender may still play a part, but a lot of that has been disputed since the late-2000's.
2. Sue and Scotty are under the robust while Stan, Duffy, and AMNH-5022 are gracile.
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PostSubject: Re: Ask a paleo question   Thu Dec 29, 2016 12:31 pm

So technically speaking, one could just make a model of sue and stand and be done with
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PostSubject: Re: Ask a paleo question   Thu Dec 29, 2016 1:22 pm

Pardon the double post but can I get some scientific feedback on Sue here?
Spoiler:
 
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PostSubject: Re: Ask a paleo question   Thu Dec 29, 2016 3:41 pm

We need more then just one model. As for that 3d model, it's not bad, but it needs teeth (of course) and a bit more detail.

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PostSubject: Re: Ask a paleo question   Thu Dec 29, 2016 4:38 pm

Thanks. I'll whip up a better Sue asap
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PostSubject: Re: Ask a paleo question   Thu Dec 29, 2016 11:05 pm

It's hard to compare to photos with the way that she is looking down, but I'd say that her head is probably too narrow. Also, and this might come into play when more detail is added, but the bottom of the feet were probably thicker as they had to cushion a lot of weight. Take a look at ostrich feet to see what I mean, and what is going to work with your style.

Otherwise I think you're off to a great start.
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PostSubject: Re: Ask a paleo question   Fri Dec 30, 2016 3:16 pm

Is this one a bit better? I'm still ironing out some stuff tho

https://sketchfab.com/models/b5a4825a22ed469fa9f797068a8309cd

And this Coelophysis
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PostSubject: Re: Ask a paleo question   Mon Jan 02, 2017 1:23 pm

@tigris115 wrote:
Is this one a bit better? I'm still ironing out some stuff tho

https://sketchfab.com/models/b5a4825a22ed469fa9f797068a8309cd

And this Coelophysis

The Coelophysis is good. As for Sue, the legs from the knees down need far more muscle mass but other then that, it's much improved.
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PostSubject: Re: Ask a paleo question   Tue Jan 03, 2017 1:41 pm

With the robust and gracile forms of C. bauri, which one was the male or female. I need to know because when I send the models to be skinned, I want muh dimporphism
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PostSubject: Re: Ask a paleo question   Tue Jan 03, 2017 5:04 pm

It was originally concluded that the gracile morph was female. However, it has since been determined that Coelophysis had a highly variable growth pattern, and that the dimorphism is likely a difference between mature and immature forms. Some of them grew large before they took on the mature form, and some made that transition at a smaller size.
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PostSubject: Re: Ask a paleo question   Wed Jan 04, 2017 12:21 pm

So the robust was just the mature form while the gracile was the immature form?
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PostSubject: Re: Ask a paleo question   Wed Jan 04, 2017 12:39 pm

The study does not make abundantly clear which morph they believe to be the mature form. However, I'd be inclined to say that the gracile was the mature form while the robust was the immature. This is because the gracile form has a fused sacrum and the robust does not, and I can't think of any instance where bones "un-fuse" over an animals life.
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PostSubject: Re: Ask a paleo question   Wed Jan 04, 2017 2:26 pm

1. What evidence do we have that cave lions and American lions lacked manes?

2. What's the status of Geosternbergia? I know Mark Witton suggested it was just a species of Pteranodon but I'm not 100% sure.
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PostSubject: Re: Ask a paleo question   Wed Jan 04, 2017 2:34 pm

1. From what I can tell, it's because cave art in France shows cave lions with only a small ruff of fur, not the full mane of the modern African Lion. It is also believed that manes evolved in African Lions after the dispersal of lions to North America.

2. I've read Witton's post on Pteranodon, and I find it pretty convincing, but for now they are still considered distinct. For that to change someone will have to do a formal study and get it peer reviewed and published.
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PostSubject: Re: Ask a paleo question   Wed Jan 04, 2017 9:25 pm

What was the purpose of the crests seen on macronian sauropods
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PostSubject: Re: Ask a paleo question   Thu Jan 05, 2017 9:33 am

@tigris115 wrote:
What was the purpose of the crests seen on macronian sauropods

Those were mainly to hold the nostrils so it won't have problems eating. They also might have served as sexual displays, at least for the males, but that's unlikely.
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PostSubject: Re: Ask a paleo question   Thu Jan 05, 2017 12:18 pm

1. What was the lifestyle of ornithomimids like Gallimimus? I've heard everything from dabbling like ducks to omnivores

2.What was the cause of the decrease in biodiversity from the Campanian to the Maastrichtian?
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PostSubject: Re: Ask a paleo question   Thu Jan 05, 2017 11:28 pm

@tigris115 wrote:
which one was the male or female. I need to know because when I send the models to be skinned, I want muh dimporphism

If they're anything like Syntarsus & T.rex (See the following quotes), probably gracile & robust, respectively.

Quoting Adler ( http://www.amazon.com/Herpetology-Current-Research-Amphibians-Reptiles/dp/0916984273 ):
Quote :
It is also worthy to note that Syntarsus seems to be a dimorphic species with both gracile and massive specimens at the same individual age (as assessed by skeletochronol- ogy). Since only the robust individuals show large perimedullar erosion cavities in their long bones, they are tentatively interpreted as females, as calcium is removed from the bones to allow for eggshell calcification (Chinsamy 1988, 1990).

Quoting Larson ( http://www.amazon.com/Tyrannosaurus-Tyrant-King-Life-Past/dp/0253350875 ):
Quote :
By use of morphometric analysis, gracile and robust morphs are confirmed to be present within the clade Tyrannosaurus rex. Extant phyloge- netic bracketing (comparison with living crocodiles and birds) leads us to conclude that the existence of these 2 morphs most parsimoniously repre- sents sexual dimorphism. The discovery of medullary bone within the medullary cavity of a robust specimen of T. rex established MOR 1125 as female (Schweitzer et al. 2005), and therefore all other robust T. rex specimens are, in all probability, also female.
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PostSubject: Re: Ask a paleo question   Fri Jan 06, 2017 9:36 am

@tigris115 wrote:
1. What was the lifestyle of ornithomimids like Gallimimus? I've heard everything from dabbling like ducks to omnivores

2.What was the cause of the decrease in biodiversity from the Campanian to the Maastrichtian?

1. Ornithomimids were mostly herbivorous, but from what we know, many did have to ability to eat some small fish, shrimp, large insects, and small mammals.

2. I heard that climate change was a factor, but considering how it changed multiple times, it doesn't seem like it was the main cause, at least in general.



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PostSubject: Re: Ask a paleo question   Fri Jan 06, 2017 2:32 pm

@tigris115 wrote:
1. What was the lifestyle of ornithomimids like Gallimimus? I've heard everything from dabbling like ducks to omnivores

See "ORNITHOMIMOSAURIA": https://www.geol.umd.edu/~tholtz/G104/lectures/104coelur.html

@tigris115 wrote:
2.What was the cause of the decrease in biodiversity from the Campanian to the Maastrichtian?

See "What does the dinosaur record show?": https://www.geol.umd.edu/~tholtz/G104/lectures/104extinct.html
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PostSubject: Re: Ask a paleo question   Sun Jan 08, 2017 1:20 pm

How are these thagomizers
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