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Troodon

My Jurassic Park: Pachycephalosaurid Domes from Hell Creek Fm

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Auspex

The "Bone Heads" are terribly interesting; they just beg the question "Why?".

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Troodon

The "Bone Heads" are terribly interesting; they just beg the question "Why?".

Why is right, we probably will never know, just lots speculation unless we get that time machine working.

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caldigger

Ya, the flux capacitor is on the brink and parts for those are hard to find these days. Mother Nature had some strange defensive mechanisms going at that time.

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Ludwigia

The "Bone Heads" are terribly interesting; they just beg the question "Why?".

I remember we once placed tacks on our history teacher's chair....

Edited by Ludwigia

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Susan from PA

The Pachycephalosaurs are some of my favorites! Your domes and spike cluster are beautiful! :)

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Arion

The morphology of the nasofrontal boss and the posterior margin of the parietal of your first specimen is more consistent with Prenocephale (Sphaerotholus), of which I believe P. edmontonense is known from the Hell Creek Formation. I'd also suggest that the specimen you have identified as Stegoceras is not identifiable at the genus level; it falls within the size range, but Stegoceras is currently restricted to the Campanian as far as I know, and that specimen lacks any observable characters I can see that would support identification with Stegoceras. It does seem to be pathologic, which is intriguing :)

Edited by Arion

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-Andy-

Once again, a set of amazing fossils any dinosaur collector would love to have :D

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Troodon

The morphology of the nasofrontal boss and the posterior margin of the parietal of your first specimen is more consistent with Prenocephale (Sphaerotholus), of which I believe P. edmontonense is known from the Hell Creek Formation. I'd also suggest that the specimen you have identified as Stegoceras is not identifiable at the genus level; it falls within the size range, but Stegoceras is currently restricted to the Campanian as far as I know, and that specimen lacks any observable characters I can see that would support identification with Stegoceras. It does seem to be pathologic, which is intriguing :)

Thank you for your comments. I did not consider Prenocephale since my understanding was that its range was Campanian/early Maastrichtian (Horseshoe Canyon Fm) and not the Hell Creek Fm. Will follow-up on that.

My call on Stegoceras was based solely on size since no other genus has been ascribed to the HC. Bigelow does show a Stegoceras sp. in his HC fauna list but it may not be current.

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Runner64

Neat finds. Did you find them yourself?

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Troodon

Unfortunately never found any of these.

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Arion

Thank you for your comments. I did not consider Prenocephale since my understanding was that its range was Campanian/early Maastrichtian (Horseshoe Canyon Fm) and not the Hell Creek Fm. Will follow-up on that.

My call on Stegoceras was based solely on size since no other genus has been ascribed to the HC. Bigelow does show a Stegoceras sp. in his HC fauna list but it may not be current.

I think a large part of it depends on your taxonomic views. Prenocephale edmontonense was originally from the Horseshoe Canyon Formation, but some (including myself) consider Sphaerotholus to be congeneric with Prenocephale and S. bucholtzae (from the HC Fm) to be conspecific with P. edmontonensis. My understanding is that all Maastrichtian Stegoceras material has been transferred to Prenocephale/Sphaerotholus and that Stegoceras sensu stricto is limited to S. validum (including Gravitholus and S. novomexicanum) plus whatever the chimera of "S. sternbergi" ultimately turns out to be. The amount of inflation on the second specimen would suggest to me that it's probably a juvenile (based on ontogenetic frontoparietal dome development in Stegoceras and Colepiocephale, I believe it was Ryan Schott who wrote a paper about that a few years ago), so size may not be a useful character for identifying it. I still think it's very interesting taphonomically/pathologically :)

I've always been partial to Pachycephalosaurs, so very cool to have those in your collection. B)

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Canadawest

I restrict my identifications to 'big' and 'small'. I have found a few small specimens in the Oldman Formation...a couple of much bigger specimens in the Horseshoe Canyon ( borderline Scollard) Formation.

I must walk by dozens of the smaller domes in the Campanian and never notice them. Unless some reason to stop and examine a specimen, they look for the most part like a 'hunk of fossil junk' mixed in with a hundred other bone bits. Even If a stegoceras dome is picked up it could be mistaken for a worn vertebra, bone end, etc. and discarded. I only found my first one because a friend showed me what to look for. Another friend, who has much sharper eyes than me has never found one although he has a knack for finding just about everything else.

Anyways, there is a real bias in what is collected because of size, shape, etc. Both domes and pachycephalosaur teeth are easily overlooked.

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Troodon

I think a large part of it depends on your taxonomic views. Prenocephale edmontonense was originally from the Horseshoe Canyon Formation, but some (including myself) consider Sphaerotholus to be congeneric with Prenocephale and S. bucholtzae (from the HC Fm) to be conspecific with P. edmontonensis. My understanding is that all Maastrichtian Stegoceras material has been transferred to Prenocephale/Sphaerotholus and that Stegoceras sensu stricto is limited to S. validum (including Gravitholus and S. novomexicanum) plus whatever the chimera of "S. sternbergi" ultimately turns out to be. The amount of inflation on the second specimen would suggest to me that it's probably a juvenile (based on ontogenetic frontoparietal dome development in Stegoceras and Colepiocephale, I believe it was Ryan Schott who wrote a paper about that a few years ago), so size may not be a useful character for identifying it. I still think it's very interesting taphonomically/pathologically :)

I've always been partial to Pachycephalosaurs, so very cool to have those in your collection. B)

Thank you for the additional information and will give me something to research. I just downloaded Ryan's paper and will take a look at it.

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Canadawest

Here's one from the Maastrichtian. No others found in the area so I just call him Bonehead...reflects both his thick skull and minuscule brain cavity.

post-19254-0-00739700-1456782247_thumb.jpeg

post-19254-0-36644700-1456782444_thumb.jpeg

Edited by Canadawest

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PFOOLEY

Very nice...juvenile material is fascinating.

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LordTrilobite

So I assume you consider Dracorex a juvenile Pachycephalosaurus then? Cool fossil.

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Susan from PA

Beautiful specimen, Troodon!  Thanks for sharing the paper as well! :)

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ynot

:dinothumb: Gotta love the juveniles!

Tony

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doushantuo

Thanks for the VERY timely posting/sharing of that paper:D

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Troodon
On 11/3/2016 at 0:57 PM, PFOOLEY said:

Very nice...juvenile material is fascinating.

 

Thanks, I agree and whenever I have an opportunity to acquire it or luckier find it it's awesome 

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Dracorex_hogwartsia

I've often wondered why Pachy skull material is always found so broken up. These are very solid bones. I wonder what forces are causing them to break up the way they do?

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