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North American Tyrannosaurids what is Described that are Sold


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This topic is more up-to-date on North American Tyrannosaurids

 

I find it interesting when I see Tyrannosaurid material for sale, from the Judith River of Montana, that so little is understood of what actually is being offered.   Most sellers call their specimen either Daspletosaurus or Albertosaurus and a few, when it comes to teeth, properly identify them as Tyrannosaurid indet.  Very few will label anything Gorgosaurus unless it's really small.  Yet none of these Tyrannosaurids have been described from this fauna and Albertosaurus may not even be represented.

 

So what is currently known with the major Tyrannosaurids that are sold.  I've tried to look around and gather what information is available and put it together in its simplest form so it's understood, if there are missteps let me know.  Sorry, it's from my narrow collector perspective :)

 

Let me prefix this by saying this is an area that is constantly evolving based with new discoveries and research.  Papers just a few years old can already be obsolete and views are changing.  The other issue is that since so little material has been discovered in some strata that there may not be consensus among paleontologist but thats not new and we also know that their ego's run high.  Not here to debate anything. 

 

Tyrannosaurids Described by age/strata: 

(Those you see sold)

 

Late Maastrichtian deposits  69 - 66 mya (Lance/HellCreek/Scollard Formations et al. )

Tyrannosaurus rex

Nanotyrannus lancensis 

 

Very Late Campanian / Mid Maastrichtian deposits 73 -67 mya (Horseshoe Canyon Formation)

Albertosaurus sarcophagus

 

Late Campanian deposits 75.1 - 74.4 mya (Two Medicine Formation)

Daspletosaurus horneri (just described) (this is described just at the very end of the TM FM not all, age of deposit where collected is very important) 

 

Mid Campanian deposits 76.6 - 75.1mya (Two Medicine Formation)

Gorgosaurus sp. does exist not nammed

 

Mid Campanian deposits 76.7 - 75.2 mya (Belly River Group) 

Daspletosaurus torosus


Mid Campanian deposits 76.7 - 75.1 mya (Dinosaur Park Formation)

Gorgosaurus libratus

 

What is important to note is that no Tyrannosaurid's have been described from the Judith River Formation (80-75 mya) of Montana.  Since the stratigraphy is similiar to that of eastern Alberta it's fair to assume the Tyrannosaurids like Daspletosaurus and Gorgosaurus would be present but not Albertosaurus which is younger in age.   A note from an article I read stated that Albertosaurus and Daspletosaurus are stratigraphically separate, with the former from the late Campanian to Maastrichtian Horseshoe Canyon Formation, and the latter coming from the middle Campanian Belly River Group. Additional discoveries and research will determine if this holds up. 

 

So as a collector you need to take a look at what you have labeled and some may need to be updated and keep this in mind with your next acquisition.  Remember when trying to acquire  tyrannosaurid material don't get hung up on the name, focus on the bone or tooth since it will be with you forever while names can change. :trex: 

 

Chart clearly showing the distribution by age

 (the Two Medicine Taxon is now D. horneri)

 

Tyrant Dinosaur Evolution Tracks the Rise and Fall of Late Cretaceous Oceans Mark A. Loewen1*, Randall B. Irmis1, Joseph J. W. Sertich2, Philip J. Currie3, Scott D. Sampson1 

PDF: journal.pone.0079420.PDF

 

journal_pone.0079420_g004.thumb.jpg.9accf7308c64f57b39c45578412c7094.jpg

 

Carr's Blog (Chart)

 

http://tyrannosauroideacentral.blogspot.com/2017/04/introducing-daspletosaurus-horneri-two.html?m=0

58e688f251bd8_7whendidDaspletosauruslive.jpg.0fed48d786807234b61edcf13938045a.jpg

 

This is an FYI:

Appalachiosaurus montgomeriensis no longer considered a Tyrannosaurid but a basal Tyrannosauroid if that's really important or relevant to collectors.

(PDF from above)

 

Screenshot_20170406-100655.jpg.95736783192eddfe98a52359a795cb7f.jpg

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Susan from PA

Thanks for putting this together for us, Troodon!  I used to get hung up on identifying specimens from the Judith River Formation down to species name.  I don't have much from this area, but not having something specific on my labels drove me crazy.  It doesn't anymore, and I changed my labels to Tyrannosaurid indet.  In my mind, I can't justify putting a name to a certain specimen unless there is scientific evidence out there to support it.  

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All of which means that i feel compelled to post a bit of testing of  tyrannosaurid cladistics.From 2009,no less,so hopelessly outdated...

In the interest of completeness.

Put 3 cladists in a room with the same dataset,and three different cladograms will emerge,even with the same outgroup choice

Seresatte2009TyraCompCladistics.pdf

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Susan from PA

The above article in lecture form.  Sometimes, it's easier to hear it than read it.  :popcorn:

 

 

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