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Identification of Troodontids Teeth


Troodon

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I noticed a number of online suppliers offering Troodon teeth that actually belong to the genus Pectinodon.   Thought it would be a good discussion item for a focused post since they can get confusing with the various morphologies of Pectinodon teeth.   I'll use publications to illustrate my points and reflect all Campanian & Maastrichtian age teeth of North America.

 

(Edit)

A new paper published late in 2017 has turned this taxon upside down.    I will try to reflect those changes here but it should not change alter how they are identified against Pectinodon teeth.  Specimens from Dinosaur Park Formation previously assigned to Troodon formosus have been reassigned to a new taxon Latenivenatrix mcmasterae  and others to a resurrected Stenonychosaurus inequalis.  Troodon formosus is now considered invalid.  At the very end of this page I will show my understanding of ID's by Formation.

 

Canadian Journal of Earth Sciences, 2017, Vol. 54, No. 9 : pp. 919-935

Troodontids (Theropoda) from the Dinosaur Park Formation, Alberta, with a description of a unique new taxon: implications for deinonychosaur diversity in North America

Aaron J. van der Reest, Philip J. Currie

https://doi.org/10.1139/cjes-2017-0031

 

(Edit 2)

Troodon formosus is still considered valid, comments from publication: 

"Given that the latter had already been synonymized into the senior T. formosus and remained unused for 30 years, Troodon formosus remains the proper name for this taxon, exclusive of L. mcmasterae, and we continue to use it here.:

https://www.nature.com/articles/s41598-018-30085-6

 

 

Troodontids -  Standard morphology

These teeth are recurved, laterally compressed and oval in cross section.  The Denticles are large and pointed upward on the distal (posterior) carina and minute or absent on the mesial (anterior) carina.    Premaxillary teeth have strong denticles on both edges (Figure 8.3 E)

 Denticles per mm is typically around 4

 Maximum length about 9.8mm

 

Figure 

Trood3.jpg

 

Examples :

Trood2.jpgTrood4.jpg

 

Troodontids:  Large Morphology

The tooth is large about 50% greater and others and can reach 14mm long, recurved and round in cross section. (See figure below 8.3 # 20-21) These have been collected from the North Slope of Alaska.  Their is nothing unique to these teeth to describe a new taxon.   I've have seen one of these jumbo teeth come from Alberta.   

Troodon Alaska.pdf

 

 

 

 

 Pectinodon bakkeri :

 

Comparison - Troodon and Pectinodon

Pectinodon - left image

#5 mesial denticles usually absent

#11 posterior denticles very large and often rounded

much smaller average length of 2.6mm

 

Troodonitid  right image

#12 posterior denticles point to the tip

#13 anterior denticles exist, can be large or absent

much larger average length 4 mm but can reach 9.8

 

Scale bar 1mm

Both.jpg

 

 

Pectinodon teeth can be put into four categories:  premaxillary, maxillary, anterior & posterior dentary and all look different.

 In Figure 9.5  A & B are Premaxillary, C & D Maxillary, E & F Anterior Dentary and G & H Posterior Dentary

 

Premaxillary teeth: long and slender, mesial carina strongly convex and distal is straight.  Distal Denticles are large, pointed to the tip and become smaller toward the base.

Maxillary teeth are compressed and bladelike.  They look like small Dromaeosaur teeth.  Anterior denticles are irregular in size and very small (5-6 denticles/mm).  Posterior denticles are 3 per/mm.

Anterior teeth are leaf shaped with no serrations on the mesial carina.  Denticles on the distal edge are 1.6/mm.  Denticles are irregular in size.

 

Please note scale bar at 5mm

Pect1b.jpg

 

 

References used:

1) Vertebrate Microfossil Assemblages by Sankey and Baszio

2) Dinosaur Systematics by Ken Carpenter and P. Currie 

 

North American Troodontids:  My best call I"m sure these will be updated with new research and discoveries.

 

Belly River Group (Alberta) :

Latenivenatrix mcmasterae  and Stenonychosaurus inequalis  (one cannot distinguish between isolated teeth of these two species ID: should be Troodontid indet.)

 

Horseshoe Canyon Formation (Alberta) : Albertavenator curriei  (multiple species may exist)

 

Kaiparowits Formation (Utah) : Talos sampsoni

 

Judith River Formation (Montana) : Troodon formosus 

 

Two Medicine Formation (Montana) : TMF Troodontid

 

Hell Creek & Lance Formation (Montana, Wyoming, South & North Dakota) : cf Troodon formosus

 

All others (Saskatchewan, Alaska, Colorado etc) :  cf Troodon formosus

 

 

Multiple Troodontids might exist in these other fauna similar to the Belly Group.  Since skeletal remains are super rare we may never know if this is true.  Identification to a family level "Troodontid indet." may be more appropriate but you can decide that.

 

 

 

 

 

 

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Great googly moogly!    They can certainly be confusing!   Yet another reason to purchase a scope for my computer!   Thanks so much fo sharing! :).  

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Taxonomy is only as confusing as the latest article.  

 

What matters is what always matters... there is a particular specimen and it was collected at a specific locality.  Everything else is subject to revision ( the very nature of science). Thus why a specimen without collecting info loses its scientific value.

 

Identifying a specimen to genus is worthwhile but also just fun. I'm going to have to get out some of my troodon teeth and try and figure them out. One of things I like about member Troodon's postings on dinos is that he brings info from a few sources together and this gives better perspective.

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On 10/3/2016 at 5:36 PM, Canadawest said:

Taxonomy is only as confusing as the latest article.  

 

What matters is what always matters... there is a particular specimen and it was collected at a specific locality.  Everything else is subject to revision ( the very nature of science). Thus why a specimen without collecting info loses its scientific value.

 

Identifying a specimen to genus is worthwhile but also just fun. I'm going to have to get out some of my troodon teeth and try and figure them out. One of things I like about member Troodon's postings on dinos is that he brings info from a few sources together and this gives better perspective.

 

Thanks, be glad to assist with any ID 

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The initial post has been updated to reflect the latest understanding of this poorly understood group of dinosaurs and the consideration that Troodon formosus is no longer a valid taxon.   

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18 hours ago, LordTrilobite said:

Such a shame too, Troodon was a nice name.

:) ha ha

Also easier to pronounce and spell

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  • 9 months later...

I noticed that some papers continue to use Troodon formosus as a valid taxon.  One paper gave the following explanation which I've seen stated before in other similar circumstances: 

 

"The species  Troodon  formosus, Leidy 1856, was originally established on a tooth from the Campanian Judith  River Formation of Montana.  In  1987,  Currie  revised  the  taxon  and  synonymized  several subsequently named species into T.  formosus.  In 2017 van der Reest and Currie recognized that  T.  formosus as defined by Currie included two taxa, one of which they named  Latenivenatrix mcmasterae  and  the  other they referred to  Stenonychosaurus  inequalis. Given that the latter had already been synonymized into the senior T. formosus and remained unused for 30 years,  Troodon  formosus  remains the proper name for this taxon, exclusive of  L.  mcmasterae, and we continue to use it here."

 

https://www.nature.com/articles/s41598-018-30085-6

 

Not sure others authors will follow this path especially with Dinosaur Park material.

 

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