Quick guide on isolated Tyrannosaur teeth

[dinosaur man]

Hi I decided to make a quick guide on how to ID Tyrannosaur teeth from the Belly River Group of Alberta, and the Judith River, Two Medicine Formations. I got this information on a study on how to ID isolated Tyrannosaur teeth from Dr. Angelica Torices. I’ll start off on saying Albertosaurus and Gorgosaurus are extremely alike not much differences in the morphology Daspletosaurus is a little bit Different, the morphology of these two Tyrannosaurs (Gorgosaurus and Daspletosaurus) are probably do to similar evolutionary history Gorgosaurus could of been Albertosaurus ancestor. Now I’ll tell you how to tell these two Tyrannosaur teeth apart (Gorgosaurus and Daspletosaurus). Gorgosaurus has two denticles (serrations) per mm where’s Daspletosaurus does not. Albertosaurus also have two denticles per mm because of Albertosaurus and Gorgosaurus evolutionary history. Also one more thing only with Albertosaurus, juvenile teeth can be different not just in there size but in there morphology too to the Adult teeth where’s Gorgosaurus and Daspletosaurus juvenile and adult teeth always have the same morphology. And thats what I’ve learned about this topic hope it helps, enjoy!!.

[dinosaur man]

This is all I’ve learned on this topic, this is a more in depth answer to my previous topic. 

[Troodon]

I understand what you are trying to do but the information you are providing is not consistent with published data, see below. Density counts of Gorgo and Daspleto teeth are generally indistinguishable from one another and vary depending on tooth and where the measurement is taken, see table below.  Its fact and hard data.

 

If you can provide a publication that clearly describes the differences in identifying Gorgosaurus and Daspletosaurus teeth that would be informative to all.   If your source can provide that information wonderful I'll be first in line to read it. 

 

My sources:

1) Dental Morphology and Variation in Theropod Dinosaurs: Implications for the Taxonomic Identification of Isolated Teeth

Joshua B. Smith,  David R. Vann, and Peter Dodson

2) Morphometry of the teeth of western North American tyrannosaurids and its applicability to quantitative classification 

Lawerence Powell, Philip Currie et al.

 

For example here is a table from one #1 paper it looked at theropod teeth including Gorgo/Daspleto teeth that were around 25mm to +50mm.  

Blue G represents Gorgosaurus data and the Red D is Daspletosaurus

 

MC : Mesial Density at the Center and DC: Distal Density at the center.  MA, DA (density at tip), MB, DB (density at base)

 

The density numbers reflect a 5 mm wide count.    You can see it varies by tooth and location but the similarity exists.

[dinosaur man]

Here’s the one I’ve been looking at @Troodon, sorry I’m not sure how to do the link to it.

[Troodon]

 

Here is the link

https://www.researchgate.net/publication/233713747_Quantifying_tooth_variation_within_a_single_population_of_Albertosaurus_sarcophagus_Theropoda_Tyrannosauridae_and_implications_for_identifying_isolated_teeth_of_tyrannosaurids

[dinosaur man]

Thanks!!, That’s the one I’ve been using for my information so far Troodon.

[Runner64]

On 12/11/2019 at 11:21 AM, dinosaur man said:

Here’s the one I’ve been looking at @Troodon, sorry I’m not sure how to do the link to it.

Hi dinosaur man. I admire your determination to solve the difference Gorgosaurua and Daspletosaurus teeth. However, it appears the reference you are using is nearly ten years old and may be outdated.

 

Something that often occurs in science is that it is wrong and revisions must be made. The paper that @Troodon highlighted takes into consideration tooth morphology variation and makes the correction.

[dinosaur man]

@Runner64 Thanks I have heard that Paleontology is changing so quick that a paper a year old could be obsolete 

[Tidgy's Dad]

2 hours ago, dinosaur man said:

@Runner64 Thanks I have heard that Paleontology is changing so quick that a paper a year old could be obsolete 

Sometimes they have been superseded before publication.  

[Mark Kmiecik]

I can assure all who read this that the rate at which information becomes obsolete nowadays in comparison to the sixties and seventies is truly mind-boggling. I would venture to guess nearly half of what was held as true in my youth is no longer valid as it applies to paleontology. I have already given up on keeping up with the changes, and just use the "old" terminology. To those who have issues with that I can only say, "Just wait. Your time will come." Change is inevitable, but at this pace can become terminal.

[Troodon]

Not sure why everyone is piling on but I find that paper very valid and it makes several key points that address the initial topic.  

 

1) "in western Canada these tyrannosaurid taxa are temporally separated: G. libratus and D. torosus are reported from deposits that are middle to late Campanian in age, whereas A.sarcophagus is reported from late Campanian to Maastrichtian deposits.

( point here is that its easy to distinguish A. sarcophagus from other tyrannosaurid teeth)

2) "However, quantitatively separating isolated teeth of G. libratus from those of D. torosus may prove to
be difficult, given the temporal co-occurrence of G. libratus and D. torosus combined with the morphologic similarity of their teeth"

(Point here is that you cannot distinguish teeth between G. libratus and D. torosus)

 

@Mark Kmiecik @Tidgy's Dad @Runner64

[Praefectus]

52 minutes ago, Troodon said:

Not sure why everyone is piling on but I find that paper very valid and it makes several key points that address the initial topic.  

 

1) "in western Canada these tyrannosaurid taxa are temporally separated: G. libratus and D. torosus are reported from deposits that are middle to late Campanian in age, whereas A.sarcophagus is reported from late Campanian to Maastrichtian deposits.

( point here is that its easy to distinguish A. sarcophagus from other tyrannosaurid teeth)

2) "However, quantitatively separating isolated teeth of G. libratus from those of D. torosus may prove to
be difficult, given the temporal co-occurrence of G. libratus and D. torosus combined with the morphologic similarity of their teeth"

(Point here is that you cannot distinguish teeth between G. libratus and D. torosus)

 

@Mark Kmiecik @Tidgy's Dad @Runner64

I don't think they were commenting on the validity of the paper. Just generally discussing how paleontology changes with time.  

[Tidgy's Dad]

Indeed. 

[dinosaur man]

@Troodon i found another paper that helps identify isolated Daspletosaur teeth "noted that Daspletosaurus is unusual for a tyrannosaurid in having the tooth denticles of the mesial carinae reach the base of the tooth".

[Troodon]

Paper?

[dinosaur man]

@Troodon peerj.com/articles/885/ in the part that says Attribution to Daspletosaurus

[Troodon]

That's does not help 

[Runner64]

5 hours ago, dinosaur man said:

@Troodon i found another paper that helps identify isolated Daspletosaur teeth "noted that Daspletosaurus is unusual for a tyrannosaurid in having the tooth denticles of the mesial carinae reach the base of the tooth".

Hi dinosaur man, I just read the paper and the part that this cites is from a 2004 paper. Something to note in their analysis is that it excludes Gorgosaurus which is usually accompanied with Daspletosaurus.

5 hours ago, Troodon said:

Paper?

E., Thomas, and Carr. “Diversity of Late Maastrichtian Tyrannosauridae (Dinosauria: Theropoda) from Western North America.” OUP Academic, Oxford University Press, 2 Dec. 2004, academic.oup.com/zoolinnean/article/142/4/479/2632290.

[Troodon]

This is the last of my discussion on this subject.

 

This is the go to paper

Morphometry of the teeth of western North American tyrannosaurids and its applicability to quantitative classification
Article in Acta Palaeontologica Polonica · April 2005  Samman, T., Powell, G.L., Currie, P.J., and Hills, L.V.

[Omnomosaurus]

On 02/01/2020 at 12:53 AM, Troodon said:

This is the last of my discussion on this subject.

 

This is the go to paper

Morphometry of the teeth of western North American tyrannosaurids and its applicability to quantitative classification
Article in Acta Palaeontologica Polonica · April 2005  Samman, T., Powell, G.L., Currie, P.J., and Hills, L.V.

 

Fully agree with Troodon.

 

I will however add some information from the very recent paper, 'Dental Features in Theropods' (Oct 2019). Hendrickx, C., etc.

 

As you can see from the chart below, Hendrickx etc identify that certain positional Daspletosaurus & Gorgosaurus teeth have distinct denticle features that can theoretically be used to differentiate the species.

 

Mesial-most mesial teeth of Daspletosaurus Torosus have larger distal denticles than mesial, translating as a DSDI greater than 1.2, a feature seemingly unique among Tyrannosaurids; whereas Gorgosaurus teeth should have a DSDI of presumably around 1.

 

Juvenile D. Torosus premax teeth are also described as having unserrated "beaded" mesial carina, reminiscent of Spinosauridae such as Irritator. The paper also states, "Transitional teeth in this taxon bear minute and, in some cases, poorly delimited mesial denticles and much larger and well-differentiated distal denticles."

 

Some distal Gorgosaurus lateral teeth can also be identified by sporting mesial denticles larger than those on the distal edge, with a DSDI below 0.8. This trait is shared with some Rex teeth, but can obviously be differentiated by locality.

 

It doesn't help us identify all teeth belonging to these Tyrannosaurids, but this info may be useful in distinguishing just a few of the indeterminate teeth out there.

 

TL;DR: If you have a Tyrannosaurid premax with noticeably larger distal than mesial serrations (or no mesial serrations on juvie teeth), it's definitely Daspletosaurus. If you have a more distal lateral tooth with larger mesial than distal serrations, then it's definitely Gorgosaurus. If the DSDI doesn't quite fit on lateral teeth, it still doesn't necessarily discount the chance of being either species. IN THEORY.

 

 

(Colour coding of the blocks is in the key on the right. White blocks are "undescribed" positions for those taxa.)

 

I'm not saying it's the golden bullet that dinosaur man has been looking for, but this is apparently the current thinking on the subject. Put as much stock into it as you dare.

[dinosaur man]

Thank you @Omnomosaurus!! some of this is what I was trying to say earlier on the last few posts, and one of my other topics.

[Omnomosaurus]

36 minutes ago, dinosaur man said:

Thank you @Omnomosaurus!! some of this is what I was trying to say earlier on the last few posts, and one of my other topics.

 

Ah, very good! The paper I've referenced the info from is very recent, submitted in 2017 and accepted only 3 months ago, so it's (as far as I'm aware) the most up to date information we have to play with. 

 

Be sure to reference it if you're making the point on this subject in other topics. The paper Troodon provided is the only other relevant one to consider when discussing these Tyrannosaurid indet. teeth.

[Troodon]

7 hours ago, Omnomosaurus said:

As you can see from the chart below, Hendrickx etc identify that certain positional Daspletosaurus & Gorgosaurus teeth have distinct denticle features that can theoretically be used to differentiate the species

Theoretically is the key word.  I have a number of tyrannosaurid teeth from the Two Med and JRF that I was planning to test this on to see if practically it works before I comment on it.   I'll let you know how it works out.  Will try to get to it before the Tucson show.   The issue I see from a study I did on Tyrannosaurid teeth from the HC is that density changes a lot depending on the size,  position and animal.  There was lots of variability with similar looking teeth.

Anyway,  what I found out on 20 Nanotyrannus teeth is that although I expected a DSDI around 1 the average was 1.09, 80% of the teeth were >1 the others were below 1.  With a range of .86 to 1.27, that's huge.  Very surprised with DSDI >1 more like you see with Dromaeosaurids.

His paper is really really good but there are so many variables like we see on the KK teeth that ambiguous results can led to misidentified teeth.  Premaxillary ones may be more straightforward.

[Omnomosaurus]

1 hour ago, Troodon said:

Theoretically is the key word.  I have a number of tyrannosaurid teeth from the Two Med and JRF that I was planning to test this on to see if practically it works before I comment on it.   I'll let you know how it works out.  Will try to get to it before the Tucson show.   The issue I see from a study I did on Tyrannosaurid teeth from the HC is that density changes a lot depending on the size,  position and animal.  There was lots of variability with similar looking teeth.

Anyway,  what I found out on 20 Nanotyrannus teeth is that although I expected a DSDI around 1 the average was 1.09, 80% of the teeth were >1 the others were below 1.  With a range of .86 to 1.27, that's huge.  Very surprised with DSDI >1 more like you see with Dromaeosaurids.

His paper is really really good but there are so many variables like we see on the KK teeth that ambiguous results can led to misidentified teeth.  Premaxillary ones may be more straightforward.

 

Wow, that is very interesting! The variation in teeth is why I'm hesitant to jump on board with it straight away too; I agree that we need to test this before committing to it as a reliable morph test. Hopefully you do get a chance before the Tucson show.

 

I'd love to help test the theory, but I don't have a wide enough sample size of Tyrannosaurid teeth from the JR or TM formations to come to any meaningful conclusions.

 

The only maybe hopeful point I see with the descriptions in the paper, is that they require a DSDI to be a whopping >1.2 or <0.8 on only certain positional teeth before identification is reliable. As you said, your measurements on Nano teeth had a surprisingly huge range, but I'm assuming those readings were from teeth of all different positions in the mouth?

 

I guess time will tell with this one, and if others across the forum with a good selection of Tyrannosaurid indet. teeth could chime in with any observations they make too, it can only help to test the reliability of this.

[dinosaur man]

I don’t have a wide selection of Tyrannosaur teeth like you either @Omnomosaurus. But later this year I am going to Alberta, B.C, Sasacachuewan and Montana. And I will also test this theory there on the teeth from different formations to see if it changes or works with teeth from around Western Canada and Montana.