Quick guide on isolated Tyrannosaur teeth

[Omnomosaurus]

43 minutes ago, dinosaur man said:

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.

 

Great! Just remember that you can only test it on mesial teeth and some of the most distal lateral teeth.

 

I wish I was in N. America to visit some of those formations!

[Omnomosaurus]

Just to get the ball rolling on data, I've taken a look at my favourite Tyrannosaurid tooth in my collection, likely from the Dinosaur Park fm.

 

I'm terrible at determining position of most teeth, but I'm guessing lateral for this one (please someone correct me if I'm off)?

 

Based on the theory here, with a massive DSDI of 1.6, it may be Daspletosaurus by default of discounting Gorgosaurus (assuming it is the right kind of distal lateral tooth). The mesial serrations are also very small & weak compared to those on the distal edge, so could also point to Daspletosaurus, if this is a transitional tooth, based on what is described in the paper.

 

CH: 45mm

DSDI: 1.6 (8 mes/5 dis serrations)

 

Mesial:

 

 

Distal:

 

 

No idea if this test has any merit, but @Troodon you can add the data to yours, when you get around to checking.

[Troodon]

34 minutes ago, Omnomosaurus said:

I'm terrible at determining position of most teeth, but I'm guessing lateral for this one (please someone correct me if I'm

whats the base look like

[Runner64]

6 hours ago, Omnomosaurus said:

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.

Don’t have any myself that would be useful for this study. Only have 1 worn Tyrannosaur tooth from the Judith River. There are some serrations but not helpful. By the way, a very nice paper you have highlighted.  This is a tooth I need to get around to obtaining.

 

Its an interesting theory nonetheless. However, I could see it being problematic given how close the numbers are and there are many variables that affect the tooth (size, age, position). Not sure if this has ever been noted before but could gender affect serration density and tooth width/height?

 

@paulyb135 @Jaimin013 @Anomotodon @-Andy-

Perhaps you guys may have some teeth that could be of assistance?

[Troodon]

I have a couple of dozen teeth from the JR and TM that I'm going to looking at but would appreciate any other input.  

 

We need consistent info

 

Distal and Mesial Density count... 2-5 mm wide midline

CH

CBL

CBW

Shape of Base  

Position in jaw :  Premaxillary, Anterior or Lateral

 

Measured like this illustration

[Omnomosaurus]

1 hour ago, Troodon said:

whats the base look like

 

Quite robust:

 

Full specs:

 

CH: 45mm

CBL: 15mm

CBW: 10mm

 

SD: (mesial) 19/5mm

       (distal) 9/5mm

[Runner64]

1 hour ago, Omnomosaurus said:

Full specs:

 

CH: 45mm

CBL: 15mm

CBW: 10mm

 

SD: (mesial) 19/5mm

       (distal) 9/5mm

So based off the tentative identification key on the previous page, this would fall under Gorgosaurus sp. correct?  Just trying to make sure I have the measurements matched correctly.

 

Also, what does DSDI on the previous page stand for?

[dinosaur man]

@Runner64 it could be a Daspletosaurus since the Distal serrations are bigger and stronger then the mesial serrations which indicates Daspletosaurus. Also I think DSDI stands for denticle density. 

[Troodon]

2 hours ago, Omnomosaurus said:

 

Full specs:

 

CH: 45mm

CBL: 15mm

CBW: 10mm

 

SD: (mesial) 19/5mm

       (distal) 9/5mm

Its a anterior dentary tooth.

 

4 hours ago, Omnomosaurus said:

CH: 45mm

DSDI: 1.6 (8 mes/5 dis serrations)

Density is different in your two posts

[Omnomosaurus]

24 minutes ago, Runner64 said:

So based off the tentative identification key on the previous page, this would fall under Gorgosaurus sp. correct?  Just trying to make sure I have the measurements matched correctly.

 

Also, what does DSDI on the previous page stand for?

 

Not quite; according to the method, you can only positively identify a posterior lateral tooth to Gorgosaurus if it has a DSDI of less than 0.8. 

 

Any number less than 1 means the mesial serrations are larger than the distal. The further the number is from 1, the larger the difference in serration density.

 

16 minutes ago, dinosaur man said:

@Runner64 it could be a Daspletosaurus since the Distal serrations are bigger and stronger the mesial serrations which indicates Daspletosaurus. Also I think DSDI stands for denticle density. 

 

Yeah, according to this paper, it would point more towards Daspletosaurus in this case.

 

DSDI is indeed the serration density index. You can work it out by measuring 5 denticles on the midline of the distal carina, then see how many denticles take up the same space on the mesial carina midline; eg my tooth took 2mm to cover 5 distal serrations, and 8 mesial serrations fit into the same 2mm space.

 

Once you have the two numbers, divide the mesial count by the distal....so for mine, 8 ÷ 5 = 1.6. The DSDI of my tooth is therefore 1.6.

[Troodon]

15 hours ago, Omnomosaurus said:

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

where are you seeing this on the chart?

[Omnomosaurus]

6 minutes ago, Troodon said:

Its a anterior dentary tooth.

 

Density is different in your two posts

 

Ah, anterior dentary, thanks!

 

The density in the first post is the ratio difference (8 mesial denticles to 5 distal denticles), whereas the second post is the standard density over 5mm at the midline.

 

Just now, Troodon said:

where are you seeing this on the chart?

 

 

The anterior mesial section on Daspletosaurus is the only Tyrannosaurid highlighted in green on the chart, which is keyed as distal>mesial serrations, with a DSDI of over 1.2. I'm just presuming Gorgo would be closer to 1, since it must by default be below the 1.2 threshold.

[paulyb135]

Over the coming days I’ll do the measurements on this tooth from the old man formation

[Runner64]

22 minutes ago, Omnomosaurus said:

 

Not quite; according to the method, you can only positively identify a posterior lateral tooth to Gorgosaurus if it has a DSDI of less than 0.8. 

 

Any number less than 1 means the mesial serrations are larger than the distal. The further the number is from 1, the larger the difference in serration density.

 

 

Yeah, according to this paper, it would point more towards Daspletosaurus in this case.

 

DSDI is indeed the serration density index. You can work it out by measuring 5 denticles on the midline of the distal carina, then see how many denticles take up the same space on the mesial carina midline; eg my tooth took 2mm to cover 5 distal serrations, and 8 mesial serrations fit into the same 2mm space.

 

Once you have the two numbers, divide the mesial count by the distal....so for mine, 8 ÷ 5 = 1.6. The DSDI of my tooth is therefore 1.6.

Incredible explanation, thank you.

[Runner64]

27 minutes ago, paulyb135 said:

Over the coming days I’ll do the measurements on this tooth from the old man formation

Perfect thanks Paul, let us know what measurements you find

[dinosaur man]

I’ll try to find serrations on my small Tyrannosaur tooth. It’s the only one I have and the serrations are so worn I’m going to need a microscope. and I will test more teeth when I’m out West later this year too!! And @Omnomosaurus amazing explanation too, Thank you!!

[paulyb135]

Will do so for this one too. From the JRF

[Troodon]

30 minutes ago, Omnomosaurus said:

green on the chart,

missed the green thanks  

 

30 minutes ago, Omnomosaurus said:

he density in the first post is the ratio difference (8 mesial denticles to 5 distal denticles), whereas the second post is the standard density over 5mm at the midline.

I know your second one DSDI 19/5 & 9/5 equals a DSDI of 2.1 

where your first one was 1.6

 

[Omnomosaurus]

52 minutes ago, paulyb135 said:

Over the coming days I’ll do the measurements on this tooth from the old man formation

 

That Tyrannosaur tooth is gorgeous, Paul!

 

40 minutes ago, Runner64 said:

Incredible explanation, thank you.

 

You're very welcome!

 

24 minutes ago, Troodon said:

missed the green thanks  

 

I know your second one DSDI 19/5 & 9/5 equals a DSDI of 2.1 

where your first one was 1.6

 

 

Yeah, from what I understood of how to measure DSDI, I read it as the comparative number of mesial serrations compared to 5 distal serrations, rather than using a 5mm measurement like usual.

 

"we consider there is a significant size variation between the mesial and distal denticulated carinae when the denticle size index (DSDI) is higher than 1.2 or lower than 0.9. The arbitrary value of 1.2 to explain the much larger size of distal denticles compared to the mesial ones, was proposed by Rauhut et al. (2010) and corresponds to more than six mesial denticles for five distal serrations."

 

Based on that info, I would assume that doing it the other way and getting 2.1 would be too high of a number, whereas 1.6 seems to line up much closer with the scale of numbers they're working with in the study.

 

Sorry if I've got that all wrong!

[Troodon]

1 hour ago, dinosaur man said:

 it could be a Daspletosaurus since the Distal serrations are bigger and stronger then the mesial serrations which indicates Daspletosaurus.

you cannot make that blanket statement... it all depends on the location of the tooth in the jaw.  

[dinosaur man]

Just now, Troodon said:

you cannot make that blanket statement... it all depends on the location of the tooth in the jaw.  

Ok Thank you, I was just repeating what Omnomosaurus had said earlier.

[Omnomosaurus]

9 minutes ago, dinosaur man said:

Ok Thank you, I was just repeating what Omnomosaurus had said earlier.

 

What you said does match what has been observed in juvenile Daspletosaurus teeth, nothing is reported about this in adult teeth though - try to remember just the youngsters on that feature.

 

Here is the exact quote:

 

"A significant difference between mesial and distal denticles has for instance been observed in the transitional dentition (i.e., teeth at the transition between the mesial and lateral dentition) of an immature specimen of Daspletosaurus (TMP 1994.143.01), the premaxillary, maxillary and dentary dentitions of a juvenile Tarbosaurus (Tsuihiji et al., 2011), and the lateral dentition of the juvenile tyrannosaurine Shanshanosaurus (Currie and , 2001a). In the young specimens of Daspletosaurus, the carinae of the premaxillary teeth are unserrated (TMP 1994.143.1; Currie, 2003) and show the beaded condition seen in Irritator (Figure 15.3). Transitional teeth in this taxon bear minute and, in some cases, poorly delimited mesial denticles and much larger and well-differentiated distal denticles."

 

 

Troodon is right about the adult teeth, identification only seems to be possible on some certain teeth (anterior mesial & posterior lateral).

[dinosaur man]

I know I was talking about your tooth above sorry if I said that wrong.

[Troodon]

3 minutes ago, Omnomosaurus said:

 

Yeah, from what I understood of how to measure DSDI, I read it as the comparative number of mesial serrations compared to 5 distal serrations, rather than using a 5mm measurement like usual.

 

"we consider there is a significant size variation between the mesial and distal denticulated carinae when the denticle size index (DSDI) is higher than 1.2 or lower than 0.9. The arbitrary value of 1.2 to explain the much larger size of distal denticles compared to the mesial ones, was proposed by Rauhut et al. (2010) and corresponds to more than six mesial denticles for five distal serrations."

 

Based on that info, I would assume that doing it the other way and getting 2.1 would be too high of a number, whereas 1.6 seems to line up much closer with the listed figures.

 

I believe 1.6 is correct but I still don't understand what you did with the second one.  But moving on 1.6 is huge and I've have not seen one that large or a Tyranno with mesial serrations of 8/mm.  Are you sure its from that locality.

[Omnomosaurus]

10 minutes ago, Troodon said:

I believe 1.6 is correct but I still don't understand what you did with the second one.  But moving on 1.6 is huge and I've have not seen one that large or a Tyranno with mesial serrations of 8/mm.  Are you sure its from that locality.

 

Sorry Troodon, I think I've confused you there. My fault!

 

The second reading I gave was just serration densities over 5mm for posterity, not numbers for calculating DSDI.

 

1.6 is the only index number I'm saying for this tooth.

 

The mesial serrations are 4/mm (and very weakly defined). 8 is the comparative number against 5 distal denticles.

 

On the subject of locality, the tooth is definitely from Alberta and the seller I originally had it from believed it was from the DP fm. but couldn't be 100% sure.