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Post by Grey on Jan 14, 2014 3:40:05 GMT 5
I only get the summary, not the whole paper.
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Post by creature386 on Jan 14, 2014 18:24:07 GMT 5
Same with me, but some members here have access to such stuff.
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Post by theropod on Jan 15, 2014 22:34:44 GMT 5
Upper jaw tooth spacing on this one seems to be ~15%: www.boneclones.com/images/s-bc-095-1-lg.jpgThis would give us a toothrow lenght of ~1.838m and accordingly yield a TL of 10.9m for the associated dentition, fairly well compatible with the other figures. |
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Post by creature386 on Jan 15, 2014 22:51:30 GMT 5
How did you estimate that, by simply scaling up from the great white shark?
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Post by theropod on Jan 15, 2014 23:03:58 GMT 5
The toothrow regression from Lowry et al. The same we were talking about previously. Toothrow lenght is summed tooth widths+percentage of interdental spacing.
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Post by creature386 on Jan 16, 2014 0:00:05 GMT 5
But when I used it, you said I shouldn't take spacing into account, but your post sounded like it is a part of your calculation.
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Post by Grey on Jan 16, 2014 0:01:48 GMT 5
15 % seems reasonnable. Unfortunately I still cannot join Mike Siversson.
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Post by theropod on Jan 16, 2014 1:55:00 GMT 5
creature386: Yes, the situation is complicated. Spacing in great whites can be as low as zero, but apparently also quite a bit higher. They are both possibilities, but as correctly noted, it seems using 0% of spacing will typically result in an underestimate. In this case, I assumes 15%, which is roughly what you get from measuring that jaw (note I did not measure every single tooth and gap, which would have been impossible simply due to the resolution of the pic, but I compared a few of them). IÂ’d be very cautious with using anything greater than that tough.
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Post by creature386 on Jan 16, 2014 2:32:42 GMT 5
I was confused at first because when I thought about the method you used, the regressions came to my mind, but the spacing confused me. Thanks for the explanation!
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Post by theropod on Jan 19, 2014 20:41:47 GMT 5
The tooth-spacing formula for great whites yields 7.4m for the IDD on the whale rib (Kallal et al. 2010).
Note that this is just an average value, depending on whether the bite marks were left by anterior, anterolateral or posterior teeth, the agressor may have been larger or smaller, but this is probably the best estimate to use (better than first translating IDD to approximate tooth width, making the same assumption that we have been debating, then that to tooth height and then calculating TL using Gottfried’s equation).
EDIT: Note there is really a fairly huge scope of possibilities here. I cannot quantify them with what I have, but think of the difference between anterior and posterior tooth spacing. The 7.4m is an average estimate, because only a small part of the bite is preserved, we can’t tell whether it’s from the larger or smaller teeth in the dentition.
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Post by creature386 on Jan 19, 2014 21:50:31 GMT 5
^This is similar to what I calculated using the tooth width table (it was roughly 7 m).
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Post by Grey on Jan 20, 2014 1:11:35 GMT 5
That sounds correct. I think spacing measurement was for the anterior teeth. Theropod, how do you possibly estimate the meg that possessed Hubbell's 15.2 cm wide tooth ?
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Post by theropod on Jan 20, 2014 2:23:48 GMT 5
either
-substitute that tooth in the tooth-sets. The question is, which position?
In terms of lenght/width proportions (1.21 ratio), this is most similar to a L2
Using L2, we get 18.5m based on CH-31, 19.9m based on CB-11, average is 19.2m. ThatÂ’s the figure I think is most feasible, with appropriate caution of course.
For comparison, if we use averages for an UA3, we get estimates of 20.2 and 23.1 respectively
-use the rooth-width directly, yielding 18.9m for the tooth width based (KentÂ’s formula which derived from HubbellÂ’s own data)
or
-use tooth-height. The piece is 6.75inch=171.5mm tall, which gives 16.24m TL using GottfriedÂ’s regression. But IÂ’m not convinced at all of this being an UA, let alone UA2.
IÂ’m fairly confident that the owner would be approaching or exceeding the 19m mark.
This is a very wide, robust piece, explaining why the root width gives a so much higher value than the tooth height.
Nobody can possibly know with what teeth the attacker impacted and caused the three preserved calluses. That those were the anterior teeth was mere speculation.
EDIT: Updated the figures, now using averages from both sides in both dentitions and looked up the tooth height in the specimen.
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Post by Grey on Jan 20, 2014 3:16:00 GMT 5
Thanks. I have to say I had a bit left the forum since days and more or less forgotten all the datas in the discussion.
Of course, this is ignoring any allometric factor (which we ignore) which still makes these numbers least worst estimates than best estimates.
On the other hand, the details surrounding the Peruvian skeleton suggest such dimensions are really possible...
From the paper of Kallal et al. it seems to we clearly see which spacing is the widest on the bite mark.
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Post by theropod on Jan 20, 2014 18:30:57 GMT 5
Yes. Also the peruvian skeleton reportedly has teeth comparable to HubbellÂ’s in size, which fits fairly well. This is as good as we can get for now, but as soon (and if) that specimen is described weÂ’ll know for sure.
My point was that there are just three impact points of teeth on a comparatively small fragment of rib.
Those could have belonged to more or less any part within the complete bitemark, hence why the mean estimate is the least bad, with appropriate caution about its real size.
For example, the posterior teeth of HubbellÂ’s tooth set could also fit that wound.
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