Giant theropods overview thread

[razor45dino]

Oct 2, 2024 3:35:10 GMT 5 theropod said:

Sure, but at least from my experience, finding size using scale bars or drawings have notoriously led to inflated estimates at times ( including the infamous UCMP 137538, if I remember correctly ),

Actually quite the opposite. That inflated estimate was based on comparing a measurement for greatest length of a phalanx to a measurement of articular length for the presumed equivalent phalanx in Sue. Analyzing the figure (there was never a drawing in that discussion) was what led to the conclusion that the inflated size estimate for that specimen was based on misunderstanding the measurement and wrongfully assuming them to be euivalent, something since confirmed by actual measurements.

Estimates based on figures and scalebars can indeed be problematic though, but the femur fragment in question actually has a relatively unambiguous measurement stated in the text of Camp et al., a midshaft width of 20 cm. So that part at least is fairly straightforward. Like with other obscure giant theropods (e.g. AMNH 5767), it would certainly be worth trying to look for the specimen and establishing that it can still be physically found and that the measurements and description are correct.

and are a source of numerous giant sizes for various creatures that I'm also skeptical of ( 15 tonne deinosuchus, 22 t palaeoloxodon, for example ).

It would be somewhat circular to use one’s own scepticism of estimates derived from a method as evidence of its unreliability. I have not reviewed these estimates in detail (although I concur that the evidence suggests Deinosuchus is likely the biggest crocodyliform), but if there is something wrong with scale bars and figures that led to these estimates then that should be clearly demonstrable for those specific cases.

I agree though that an estimate based only on a scalebar can be quite problematic. Whenever possible it should be cross-validated against other figures and other scalebars (to see if they match up or contradict each other) or, better yet, measurements given in the text. That seems to be the case here, the measurement is from the text.

EDIT: oh sorry, I think I erroneously thought you were discussing the giant femur fragment with that statement.

"I agree though that an estimate based only on a scalebar can be quite problematic. Whenever possible it should be cross-validated against other figures and other scalebars (to see if they match up or contradict each other) or, better yet, measurements given in the text. That seems to be the case here, the measurement is from the text."

This is basically what I was trying to say, I don't have an inherent aversion to using scale bars if nothing else is there ( although I still remain skeptical depending on the situation ) but if there are actual measurements I rather use those, so I didn't agree that the superimposition getting giant numbers of 150-160 ( 200 in the case of Sinraptor ) is the same reliability as the 140 stated by camp and the 133 calculated by mortimer. 

However, having looked further into it now, the femur length of 00216 Yangchuanosaurus may be irrelevant to the size of this thing, because Mortimer estimated the size of 133 cm for Camp's theropod femur assuming yang had a FL of the 95 cm anyway. So even if it had a Fl of 100, or 110, or 120, the femur length of Camp's theropod would just increase correspondedly because it would be the same size comparatively. The real important thing to know would be Yang's shaft width instead I think. So I guess this rules out smaller estimates? Anywho, I get ~11 tonnes scaling off of Dan's yang, this might be the best estimate. Funnily enough it also is close to one estimate of the allometry estimate from the calculator I linked earlier.

"EDIT: oh sorry, I think I erroneously thought you were discussing the giant femur fragment with that statement."

ye, the shaft's size has been confirmed by someone who works at UCMP, the only other thing to do would be to get actual pictures of it, but at this point the size of the fragment is a non-issue.