How do you measure a dinosaur? Scaling help needed.

[Blade-of-the-Moon]

I've often wondered if I measure dinosaurs correctly. Normally I'll take a skeletal like this :



lay a sheet of paper over it and draw points or dots then connect them, say from the elbow to the foot to get a measurement.

While attempting to do the same recently to a Chasmosaurus skeletal I ran into issues comparing it with a 1:10 skull replica I have, the Dinostoreus one : https://www.dinostoreus.com/chasmosaurus-skull.html

I'm trying to scale up to life size ( 14' for the entire length) but I keep getting conflicting data.  The skull I've seen is said to be 7', the model works out to 7 and a half feet. I try and take that and place it in the skeletal and the whole animal works out to 16 or more feet?  Just about all the reconstructions I've seen give Chasmosaurus a pretty large head about the same length as the body but that's not what I'm finding here.

Perhaps I'm not measuring it the same way that it was meant to be?

[SBell]

Part of it is that the measurements are affected by incomplete skeletons, so lengths are fairly difficult. Especially since most of the vertebral column and tail is missing.

As with most modern quadrupeds, shoulder height is often a preferred tool--judging by your image, that should be relatively easy to determine.

[Blade-of-the-Moon]

Part of it is that the measurements are affected by incomplete skeletons, so lengths are fairly difficult. Especially since most of the vertebral column and tail is missing.

As with most modern quadrupeds, shoulder height is often a preferred tool--judging by your image, that should be relatively easy to determine.

The skeletal i'm actually using is the Chasmosaurus one  from the Princeton Field Guide, no scale bar unfortunately.

[Lanthanotus]

Especially the length of tails may vary to a certain and high degree in several species, so even individuals of the same species (as in species, not genus) and sex may vary considerably in tail lenght and therefor total lenght. Total lenght however may be an uncommon measurement for several species as it is either measured in a direct line from tip of snout to the tip of the tail or following the bodyline. In some cases total lenght is usually not given or ment or measured quite uncommonly, for example the total lenght of an elephant is usually not given, but if it is not measured from the tip of the trunk to the tip of the tail but rather from the base of the nose to the base of the tail.
Shoulder height, as SBell said, is the common measurement in quadrupeds with an erect stance. One has to consider though that usually not the height of the actual shoulder (arm/shoulder joint or shoulder blade) is measured, but the height of the withers, the vertebral ridge between the shoulder blades. I am unsure about the English tradition of measurement here, because in German "Schulterhöhe" (shoulder height) lead to some misconceptions and therefore is replaced by "Widerristhöhe" (withers height).

[Doug Watson]

I've often wondered if I measure dinosaurs correctly. Normally I'll take a skeletal like this :
lay a sheet of paper over it and draw points or dots then connect them, say from the elbow to the foot to get a measurement.

While attempting to do the same recently to a Chasmosaurus skeletal I ran into issues comparing it with a 1:10 skull replica I have, the Dinostoreus one : https://www.dinostoreus.com/chasmosaurus-skull.html

I'm trying to scale up to life size ( 14' for the entire length) but I keep getting conflicting data.  The skull I've seen is said to be 7', the model works out to 7 and a half feet. I try and take that and place it in the skeletal and the whole animal works out to 16 or more feet?  Just about all the reconstructions I've seen give Chasmosaurus a pretty large head about the same length as the body but that's not what I'm finding here.

Perhaps I'm not measuring it the same way that it was meant to be?

What I do when there is or isn't a scale bar is first measure the length by laying a string along the skeletal starting at the far end of the rostral along a straight line to where the occipital condyle would attach to the vertebral column then follow along the column to the tip of the tail following all the natural curves. I then mark the string and measure the length. If I know what the length is supposed to be I can determine the scale. I can also determine or check the scale if I have any known measurements for a femur etc. That can be worked out with the scale bar when given. But then it would help to know what specimen the skeletal was based on but with the Paul version he doesn't tell us. For individual measurements of bones I use proportional dividers and then the scale that I have determined.
Now it seems you are doing Chasmosaurus russelli since you mentioned 14 feet as the length. Why wouldn't you do the better known 16 foot C. belli since complete skeletons have been found whereas C. russelli is only known from incomplete specimens? When I checked Paul's C. belli from the Princeton guide with some measurements I have from actual specimens it seems he has put a larger skull on there compared to a previous skeletal he did.  At 1:25.6 that skull comes out to 6' 6" long. That would be one of the longest skulls found. In a paper I have on Chasmosaur cranial morphology from 1995 the longest skull listed of either species is a C. belli at 6'10" just shy of your 7'. If you want I also have a copy of Sternberg's 1925 description of two very complete specimens of C. belli that has measurements given for skull, body length, major limb bones etc. He gives total length for the two at 16'2" & 16'3" respectively so close to Paul's 16'. Those two skulls however are 5'6" & 5'5". Strangely Paul's original skeletal has a skull of 5'6", so he originally went with a smaller skull on a 16' length and enlarged the skull in his new rendition but kept the 16' length. Let me know if you want the two papers and I'll see if I can send you copies. If I can't I can photocopy the measurements. Unfortunately there are no skeletals so I would just scale the skull to the size you want. Personally I would go with the smaller skull on the 16' since those large skulls weren't found with associated post cranial material so I would be dubious of them having the same size body as the ones with the smaller skulls.

[Blade-of-the-Moon]

I've often wondered if I measure dinosaurs correctly. Normally I'll take a skeletal like this :
lay a sheet of paper over it and draw points or dots then connect them, say from the elbow to the foot to get a measurement.

While attempting to do the same recently to a Chasmosaurus skeletal I ran into issues comparing it with a 1:10 skull replica I have, the Dinostoreus one : https://www.dinostoreus.com/chasmosaurus-skull.html

I'm trying to scale up to life size ( 14' for the entire length) but I keep getting conflicting data.  The skull I've seen is said to be 7', the model works out to 7 and a half feet. I try and take that and place it in the skeletal and the whole animal works out to 16 or more feet?  Just about all the reconstructions I've seen give Chasmosaurus a pretty large head about the same length as the body but that's not what I'm finding here.

Perhaps I'm not measuring it the same way that it was meant to be?

What I do when there is or isn't a scale bar is first measure the length by laying a string along the skeletal starting at the far end of the rostral along a straight line to where the occipital condyle would attach to the vertebral column then follow along the column to the tip of the tail following all the natural curves. I then mark the string and measure the length. If I know what the length is supposed to be I can determine the scale. I can also determine or check the scale if I have any known measurements for a femur etc. That can be worked out with the scale bar when given. But then it would help to know what specimen the skeletal was based on but with the Paul version he doesn't tell us. For individual measurements of bones I use proportional dividers and then the scale that I have determined.
Now it seems you are doing Chasmosaurus russelli since you mentioned 14 feet as the length. Why wouldn't you do the better known 16 foot C. belli since complete skeletons have been found whereas C. russelli is only known from incomplete specimens? When I checked Paul's C. belli from the Princeton guide with some measurements I have from actual specimens it seems he has put a larger skull on there compared to a previous skeletal he did.  At 1:25.6 that skull comes out to 6' 6" long. That would be one of the longest skulls found. In a paper I have on Chasmosaur cranial morphology from 1995 the longest skull listed of either species is a C. belli at 6'10" just shy of your 7'. If you want I also have a copy of Sternberg's 1925 description of two very complete specimens of C. belli that has measurements given for skull, body length, major limb bones etc. He gives total length for the two at 16'2" & 16'3" respectively so close to Paul's 16'. Those two skulls however are 5'6" & 5'5". Strangely Paul's original skeletal has a skull of 5'6", so he originally went with a smaller skull on a 16' length and enlarged the skull in his new rendition but kept the 16' length. Let me know if you want the two papers and I'll see if I can send you copies. If I can't I can photocopy the measurements. Unfortunately there are no skeletals so I would just scale the skull to the size you want. Personally I would go with the smaller skull on the 16' since those large skulls weren't found with associated post cranial material so I would be dubious of them having the same size body as the ones with the smaller skulls.

I like that method of using the string, I normally do just measure a straight line, but that runs into missing all those curves and your not sure if that was being accounted for or not. I actually just liked the reconstructions I've seen of C.Russelli and the skull seemed more appealing to me to be honest.  My preconceptions , my idea of Chasmosaurus was a shorter body and a larger skull..probably due to my only Chasmosaurus replica for the longest time has been the Kaiyodo vinyl.   I honestly prefer Scott's work if I can find the species I'm aiming for and even there is a discrepancy anywhere he will take the time to mention it and even offer a reason behind it.
That would be great Doug and much appreciated!   

[Doug Watson]

I like that method of using the string, I normally do just measure a straight line, but that runs into missing all those curves and your not sure if that was being accounted for or not.

In palaeontology length is measured as though the skull and vertebrae were laid out on the floor in straight  line so if you don't measure the curves it will be wrong. As a result a straight line through the body will always be shorter than the length given.
I have to figure out how to scan the complete Sternberg paper and keep it as one document since I can't find it online. I actually copied it in the Sternberg Library at CMN from their collection.

[Blade-of-the-Moon]

I like that method of using the string, I normally do just measure a straight line, but that runs into missing all those curves and your not sure if that was being accounted for or not.

In palaeontology length is measured as though the skull and vertebrae were laid out on the floor in straight  line so if you don't measure the curves it will be wrong. As a result a straight line through the body will always be shorter than the length given.
I have to figure out how to scan the complete Sternberg paper and keep it as one document since I can't find it online. I actually copied it in the Sternberg Library at CMN from their collection.

That could be where I often run into problems with scaling and translating from paper to 3D.  If an animal is 11' I try to scale 1" -1' or like this Chasmosaurus , on my sketch, the head was 7' so I took another piece of paper made two marks at either end of the head on it and folded it, that gave me 3 1/2' and I keep doing that and that way I build my own scale bar by folding paper . So far I've adjusted as I went when something looked a bit off.  Somehow it's worked out?

If it's any easier, just images and measurements would be fine, they would give me the specs and a reference of some sort of base this guy on.

[Doug Watson]

That could be where I often run into problems with scaling and translating from paper to 3D.  If an animal is 11' I try to scale 1" -1' or like this Chasmosaurus , on my sketch, the head was 7' so I took another piece of paper made two marks at either end of the head on it and folded it, that gave me 3 1/2' and I keep doing that and that way I build my own scale bar by folding paper . So far I've adjusted as I went when something looked a bit off.  Somehow it's worked out?

If it's any easier, just images and measurements would be fine, they would give me the specs and a reference of some sort of base this guy on.

Thanks to my wife I was able to scan both documents and I have e-mailed them to you. Have fun.

[Doug Watson]

I also just e-mailed you a scan of Paul's original 1998 rendition of Chasmosaurus belli from his Complete Illustrated Guide to Dinosaur Skeletons from Gakken. It has dorsal, anterior and posterior views as well. This one shows it with a 5' 6" skull so he probably took his measurements from one of the specimens described by Sternberg in the 1925 paper.
I was wondering do you know how to determine scale mathematically for a skeletal when you have a known value and then use that scale to determine other measurements? If not I could describe the process here.

[Blade-of-the-Moon]

That could be where I often run into problems with scaling and translating from paper to 3D.  If an animal is 11' I try to scale 1" -1' or like this Chasmosaurus , on my sketch, the head was 7' so I took another piece of paper made two marks at either end of the head on it and folded it, that gave me 3 1/2' and I keep doing that and that way I build my own scale bar by folding paper . So far I've adjusted as I went when something looked a bit off.  Somehow it's worked out?

If it's any easier, just images and measurements would be fine, they would give me the specs and a reference of some sort of base this guy on.

Thanks to my wife I was able to scan both documents and I have e-mailed them to you. Have fun.

Awesome! Thank you both!

I also just e-mailed you a scan of Paul's original 1998 rendition of Chasmosaurus belli from his Complete Illustrated Guide to Dinosaur Skeletons from Gakken. It has dorsal, anterior and posterior views as well. This one shows it with a 5' 6" skull so he probably took his measurements from one of the specimens described by Sternberg in the 1925 paper.
I was wondering do you know how to determine scale mathematically for a skeletal when you have a known value and then use that scale to determine other measurements? If not I could describe the process here.

If only views like that existed for all species..lord knows i've bugged Scott about often enough..lol  Math was never my strong suit , i normally just use an online converter like this : http://webpages.charter.net/sinkwich/sdventure/html/sd_scalecalc2.htm  if you'd like to i will do my best to understand, it may help others as well.

[Doug Watson]

If only views like that existed for all species..lord knows i've bugged Scott about often enough..lol  Math was never my strong suit , i normally just use an online converter like this : http://webpages.charter.net/sinkwich/sdventure/html/sd_scalecalc2.htm  if you'd like to i will do my best to understand, it may help others as well.

Okay, I'll do the C. russelli in the Princeton guide. A little tricky since it is missing the rear end. The string measurement gives 8". Paul says it is 14' long which is 168".
To get scale divide 168" by 8" which gives you 21 so your scale is 1:21
Now if you want to find out the size of a particular bone using the scale, for example this skull measures 3.875" at the longest so multiply 3.875" x 21 = 60.37". So the skull on Paul's restoration is a tick over 5 feet long
So not too hard.

[Blade-of-the-Moon]

Yeah not too bad, i'll have to write it down though to keep on hand, my memory has went to pot in recent years.

Maybe it's due to me being so large but 5' seems so small I guess it makes sense though with Triceratops having a such a larger one.

[Doug Watson]

............., my memory has went to pot in recent years.

I didn't know pot was legal in Tennessee?

[Blade-of-the-Moon]

............., my memory has went to pot in recent years.

I didn't know pot was legal in Tennessee?

Doesn't mean can't "find" it..if only you can remember where to look.

I guess maybe my brain was operating under a delusion..kid impressions rarely jive with adult reality I guess...wonder how big Pentaceratops is?   

[Dinoguy2]

I can tell you from experience of scaling lots of dinosaurs: most published length estimates are total nonsense based on gut feeling and guesstimating. The exception is estimates in papers specifically devoted to estimating size.

You proved it to yourself using the Chasmisaurus example. The only correct way to estimate size is to take a skeletal and scale to a completely known element. But what many people do is take a known element and use some standard algorithm (as if there could possibly be such a thing) and calculate total length that way with zero regard for proportional differences.

The method Doug outlined is unfortunately why many models are off. You can't start with a "known" total length because most "known" lengths in the lit are flat out preposterous. Gotta start with an inflexible element like skull or femur length, scale that part and let it drag the rest of the correctly proportioned body with it.

"In palaeontology length is measured as though the skull and vertebrae were laid out on the floor in straight  line"
This is usually true but not always, and I challenge you to find a single paper that explains which way they did it!

[Blade-of-the-Moon]

It's a shame all artists can't check the actual specimens.  I did try to base our triceratops on a skeletal mount that was on loan to our local museum..problem was it was cast from an incomplete skeleton that was as much plaster as it was bone i found out later. 

I'm currently using a skull that is 5' 6" long and basing the rest of the body around that, while also checking the papers Doug sent me to see how close i'm getting and making small adjusts as needed..hopefully it will work out.

[Newt]

I've run into the same trouble when scaling my Lambeosaurus magnicristatus. I got as many measurements of individual bones from the (incomplete) type specimen as I could find in the literature and entered them into a spreadsheet. Then I got measurements from the single referred specimen and from specimens of other lambeosaurines and entered those in a separate column for each specimen; then I calculated the proportion of the femur length of each specimen to the type specimen and used that to correct for size differences between specimens. This gave me a table of measurements of individual skeletal elements which I used to lay out the skeletal drawing. It was a lot of tedious work, but it hopefully resulted in as accurate proportions as I can get without access to a complete skeleton of the animal.

One other caveat to accepting total length estimates at face value is that few specimens include the entire tail - especially for things like diplodocids and many theropods whose tails just taper away to nothing. Who knows how long the missing piece was?

[Doug Watson]

"In palaeontology length is measured as though the skull and vertebrae were laid out on the floor in straight  line"
This is usually true but not always, and I challenge you to find a single paper that explains which way they did it!

Never found it stated in a paper but what I did do is ask a couple palaeontologists who wrote the papers I was using, plus the palaeontologists at CMN when I worked there and that is how they said they measured specimens and it was their contention it was the norm, so I take them at their word.

[Halichoeres]

"In palaeontology length is measured as though the skull and vertebrae were laid out on the floor in straight  line"
This is usually true but not always, and I challenge you to find a single paper that explains which way they did it!

Never found it stated in a paper but what I did do is ask a couple palaeontologists who wrote the papers I was using, plus the palaeontologists at CMN when I worked there and that is how they said they measured specimens and it was their contention it was the norm, so I take them at their word.

Yeah, it's similar with fish in that there's a convention, though the convention itself is different. We basically always measure in a straight line, and if you're reading a fish description that gives the length, everyone assumes you measured in a straight line, but rarely does anyone go to the trouble to specify.