How are dinosaur lengths measured?

[CarnotaurusKing]

I've been trying to figure out the scales of some of my figurines, and I was wondering if the lengths typically given for dinosaurs are measured along the curves of the spine, or along the centra.
Any help is appreciated.

[Stegotyranno420]

I will typically go for centra as its less variable. Over the curves is kind of vague and I'm not sure to what extent.

[Newt]

The lengths for dinosaurs are virtually always guesswork. Fully intact articulated specimens are incredibly rare, and for most species, even overlapping articulated partial specimens do not provide a totally reliable count of vertebrae (especially tail vertebrae). Without knowing how many bones the animal had in its axial column, how can you get a reliable length estimate? Then there's the issue of how close together the vertebrae were in life, i.e. how much soft tissue there was between the bones. This is variable in extant animals and difficult to impossible to determine in extinct ones. All of which is to say, all length measurements for extinct animals should be taken with a grain of salt.


Another issue is that "maximum" length estimates are often based on fragmentary specimens and scaled to better known ones; so if you have a good specimen of Dinosaur X that you think is 10 m long, but you find a toe bone that is 40% longer than the corresponding bone in the good specimen, you would estimate that it came from an animal 14 m long. This process is very iffy; allometric growth is poorly understood in most species, and extrapolation is always dangerous.


Yet another issue is that secondary sources often round up. All my childhood dinosaur books assured me Tyrannosaurus rex was 50 feet long, but no specimen of that size has ever been discovered.


All that aside, lengths are typically not measured over the curves or along the centra; instead, they are measured from the skeletal diagram as a straight line, parallel to the ground, from nosetip to tailtip.



Scaling figures is probably more reliably achieved by measuring a major bone, such as the skull or femur, for which a proper measurement is available.

[andrewsaurus rex]

Newt is spot on.  Another reason why dinosaur lengths vary so much is because most of the tail is missing, which is common, and it has to be guesstiimated how long the tail was.  A good example of this is ankylosaurus, whose maximum lengths vary from low 20's to over 30 feet.  Much of the reason for such a big range is because the complete tail is unknown and it is uncertain just how long the tail was.

There is also a tendency towards exaggeration of total lengths to make the animal seem more impressive.

For a long time now I have measured lengths by finding something known, as Newt said......skull or femur, something of good size and then find an accurate skeletal drawing.  Then it's a simple matter to figure out a straight line length for the whole animal, keeping in mind a lot of guess work probably went into the skeletal drawing as many bones were probably missing and had to be estimated.  Also, skull lengths are often a matter of some guesswork if they are incomplete or deformed during fossilization.

Doing this really opened my eyes to just how often lengths are exaggerated in even seemingly quality reference material.

[Kapitaenosavrvs]

Because of all this, i often ask myself why there is so much fighting over scale. Not here (just a bit sometimes), but in the whole Internetworld. Fights about a detail in a 1:30/35 Figure, where 2mm mean a big difference. But maybe i am just looking at a weird angle on the whole topic :-D

Also, if theres a lengh of a Figure. No one knows how and where exactly this was measured. Even with existic Figures, People measure different Sizes :-D

[andrewsaurus rex]

the fighting over small differences in size may stem from other hobbies that those people have participated in.  If they have collected model planes, cars, tanks etc at some point in there lives, objects where items are made in a factory and are of an exact size, then 2mm can be a significant difference, at least to some people.  I've seen debates on other forums where some people were freaking out because a model tank or car, which is roughly 6 inches long, was 2mm shorter or 2mm longer than it should be in that scale.

Collecting animal figures provides a lot of freedom from that because of the natural size ranges of animals, which is normally at least plus or minus 10% from the average size and often more.  There is also the posture the animal is in to consider.  How upright is the head, is the tail straight out behind it or does it have some waviness to it etc. when it was measured.

Someone on here recently told me that paleontologists measure the size of large animals by adding up the sizes of the individual bones, guesstimating the sizes of the bones that are missing.  This makes a lot of sense and is the equivalent of measuring along the curves.  That plus the fact most paleontologists don't seem overly concerned with precise sizes ie  was the animal 25 feet long or was it 26 feet long and usually express overall size more generally ie about 25 feet, about 30 feet etc  It is different with individual bones, where precise measurements can be taken and small differences can be meaningful but with overall lengths, hip heights it's more generalized for all the reasons discussed in this thread.

[Kapitaenosavrvs]

the fighting over small differences in size may stem from other hobbies that those people have participated in.  If they have collected model planes, cars, tanks etc at some point in there lives, objects where items are made in a factory and are of an exact size, then 2mm can be a significant difference, at least to some people.  I've seen debates on other forums where some people were freaking out because a model tank or car, which is roughly 6 inches long, was 2mm shorter or 2mm longer than it should be in that scale.

Collecting animal figures provides a lot of freedom from that because of the natural size ranges of animals, which is normally at least plus or minus 10% from the average size and often more.  There is also the posture the animal is in to consider.  How upright is the head, is the tail straight out behind it or does it have some waviness to it etc. when it was measured.

Someone on here recently told me that paleontologists measure the size of large animals by adding up the sizes of the individual bones, guesstimating the sizes of the bones that are missing.  This makes a lot of sense and is the equivalent of measuring along the curves.  That plus the fact most paleontologists don't seem overly concerned with precise sizes ie  was the animal 25 feet long or was it 26 feet long and usually express overall size more generally ie about 25 feet, about 30 feet etc  It is different with individual bones, where precise measurements can be taken and small differences can be meaningful but with overall lengths, hip heights it's more generalized for all the reasons discussed in this thread.

Yes, my "I often ask myself" was more of a phrase. Freaking out about stuff in a Hobby or the Internet in general is a thing. And i understand that. Its just a question i ask myself if it is that important now, that i am telling everyone, that i am upset about a Figure and I know why.. This is mostly because of expectations and the lack of Understanding. Discussion is fine. But a typical Internetargument is nothing i would need. Sometimes i feels like someone needs that, but this has another origin, i would say.

There is also the posture the animal is in to consider.  How upright is the head, is the tail straight out behind it or does it have some waviness to it etc. when it was measured.

Thats why i often thought, that measuring along the Spine is the best way to measure an Animal. But i may be wrong. On the other Hand, we measure our Height not along the Spine and our Size depends on how upright we stand.

That plus the fact most paleontologists don't seem overly concerned with precise sizes

This also makes just sense to me.
But i didn't want to change the Topic here and i guess most of it was said already :-D

[CarnotaurusKing]

So far, I've measured most figures along the centra, but now I see how iffy that can be. Sizes for some animals are more reliable than others, but there is still guesswork involved. Sauropods with their enormous tails are especially risky. Measuring a certain bodypart seems the way to go, but it may be difficult since, for example, femurs are covered in flesh and soft tissue, so measuring that way might also have some leeway. Plus some figures have rather wacky proportions (Papo Gorgosaurus comes to mind). But this is a more reliable method than measuring along the spine. Thanks for all the replies.