Mounting a skeleton: bones or casts?

If a museum plans to exhibit a new dinosaur (or fossil mammal) skeleton, the first question that needs to be answered is whether to mount the real fossils, or casts of them. In some cases, the decision is fairly easy, e.g. if the fossil is physically or chemically too instable to be mounted. In others, however, a number of factors play a role.

Two casts (Diplodocus, Allosaurus), several real skeletons (Dicraeosaurus,
Elaphrosaurus
, Dysalotosaurus) and a chimera (Giraffatitan: most is real
bones, but the sacrum and neck are casts) in the MfN Dinosaur Hall.

There are a number of compelling arguments against mounting real bones, and for mounting casts:

  • real bones are heavier than casts, thus need sturdier = more visible support, put higher stresses on any supporting structure, and require more effort to mount.
  • casts can therefore be mounted in extreme positions easily (rearing sauropods, anyone?)
  • real bones are both more fragile and more precious than casts, requiring support to be built to higher safety standards, and make mounting and dismounting them a more complex task, because more care is needed.
  • bones may require regular checks by technical personnel, because they may become brittle over time, which entails cumbersome work on ladders or hoisting platforms, or even periodic de-mounting.
  • mounts are subjected to the temperatures and humidity of exhibition rooms, which are much harder to control than those of non-public collection rooms. Casts will not suffer where real bones may.
  • bones are also much less accessible to researchers, curators and other interested persons when they are high up in the air on a mount.
  • casts can be colored any way you wish, and can (via digitizing and rapid prototyping) be exact mirror images or composites of existing specimens.

Additionally, if you decide to loan your dinosaur (or other skeleton) to a temporary exhibition at the other end of the world, as the MfN did with its Giraffatitan (then Brachiosaurus) mount in 1984, it is much simpler to use casts – and casts can be replaced! That’s probably the most important point about mounting casts: you can always get new casts, but if you break or loose the real fossil, you just ruined an irreplaceable specimen.

On the other hand, there are good reasons for using real material, too:

  • Anybody can mount casts. Only you can mount the real fossil you own.
  • You can be as thorough as you want, casts will never look real to a careful observer.
  • Casts cost money, even the shittiest versions. That offsets the higher cost for the sturdier support for real bones. Excellent casts (rapid prototyped on the basis of CT or laser scans) may end up much more expensive than a “simple” mount of fossils you already own.

Here’s an example of a typical cast mount:

A Utahraptor cast, at the Museum of Ancient Life at Thanksgiving Point.
I showed you this mount before.

It’s a bit harder to notice on the black-like-the-Morrison-Formation colored bones, but the entire thing screams “fake!”, despite being very well done. You just can’t get the natural variation in color just right, and it is an eternal bother to get the breaks and hairline cracks to look natural. On the other hand, there is very little armature visible.

Now here is a real-bone mount:

The Real Deal(TM)Kentrosaurus aethiopicus mount in the
MfN Dinosaur Hall (photographed through the legs of
the Diplodocus cast). Note how the fake skull sticks out like
a sore thumb! (I know, I know, Peter, you will ignore the rest
of this post and just salivate over this image. Real Dinosaur palaeo!)

Should researchers want casts mounted?

So there you have it: almost everything that matters to a scientist says you should mount casts, and keep the precious originals in well-tended collections. On the other hand, the issue of communicating our work to the public is a huge, important one. And there is a difference between casts and real bones, a difference in how people react to them, a difference in the awe and wonder they inspire. It’s a bit like Ancient Greece’s temples and a  Las Vegas replica, or like the Forum in Rome and the Caesar’s Palace casino. People will like and enjoy the casts, but they will not admire them, they will not be awed!

So overall, I am slightly in favor of mounting real specimens. Provided, that is, that they are not exposed to unnecessary risks, and that they are sturdy enough to take no perceptible damage. That means keeping them separated from visitors enough to make sure no bones are stolen, mounting them on more rather then less steel than necessary, air conditioning the room if necessary, and having sufficient personnel present all the time. Furthermore, I want the material available for study. Either close one day per week, or allow scientists to work during opening hours – and if needs be, close a room to the public while a researcher is in there! Places like the AMNH, where fossils are protected by glass walls that usually can’t be taken off for such unimportant research as yours (making the wording up, but that’s the essence of the message you’ll normally get) do science a disservice by it – while at the same time doing it a service by allowing the public to study the fossils up close, which does wonders for teaching!

Compromises

Luckily, there are a number of things a museum can do to minimize the problems resulting from showing real bones. Above, I used the ugly word “chimera” for the MfN Giraffatitan. The reason is simple: it is composed not only of real bones, supplemented with plaster models where there was no real bone available (which I would count as “real bones mount”). Rather, the sacrum and neck are models! The reason is quite simple – but I’ll let the guy responsible for it speak for himself (Janensch 1950, p. 97):

“Die ganze präsakrale Wirbelsäule, deren sämtliche Wirbel, wenn auch zu einem erheblichen Teil unvollständig, erhalten sind, wurde mit den Halsrippen in Gips modelliert. Sie in Originalstücken zu montieren, hätte bei dem gewaltigen Gewicht und der außerordentlichen Zerbrechlichkeit der höchst kompliziert gebauten Wirbel, kaum zu überwindende Schwierigkeiten verursacht, hätte aber auf jeden Fall so umfangreiche Tragkonstruktionen erfordert, daß das Gesamtbild sehr stark beeinträchtigt worden wäre;”

(The entire presacral vertebral column, the vertebrae of which are all preserved, albeit mainly significantly incomplete, was modeled in plaster along with the cervical ribs. Mounting it from original pieces would, given the enormous weight and the extreme fragility of the most complexly built vertebrae, have posed nearly insurmountable difficulties, but had in any case required such an extensive armature that the overall view would have been significantly compromised.)

Ah, yep, that’s a reason right there! And the good thing is that all the cervicals rest in the Bone Cellar, where nerds like me can get all close and cozy with them :D

Now, you can obviously choose a way of mounting that is as unobtrusive (thank you, spell checker!) as possible, but still keeps the bones secure, as Dave Hone pointed out. And, as I pointed out in comments there, this is not an idea that only gained a foothold recently:

Left forelimb of “GPIT 2″ you-know-who. Note how little the armature
and the wires fixing the bones in place distract from the fossil!

Here’s an example where the bones have been taken out for study (by me, who else?):

GPIT/RE/7288. Non-regulars will now be forced to read my fuckinblog ;)

Pubis, ischia, left ilium, left femur, left tibia, left metatarsals, left pedal phalanges removed. All it took to get them back in later was 20 cm of wire and pliers. Yay! for Friedrich von Huene and the preparator(s) who mounted this skeleton! Aside from being anatomically almost entirely correct, they did an awesome job of making the armature NOT show too much!

Another option is not mounting the bones, but still showing them. Here’s two examples:

Panorama image of HQ 1, a composite Diplodocus in the Sauriermuseum Aathal.

A Chinese Lystrosaurus in the Institute for Geosciences of Tübingen University (at least, that was the name it had back then).

Yep, lay those bones out on the ground! If you can, and if it is not too confusing, lay them out in the position you found them in. In either case, btw, the display is (Aathal) / was (Tübingen) accompanied by a mounted cast.

Thus, whatever you do: show people the real stuff! It really makes a diff, and all the inconveniences considered, what is our prime goal? Yep, teachin’ folks! And that’s best achieved if the real stuff is out there!

About these ads

About Heinrich Mallison

I'm a dinosaur biomech guy working at the Museum für Naturkunde Berlin.
This entry was posted in Dinosauria, Kentrosaurus, Maniraptora, MfN Berlin, Ornithischa, Stegosauria, Theropoda. Bookmark the permalink.

20 Responses to Mounting a skeleton: bones or casts?

  1. Mike Taylor says:

    Giraffatitan: most is real bones, but the sacrum and neck are casts.”

    Just two minor corrections. As you note later, the replacement bones are not casts, but models (and the models in the new remount are much, much better the the old ones in Janensch’s mount). And the replacements include the dorsals as well as the cervicals.

    • Not quite, Mike – the cervicals are not plaster models, but fiberglass casts of plaster models…. I didn’t want to get caught in all the ugly details. The dorsals I simply didn’t think about, thanks for pointing that out.

  2. David Hone says:

    A couple of quick observations:
    Well pained casts can be incredible. While working on Zhuchengtyrannus we had both the original dentary and a painted cast to work from. Despite all the time spent on the material and obviously our in depth knowledge of bones and casts etc. in general, more than one we mistook the cast for the real thing. It IS possible to make casts that are almost indistinguishable from the original material, but yes, obviously it costs more!
    Second it’s not always the case that *anyone* can have a cast. Not if you don’t pass out the moulds or copies! People can control what leaves the museum and still have prestigiously mounted casts.
    Finally, there’s an obvious (well, to me) compromise. Mount a cast, but put a number of the real elements on display in cases. While obviously this costs money, the bones are there to be seen by the public (and indeed maybe even more closely than if mounted) but are protected and also accessible to researchers. But the mounts can be big and dramatic and provide a better ‘big picture’ of the whole animal. Best of both worlds?

    • Marc Vincent says:

      I think that’s a good compromise. As a layman, it does impress me that much more to see real material, for the reasons that Heinrich described (although people can be awed by casts, knowing that they are based on real fossils!). However, at the same time I can appreciate that casts are much easier to mount, and mounting real material can be a pain in the arse for researchers. I like the approach of mounting casts/models and having some real material on display in a case up front.

    • Best of both worlds, which is why I figured the Aathal and Tübingen examples of this.

  3. steve cohen says:

    As a “fossil explainer” at AMNH I can attest to the awe of visitors when they are informed that the vast majority of what is on display contains fossil material.

    Most visitors know little about paleontology but the impact of what they are seeing is dramatically increased once they realize they are looking at “real fossils.”

    To most laymen, the alternative to “fossil” is not “cast,” it is “fake.”

    Of course I have no direct knowledge of the implications to researchers of mounting fossil material.

  4. Peter Falkingham says:

    I was always convinced that displaying casts was the best way forward, but over time grew to realise the point Steve Cohen makes: that to the average Joe, if it’s not ‘real’ it may as well be fiction. I’d taken it for granted that as a kid I knew they were casts (or models) of real bones, but a lot of people don’t make the connection.

  5. Paul Heaston says:

    Excellent post, but there’s one thing I would add to the advantages of using casts. People can see dinosaurs they might not otherwise be able to. I realize you’re talking about the advantages of using casts from one’s own collection versus the real thing, but what if one has no “real” collection? I co-manage a private educational exhibit with 18 cast skeletons (some of which are mostly “modelled” material) and over 65 skulls, also all casts. Dinosaurs in museums are scarce in Texas. San Antonio has only one small natural history museum, and that museum has only one dinosaur– a 50-year-old mount of Triceratops. We opened our exhibit to fill the dinosaur exhibit void here in poor South Texas, where most families don’t have the means to travel to real museums (Texas is a big state). You can’t see more dinosaurs together in one place anywhere else in Texas.

    Yes, Steve Cohen is right when he says people want real fossils. Often the first question we are asked is “are they real?” and they are frequently disappointed to hear that they are casts.
    Even after I explain to folks that even large institutions often show casts and that many dinosaurs are only known from a few remains folks are still skeptical. I’d love to shout “There aren’t enough T. rexes to have a real one in every museum, and the casts still cost a fortune!” but I understand their frustration. The kids love seeing the dinosaurs anyway, and because we have mostly dinos they’ve never heard of (Yangchuanosaurus, Saurophaganax), it’s an educational opportunity to point out there are other theropods besides T. rex and Velociraptor.

    We’d love to have the real thing, and some of the mounts we have look painfully fake to me, but that’s just not possible for a community like ours at the moment. I think casts let us reach kids who would otherwise never get to see bones at all.

    • Well, I fully understand, and I did address this a bit by noting that “anyone can have a cast”. As Dave Hone pointed out, not necessarily ANY cast, just some….. and it certainly better to show (good) casts than nothing at all! I only wish the plethora of finds of some taxa would allow each and every museum to have at least one or two originals, because of the teaching implications mentioned.

    • steve cohen says:

      “Often the first question we are asked is “are they real?” and they are frequently disappointed to hear that they are casts.”

      The way I usually get the question is “these aren’t real, are they?” Always asked as a negative and implying that someone just made something up to fill an exhibit hall.

      And what happens when there is no-one around who can answer the question — visitors assume they are seeing something akin to Jurassic Park or a NYC version of DisneyWorld.

      • Say what?

        Must be the creationist propaganda! Here, they all ask: “Are these real?” or “But that’s not all real, right? Some of it is repaired?”

        Well, come to think of it, some can’t believe it, given the size of the Giraffatitan mount, and do ask a negative. But these people are rare.

        • steve cohen says:

          I’ve been volunteering at AMNH for six years and the question is asked as a negative 90% of the time.

          We volunteers find it very amusing.

          I once had a middle-aged couple look at the fossil t rex head on display (in a case) and ask (completely seriously) “where does the fire come out?” When I looked perplexed they responded”don’t all dragons breathe fire.”

          I also had a creationist try to argue that the dinosaurs went extinct (5,000 years ago) because they were too big to fit on the ark!!

          Sounds like the German museum visitors are more sophisticated.

      • Paul Heaston says:

        Strangely enough, we have a number of real fossils at the exhibit– not dinosaurs, but marine fossils from the local Cretaceous sediments, found and prepared by our staff. People often say they look fake. Go figure.

  6. Matt Wedel says:

    A bit late, but: one more option is to put the squashed fossils and the 3D cast into the same exhibit, as the OMNH did with their excellent Cotylorhynchus. Photos here.

  7. Pingback: TractorFace – Farm Truck for the Ages » The Beatnik Brotherhood

  8. Pingback: 2012 in review | dinosaurpalaeo

  9. Pingback: Scientific uses for fossil mounts « DINOSOURS!

  10. Claudia Macleay says:

    Hi I am not casting something so old but I am wanting to caste a horse skeleton, mainly so that students can pick up the ‘resin bones’ and I am not worried about having them break. I know that I can use alginate but it seem very expensive and wasteful…I can only 1 cast and then it useless. Have you used or do you know of anything like plasticine which can be remoulded and casts into again?

  11. Pingback: Dinosaur mounts at the NHM L.A.: Triceratops | dinosaurpalaeo

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s