Scientific uses for fossil mounts

I have a question for the paleontological community. I know this blog doesn’t get anywhere near the traffic to expect many answers, if any, but I’m going to ask it anyway.

How do fossil mounts factor into your research? What information can be gained from an assembled and articulated vertebrate skeleton that cannot be determined (or is more difficult to determine) from the study of individual bones? Mounts did have a role in research historically: for instance, Gilmore used the process of creating the Triceratops, Camptosaurus and Diplodocus mounts for the United States National Museum to correct anatomical errors and assumptions previously published by Marsh. But are we still learning from the process of physically assembling skeletons (digital models don’t count)?

I ask because my immediate assumption is that mounts do not benefit research. Fossil mounts clearly have (admittedly difficult to quantify) educational value. They are spectacular, awe-inspiring displays with a physical presence that no book, film or shoddy cable documentary could hope to achieve. For many, including myself, fossil mounts were a first encounter with science in general, inspiring me to ask questions about the natural world and seek ways to answer them. But if we focus entirely on the process of studying and learning from fossils, do mounts have any value?

There is no shortage of reasons why mounts utilizing original fossils are problematic for researchers. Mounted fossils, which are often all-important holotypes, are difficult for researchers to access, and certain parts of the skeleton, like the back of the skull or the vertebral bodies, cannot be reached at all. The mounting process, while better than it was a century ago,  is invasive, destructive and sometimes irreversible.  Mounted fossils in public spaces inevitably suffer damage from fluctuating temperature and humidity (such as pyrite disease), uneven weight distribution and vibration from passing crowds. Many historic mounts used plaster or shellac to seal bones together or to reconstruct broken pieces, which is effectively impossible to remove without damaging the fossils. In the case of the Peabody Museum Apatosaurus, modern researchers do not know how much of certain bones are real and how much was reconstructed.

There is a long, worthwhile discussion to be had on whether the needs of research or the needs of education are more important in this scenario (David Hone and Heinrich Mallison make a case for each side on their respective blogs). But before I get to that point, I’d like to sort out if the distinction is as clear cut as “mounts good for education, mounts bad for research.” Any comments or experience on the matter would be very much appreciated!

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8 Comments

Filed under dinosaurs, fossil mounts, history of science, museums, NMNH, science communication

8 responses to “Scientific uses for fossil mounts

  1. Hm, I guess I am the wrong person to ask, as I prefer to use digital mounts, and also because I know how important it is to handle specimens to really grasp their shape (the verb here is the dead giveaway: to grasp something).

    Overall, I think a RHQ (really high quality) model would do – if it provides 100% of the useful detail of the real skeleton in a mount. That is, the surfaces must be so exactly reproduces that I can see all the structures I need. That includes faint muscle marks – so I can detect them, then see the full path of the muscle across the skeleton. And thus we are talking about rapid prototyping entire skeletons. Costs an awful lot.

    Other things a mount does is show shapes much better than individual bones – again, a really good model should be good enough to give that info too. Many existing mounted casts don’t, though.

    To me the perfect compromise is the “in situ” display of the original, accessible to researchers, combined with a RHQ mount above it.

  2. Kenneth Carpenter

    You ask a very good question. I suppose I am the best person to answer your post, given that I mount dinosaur skeletons AND I publish. Among my works are most of the mounts at the Academy of Natural Sciences (but not the new Hadrosaurus) and the Denver Museum of Science and Nature. I have long taken the opportunity of studying the bones of the specimen I am mounting, especially their joint anatomy. I do what is called “actualistic studies”, meaning I experiment with the actual fossils, rather than on a computer screen (e.g., Kent Stevens and his sauropod neck movement studies). I have heard claim that CG studies are somehow “more scientific” because bones are too often crushed and CG can “remove” this distortion. True, but it still takes some interpretation as to how much distortion to remove and what it “should” look like undistorted, so it isn’t completely free of bias. Besides, not all bones are crushed or distorted.

    My career has been influenced by Charles Gilmore and Charles M. Sternberg, both who have published observations made while mounting skeletons. The most important lesson is: let the bones “speak” for themselves. Some of the worse skeletal mounts are those in which the person doing the mounting tries to impose their preconceived notions into the pose. The result are limbs out of socket, vertebrae disjointed, etc. I have published some of these observations in articles on the mounting of skeletons (articles available at the link below). It was the lessons learned while mounting skeletons that made me realize the limitations on forelimb limb movement in theropods, and that resulted in my scientific publication on the topic. Basically, I concluded that the greatest amount of movement is backwards, rather than forwards, thus the forearms cannot reach the mouth (unlike some artistic interpretations). This makes sense if the arms are used to pull or hold prey while killing it. In another example, the mounting of the Stegosaurus at Denver resulted in my paper on the use of armor in Stegosaurus.

    Articulated skeletons (or articulated parts) as excavated can tell a lot about what joints can and cannot do, but oddly, this information is often not considered. It was Gilmore who first pointed out in his study of a juvenile Camarasaurus skeleton that the angle and position of the shoulder blade relative to the first dorsal rib says where this bone should go. He’s right. In most articulated dinosaur skeletons, the rib cuts across the middle of the scapula. That means the shoulder blades of many mounted dinosaurs are too far back. In addition, 3-D skeletons (such as the hadrosaur mummies, or Protoceratops in sand dune deposits) show that the bones of the chest, the coracoids, practically met on the midline. In mounted skeletons, especially of sauropods and ceratopsians, these are often too far apart. Not surprisingly, moving the shoulder blades forwards brings the coracoids closer together (duh!).

    Finally, back to Kent Stevens and his CG work. Before I mounted the Diplodocus at Denver, I manipulated the neck bones on the floor (which was hard to do given their weight). I concluded that there was more vertical movement than Kent concluded from his CG work. Still, my results were less than the vertical neck of Bakker’s Barosaurus drawing. In this, Kent and I were closer in agreement. The lesson here is that you can make dinosaurs do anything on paper, including making sauropods stand on their nose!

    Next year I’ll be mounting a Camarasaurus skeleton with virtually uncrushed bones from the Cleveland Lloyd Dinosaur Quarry. I can’t wait to see what the bones will teach me!

    • Ben

      Hi Dr. Carpenter, I really appreciate your taking the time to write such a thorough reply! Clearly there is much that can be learned from the process of making a mount. I’m wondering, how common would you say your actualistic methods are among vertebrate paleontologists, these days?

      You mentioned you had published multiple articles on mounting. I have your chapters in Vertebrate Paleonological Techniques and the Complete Dinosaur, but are there others that you might be able to share?

      • Kenneth Carpenter

        Probably the best use of actualistic studies in early paleontology was a series of rather heated articles about the pose of Diplodocus. In many ways, it could be argued that this debate marked the beginning of actualistic studies. It started when German paleontologist Tornier criticised the mounted cast skeleton of Diplodocus that Andrew Carnegie had erected in London. Tornier argued that because Diplodocus was a reptile, it should have been mounted in a reptilan sprawl. This then led to a series of heated articles in the American Naturalist (1908-1911) between Hay (who supported Tornier) and Holland and Matthew (who argued for an erect posture). (My favorite zinger was lobbed by Holland towards Tornier, who illustrated his criticism of the Diplodocus mount with sketches of a sprawled Diplodocus: “[Torrnier]… with the help of a pencil, the powerful tool of the closet-naturalist, … squeeze[d] the animal into the form which his brilliantly illuminated imagination suggested.” – Today, Holland might write: “with the help of CG, the powerful tool of the armchair paleontologist, squeeze the animal into the form which his brilliantly illuminated imagination suggested..”)

        In his lengthy response Holland presented photographs of the fore- and hindlimbs of the Diplodocus mounted in the spawled position in order to show why this was not possible anatomically. Given the huge size and weight of the bones (probably plaster casts), it was a remarkable feat. Roland Bird’s discovery of sauropod tracks along the Paluxy River in 1939 proved sauropods walked erect, and indirectly validated Holland’s actualistic study. So, actualistic studies can be a powerful tool, which are sometimes under appreciated.

        Phil Senter has followed my initial work with a series of actualistic studies on various dinosaurs, and John Hutchinson uses computer graphics in his studies. You can find examples using Google Scholar (some returns are for free PDFs).

        As to my other articles, there is the mounting of a primitive whale and two versions of Dinosaurs in Museums in the two editions of the Complete Dinosaur.

  3. Kenneth Carpenter

    NEWS FLASH!
    We are remounting an Allosaurus skeleton and this morning I made an “Ah, hah!” discovery. Although this is the second Allosaurus I have mounted, I never paid much attention to the elbow. My previous attention was the shoulder, which led to an article on theropod forelimb motion. I have always wondered why Allosaurus has a peculiar twist in the shaft of the upper arm bone, the humerus. Today I figured it out. The shaft is characterized by a lazy S-shape (called a sigmoid curve in paleo-speak) and the elbow region is rotated 45 degrees towards the outside relative to the shoulder end (humeral head). Taken out of context, it would seem that the lower arm and hand would face about 45 degrees away from the body. Turns out, when the shoulder blades are articulated so that the chest plates (coracoids) almost meet and the wish-bone (furcula) connects the two shoulder blades thereby reinforcing the chest, the front face of the humerus actually face slightly inwards at about 40-45 degrees. Therefore, the twist in the humerus counters the inward rotation so that the lower arm and hands face forwards.

    • Oh yeah, we see the influence of that rotation between proximal and distal ends very well in Plateosaurus.

      http://www.app.pan.pl/article/item/app20090075.html

      Why is it that EVERYBODY talks about Kent Steven’s mostly hand-modeled digital bones, but ignores that there are studies out there using complete digital skeletons of near-complete individuals?

      • Kenneth Carpenter

        Fair enough Heinrich. I used Stevens only because he has published a lot on the topic and many people are familiar with his work. No insult meant to you and your colleagues. For the readers, Heinrich did computer modeling of rearing in sauropods: “Rearing giants: kinetic-dynamic modeling of sauropod bipedal and tripodal poses.” It was published in 2011 in the book “Biology of the Sauropod Dinosaurs”.

        Rearing in sauropods, of course, remains a topic of much debate. There is little doubt, however, that the males had to have rear to get onto the back of females to mate.

  4. Ken, I know you’d never knowingly ignore a colleagues work! It is the general pattern – my work seems to be invisible. For example, there’s the range of motion work on Plateosaurus, cited above, but there also is the paper on the same topic in Kentrosaurus:

    http://link.springer.com/article/10.1007%2Fs00015-010-0024-2
    :)
    Heinrich

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