I am interested in dinosaur locomotion. In particular, I am interested in how the various parts of a dinosaur skeleton moved in relation to one another, especially when capped in cartilage, actuated by muscles and tendons, and ensheathed in flesh. Of course, until time travel becomes reality or until Jack Horner brings to life his “chickenosaurus,” knowing just how dinosaurs moved is fraught with difficulties and unknown variables.
Take, for example, the recent, independent confirmations by Casey Holliday and colleagues, and that of my own group’s research, on archosaur long bone articular cartilage thickness and shape. It turns out, frustratingly, that a good amount of joint shape and thickness are lost to time in dinosaurs. Part of my current research focus is to develop empirical methods for reconstructing the missing cartilage shape at the ends of dinosaur long bones, but that is a long work in progress.
However, you would think that at the very least, we should be able to quite readily determine the range of movements and interactions of the living skeleton in crocodylians and birds. Strange as it may seem, understanding how the skeleton of a vertebrate moves in real life is not easy. An actual, physical skeleton of any given animal can only be articulated in one pose at a time, and in any case the limitations or freedom of movement resulting from soft tissues are very difficult to establish — just ask Larry Witmer and his group of dedicated students. One could, of course, pose a dead animal in various ways and then CT-scan or take a radiograph (an X-ray photograph) of each pose, but dead animals don’t always assume natural poses.
Another technique used for a number of analyses of skeletal movement has been fluoroscopy combined with the capture of X-ray movies of live animals, called cineradiography. Several papers have been published on various aspects of vertebrate animal movement, breathing, and other activities using cineradiography. Whereas these previous studies have been invaluable in revealing heretofore unknown or unanticipated movements of the vertebrate skeleton (e.g., the furcula of birds acts as a flexible spring), they are limited in that they are 2-D. All bones of the animal are compressed into a flat plane, and you have to be able to recognize and follow the movements of the bones you are interested in while they merge and pass over all the other bones in the movie.
Therefore, I am thrilled to report that I have been accepted into a 1 week course at Brown University where myself and other faculty, postdocs, and graduate students will learn a new, 3-D cineradiographic technology that enables accurate three-dimesnional animations of vertebrate skeletons! Called XROMM (X-ray Reconstruction of Moving Morphology), this new technology uses combined, multiple fluoroscopic and standard video sequences of a moving animal in combination with three-dimensional representations of its bones to produce a scientifically accurate moving skeletal model of particular behaviors and motions. The three-dimensional bones are obtained using standard CT-scan or laser-scanning technology. Check out the following examples under the Movies link on the XROMM site:
- Mini-pig feeding
- Ray-finned fish mouth mechanics
- Iguana breathing and rib movements
- Bird hindlimb movements
- Duck feeding
The advantages of XROMM over traditional fluoroscopic movies or the attachment of external markers to skin is easy to appreciate. For the first time, you can watch the movement of bones in three dimensions from any angle and in any perspective. Moreover, you can easily export the ranges of movements generated by the animation for further quantification and analysis of how the bones actual move in space, in time, and in relation to one another.
I will be blogging and tweeting (@MattBonnan) about my experiences in this course, which will take place Monday, June 11 through Friday, June 15, 2012. This sort of experience will not only open new doors for the research of all those involved in the course, but it will inform projects I will conduct in the future with my students.
- Beth Brainerd
- Steve Gatesy
- Dave Baier
- Ariel Camp
- Sabine Moritz
It is wonderful to be a paleontologist in the 21st century!