It’s Alive! Dr. Bakker Tells us how to make skeletons dance

Bakker Skeleton Mount

A life restoration of the great mammal-like reptile, Placerias, chasing an early dinosaur, Chindesaurus.

Some museums buy fossil-kits, all the bones drilled and filled with pipe fittings so that they click together to make the whole skeletal assembly. It’s quick. But if you have an anatomically sophisticated eye, and you scrutinize the kits, you’ll see serious errors of articulation as well as a general clunkiness.

For our Houston Hall (The Morian Hall of Paleontology), Pete Larson and I and Pete’s co- workers constructed every joint from scratch. We drew up dozens of pages of diagrams for shoulders and elbows, hips and knees, for every skeleton. The dinosaurs are tough but not the biggest challenge.

The Triassic Placerias, last of the big mammal-like reptiles, seemed to be a chimaera , croc-like thighs combined with the forequarters of a duck-bull platypus and the body cavity of a small ox. This barrel-chested beast took three weeks to pose in a believable full-speed run.

Here are the steps we took to capture the live beast:

I). Basic kinesiology.

A). Motion studies of extant species are reviewed to help in determining the limb posture and gait of the extinct species. In the case of Placerias the forelimb is close to that of a platypus and a terrestrial lizard, while the hindlimb is closer to that of a crocodilian and a chameleon.

Bakker Skeleton Mount

Motion studies of an Alligator mississippiensis, left, and a Tupinambis nigropunctata, right, part of the documentation for posing the HMNS Placerias and Smilosuchus.

B). The motion studies are reviewed to determine the range of lateral and vertical movement of the vertebral column, plus torsion in the extinct species. For Placerias the neck and dorsal column is compact but free to twist and flex as much in a Mississippi Alligator.

Bakker Skeleton Mount

Flexibility study of Placerias, top and side view, showing lateral flexibility of vertebral column and twisting, so head rotates down on the right and the pelvis rotates down on the left.

C). Placerias limb joints were like those of lizards and platypuses — motion was not simple flexion-extension in one plane, as occurs in humans, but included rotation in planes at right angles to the flexion-extension. Consequently, detailed diagrams for shoulder, elbow, hip and knee were drawn to guide the mounting process.

Bakker Skeleton Mount

Details of how shoulders and hips, elbows and knees rotate during the restored step cycle in Placerias.

Bakker Skeleton Mount

The movements at the elbow are especially complex — motion studies combined with detailed dissections of elbows of a tegu lizard, shown here, are used as a guide for Placerias.

II). The main limb and axial muscles are restored to determine which motions would be most powerful in locomotion and in combat.

A.) Our library of dissections shows which combination of extant species are most appropriate for restoring the extinct species. For Placerias, forelimb and hindlimb musculature are best reconstructed from the conditions in an echidna (Tachyglossus) or platypus (Ornithorhynchus). The reconstruction was used by the mural artist as he mapped out the body masses for the painting.

Bakker Skeleton Mount

Top and side reconstruction of muscles in Placerias.

B.) The relative strength of the muscles informs our choice of posture and gait. In the case of Placerias, the domination by the forelimb suggests that the animal could dig or climb uneven ground more easily than archosaurian potential predators.

III). Choosing an interactive choreography.

Bakker Skeleton Mount

The Placerias cast being mounted at the BHIGR. Pete Larson on right.

A). A review is carried out for all the species known from the particular habitat and time, and available as skeletons. Placerias occurs in the lower Chinle Formation of Arizona. In the same beds are found three other large tetrapods that are represented by casts: 1). The large terrestrial predator Postosuchus. 2). The very large semi-aquatic predator Smilosuchus. 3). The large terrestrial armored herbivore Desmatosuchus. For the Placerias mount we chose Smilosuchus as the attacker because the body form — long snout, long, low body, long tail — made a dramatic contrast with the rotund compact design of Placerias.

Bakker Skeleton Mount

Final mount of the Placerias cast, viewed from the front.

B). Multiple sketches are generated to test various combinations of poses. The most pleasing pose for the predator-prey dyad was the Smilosuchus lunging from behind the Placerias.

Bakker Skeleton Mount

Antepaenultimate plan for Placerias-Smilosuchus mount.

Summary: The final mounts of a Smilosuchus lunging after a Placerias were not “out of the kit” exhibits. Rather than using pre-fabricated skeletons ready to assemble, we cut apart most of the bone units and studied the range of movements indicated by the joint surfaces and by the attachment sites for major muscles. Analysis of the locomotion adaptations led to choosing posture and gait that are documented by the anatomy in the extinct animal and by study of living species which demonstrate similarities in form and function.

Bakker Skeleton Mount


Come see Placerias and more amazing specimens in the Morian Hall of Paleontology at HMNS! Open extended holiday hours (9:00 a.m. – 6:00 p.m.) through January 4!


Check out this Megalodon’s megawatt smile, and step inside if you dare

Meet our Megalodon! Among the 60 new mounts set to debut this summer at HMNS’ brand spanking new Paleontology Hall is this Megalodon jaw, which spans 12 feet.

Megalodon Jaws

The Paleontology Hall was designed to be interactive, so most of the mounts were designed in action poses. Not to be left out, the jaws of this Megalodon will be displayed swallowing a swimming elephant.

Look how they dwarf our Paleontology curator, David Temple:

Megalodon Jaws

Check out the rest of this sneak peek and be sure to stay up-to-date on all our Paleo plans:

Megalodon Jaws

Megalodon Jaws

Megalodon Jaws

New Blogger! Meet Susanna, HMNS Construction Project Manager

If you’ve been by the Museum lately, you may have noticed the giant hole in the ground between the Butterfly Center and the parking garage – as well as the steady stream of dump trucks along Hermann Drive. Construction of our new wing is solidly underway, and I’m excited to introduce our newest blogger!

Susanna is the Museum’s Project Manager for the construction, and she’s going to be giving us monthly updates on our progress towards the construction of the world’s best paleontology hall at HMNS – plus scores more classrooms for educating tomorrow’s scientists and leaders. We caught up with her to find out more about her role here – and get an update on progress so far.

Check back next week for Susanna’s first post!

Your title is HMNS Construction Project Manager. What does your job entail?

My job is to ensure that all the members of the HMNS Expansion project team approach every decision and task on the Expansion with the museum’s goals and interests in mind. That means I ask the contractor and the design team a lot of annoying questions, pester HMNS staff for operational details and feedback, bore everyone by repeating myself, further bore them by repeating what I think they just said to me, and generally worry there’s a question I haven’t asked or a point I haven’t made clear. When I’m not acting like a parrot or trying to imagine worst case scenarios, I get to play in the dirt in a hard hat and boots, which is pretty darn fun.

What is a typical day like?

Most days I send emails back and forth to the architect and contractor, shuffle paper, create paper, answer questions that arise, occasionally react to surprises from the contractor, occasionally react to surprises from the museum president, and hang out on the roof of the garage and take pictures and watch the construction. At this phase of construction I’ll usually walk the site once a week – most of the activity is big enough that you can see what’s going on from far away, plus they don’t need me wandering around threatening to fall in open trenches or totter in front of a backhoe or dump truck.

September 2010
The latest panorama image of the construction, taken just a few days ago.
Check out our set on Flickr for monthly images of the progress until now.

How similar or different is this project to others you have worked on?

This project has components that are similar to each of the other projects I’ve worked on. Managing the addition of a new wing onto an existing (and operational) building requires thinking about the project as being both a ground-up construction job and an interior renovation project.

While the Expansion work doesn’t include renovating the public spaces in the existing museum, the construction of a brand new central plant in the new wing does involve significant work to tie into existing infrastructure, and the contractor and the HMNS Building department have taken great care to make sure this process is seamless and unnoticeable to museum visitors and staff. I’ve also worked on projects for other prominent non-profit organizations in the Museum District and Texas Medical Center, and like those projects the HMNS Expansion benefits from the involvement of multiple key staff members as well as an involved Board of Trustees and Building Committee.

Technically speaking, this is the first project I’ve been involved with that has the foundation system the HMNS project does. Rather than digging the basement pit and temporarily retaining the earth until the foundation walls can be formed and poured, the contractor first drilled large, deep concrete soldier piles side-by-side around the building perimeter and then began excavating the pit for the foundation and basement level. The piles then serve both to retain the earth and as an integral part of the foundation wall system. As the foundation work has progressed I’ve really enjoyed geeking out over it.

What’s the most exciting part of the Museum expansion project?

So far, watching the tower crane go up and excavation get under way have been the most exciting part because they are such visible signs of progress. Many people might not know that construction has been underway since late February. Because the underground utility re-routing, other site work, and the drilling and pouring of the 261 soldier piles happened entirely underground, from street level the first six months of construction activity looked like little more than gardening. NOW even a casual observer can see the work progressing.

What’s the strangest thing that’s happened so far?

It’s hard to classify something as strange at a place as lively as HMNS, but the excitement about Lois this summer was one of those “only at the museum” kinds of experiences. Just one construction activity was impacted – very minimally – by Lois’s late-night and all-night schedule, but I can assure you that no one on the project team had “corpse flower” on their risk assessment radar.

Otherwise, like most inner city projects, we had a few surprises underground as we prepared the site this spring, but nothing more than old and abandoned utilities. Next time we’re hoping for something cooler than that, like treasure.

I also enjoy learning construction terminology that would sound strange in any other context. So far my favorite on this job has been “butt fusion.”

What are you most looking forward to?

The Grand Opening! Watching a new building grow up out of the ground is a thrill, but a beautiful new space is lifeless until people inhabit it. I’m excited to watch the team at HMNS fill the Expansion Wing with exhibits, collections, programs, and events. When the first visitors walk through the doorway to the new Paleo Hall, the reward will be tremendous.

What can our readers expect over the next few months?

The next 6 months will be the period when rapid progress is most visible to the public. In the next few weeks the building’s foundation will be complete, and the concrete structure will begin to emerge, with topping out expected in March 2011. The building enclosure should follow the structure up out of the ground, at which time readers will have to check back here for an insider’s view of what’s going on with the Expansion project.