Guest Post: How to collect a skeleton from a cliff face with 200 meters of sandstone as overburden

Reconstruction of Seitaad ruessi. Image courtesy of Mark Loewen.

Some of you may have already spotted the new paper out covering the delightful little Seitaad ruessi – a brand new sauropodomorph from the Middle Jurassic of Utah. (Some coverage is here if you have missed it, and the paper is freely available here).  Mark Loewen, one of the authors of the new paper, tells of how the material was found and then how they got the specimen out of the quarry:

Seitaad ruessi is a new basal sauropodomorph dinosaur reported in PLoS ONE by Joe Sertich and myself. Fossils are extremely rare in the Navajo Sandstone and our knowledge of the fauna that lived in the Navajo deserts is scrappy at best. Seitaad is now the first dinosaur discovered from the Navajo Sandstone of Utah and is the best preserved, oldest known dinosaur from Utah.

Eagle's Nest Canyon Comb Ridge. Image courtesy of Mark Loewen.

The skeleton was found by Joe Pachak, a local archaeologist and artist from Bluff, Utah. Pachak was hiking in the Navajo Sandstone near the four corners region of Utah looking to document petroglyphs and pictographs from the ancestral Puebloan (Anasazi) culture. He reported the specimen to the Bureau of Land Management and passed on word to us at the Utah Museum of Natural History. When we heard about a possible specimen from the Navajo we immediately went down to check it out, since we knew that anything from this time in the Early Jurassic of North America would be important. The specimen turned out to be a string of vertebrae, an arm and a “v” shaped bone that looked like articulated dentaries eroding out of the cliff wall. Initially we thought it might be a pterosaur and set about to collect the skeleton a few weeks later.

Our first problem in excavation was that the skeleton was preserved in a nearly vertical cliff wall that extended 200 meters above. Chisels and crack hammers would hardly dent the hard sandstone. UMNH collections manager Mike

The specimen as it was found. Image courtesy Mark Loewen.

Getty suggested that we cut it out with a diamond bladed rock saw. We soon found that a 14 inch rock saw blade will only cut about 10 cm into the wall due to the armature of the saw. The best method we found was to cut a series of perpendicular cuts producing a 10 cm grid pattern about a half a meter wide all around the skeleton. We then removed the 10 cm cubes of sandstone with broad bladed chisels and crack hammers. Then we started over with the saw and 10 cm grids. We figured the skeleton would fit in a 1 meter cube and tried to shape a block for jacketing that would fit all the possible bones in the skeleton that we couldn’t see. After several days of trenching with saw, chisel, and hammer we had a block ready to be pried loose from the canyon wall.

Unfortunately, when we broke the jacket loose, it split right along a perfect articulate series of gastralia. By looking at the pattern of the gastralia we knew we had the skeleton turned around in our heads and that the “dentaries” were ischia. Now the skeleton was looking like a theropod. We jacketed the surface, started up the saw and trenched deeper to remove what we hoped would be the arms and legs. When all of this was finished, we had two 150 kg blocks that had to be carried about 2 kilometers down the slot canyon. We used a rescue backboard and a team of 12 people (8 lifting the backboard and 4 rotating in) to carry the skeleton down the canyon.

Excavating the material. Image courtesy of Mark Loewen.

Back at the UMNH lab preparator Jerry Golden worked for six months to remove the sand from the two blocks. As the skeleton was being revealed, we saw we had more than three toes and fingers along with the big thumb claw. Then we knew we knew we had a “prosauropod” and the real research began.

The prepared specimen. Image modified from the PloS1 paper.

11 Responses to “Guest Post: How to collect a skeleton from a cliff face with 200 meters of sandstone as overburden”

  1. 1 Traumador the Tyrannosaur 24/03/2010 at 11:46 pm

    awesome stuff.

    i rather enjoyed hearing the collection technique.

    thank you Dr. Loewen for the guest post!

  2. 2 Allen Hazen 25/03/2010 at 7:31 am

    Utterly off topic note to Dave Hone–
    “Ask a Biologist” is a WONDERFUL site, but doesn’t seem allow the public to ask follow-up questions or add comments. On their “Mammals” section, you recently reassured someone named Caitlin that Narwhals really exist. You might cheer her up further by pointing out that, though no zoos/aquaria currently have Narwhals, many (including Vancouver, BC) have belugas: the beluga being (on current classifications of Cetacea) the closest living relatives of Narwhals, and resembling them in several ways (small head for a whale, no dorsal fin…).

    And that if she wants to think about really HARD TO BELIEVE whales, possibly also closely related to Narwhals, paleontologists believe in the former existence of Odobenocetops! (Grin!)

    • 3 David Hone 25/03/2010 at 8:43 am

      Hi Allen,

      Yes we know people can’t reply. The problem here is complex. We think it critically important that the site serve as a repository for information and people to get the answers they want, it’s not a discussion site so we don’t want to make the boards free for anyone to comment on. If noting else we risk being spammed to death or creationists etc. wanting to argue or debate every point. We don’t have the time or money to moderate the boards and this is the simplest solution.

      We can set it up so that everyone can register to use the site and then feed into the boards but this still risks people wanting to endlessly turn over details, and more moderation. In most cases people don’t want or need a follow up so it’s not much of an issue and we usually paste any direct replies / follow-ups into the thread ourselves.

      It’s basically a function of practicality. We’re a small group of people doing this for fun / to help out on our time and with minimal budget. Give me the cash and we’ll install a permanent server and hire a moderator on the site, but even then I still suspect AAB would become just another discussion site and lack the simplicity of a question and answer and the ability for people to search for and find accurate information.

      Thanks for the nice comments!

  3. 4 Tom 25/03/2010 at 11:21 am

    First Ceratosaurus want to be Ornithomimosaurs (Limusaurus), now apparently Sauropodomorphs do too…

  4. 5 Allen Hazen 26/03/2010 at 9:44 am

    I think I had figured out the reasons for not allowing commentsbefore you replied: they all make good sense to me. I’ve asked questions on the site and occasionally wished I could post a follow-up question (or have done the homework I SHOULD have done before asking and wanted to add the new information) and been frustrated I couldn’t add it to the original string… but minor annoyance to me is certainly outweighed by the major annoyance to many of “being spammed to death or creationists etc. wanting to argue or debate every point”!

    Anyway… “Ask a Biologist” is a great idea!

    • 6 David Hone 26/03/2010 at 10:01 am

      Hi ALlen, glad you like the site. The criticism / curiosity was perfectly reasonable and it is something we tried to include with the upgrade but it was too expensive and time consuming to instigate and maintain. I think we do a pretty good job all things considered given the general lack of support we get for the site (financially). We get the pleasure form people using it and learning about biology so keep coming back! Cheers.

  1. 1 DinoAstur - » Seitaad, nuevo dinosaurio jurásico de Estados Unidos Trackback on 25/03/2010 at 6:18 am
  2. 2 Uncovering Seitaad: An Interview With Mark Loewen | Dinosaur Tracking Trackback on 27/03/2010 at 1:10 am
  3. 3 Uncovering Seitaad: An Interview With Mark Loewen | Trackback on 29/03/2010 at 1:56 am
  4. 4 Weekly PLoS ONE News and Blog Round-Up « everyONE – the PLoS ONE community blog Trackback on 01/04/2010 at 4:29 am
  5. 5 Newsflash « Dave Hone's Archosaur Musings Trackback on 07/12/2011 at 4:34 pm
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