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.
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
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.
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.