July 3, 2011: The South Side Ceratopsian Quarry
At the end of last field season, one of our crew made a very intriguing discovery – some vertebrae and a good skull bone from a single small site on the south side of the Milk River. The skull bone was a squamosal, a bone that forms the bottom of the neck shield, or frill, of a horned ceratopsian dinosaur. Ceratopsian material is rare, especially in the lower part of the Oldman Formation, so this was a promising find that we wanted to investigate this season. Upon returning to the site this year, we found a number of bones starting to emerge at the surface, so this looked like a very good prospect. We decided to start an exploratory quarry to see if there may be the potential for an associated skeleton.
In order to see if any more fossils of this animal can be found in the layer, we first need to remove the overburden, or the unfossiliferous rock, that is on top of the specimen we are interested in. The ‘burden’ part of overburden can be very clear when the fossil bones are coming out of the base of a large steep hill, as in the case of the South Side Ceratopsian. We spent most of the day with pick-axe and shovel, trying to open up a good-size quarry.
July 4-5, 2011: Pay dirt!
After the overburden was removed, we had about 6 square meters of area that we could easily work with hand tools. We stopped using the pick-axe about a meter above the bone layer and switched to using careful excavation techniques so we wouldn’t damage any of the bones. The ceratopsian bones at the South Side Quarry are preserved in a soft mudstone, which is best worked with a pen knife.
The first day of quarry work was exhilarating, as we quickly began to unearth more bones of the skull. First, Michael Ryan, a fellow paleontologist, found another piece of squamosal bone, and then a very bizarre roughened horn over the nose. I found a beautiful piece of the side of the frill, part of the parietal bone, which forms the main structure of the stunning frills of ceratopsians. But we really wanted to find the back bar of the parietal bone, which forms the top of the frill and bears the species-specific horny ornamentation that allows us to distinguish between horned dinosaur species. This is the prize of any ceratopsian excavation, as it is scientifically the most important part of the skull.
We didn’t have to wait long – on July 5th, I found another large piece of frill, which had very unusual ornamentation on it. We very excitedly excavated the specimen and removed it in a plaster field jacket. The strange pattern of small horns projecting from the frill piece suggests that we might actually have found a brand new species of horned dinosaur, but confirmation of its status will have to wait until we fully prepare the fossil in the lab and compare it with other ceratopsians. We still have lots to find, and there is a lot of quarry work ahead in the next two weeks, but we couldn’t ask for a better start.
Read more about David’s dinosaur adventures in the field and see our Summersaurus Dino series for more on the ROM’s hunt for dinos!