Juan Cisneros (left) and Márcio da Silva Mendes (right) the local quarry worker who led us to a great fossil locality. Photo by Ken Angielczyk.
A truism of paleontology is that you always find the best specimens on the last day of fieldwork, often late in the afternoon just as a rainstorm is starting. We managed to avoid the rain, but today was our last day of collecting fossils and we did find some great material. The story of how we got to the fossil locality is an example of the happy accidents that sometimes happen when you're in the field.
Yesterday, we set out to explore two quarries located in the same area near Timon as the quarry in which we found the articulated amphibian specimen. They are close enough that there was a good chance that they would have similar lock layers exposed, and both are somewhat larger than the original quarry, providing more exposures in which we could look for fossils. Unfortunately, they both turned out to be unproductive. The rocks exposed in the new quarries were somewhat higher in the sequence that the ones in the original quarry, and they do not seem to preserve fossil vertebrates. While we were at the quarry, Juan started talking to a worker named Márcio da Silva Mendes who knew right away what we were interested in when Juan told him we were searching for fossils. He said they never find fossils in that quarry, but there was another one that he used to work in near the town of Nazaria (located south of Teresina) where he frequently saw fossils, and that he could take us there today. So this morning we piled into the trucks and drove the 25 kilometers or so to Nazaria.
The quarry near Timon where we met Márcio. The rocks in this quarry are slightly higher in the sequence than the fossil-bearing rocks at the original Timon quarry, and do not seem to preserve vertebrate fossils. Photo by Ken Angielczyk.
The quarry in Nazaria is no longer in use, so it now consists of a couple large piles of rocks surrounded by vegetation that is busily reclaiming the place. We climbed down through some of the weeds, and Juan Cisneros and Márcio walked up to the top of one of the piles. Then Juan reached down, turned to us, and said “I found a skull!” After that, the hunt was on, with all of us sorting through the rocks on the spoil pile looking for exposed pieces of bone in each one. We were even joined in our efforts by some local kids that followed us down to the quarry.
Roger Smith (foreground), Claudia Marsicano (middle), and Christian Kammerer (background) search for fossils in the spoil pile in Nazaria, while Jeff Johnson (right) works to set up a shot. Photo by Ken Angielczyk.
Not all of the rocks contained fossils, and we didn't make it to the bottom of the piles (despite our best efforts), but we did find a lot of specimens that we think will be very informative. Probably the best-looking one that we found is the very first skull that Juan picked up just after we arrived. There's a good chance that this specimen is part of the same species as the articulated skeleton that we found a couple days ago. However, different parts of the skull are exposed in each specimen, so we're limited in what parts of their anatomy we can compare at this point. In addition to this specimen, we found parts of several other amphibian skulls, part of the shoulder region of an amphibian (which Claudia Marsicano thinks will be very useful in identifying the larger group(s) to which our new specimens belong), and some well-preserved fish remains. Overall, it was a nice way to round out our work in the field.
Temnospondyl amphibian skull discovered by Juan Cisneros at the Nazaria quarry. The front end of the skull is toward the top of the picture, and the two oval openings near its midpoint are the eye sockets. Scale bar is in centimeters. Photo by Ken Angielczyk.
Tomorrow, we will spend the day in Juan's lab unpacking and organizing fossils. This will be important for determining our priorities when it comes to preparing the specimens, and also will give us a little time to directly compare some of the specimens we collected this year. For example, it would be nice to sit down with the amphibian material from Teresina and Nova Iorque to see if there is overlap among the species that are present. It will also give us a little time to get some last-minute pictures of the specimens before we we all start heading home. As always, the time has gone really quickly, and it's funny to think that we've reached the end stages of the trip already.