Prospecting for fossils at an outcrop near Nova Iorque. Photo by Ken Angielczyk.
An idiosyncrasy of traveling to and from Teresina is that many of the flights arrive and depart between about midnight and 4:00am. So, it's currently 3:00am and I'm in the departure lounge waiting for my flight to São Paulo, where I will pick up my flight back to the U.S. Most of my collaborators have already left, so the trip is nearly completely over. Over the last three days, though, we've spent time doing some sorting and comparisons of the specimens we collected this year, as well as thinking about the next steps in this particular project.
One of the things that I've found to be a constant in my time as a scientist is that science itself is an evolutionary process of sorts. Very few are the projects that end in exactly the way you would think when you embark on them. Instead, each new piece of data causes a rethinking of your previous ideas, your expectations for future results, and your thoughts about what the interesting and important parts of the project really are. Sometimes the changes are minor, but in other cases things can change fairly significantly as you go, and I consider it important that we as scientists be open to following the data wherever they may lead. In the case of our research in the Parnaíba Basin, I think our discoveries are leading us in a different direction than we thought when we first started collecting specimens last year, or even at the beginning of this trip, but the questions along the new path are equally promising.
As I noted previously, it seems increasingly unlikely that we will find fossil synapsids in the Pedra de Fogo Formation. Even though the rocks of the formation were formed at about the right time and in a seemingly well-situated place to preserve such fossils, the specific environments that were present in the basin apparently weren't conducive to synapsids living there (or at least leaving a fossil record for us). So even as work was proceeding this year, the importance of synapsids in our minds was diminishing as we were thinking about the meanings of the fossils we were finding and our new geological data.
Rock outcrop near Nova Iorque. The slanting beds above and to the right of the rock hammer are called crossbeds, which form when sediment grains are moved by water or air currents. The particular style of crossbeds in this outcrop form in sand dunes that are being moved by the wind. Photo by Ken Angielczyk.
Even though we did not find synapsids, we did discover a lot of animals that we think are either new species or new records of species known from elsewhere that were not thought to be present in the Parnaíba Basin. As a result, the assemblage of animals preserved in the Pedra de Fogo Formation seems to be much more diverse than previously appreciated. That's a nice result because we really don't have much information about what animals were living in central Pangaea during the Permian, and our work will help to fill in that gap. The geographically closest areas that preserve similarly-aged fossils are found in places like Morocco and Niger. There is little overlap between the animals present in those places and in the Parnaíba Basin, even though there seems to be similarities in the environments in which the animals were living. This might mean that the assemblages are of slightly different ages, or there might have been more differentiation among environments and the animals they supported than is often thought to be the case for Pangaea (where an animal could theoretically walk from Antarctica to Siberia).
With this in mind, I think a lot of our work on this project going forward will focus on the biogeographic implications of the specimens that we collected. For example, as we study our new amphibian specimens, it will be very interesting to see where their closest relatives are found. Do they represent southern range extensions for groups that are mainly known from the northern hemisphere, as seems to be the case for Prionosuchus plummeri? This could imply that the Parnaíba Basin did lie along an important dispersal corridor, even if synapsids didn't pass through the area. Likewise, how many species in the assemblage are endemic to the Parnaíba Basin (i.e., occur there and nowhere else), like Anisopleurodontis pricei? If many of the species are endemic, it could mean that the animals in the basin were relatively isolated for an extended period of time, giving them time to diverge from their close relatives living elsewhere. Or it might mean conditions in the basin were unusual, and animals living there were forced to adapt to them or become extinct. We'll see where the data lead us, and I'm happy that my collaborators and I will be able to follow them into unexplored territory.
Jaw fragment of Prionosuchus plummeri, as it was found in the field. Scale bar is in centimeters. Photo by Ken Angielczyk.
It's time to get on the plane now. Hopefully I can get some sleep, and perhaps dream of an oasis in a sandy desert, surrounded by tree ferns, with a Prionosuchus lurking just below the water's surface, waiting for a breakfast-sized lungfish to swim by...