Rethinking the Past of the Parnaíba Basin Tuesday, May 1 It's 3 a.m. and I'm in the departure lounge waiting for my flight to São Paulo, where I will pick up my flight back to the United States. Most of my collaborators have already left, so the trip is nearly 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 projects 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 it's important to be open-minded toward 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 from what 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. It seems more 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 to their leaving a fossil record for us. But as we continued working, we thought less of the synapsids and thought more about the meanings of our new fossil discoveries and our new geological data. We discovered a lot of animals that might be either new species or new records of species known from elsewhere that we didn't think existed before 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 Pangea during the Permian. Our work this past month will help to fill in that gap. Places like Morocco and Niger are, geographically, the closest areas that preserve fossils of a similar age. There is little overlap between the animals present in those places and in the Parnaíba Basin, even though there seem to be similarities in the environments the animals once lived in. 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 Pangea, 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, meaning that they 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. 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-size lungfish to swim by.