This past month I co-chaired a technical session at the national Geological Society of America conference in Denver. The session was entitled "Paleontology, Paleobiogeography, and Stratigraphy of the Late Cretaceous North America Seas: A Tribute to Bill Cobban." Dr. Cobban is a scientist at the US Geological Survey who has over 60 years of experience working on the statigraphy and paleontology of the Late Cretaceous Western Interior Seaway. The Western Interior Seaway (WIS) ran through the middle of the U.S. during the Cretaceous (about 65-100 million years ago) and was home to some amazing seafaring creatures, including the mosasaur that hangs over the doorway to the KU Natural History Museum.
I gave a talk entitled "Using GIS to investigate bias in the fossil record: a case study of the Late Cretaceous Western Interior Seaway of North America." In that talk I presented some tests that I performed to assess how good the fossil record in the WIS is. I was curious if the fossil record is biased in any way that would prevent us from mapping out the ranges of prehistoric species. The factors that I'm particularly interested in are competition, environmental change, and whether biological interactions between species are more or less important than environmental changes in determining which species go extinct and which do not.
I relate my research to the current biodiversity crisis: when you are trying to understand how invasive species, habitat fragmentation, and climate change are going to affect species in the future, there is a WEALTH of information (~544 million years in fact) in the fossil record that provides exactly that. The fossil record tells stories of how critters responded to species invasions and habitat loss and it teaches us about the effects of climate change and sea level fluctuations. These are the very factors that conservationists consider when attempting to save habitats and species.
One of the symposium's invited talks was by Neil Landman, a renowned cephalopod paleontologist from the American Museum of Natural History. He spoke eloquently on the life history of scaphite ammonites. Scaphites are shelled cephalopods (similar looking to modern Nautilus, also related to squid and octopi), but instead of having a properly coiled shell (like the Nautilus, their shell straightens out a bit at the end. Neil is probably one of the world's expert on scaphites. His talk described his latest interpretation of how these animals caught prey, what kind of prey, how they swam, at what orientation they held their body in the water column, how they reproduced, etc. Late Cretaceous cephalopds got SUPER weird, so this sort of talk is *really* exciting for folks like me who are into cephalopods and life in general in the WIS.
Overall, we had a very nice day talking about the current status of Late Cretaceous WIS research from a variety of geologically related fields: geochronology (age-dating the rocks), biology (mostly cephalopods, but also foraminifera, mosasaurs, sharks, etc.), biogeography, mapping, stratigraphy, and biostratigraphy. We are still working to better understand a number of the animal groups and how they might be used to date rocks. The great news is that it looks like the fossil and rock records are good enough to test many of our questions!
While a recent discovery may change textbooks and the way that many scientists think about bird and dinosaur evolution, it comes as no surprise us.
This week, Xing Xu, H. You, K. Du and F. Han published in the journal Nature a reanalysis of early bird evolution. The analysis knocks Archaeopteryx off its perch as a grandfather to later birds.
KU has been the central hub for the discovery of the fossil bird beds in the Early Cretaceous of China with the description of the primitive bird, Confuciusornis, and has continued to be involved with all the new discoveries coming out of this region in part through an alumnus of the KU vertebrate paleontology program.
The alumnus, Zhonghe Zhou, presently leads Chinese studies in that region and was recently elected to the prestigious National Academy of Sciences. Zhou and one of the paper’s authors, Xing Xu, had already precipitated a revolution in our understanding of bird evolution with the discovery of the four-winged gliding bird/dinosaur, Microraptor. With Microraptor, they showed that bird flight began with gliding.
Zhou has a long-term collaboration with KU vertebrate paleontology researchers at the Biodiversity Institute. Preparator David Burnham, collection manager Desui Miao and I regularly visit China to work on early birds. Our research also has suggested that Archaeopteryx along with other archaic birds represents a side branch that split off much earlier than the new bird, Xiaotingia, and its sister Anchiornis, another four-winged gliding animal.
While the recent paper in Nature calls these animals “feathered dinosaurs,” we think that they and their common ancestor with modern birds can be best considered true birds. Rather than removing Archaeopteryx from Aves because its avian features were shared with birdlike dinosaurs, we place a stronger emphasis on these features thereby pulling the dinosaur-like birds into Aves. This limits these flying, feathered animals to the Class Aves and pushes the origin of birds into the Early Jurassic or Late Triassic at about the same time as the dinosaurs themselves.