Tappania are microfossils found mostly in shale that range in age from the late Paleoproterozoic to the middle Mesoproterozoic. They are known for being morphologically complex, with tubes (known as processes) that protrude from a central vesicle, and conspicuous ear-shaped extensions that make the fossils resemble budding yeast. The group of Tappania fossils that I discovered in the Belt Supergroup of Montana, however, provide many new insights into the anatomy of these original organisms. As you can see in the specimen above, Belt Tappania possessed not one but two complex walls, each of which could grow processes independently of the other. Processes could bifurcate, but it is also clear that they could split at multiple points along a single process, that there were distinct asymmetries in the diameters of the primary and spur processes, and that the outer wall could also reshape in concert with such a complex inner wall process. This indicates an incredibly high degree of morphogenetic coordination, possibly equivalent to extant protistan-grade eukaryotes.
This degree of complexity indicates that the underlying paleobiology of the original Tappania organisms is far from being fully explored! This complexity opens new possibilities for inferring biostratigraphic and biochronological relationships among the earliest eukaryotes on Earth.
For more details, watch for my upcoming paper in Geology!