Introductions to the Wayan and Vaughn: An apparent Oryctodromeus paradise

Does the world need another paleontology blog? Probably not, but here it is (you're welcome). Here the focus will be on general Mesozoic paleontology with some focus on work I am doing in the Cretaceous of Idaho and Montana, as well as reports on occasional paleontological outings and whatever else garners my interest. On that note, lets jump to an introduction of the work I will be doing as a PhD student, work in the mid-Cretaceous. of Idaho and Montana.

Since my time as an undergraduate, I have been involved in working in the Cretaceous formations of eastern Idaho, with most work being in the mid-Cretaceous (latest Albian-Cenomanian) Wayan Formation. Persistence in annually prospecting for outcrops (which are few and far-between) and fossils is slowly allowing a better understanding of the mid-Cretaceous Wayan fauna. The fossil assemblage (Krumenacker, 2010) is dominated by partial skeletons of the small burrowing ornithopod Oryctodromeus, but includes fragmentary remains that indicate the presence of nodosaurs, iguanodonts, large theropods, dromaeosaurs, possible neoceratopsians, turtles, and various crocodylians (including a large Deinosuchus-like form that is currently undergoing description). Eggshell and large eggs of the oogenus Macroelongatoolithus are also known (Simon et al., 2012), with isolated eggshell being fairly common; the presence of this form suggests the presence of a large oviraptorid (hence the silly title banner). Some recent ongoing work by my PhD advisor Dr. Dave Varricchio, others, and myself  is demonstrating the presence of a diverse microvertebrate fauna. Also, if we are really lucky, it sounds as if we may have a new type of unexpected dino to add to the Wayan fauna, once I can see the fossil for myself...

A rare good outcrop of the Wayan Formation.

In southwest Montana, there is a rock formation with numerous Oryctodromeus fossils as well, in fact, it was first described from these rocks (Varricchio et al., 2007), the Vaughn Member of the Blackleaf Formation. The dominance of Oryctodromeus in both the Wayan and Vaughn, and their equivalent Cenomanian ages, suggest that both of these formations represent the same depositional system, the deposits of which have been disrupted by more recent volcanism and tectonic activity. Regional thickness differences in both rock units reflect subsidence rates, while lithological variations reflect, partially, the volcanic input from volcanism associated with the Idaho batholith, to the west.

Vaughn Member near Lima, Montana.

I'm interested to know why a small ornithopod, a dinosaur type typically rare in dinosaurian faunas, is the most common vertebrate in both rock units, while those dinosaurs that are usually most common in other Early to mid-Cretaceous faunas (nodosaurs, large ornithopods, sauropods, theropods) are so poorly represented. I have some suspicions, but they will be hard to prove.

To help address these questions, we plan to do a taphonomic study looking at patterns in fossil preservation and types of fossils found in both rock units, and how these may relate to subsidence rates, depositional environments, and proximity to the Cretaceous Interior Seaway. This may not directly answer my questions, but it will give a better idea of preservational constraints in the area at the time. Of course all this depends on availability of funding, which in paleo and science generally, is hard to come by. If funding is not as forthcoming, my doctoral work will be more Orycto-centric and focus on histology, phylogeny, and morphology. There are plenty of questions in these areas to answer about this wonderful little dinosaur.

There you are, you rare mid-Cretaceous lovers, more rare ornithopod enthusiasts, and unlucky fellows who stumbled across this by accident. More on this and other things later....

Useful references:

Krumenacker, L. J., 2010. Chronostratigraphy and paleontology of the mid-Cretaceous Wayan Formation of eastern Idaho, with a description of the first Oryctodromeus specimens from Idaho. BYU Provo MS.

Simon, J. D., D. J. Varricchio, F. D. Jackson, and S. R. Robison, 2012. Giant theropod eggs from the Albian- Cenomanian Wayan Formation of Idaho: Taxonomic, paleogeographic, and reproductive implications. Journal of Vertebrate Paleontology 32 (3, supplement):174.

 

Varricchio, D. J., A. J. Martin, and Y. Katsura. 2007. First trace and body fossil evidence of a burrowing, denning dinosaur. Proceedings of the Royal Society B: Biological Sciences 274: 1361–1368.