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Deinosuchus

I was recently asked a question about the possibility of Deinosuchus being in the Hell Creek and interacting with Tyrannosaurus rex. Since the Hell Creek is well-sampled and there are no Deinosuchus fossils it is safe to assume that it was absent from the Hell Creek. However, the person asking the question was fully aware of that so the question actually was, "if Deinosuchus were to be known from surrounding areas of the same age, would it be scientifically plausible to infer its presence in the Hell Creek?" To be perfectly honest, I had no idea of the temporal and geographic range of Deinosuchus and so it turned out to be an interesting afternoon of researching this.

As far as I can gather from the literature and also from colleagues that work on fossil crocs, there are no peer-reviewed scientific articles that ever state the presence of Deinosuchus in strata younger than the late Campanian. Lucas et al. (2006) include a review of Deinosuchus occurrences in one of their papers and they conclude the temporal range of Deinosuchus as being ~73-80 Ma, the younger of the range being about 12 Ma prior to the Hell Creek environment. David Schwimmer (not Ross from friends) states in his book that the supposed Maastrichtian (70.6 - 65.5 Ma) Deinosuchus remains (unpublished accounts) may be a misidentification of large (marine?) crocs. As I only had access to an on-line preview of the book, I couldn't track down the exact identity of this mystery croc...These are also supposed to be from the Atlantic Coastal Plain.

There was one thing that baffled me though, the exact age of the Black Creek Group, where the holotype material of Deinosuchus rugosus is from, and this took a bit of digging around the interweb and stratigraphy literature. Although according to Lucas et al. (2006) citing Schwimmer (2002), the Deinosuchus-bearing horizon of the Black Creek is supposed to be ~73-74 Ma, I couldn't find support for this figure mostly because there is no mention of exactly which formation of the Black Creek Group the holotype is from. This presents a bit of a problem, as according to this website, the Black Creek Group of North Carolina has three formations spanning from Early Campanian (Tar Heel Formation), Upper Campanian (Bladen Formation), and to the Early Maastrichtian (Donoho Creek Formation). So depending on which formation of the Black Creek Group the holotype material is from, the upper range of Deinosuchus can be as young as the Early Maastrichtian. The overlying marine strata, the Peedee Formation, is regarded as being Late Maastrichtian and dated at 66.7 Ma (Schwimmer 2002). D. rugosus is supposed to be from the upper part of the Black Creek thus placing it relatively younger than other Deinosuchus-bearing strata with an absolute younger bound at >66.7 Ma.

Fortunately, I stumbled across a PhD thesis that pretty much resolved this issue. According to Mitra (2002), Elizabethtown, the locality of the type specimen of D. rugosus, belongs to the Tar Heel Formation and Early Campanian in age. Further, the Phoebus Landing locality, where some referred D. rugosus specimens are known from, is supposed to be Campanian. So I've finally managed to find support for the ~73-74 Ma age of the Deinosuchus-bearing horizon of the Black Creek (Lucas et al. 2006, citing Schwimmer (2002)). Perhaps if I actually had read Schwimmer (2002) and not just the on-line previews, I wouldn't have had to go through all this effort but I wouldn't know if it's discussed in the book because our library doesn't have a copy....In any case, N Carolina would have been on the eastern side of the Western Interior Seaway anyway and all Deinosuchus specimens from Montana are definitively Campanian in age.

So in summary, all known Deinosuchus materials are from the Campanian, temporally ranging between ~73 and 80 Ma, thus making its presence in the Late Maastrichtian and in particular in the Hell Creek unlikely.

One thing that I thought was quite interesting is that Deinosuchus seems to be abundant in places and times where large theropods are absent or rare.

References:
Lucas, S. G., R. M. Sullivan, and J. A. Spielman. 2006. The giant crocodylian Deinosuchus from the Upper Cretaceous of the San Juan Basin, New Mexico. New Mexico Museum of Natural History and Science Bulletin 35:245-248.

Mitra, M. 2002. Paleopalynology of the Tar Heel Formation of Atlantic Coastal Plain of North Carolina, United States. North Carolina State University.

Schwimmer, D. R. 2002. King of the crocodylians: the paleobiology of Deinosuchus. Indiana University Press. 220 pages.

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