Anyone reading this who has ever known me from Dinosaur Home has certainly read my repeated and updated thoughts on this topic before, but this post deals not with the geographical range of Deinosuchus but rather which states/areas might be added to those where its fossils have already been found. Of course, those who do not know me from Dinosaur Home are probably hearing about this topic for the first time!
Deinosuchus, one of the largest crocodilians of all time, has long been one of my favorite prehistoric animals. It lived from about 82 to 73 million years ago, almost exactly matching the time of the Campanian age of the Cretaceous period, and its neighbors were dinosaurs, who were also some of its prey. It was a North American animal, and its fossils have been found in a variety of American/Mexican states stretching from Montana to Chihuahua in the west, along a crescent-shaped arc from Mississippi to North Carolina, and along a line going roughly from just east of Washington, D.C. to just southwest of New York City. The gaps in between these are what makes this topic so interesting.
Most paleontologists who have studied Deinosuchus recognize it as a shoreline animal, though it apparently existed further inland at times, as long as the land was warm and wet, just like most crocodilians today. Therefore, the starting point for me has been to look at paleogeographic maps of North America during Campanian times. There is a wonderful website called Deep Time Maps that has three different times represented that are useful for this topic: 82 Ma ("Ma" means million years), 80 Ma, and 77 Ma. I have tried in the past to extend the range along the coastlines far to the north, south, east, and west, but I'm not going to try that now, except for what I think would be an important bridge in the gap between Mississippi and Texas. (The maps are prominently copyrighted, so I'm not going to share them here; you'll have to look them up yourself). The farthest north that Deinosuchus fossils have been found in the west is in Montana, so I will assume that's the northmost it got (especially considering how Alberta, Montana's northern neighbor, has produced many Campanian crocodilian fossils but not Deinosuchus specifically). As for the southmost area, that would be either Chihuahua or Coahuila, and the fossils there are all clustered around the tri-corner of those two Mexican states and Texas. I will consider that the southmost point. Looking to the east, across the former Western Interior Seaway, the westernmost area is currently Mississippi. The northeast-most area is in New Jersey, just across from Staten Island, New York. Here, too, I will not assume that Deinosuchus was present any further up the coast than this. However, Deinosuchus must have crossed the Western Interior Seaway if it was present in the west and east halves of North America that existed at the time.
A significant gap exists between the fossils in Texas and those in Mississippi, made up of sea (in central and eastern Texas) and some of the coastline of the eastern half of North America, running northeast through southeast Oklahoma, Arkansas, southeast Missouri, and far southern Illinois, then bending southeast through western Kentucky and Tennessee. Surely Deinosuchus lived on this coast too, or it would be a huge distance across the sea to populate Texas and other coastlines on that side. Some geologists have argued that a line of volcanic islands was present in northeast Texas, making the ocean crossing even shorter.
Therefore, after taking a look at the shorelines and coastal plains 82, 80, and 77 million years ago, I would say that Deinosuchus lived in parts of the following American and Mexican states: Montana, Wyoming, Utah, Colorado, Arizona, New Mexico, Texas, Chihuahua, Coahuila, Louisiana, Arkansas, Missouri, Illinois, Kentucky, Tennessee, Mississippi, Alabama, Georgia, South Carolina, North Carolina, Virginia, Maryland, Delaware, Pennsylvania, and New Jersey. However, it's one thing to say that Deinosuchus lived in those places, and another to say you could find its fossils in those places. So far, Deinosuchus fossils have been confirmed from Montana, Wyoming, Utah, New Mexico, Chihuahua, Coahuila, Mississippi, Alabama, Georgia, South Carolina, North Carolina, Delaware, and New Jersey. Some disagree over whether Deinosuchus fossils have already been found in Maryland or Colorado. In Maryland, there is a fossil that has been assigned to Deinosuchus, but it is from younger rocks than the Campanian age and could be some other large crocodilian. As for Colorado, there is a report of a large crocodilian fossil of Campanian age, but the authors of the paper describing the fossil refuse to assign Deinosuchus as the genus.
The next step after discerning a range from looking at paleogeographic maps is to look at detailed geologic maps of the areas within that range. I've looked at many over the years, but the best resource I've found is the US Geological Survey's geologic maps database. After looking at many of the maps there, I've noticed that some of the parts of states I've mentioned in the hypothetical range of Deinosuchus lack Campanian sedimentary rocks, namely Arizona, Louisiana, Virginia, and Pennsylvania. That leaves Colorado, Arkansas, Missouri, Illinois, Kentucky, Tennessee, and Maryland as our potential Deinosuchus fossil-bearing areas (I include the debatable states of Colorado and Maryland here). In reading the paleontologist David Schwimmer's book, King of the Crocodylians, he too imagines that Deinosuchus fossils could be found in Tennessee and Missouri - but only those two states for some reason.
Now, we are finally left with this map, which shows the American states where I expect that Deinosuchus fossils exist, along with the states where they are confirmed or unconfirmed.
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