Sometimes in life, expectations are not always met. Growing up I used to pore over dozens of books depicting old photographs from the American Museum of Natural History, making a mental inventory of all the fossil marvels I had to see. Outside of the dinosaurs (some of which still look very much like they did when Henry Fairfield Osborn was at the museum), I absolutely had to see the enormous reconstructed maw of Carcharodon megalodon and the massive skull of the crocodile Deinosuchus. Perhaps I did see them, but unfortunately all I recall from my early visits were the trip to the fossil halls in a cramped elevator, a museum logo featuring a human skeleton next to the skeleton of a horse, and the immensity of the “Brontosaurus” skeleton in the dim light of the dinosaur halls. Returning many years later, I made sure to take my time through the Hall of Vertebrate Origins, leaving no cladistic nook left unexplored, but alas, the massive C. megalodon jaws had been properly downsized and Deinosuchus was nowhere to be found.
All is not lost, however, as the AMNH has kindly allowed the public access to old museum documents by the likes of Barnum Brown, G.G. Simpson, Edwin Colbert, Henry Fairfield Osborn, and many others, and one 1954 publication allows me a look at the giant crocodilian I never had a chance to meet in person. Entitled “A Gigantic Crocodile from the Upper Cretaceous Beds of Texas” (by Edwin Colbert and Roland Bird from the November 12, 1954 edition of American Museum Novitiates), the paper describes a “new species” dubbed Phobosuchus riograndensis. We now know that the genus Phobosuchus riograndensis = Deinosuchus riograndensis (the type species for the genus is Deinosuchus hatcheri), and so the paper serves our interests here just fine.
The restored skull of Deinosuchus from the Colbert/Bird paper. Note the darker areas, which are the actual fossil material used in the reconstruction.
While the reconstructed skull is impressive in and of itself, it becomes even moreso when we can see its size relative to some AMNH scientists;
The restored skull of Deinosuchus, featuring (left to right) B. Brown, R. T. Bird and E. M. Schlaikjer [ref: "How the 'terror crocodile' grew so big" by Erickson and Brochu, Nature 398, 205-206 (18 March 1999)]
Given that a complete (or reasonably complete) skeleton of Deinosuchus has yet to be found, we can only estimate how large it was from the material at hand, likely 10-12 meters long when fully grown. But how did they get so big? It’s not easy to attain such large sizes, and it’s important to know whether huge crocodilians followed a growth curve similar to that of their living relatives or were instead fast-growing like some dinosaurs. According to this 1999 Nature correspondance by Erickson and Brochu ["How the 'terror crocodile' grew so big" Nature 398, 205-206 (18 March 1999)], it appears that Deinosuchus followed the standard grow-throughout-life pattern exhibited in its modern relatives, perhaps taking upwards of 35 years to fully attain the monstrous sizes we’re familiar with. Given that many extant crocodilians do not live long enough to reach maximum size, perhaps the largest individuals would be more rare than smaller ones, although I am not familiar enough with what has been recovered from these animals to prove or disprove such an idea. While I’m on the subject, of course, Darren Naish has a great post (just posted yesterday, as a matter of fact) involving giant crocodylians, so be sure check his writing out as well.
As for the fossil material discussed in the Colbert/Bird paper, here is what was recovered;
TYPE: A.M.N.H. No. 3073. Almost complete premaxillae and part of a right maxilla, portions of left articular, angular, and surangular, right and left dentaries and right and left splenials; one dorsal vertebra, probably the twelfth vertebra of the presacral series; right scapula, possible portion of a right ilium; scutes and other fragments.
For an animal Colbert and Bird estimated to be up to 50 feet long (6 feet of which being skull), not very much was left over. The reconstructed skull itself belies this, the very front of the jaws and the very back of the lower jaw making up most of the skull material, the skull as a whole being based upon the notoriously bad-tempered Cuban crocodile (http://en.wikipedia.org/wiki/Crocodylus_rhombifer). Colbert and Bird did argue, however, that their fragmentary crocodilian could be even longer than 50 feet in length because they the cuban crocodile had a more blunt snout, and if they had based the reconstruction on the Saltwater Crocodile (Crocodylus porosus) and American Crocodile (Crocodylus acutus) (which have comparatively longer snouts), the size estimate for their specimen would increase further.
It would be wonderful if I could now go on to describe Deinosuchus as we now know it, but (outside of a decrease in size) it doesn’t seem to be very different from the way it is depicted in the Colbert/Bird paper; as the Cretaceous equivalent of the modern-day alligator. Perhaps someday some more skeletal material will help us further flesh out this animal, but the lack of material hasn’t stopped it from becoming a “fan favorite” of paleontology; it often shows up along dinosaurs in model sets, books, and television shows. A more complete crocodilian is the famous Sarcosuchus imperator (and if you haven’t already seen it, check out National Geographic’s documentary SuperCroc),but hopefully more fossils from other giant crocodilians will be discovered so that some comparisons can be made among the giants.
While today New Jersey is usually free of alligators and crocodiles (I say usually because every now and then a release “pet” shows up), this was not always the case. Just in the past year, one of the most well-preserved Thoracosaurus neocesariensis skeletons was extracted from the green marl (stuff gets everywhere, let me tell you) of the Inversand pit in Gloucster County, New Jersey, by Drexel University students and Dr. William Gallagher of the State Museum in Trenton. You can have a look at the recovered material via Drexel’s website here, read a Philadelphia Enquirer article about the discovery here, see an early artistic depiction by Cope at the HMNH, or see a more recent depiction by Dan Varner at Oceans of Kansas.
When I was at the pit last fall, I found a croc scute, but there are several species of crocodilian known from the pit and I could not discern to which it belonged to. I also checked out the location from which Dr. Gallagher found the Drexel Thoracosaurus, but there didn’t seem to be any lingering fossils either, so I focused on trying to extract some bone from a spot that was bearing well in the Main Fossiliferous Layer. The bone was beige on top, dark brown in the middle, but came out only in fragments and I could not tell what I had found. Hopefully when I return on Wednesday I’ll be in luck, and you can expect a post all about what I find on Wednesday.