When I was a kid the movie Alligator seemed to be on television almost every other weekend. It was one of the first movies I can remember seeing, although truth be told I probably should not have been allowed to watch it. The pool scene alone was enough to give me nightmares.
For those who have not seen it, the film features an enormous, marauding alligator that grew to such prodigious size by feeding on test animals a biomedical corporation dumped in the sewer. It was a pretty clever explanation for how an ordinary alligator could become so gigantic, but long before Hollywood screenwriters evolved there really were enormous crocodylians. In some of the books I had taken out of the elementary school library there were photos of the skull of an enormous Cretaceous crocodylian named Deinosuchus. That such a monstrous reptile had once existed made the 1980 horror film that much scarier.
The restored skull of Deinosuchus. The darker colored parts are actual fossils, while the rest is made of plaster. It was formerly on display at the AMNH.
By the time I first encountered it, though, Deinosuchus had already been known for about 80 years. In 1903 paleontologists John Bell Hatcher and T.W. Stanton were looking for fossils among some Cretaceous-age deposits in Montana when they found the fragmentary remains of a large vertebrate. Hatcher picked up a few scutes, small plates of bone that would have been embedded under the animal’s skin in life, and he thought that they might have belonged to a kind of anklyosaur called “Stereocephalus” at the time.
A few months later Hatcher sent his colleague, William Utterback, to have another look at the site. While many of the bones had been broken down into tiny fragments, Utterback succeeded in collecting a few ribs, vertebrae, and scutes. All together, they showed that the fossils Hatcher originally picked up did not belong to an armored dinosaur but to an enormous crocodile!
For some unknown reason, however, the revelation that the animal was a crocodylian caused Hatcher to lose interest in it. He moved on to other projects and soon died before any full description of the fossils was undertaken. Such a prodigious animal needed to make its way into the literature, though, and around 1905 the marine reptile expert S.W. Williston urged W.J. Holland, inheritor of Hatcher’s legacy at the Carnegie Museum, to undertake the description. Holland started up the project almost immediately, but it would not be until 1909 that he would finally publish the first brief sketch of Deinosuchus.*
[Many thanks to Mo, who sent me Holland’s paper.]
The bones Holland described had been through a lot. Many appeared to be worn down by water, and some even bore the marks of prairie fires that may have swept over the skeleton as it weathered out of the ground. Still, some of the more complete bones, like some of the ribs and vertebrae, were essentially enlarged versions of the same bones in modern crocodylians. Based upon what was known of living alligators and crocodiles, Holland estimated the size of Deinosuchus to be around 35-40 feet, considerably larger than even the largest modern crocodiles ever recorded. He concluded;
Deinosuchus hatcheri was undoubtedly one of the hugest representatives of the Crocodilia which has existed on our globe.
If there were no large pieces of skull among the “original” Deinosuchus material, though, where did the frightening restoration I recall from my youth come from? The answer is provided in a 1954 paper written by Edwin Colbert and Roland Bird.
In 1940 the famed fossil hunter Barnum Brown found more Deinosuchus bones in Big Bend National Park in Texas. The remains consisted primarily of bits of jaw and a partially crushed vertebrae, but these pieces filled in gaps left open by Holland’s original description. Interestingly, S.W. Williston may have found Deinosuchus bones from this same location in 1907, which he attributed to “a crocodile not previously known.” Apparently he did not look into the matter further, though, even during the time when he was urging Holland to publish the Montana Deinosuchus bones.**
**[A word should also be said about name changes. When Holland published his paper there was already a large, but geologically-younger, crocodylian named Dinosuchus known from South America. This was awfully close to Deinosuchus, and in 1924 the eccentric paleontologist Franz Nopcsa proposed that Holland’s fossils be renamed Phobosuchus. Colbert and Bird followed this change, but it has since been recognized that Deinosuchus is still the valid name for the enormous Cretaceous alligatoroid from North America.]
The business end of a Cuban crocodile (Crocodylus rhombifer), photographed at the National Zoo.
Nevertheless, Colbert and Bird thought the bits of jaw that were recovered from Texas most closely resembled those of the Cuban crocodile (Crocodylus rhombifer). This choice is important as it dictated the shape of the reconstructed skull they produced. Had the authors chosen to model Deinosuchus on a saltwater crocodile (Crocodylus porosus), for example, the snout would have been longer and estimates of the extinct crocodylian’s size would have been altered. As it would later turn out, however, Deinosuchus was more closely related to the living American alligator (Alligator mississippiensis) than to the Cuban crocodile, and it had a more alligator-like skull shape than the one Colbert and Bird envisioned.
Regardless of skull-shape, though, Colbert and Bird knew they were working with the remains of one big honkin’ crocodylian. What did such a large creature feed on? The presence of dinosaur bones in the area hinted that Deinosuchus might have preyed upon dinosaurs, and in the conclusion of their paper the paleontologists wrote;
It seems very probable that [Deinosuchus] was one of the great predators of Cretaceous times, and this crocodile may very well have hunted and devoured some of the dinosaurs with which it was contemporaneous.
Deinosuchus prepares to attack a Chasmosaurus. From Colbert’s Dinosaurs: An Illustrated History.
Such a scene was vividly brought to life by an artist commissioned by the American Museum of Natural History in which Deinosuchus prepares to bite down on a frightened Chasmosaurus at the water’s edge. (I do not know the name of the artist who created this painting. Does anyone out there know?) It was a vivid image that stuck with me for a long time. Did the dinosaur escape, or did the tooth-studded jaws of Deinosuchus slam down on the puny-looking Chasmosaurus and drag it beneath the roiling water of the lake? The outcome is left up to the viewer, but the attack of a 35-foot Deinosuchus is a frightening thing to imagine.