Deinosuchus: Description

Description:

Morphology:

Despite its massive size, the overall physical appearance of Deinosuchus was not considerably different from that of modern crocodilians. Deinosuchus had an alligator-like broad snout, with a slightly bulbous tip. The teeth were thick and robust; those close to the rear of the jaws were short, rounded, and blunt. The osteoderms (scutes) covering the back were unusually large, heavy, and deeply pitted; some were of a roughly semicircular shape

Physiology:

The bite force of Deinosuchus has been estimated to exceed 18,000 newtons. In contrast, modern American alligators, with the strongest bite of any living animal, have been measured no higher than 9,452 newtons.[6] Even the largest and strongest theropod dinosaurs, such as Tyrannosaurus, probably had a bite force weaker than that of Deinosuchus.

Deep pits and grooves on the osteoderms of Deinosuchus served as attachment points for connective tissues. Together, these osteoderms and connective tissues would have served as load-bearing reinforcement to support the massive body of Deinosuchus on land. Consequently, despite its massive bulk, Deinosuchus was probably capable of a "high walk," "belly run," or even a full gallop, just like most modern crocodilians.

Deinosuchus had a secondary bony palate, which would have permitted it to breathe through its nostrils while the rest of the head remained submerged underwater. The vertebrae were articulated in a procoelus manner, meaning that they had a concave hollow on the front end and a convex bulge on the rear; these would have fit together to produce a ball and socket joint. The secondary palate and procoelus vertebrae are advanced features also found in modern eusuchian crocodilians.

Size:

Because the known remains of Deinosuchus are so fragmentary, estimates of its size have varied significantly. In 1954, Edwin H. Colbert and Roland T. Bird reconstructed the lower jaw of Deinosuchus with a length of 2 m (6.6 ft), and calculated "on the basis of comparative measurements" that the giant crocodilian's total body length could have been up to 15 m (50 ft). A much lower estimate — 8 to 10 m (26 to 33 ft) — was given by Gregory M. Erickson and Christopher A. Brochu in 1999. David R. Schwimmer suggested in 2002 that the smaller and more common form of Deinosuchus found in eastern North America usually grew to about 8 m (26 ft) and 2.3 tons. According to Schwimmer's research, Deinosuchus reached larger sizes in the western portion of the continent; he estimates that the biggest specimens had a total body length of up to 12 m (40 ft), and perhaps weighed 8.5 tons or more.

Although there is some disagreement as to its exact size, the fossil remains are nonetheless sufficient to indicate that Deinosuchus was substantially larger than any modern crocodilian. Even the relatively low estimate provided by Erickson and Brochu suggests that the maximum weight reached by Deinosuchus exceeded that of currently living species by a factor of three to five.

Habitat

Deinosuchus specimens have been discovered in freshwater and marine deposits.
Diet

In 1954, Edwin H. Colbert and Roland T. Bird speculated that Deinosuchus "may very well have hunted and devoured some of the dinosaurs with which it was contemporaneous." In 1961, Colbert more confidently restated this hypothesis: "Certainly this crocodile must have been a predator of dinosaurs; otherwise why would it have been so overwhelmingly gigantic? It hunted in the water where the giant theropods could not go." It is generally assumed that Deinosuchus would have employed similar hunting tactics to modern crocodilians, ambushing dinosaurs and other terrestrial animals at the water's edge and then submerging them until they drowned. Several hadrosaurid tail vertebrae found near Big Bend National Park show evidence of Deinosuchus tooth marks, strengthening the hypothesis that Deinosuchus fed on dinosaurs in at least some instances.

Research by David R. Schwimmer and G. Dent Williams indicates that Deinosuchus may have preyed on marine turtles. Deinosuchus would probably have used the robust, flat teeth near the back of its jaws to crush the turtle shells. The "side-necked" sea turtle Bothremys was especially common in the eastern habitat of Deinosuchus, and several of its shells have been found with bite marks that were most likely inflicted by the giant crocodilian.

Growth rates

A 1999 study by Gregory M. Erickson and Christopher A. Brochu suggested that the growth rate of Deinosuchus was comparable to that of modern crocodilians, but was maintained over a far longer period of time. Their estimates, based on growth rings in the dorsal osteoderms of various specimens, indicate that each Deinosuchus might have taken over 35 years to reach full adult size, and that the oldest individuals may have lived for more than 50 years. According to Erickson, a full-grown Deinosuchus "must have seen several generations of dinosaurs come and go."

David R. Schwimmer noted in 2002 that Erickson and Brochu's assumptions about growth rates are only valid if the osteodermal rings reflect annual periods, as they do in modern crocodilians. According to Schwimmer, the growth ring patterns observed in Deinosuchus could have been affected by a variety of factors, including "migrations of their prey, wet-dry seasonal climate variations, or oceanic circulation and nutrient cycles". If the ring cycle was biannual rather than annual, this might indicate that Deinosuchus grew faster than modern crocodilians, and had a similar maximum lifespan

Discovery and classification:

In 1858, geologist Ebenezer Emmons described two large fossil teeth found in Bladen County, North Carolina. Emmons referred these teeth to Polyptychodon, which he then believed to be "a genus of crocodilian reptiles." Later discoveries showed that Polyptychodon was actually a pliosaur. The teeth described by Emmons were thick, slightly curved, and covered with vertically-grooved enamel; he assigned them a new species name, P. rugosus. Although not initially recognized as such, these teeth were probably the first Deinosuchus remains to be scientifically described.

In 1903, at Willow Creek, Montana, several fossil osteoderms were discovered "lying upon the surface of the soil" by John Bell Hatcher and T.W. Stanton.These osteoderms were initially attributed to the ankylosaurid dinosaur Euoplocephalus.[4] Excavation at the site, carried out by W.H. Utterback, yielded further fossils, including additional osteoderms as well as vertebrae, ribs, and a pubis.[4] When these specimens were examined, it became clear that they belonged to a large crocodilian and not a dinosaur; upon learning this, Hatcher "immediately lost interest" in the material. After Hatcher died in 1904, his colleague W.J. Holland studied and described the fossils. Holland assigned these specimens to a new genus and species, Deinosuchus hatcheri, in 1909.
A 1940 expedition by the American Museum of Natural History yielded more fossils of giant crocodilians, this time from Big Bend National Park in Texas. These specimens were described by Edwin H. Colbert and Roland T. Bird in 1954, under the name Phobosuchus riograndensis. Donald Baird and Jack Horner later determined that the genus name Phobosuchus was taxonomically invalid, and that the Big Bend remains described by Colbert and Bird should therefore properly be assigned to Deinosuchus.

The American Museum of Natural History incorporated the skull and jaw fragments into a plaster restoration, modeled after the present-day Cuban crocodile. Colbert and Bird stated that this was a "conservative" reconstruction, since an even greater length could have been obtained if a long-skulled modern species such as the saltwater crocodile had been used as the template. Because it was not then known that Deinosuchus had a broad snout, Colbert and Bird miscalculated the proportions of the skull, and the reconstruction greatly exaggerated its overall width and length.[5]

Despite its inaccuracies, the reconstructed skull became the best-known specimen of Deinosuchus, and brought public attention to this giant crocodilian for the first time.

Specimens have also been found in Alabama, Mississippi, Georgia, New Jersey, North Carolina, Wyoming, New Mexico and recently also in Mexico.

Originally classified in the family Crocodylidae, a better skull specimen shows it is most likely a basal member of Alligatoroidea.