Deinosuchus is an extinct genus of eusuchian, either an alligatoroid crocodilian or a stem-group crocodilian, which lived during the Late Cretaceous around . The first remains were discovered in North Carolina (United States) in the 1850s, and the genus was first described in 1909. Additional fragments were discovered in the 1940s and were later incorporated into an influential, though inaccurate, skull reconstruction at the American Museum of Natural History. Knowledge of Deinosuchus remains incomplete, but better cranial material found in recent years has expanded scientific understanding of this massive predator.
Although Deinosuchus was far larger than any modern crocodile or alligator, with the largest adults measuring in total length, its overall appearance was fairly similar to its smaller relatives. It had large, robust teeth built for crushing, and its back was covered with thick hemispherical osteoderms. One study indicated Deinosuchus may have lived for up to 50 years, growing at a rate similar to that of modern crocodilians, but maintaining this growth over a much longer time.
Deinosuchus fossils have been discovered in 12 U.S. states, including Texas, Montana, and many along the East Coast. Fossils have also been found in northern Mexico. It lived on both sides of the Western Interior Seaway, and was an opportunistic apex predator in the coastal regions of eastern North America. Deinosuchus reached its largest size in its western habitat, but the eastern populations were far more abundant. Opinion remains divided as to whether these two populations represent separate species. Deinosuchus was probably capable of killing and eating large dinosaurs. It may have also fed upon sea turtles, fish, and other aquatic and terrestrial prey.
Discovery and naming
thumb|left|Ebenezer Emmons illustrated two fossil teeth in 1858. Most likely, they belonged to the crocodilian that would later be named Deinosuchus.
In 1858, geologist Ebenezer Emmons described two large fossil teeth found in the Tar Heel Formation of Bladen County, North Carolina. Emmons assigned these teeth to Polyptychodon, which he then believed to be "a genus of crocodilian reptiles". Later discoveries showed that Polyptychodon was actually a pliosaur, a type of marine reptile. The genus name Phobosuchus, which was initially created by Baron Franz Nopcsa in 1924, has since been discarded because it contained a variety of different crocodilian species that turned out to not be closely related to each other.
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 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. Better cranial material was also found; by 2002, David R. Schwimmer was able to create a composite computer reconstruction of 90% of the skull. This classification was bolstered in 2005 by the discovery of a well-preserved Deinosuchus brain case from the Blufftown Formation of Alabama, which shows some features reminiscent of those in the modern American alligator, although Deinosuchus was not considered a direct ancestor of modern alligators.
The species pertaining to Deinosuchus since the resurrection of the generic name in 1979 have been traditionally recognized as D. rugosus from Appalachia and the larger D. hatcheri/riograndensis from Laramidia, characterized by differences of the shape of their osteoderms and teeth. However, based on the lack of distinctive enough differences beyond size, they have increasingly been considered all the same species.
Phylogenetic analysis places Deinosuchus as a basal member of Alligatoroidea, as shown in the simplified cladogram below:
Description
Morphology
Despite its large size, the overall appearance of Deinosuchus was not considerably different from that of modern crocodilians. Deinosuchus had an alligator-like, broad snout, with a slightly bulbous tip. Each premaxilla contained four teeth, with the pair nearest to the tip of the snout being significantly smaller than the other two. Each maxilla (the main tooth-bearing bone in the upper jaw) contained 21 or 22 teeth. The tooth count for each dentary (tooth-bearing bone in the lower jaw) was at least 22. When the mouth was closed, only the fourth tooth of the lower jaw would have been visible. The bite force of Deinosuchus has been estimated to be The secondary palate and procoelous vertebrae are advanced features also found in modern eusuchian crocodilians.
The osteoderms (scutes) covering the back of Deinosuchus were unusually large, heavy, and deeply pitted; some were of a roughly hemispherical shape. Deep pits and grooves on these osteoderms served as attachment points for connective tissue.
Size
thumb|D. riograndensis (in yellow) compared to other large crocodyliforms
The large size of Deinosuchus has generally been recognized despite the fragmentary nature of the fossils assigned to it. However, estimates of how large it really was have varied considerably over the years. The original estimate from 1954 for the type specimen of the then-named "Phobosuchus riograndensis" were based on a skull of and a lower jaw of long, reconstructed with similar proportions to the Cuban crocodile giving a total estimated length of . This was later corroborated when it was noted that most known specimens of D. rugosus usually had skulls of about with estimated total lengths of and weights of . A reasonably well-preserved skull specimen discovered in Texas indicated the animal's head measured about , and its body length was estimated at . Schwimmer (2002) suggested the very largest individuals of D. riograndensis could reach sizes up to , 1.5 times that of the average D. rugosus, based on isometrically scaling vertebral lengths from the type specimens of "Phobosuchus riograndensis" (AMNH 3073) and Deinosuchus hatcheri, which he estimated would represent animals nearly .
A particularly large mandibular fragment from a D. riograndensis specimen was estimated to have come from an individual with a skull length of . This length was used in conjunction with a regression equation relating skull length to total length in the American alligator to estimate a total length of for this particular specimen. This is only slightly lower than previous estimates for the species. Deinosuchus has often been described as the largest crocodyliform of all time. In their 2025 reclassification of Deinosuchus as a eusuchian, Walter and colleagues stated that previous estimates may have overestimated its size as the genus has a relatively long snout, but these were based on taxa with shorter snouts such as the American alligator. The authors estimated the maximum total body length of D. riograndensis and D. schwimmeri at and respectively and a mean body length of and respectively. They also suggested that Purussaurus would have been larger than Deinosuchus.]]
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". David R. Schwimmer proposed in 2002 that 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. Deinosuchus is generally thought to have employed hunting tactics similar to those of modern crocodilians, ambushing dinosaurs and other terrestrial animals at the water's edge and then submerging them until they drowned. A 2014 study suggested that it would have been able to perform a "death roll", like modern crocodiles. A 2010 review by Schwimmer noted NJSM 13096, a tyrannosauroid leg bone in the collection of the New Jersey State Museum recovered from the Ellisdale Fossil Site had bite marks on it.
thumb|left|Reconstructed skull and upper body of Deinosuchus
Schwimmer and G. Dent Williams proposed in 1996 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.
Growth rates
thumb|The osteoderms of Deinosuchus, as illustrated by W.J. Holland. They are proportionately much thicker than those of modern crocodilians.
A 1999 study by Gregory M. Erickson and Christopher A. Brochu suggested the growth rate of Deinosuchus was comparable to that of modern crocodilians, but was maintained over a far longer time. Their estimates, based on growth rings in the dorsal osteoderms of various specimens, indicated each Deinosuchus might have taken over 35 years to reach full adult size, and the oldest individuals may have lived for more than 50 years. This was a completely different growth strategy than that of large dinosaurs, which reached adult size much more quickly and had shorter lifespans. According to Erickson, a full-grown Deinosuchus "must have seen several generations of dinosaurs come and go".
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 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 were <!--subjunctive--> biannual rather than annual, this might indicate Deinosuchus grew faster than modern crocodilians, and had a similar maximum lifespan. Specimens have been described from 12 U.S. states: Utah, Montana, Wyoming, New Mexico, New Jersey (Marshalltown Formation), Delaware, Georgia, Alabama, Mississippi, Texas, and North & South Carolina (Tar Heel/Coachman & Bladen Formations). A Deinosuchus osteoderm from the San Carlos Formation was also reported in 2006, so the giant crocodilian's range may have included parts of northern Mexico. There is also a report describing a possible Deinosuchus scute from Colorado. Deinosuchus fossils are most abundant in the Gulf Coastal Plain region of Georgia, near the Alabama border. Deinosuchus remains have been unearthed in New Mexico's Menefee Formation.
The distribution of Deinosuchus specimens indicates these giant crocodilians may have preferred estuarine environments. Although some specimens have also been found in marine deposits, it is not clear whether Deinosuchus ventured out into the ocean (like modern-day saltwater crocodiles); these remains might have been displaced after the animals died.
It has been suggested that the presence of Deinosuchus may have been responsible for the lack of very large predatory theropods from the Late Cretaceous of Appalachia, with the giant crocodilian replacing such large theropods as the top predator of the Appalachian coastal plains.
See also
- Sarcosuchus
- Stomatosuchus