Deinosuchus

Discovery and naming

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 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. Another large tooth that likely came from Deinosuchus, discovered in Tar Heel sediments from neighboring Sampson County, was named Polydectes biturgidus by Edward Drinker Cope in 1869.

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. Excavation at the site, carried out by W.H. Utterback, yielded further fossils, including additional osteoderms, as well as vertebrae, ribs, and a pubis. 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. Deinosuchus comes from the Greek δεινός/deinos, meaning "terrible", and σοῦχος/suchos, meaning "crocodile".

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 assigned the Big Bend remains to Deinosuchus, which has been accepted by most modern authorities. 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. In 2024, the replacement of the type species of Deinosuchus with Phobosuchus riograndensis has been petitioned to the ICZN.

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. 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. 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.

Numerous additional specimens of Deinosuchus were discovered over the next several decades. Most were quite fragmentary, but they expanded knowledge of the giant predator's geographic range. As noted by Chris Brochu, the osteoderms are distinctive enough that even "bone granola" can adequately confirm the presence of Deinosuchus. Better cranial material was also found; by 2002, David R. Schwimmer was able to create a composite computer reconstruction of 90% of the skull.

Classification and species

Since the discovery of the earliest fragmentary remains that would come to be known as Deinosuchus, it was considered a relative of crocodiles and initially placed in their family (Crocodylidae) in 1954 based on dental features. However, the finding of new specimens from Texas and Georgia in 1999 led to phylogenetic analysis placing Deinosuchus in a basal position within the clade Alligatoroidea along with Leidyosuchus. 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. In their overview of crocodyliform material from the Kaiparowits Formation of Utah, Irmis et al. (2013) noted that D. rugosus is dubious due to its holotype teeth being undiagnostic, and recommended using Deinosuchus hatcheri for Deinosuchus material from Laramidia, while stressing that cranial Deinosuchus material from Appalachia has not been described. In a 2020 study, Cossette and Brochu agreed that D. rugosus is dubious and undiagnostic, rendering it a nomen dubium, and alternatively named a new species D. schwimmeri (named after fellow paleontologist David R. Schwimmer) from Appalachia, which included several specimens previously ascribed to D. rugosus. They also noted that the highly incomplete D. hatcheri holotype can be distinguished by the unique shape of the edge of its indented osteoderms, although this may not be reliable because the osteoderms of the other species may simply not be as well preserved. However, due to the incomplete nature of the type species D. hatcheri, Cossette and Brochu proposed to transfer the type species to the better preserved D. riograndensis, which would allow for improved identification and differentiation of the Deinosuchus species.

Phylogenetic analysis places Deinosuchus as a basal member of Alligatoroidea, as shown in the simplified cladogram below:

In a 2025 study, Jules D. Walter and colleagues argue that many character states previously thought to be diagnostic for alligatoroids were actually much more widespread. In their analysis several genera traditionally viewed as basal alligatoroids, among them Deinosuchus, were found to not only fall outside of Alligatoroidea but to not even be true crocodilians, instead representing derived non-crocodilian eusuchians. Deinosuchus was recovered as having split from the lineage leading up to Crocodilia after Leidyosuchus but before the terrestrial Planocraniidae.

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.{{cite book |title=King of the Crocodylians: The Paleobiology of Deinosuchus |last=Schwimmer |first=David R. |publisher=Indiana University Press |pages=1–16 |chapter=The Life and Times of a Giant Crocodylian

Modern saltwater crocodiles (Crocodylus porosus) have the strongest recorded bite of any living animal, with a maximum force of 16414 N for a 4.59 m, 531 kg specimen. The bite force of Deinosuchus has been estimated to be 18000 N to 102803 N.

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 procoelous manner, meaning 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 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. Together, the osteoderms and connective tissue would have served as load-bearing reinforcement to support the massive body of Deinosuchus out of water. These deeply pitted osteoderms have been used to suggest that, despite its bulk, Deinosuchus could probably have walked on land much like modern-day crocodiles. However, more recent analyses of the taxon's hindlimb biomechanics find that Deinosuchus would have run into issues generating enough muscular force to support its body and prevent the adoption of an erect-limbed "high walk" gait. This would have limited Deinosuchus terrestrial capabilities to belly-dragging as its primary mode of locomotion over land, and would suggest the taxon would have spent most of its life in the water.

Size

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 1.5 m and a lower jaw of 1.8 m long, reconstructed with similar proportions to the Cuban crocodile giving a total estimated length of 15 m. However, this reconstruction is currently considered to be inaccurate. Using more complete remains, it was estimated in 1999 that the size attained by specimens of Deinosuchus varied from 8 to with weights from 2.5 to.{{cite journal

A particularly large mandibular fragment from a D. riograndensis specimen was estimated to have come from an individual with a skull length of 147.5 cm. 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 10.64 m 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 10.5 m and 7.64 m respectively. They also suggested that Purussaurus would have been larger than Deinosuchus.

Paleobiology

Diet

|access-date=November 2, 2009 |archive-url=https://web.archive.org/web/20110719181856/http://geology.csustan.edu/julia/pdf/sankey-2001.pdf |archive-date=July 19, 2011 }}]] 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". Colbert restated this hypothesis more confidently in 1961: "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."{{cite book |url-access=registration

Schwimmer and G. Dent Williams proposed in 1996 that Deinosuchus may have preyed on marine turtles.{{cite journal

Schwimmer concluded in 2002 that the feeding patterns of Deinosuchus most likely varied by geographic location; the smaller Deinosuchus specimens of eastern North America would have been opportunistic feeders in an ecological niche similar to that of the modern American alligator. They would have consumed marine turtles, large fish (such as Megalocoelacanthus), and smaller dinosaurs (including young theropods). The bigger, but less common, Deinosuchus that lived in Texas and Montana might have been more specialized hunters, capturing and eating dinosaurs (such as hadrosaurs, ceratopsians, and small and large theropods). Schwimmer noted no theropod dinosaurs in Deinosuchus eastern range approached its size, indicating the massive crocodilian could have been the region's apex predator.

Growth rates

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 biannual rather than annual, this might indicate Deinosuchus grew faster than modern crocodilians, and had a similar maximum lifespan.

Paleoecology

Deinosuchus was present on both sides of the Western Interior Seaway.{{cite book |access-date=December 27, 2008 |archive-url=https://web.archive.org/web/20160222235454/https://gsa.confex.com/gsa/2008CD/finalprogram/abstract_133900.htm |archive-date=February 22, 2016

The distribution of Deinosuchus specimens indicates these giant crocodilians may have preferred estuarine environments. In the Aguja Formation of Texas, where some of the largest specimens of Deinosuchus have been found, these massive predators probably inhabited brackish-water bays.{{cite journal

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.

References

References

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