Deinosuchus is an extinct genus related to the alligator that lived 80 to 73
million years ago, during the late Cretaceous period. The name translates
as "terrible crocodile" and is derived from the Greek deinos, "terrible", and
soukhos, "crocodile". The first remains were discovered in North Carolina in the
1850s; the genus was named and 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 10.6 m 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 found in 10 US 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.
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 contained 21 or 22
teeth. The tooth count for each dentary was at least 22. All the teeth were very
thick and robust; those close to the rear of the jaws were short, rounded,
and blunt. They appear to have been adapted for crushing, rather than
piercing. When the mouth was closed, only the fourth tooth of the lower jaw
would have been visible. Modern saltwater crocodiles have the
strongest recorded bite of any living animal, with a maximum force of 16,414
N. The bite force of Deinosuchus has been estimated to be 18,000 N. to
102,803 N. It has been argued that even the largest and strongest theropod
dinosaurs, such as Tyrannosaurus, probably had bite forces inferior to
that of Deinosuchus. 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 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. = 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 10 m with
weights from 2.5 to 5 t. This was later corroborated when it was noted that most
known specimens of D. rugosus usually had skulls of about 1 m with estimated
total lengths of 8 m and weights of 2.3 t. A reasonably well-preserved skull
specimen discovered in Texas indicated the animal's head measured about 1.31 m,
and its body length was estimated at 9.8 m. However, the largest fragmentary
remains of D. riograndensis were 1.5 times the size of those of the average
D. rugosus and it was determined that the largest individuals of this species
may have been up to 12 m in length and perhaps weighed as much as 8.5 t.
A particularly large mandibular fragment from a D. riograndensis specimen was
estimated to have come from an individual with a skull length of about
1.47 m. 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 10.6 metres for this particularly specimen. This is only
slightly lower than previous estimates for the species. Deinosuchus has often
been described as the largest crocodyliform of all time. However other
crocodyliformes such as Purussaurus, Rhamphosuchus, and Sarcosuchus may have
equaled or exceeded it in size. Paleobiology
= Habitat = Deinosuchus was present on both sides of
the Western Interior Seaway. Specimens have been found in 10 of the modern-day
United States. 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. Deinosuchus fossils are most abundant in the Gulf
Coastal Plain region of Georgia, near the Alabama border. All known specimens
of Deinosuchus were found in rocks dated to the Campanian stage of the Late
Cretaceous period. The oldest examples of this genus lived approximately 80 Ma,
and the youngest lived around 73 Ma. 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. Although some specimens have also been
found in marine deposits, it is not clear whether Deinosuchus ventured out
into the ocean; these remains might have been displaced after the animals died.
Deinosuchus has been described as a "conspicuous" component of a purportedly
distinct biome occupying the southern half of Late Cretaceous North America.
= 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". 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." 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. In 2003, Christopher A. Brochu agreed that Deinosuchus "probably
dined on ornithopods from time to time." 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.
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. 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.
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, and smaller dinosaurs. The bigger, but less
common, Deinosuchus that lived in Texas and Montana might have been more
specialized hunters, capturing and eating large dinosaurs. Schwimmer noted
no theropod dinosaurs in Deinosuchus's 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. Discovery and naming
In 1858, geologist Ebenezer Emmons described two large fossil teeth found
in 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 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. 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 will come to be known as Deinosuchus, it was found that
it was a relative of crocodiles, going as far as placing it in the same family
in 1954, this assignment was mostly supported by dental features but was
overturned in 1999 when the finding of new specimens from Texas and Georgia
helped place Deinosuchus in a phylogenetic analysis, finding it 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,
Deinosuchus however, was not 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 the
eastern side of the Western Interior Seaway and the larger D. riograndensis
from the western side, characterized by differences of the shape of their
osteoderms and teeth, this view was not always favored by all researchers and in
2002 it was proposed that there was only one species, Deinosuchus rugosus, with
the differences found between the two species explained as the result of the
larger size of the western morph. This proposal faced support and criticism and
was dropped in 2010 when new fossils of specimens from both sides of the
interior seaway showed that the differences between the two morphs were
not just size related, teeth from large eastern specimens retained the common
characteristics of other specimens of the region and osteoderms from small
specimens of the western morph were no different from those of large ones,
supporting the specific separation of the two morphs, now formalized as D.
rugosus and D. riograndensis. See also
Sarcosuchus Stomatosuchus
References