Deinosuchus
Deinosuchus | |
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Reconstructed D. hatcheri skeleton at the Natural History Museum of Utah | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Reptilia |
Clade: | Archosauromorpha |
Clade: | Archosauriformes |
Order: | Crocodilia |
Superfamily: | Alligatoroidea |
Genus: | †Deinosuchus Holland, 1909 |
Type species | |
†Deinosuchus hatcheri Holland, 1909
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Other species | |
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Synonyms | |
Deinosuchus (
Although Deinosuchus was far larger than any modern crocodile or alligator, with the largest adults measuring 10.6 meters (35 ft) 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 described from 10 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
In 1858,
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".[4]
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.[3][5] 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.[3]
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.[6] 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.[3]
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.[3][7] Better cranial material was also found; by 2002, David R. Schwimmer was able to create a composite computer reconstruction of 90% of the skull.[8][9]
Classification and species
Since the discovery of the earliest fragmentary remains that will come to be known as Deinosuchus, it was considered a relative of
The species pertaining to Deinosuchus since the resurrection of the
Alligatoroidea |
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Description
Morphology
Despite its large size, the overall appearance of Deinosuchus was not considerably different from that of modern crocodilians. Deinosuchus had an
Modern saltwater crocodiles (Crocodylus porosus) have the strongest recorded bite of any living animal, with a maximum force of 16,414 N (1,673.8 kgf; 3,690 lbf) for a 4.59 meters (15.1 ft), 531 kilograms (1,171 lb) specimen.[20] The bite force of Deinosuchus has been estimated to be 18,000 N (1,835 kgf; 4,047 lbf)[8] to 102,803 N (10,483 kgf; 23,111 lbf).[20]
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 osteoderms (scutes) covering the back of Deinosuchus were unusually large, heavy, and deeply pitted; some were of a roughly hemispherical shape.[4][3] Deep pits and grooves on these osteoderms served as attachment points for connective tissue.[3] Together, the osteoderms and connective tissue would have served as load-bearing reinforcement to support the massive body of Deinosuchus out of water.[16][3] 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.[16][21]
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 meters (4.9 ft) and a lower jaw of 1.8 meters (5.9 ft) long, reconstructed with similar proportions to the Cuban crocodile giving a total estimated length of 15 meters (49 ft).[6] However, this reconstruction is currently considered to be inaccurate.[16] Using more complete remains, it was estimated in 1999 that the size attained by specimens of Deinosuchus varied from 8 to 10 meters (26 to 33 ft) with weights from 2.5 to 5 metric tons (2.8 to 5.5 short tons).[24] This was later corroborated when it was noted that most known specimens of D. rugosus usually had skulls of about 1 meter (3.3 ft) with estimated total lengths of 8 meters (26 ft) and weights of 2.3 metric tons (2.5 short tons). A reasonably well-preserved skull specimen discovered in Texas indicated the animal's head measured about 1.31 meters (4.3 ft), and its body length was estimated at 9.8 meters (32 ft). 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 meters (39 ft) in length and perhaps weighed as much as 8.5 metric tons (9.4 short tons).[16]
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 centimeters (4.84 ft). This length was used in conjunction with a regression equation relating skull length to total length in the
Paleobiology
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".
Schwimmer and G. Dent Williams proposed in 1996 that Deinosuchus may have preyed on marine turtles.[32] Deinosuchus would probably have used the robust, flat teeth near the back of its jaws to crush the turtle shells.[17] 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.[17][32]
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
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
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.[16]
Paleoecology
Deinosuchus was present on both sides of the Western Interior Seaway.[9] Specimens have been described from 10 U.S. states: Utah, Montana, Wyoming, New Mexico, New Jersey, Georgia, Alabama, Mississippi, Texas, and North Carolina.[34] David Schwimmer has said Deinosuchus fossils have been found in South Carolina and Delaware as well, but none of them from those two states have been formally described.[9] 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.[35] There is also a report describing a possible Deinosuchus scute from Colorado.[36] Deinosuchus fossils are most abundant in the Gulf Coastal Plain region of Georgia, near the Alabama border.[9] 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 82 Ma, and the youngest lived around 73 Ma.[37]
The distribution of Deinosuchus specimens indicates these giant crocodilians may have preferred
See also
References
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- ^ Baird, D.; Horner, J. (1979). "Cretaceous dinosaurs of North Carolina". Brimleyana. 2: 1–28.
- ^ a b c d e Colbert, Edwin H.; Bird, Roland T. (1954). "A gigantic crocodile from the Upper Cretaceous beds of Texas" (PDF). American Museum Novitates (1688): 1–22. Archived from the original (PDF) on March 4, 2009. Retrieved February 22, 2009.
- ^ Brochu, Christopher A. (February 7, 1998). "Deinosuchus occurrences". Dinosaur Mailing List (Mailing list). Archived from the original on August 9, 2016. Retrieved January 2, 2009.
- ^ ISBN 978-0-253-34087-0.
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- ^ Knight, Terrell K.; Schwimmer, David R. (2005). "Anatomy of the skull and braincase of a new Deinosuchus rugosus specimen from the Blufftown Formation, Russell County, Alabama". Geological Society of America Abstracts with Programs. 37 (2): 12. Archived from the original on February 22, 2016. Retrieved January 11, 2009.
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- ^ ISBN 978-0-253-34087-0.
- ^ Lucas, Spencer G.; Sullivan, Robert M.; Spielmann, Justin A. (2006). "The giant crocodylian Deinosuchus from the Upper Cretaceous of the San Juan Basin, New Mexico" (PDF). New Mexico Museum of Natural History and Science Bulletin. 35: 247. Archived from the original (PDF) on June 17, 2009.
- ^ a b Irmis, R. B.; Hutchison, J. H.; Sertich, J. J. W.; Titus, A. L. (2013). "Crocodyliforms from the Late Cretaceous of Grand Staircase–Escalante National Monument and vicinity, southern Utah, U.S.A.". In Titus, A. L.; Loewen, M. A. (eds.). At the Top of the Grand Staircase: The Late Cretaceous of Southern Utah. Bloomington, Indiana.: Indiana University Press. pp. 424–444.
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- ^ Titus, Alan L.; Knell, Michael J.; Wiersma, Jelle P.; Getty, Mike A. (2008). "First report of the hyper-giant Cretaceous crocodylian Deinosuchus from Utah". Geological Society of America Abstracts with Programs. 40 (1): 58. Archived from the original on February 22, 2016. Retrieved December 27, 2008.
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