Gorgosaurus

Source: Wikipedia, the free encyclopedia.
For the fictional monster, see
Gorosaurus
.

Gorgosaurus
Temporal range:
Ma
↓
Skeletal mount, Royal Tyrrell Museum of Palaeontology
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Clade: Saurischia
Clade: Theropoda
Clade: †Eutyrannosauria
Family: †Tyrannosauridae
Subfamily: †Albertosaurinae
Genus: †Gorgosaurus
Lambe, 1914
Type species
†Gorgosaurus libratus
Lambe, 1914
Synonyms
List
  • Deinodon horridus?
    Leidy, 1856
  • Laelaps falculus?
    Cope, 1876
  • Laelaps hazenianus?
    Cope, 1876
  • Laelaps incrassatus
    Cope, 1876
  • Dryptosaurus kenabekides?
    Hay, 1899
  • Gorgosaurus sternbergi
    Matthew & Brown, 1923
  • Albertosaurus libratus
    (Lambe, 1914)

Gorgosaurus (

Paleontologists recognize only the type species
, G. libratus, although other species have been erroneously referred to the genus.

Like most known tyrannosaurids, Gorgosaurus was a large

junior synonym
of that genus.

Gorgosaurus lived in a lush

niche differentiation between the two. Gorgosaurus is the best-represented tyrannosaurid in the fossil record, known from dozens of specimens. These plentiful remains have allowed scientists to investigate its ontogeny, life history and other aspects of its biology
.

Discovery and naming

Type specimen of Gorgosaurus sternbergi (AMNH
5664), now recognized as a juvenile Gorgosaurus libratus

Gorgosaurus libratus was first described by

past participle of the Latin verb librare, meaning "to balance".[2]

The

Charles M. Sternberg. This specimen was the first tyrannosaurid found with a complete hand.[1] It was found in the Dinosaur Park Formation of Alberta and is housed in the Canadian Museum of Nature in Ottawa.[4] Prospectors from the American Museum of Natural History in New York City were active along the Red Deer River in Alberta at the same time, collecting hundreds of spectacular dinosaur specimens, including four complete G. libratus skulls, three of which were associated with skeletons. Matthew and Brown described four of these specimens in 1923.[5]

Specimen AMNH 5458

Matthew and Brown also described a fifth skeleton (

sutures between bones were unfused in this specimen as well. Matthew and Brown noted that these features were characteristic of juvenile tyrannosaurids, but still described it as the holotype of a new species, G. sternbergi.[5] Today's paleontologists regard this specimen as a juvenile G. libratus.[6][4] Dozens of other specimens have been excavated from the Dinosaur Park Formation and are housed in museums across the United States and Canada.[7][4] G. libratus is the best-represented tyrannosaurid in the fossil record, known from a virtually complete growth series.[6][8]

Specimen USNM 12814 (formerly AMNH 5428)

In 1856,

Dryptosaurus kenabekides.[11]

Several tyrannosaurid skeletons from the

Children's Museum of Indianapolis, shows evidence of severe pathologies, including healed leg, rib, and vertebral fractures, osteomyelitis (infection) at the tip of the lower jaw resulting in permanent tooth loss, and possibly a brain tumor.[12][13]

Formerly assigned species

Cast of specimen PIN 553–1, holotype of now invalid Gorgosaurus lancinator

Several species were incorrectly assigned to Gorgosaurus in the 20th century. A complete skull of a small tyrannosaurid (

Tarbosaurus bataar.[6][8][18]

Description

G. libratus adult and subadult with a human for scale

Gorgosaurus was smaller than Tyrannosaurus or Tarbosaurus, close in size to Albertosaurus. Adults reached 8 to 9 m (26 to 30 ft) in length from snout to tail,

fenestrae) between bones reduced its weight. Albertosaurus and Gorgosaurus share proportionally longer and lower skulls than Daspletosaurus and other tyrannosaurids. The end of the snout was blunt, and the nasal and parietal bones were fused along the midline of the skull, as in all other members of the family. The eye socket was circular rather than oval or keyhole-shaped as in other tyrannosaurid genera. A tall crest rose from the lacrimal bone in front of each eye, similar to Albertosaurus and Daspletosaurus.[6] Differences in the shape of bones surrounding the brain set Gorgosaurus apart from Albertosaurus.[4]

Gorgosaurus teeth were typical of all known tyrannosaurids. The eight

dentary bones of the lower jaw. This number of teeth is similar to Albertosaurus and Daspletosaurus but is fewer than those of Tarbosaurus or Tyrannosaurus.[23]

Life restoration

Gorgosaurus shared its general body plan with all other tyrannosaurids. Its massive head was perched on the end of an S-shaped neck. In contrast to its large head, its forelimbs were very small. The forelimbs had only two digits, although a third

center of gravity over the hips.[6]

In 2001, paleontologist

hadrosaurid scales and approximately as fine as a Gila monster's).[25] Neither of these specimens was associated with any particular bone or specific body area.[25] In the Encyclopedia of Dinosaurs Kenneth Carpenter pointed out that traces of skin impressions from the tail of Gorgosaurus showed similar small rounded or hexagonal scales.[26]

Classification and systematics

Gorgosaurus is

phalanges).[23][29]

The close similarities between Gorgosaurus libratus and Albertosaurus sarcophagus have led many experts to combine them into one genus over the years. Albertosaurus was named first, so by convention it is given

Phil Currie claims there are as many anatomical differences between Albertosaurus and Gorgosaurus as there are between Daspletosaurus and Tyrannosaurus, which are almost always kept separate. He also notes that undescribed tyrannosaurids discovered in Alaska, New Mexico and elsewhere in North America may help clarify the situation.[4] Gregory S. Paul has suggested that Gorgosaurus libratus is ancestral to Albertosaurus sarcophagus.[31]

Skeletal mount in Japan

Below is the cladogram of Tyrannosauridae based on the

phylogenetic analysis conducted by Loewen et al. in 2013.[32]

Tyrannosauridae

Gorgosaurus libratus

Albertosaurus sarcophagus

Tyrannosaurinae

Dinosaur Park tyrannosaurid

Daspletosaurus torosus

Two Medicine tyrannosaurid

Teratophoneus curriei

Bistahieversor sealeyi

Lythronax argestes

Tyrannosaurus rex

Tarbosaurus bataar

Zhuchengtyrannus magnus

Paleobiology

Diet and feeding

Gorgosaurus juvenile specimen TMP 2009.12.14, featuring stomach contents comprising remains of Citipes

Just like other tyrannosaurids, bite force of Gorgosaurus and Albertosaurus increases slowly among young individuals, and then it increases exponentially when they reach the late juvenile stage.[33] In 2012, Jovannelly and Lane estimated that Gorgosaurus could exert a bite force of at least 22,000, possibly up to 42,000 newtons.[34] Other paleontologists have produced significantly lower bite force estimates. In 2021, given that the largest known Gorgosaurus had a similar bite force to the similar-sized Tyrannosaurus, Therrien and colleagues proposed that the maximum bite force that could be produced by adult albertosaurines is around 12,200 to 21,800 newtons.[33] In 2022, Sakamoto estimated that Gorgosaurus had an anterior bite force of 6,418 newtons and a posterior bite force of 13,817 newtons.[35]

In 2023, a juvenile Gorgosaurus (TMP 2009.12.14) with its in situ stomach contents containing two Citipes juveniles about a year old intact was reported from the Dinosaur Park Formation. This juvenile would have been 5-7 years old at the time of death, measuring about 4 metres (13 ft) long and weighing around 335 kilograms (739 lb). It is much larger than the two Citipes juveniles that weigh about 9–12 kilograms (20–26 lb), contrary to the assumption that tyrannosaurids fed on prey of their size once they reached 16–32 kilograms (35–71 lb), indicating that juvenile tyrannosaurids still consumed much smaller prey after exceeding a certain size threshold. The discovery of this specimen indicated that tyrannosaurids probably did not hunt in multigenerational packs, since its prey size is too small to share with the conspecifics. It is also a direct dietary evidence that reinforces the theory of 'ontogenetic dietary shift' for tyrannosaurids, as previously inferred by ecological modeling and anatomical features among different age groups. Only the remains of the hindlimbs and caudal vertebrae of juvenile Citipes were present in the tyrannosaurid's stomach cavity, suggesting that a juvenile Gorgosaurus may have had preferential consumption of the muscular hindlimbs.[36][37] Thomas R. Holtz Jr., a paleontologist who also previously theorized that tyrannosaurs underwent a big dietary shift with maturation, said that the fossil "looks like it was Thanksgiving," as the juvenile Gorgosaurus was mostly eating the legs of Citipes.[38]

Life history

A graph showing the hypothesized growth curves (body mass versus age) of four tyrannosaurids. Gorgosaurus is shown in blue.

Gregory Erickson and colleagues have studied the growth and life history of tyrannosaurids using bone histology, which can determine the age of a specimen when it died. A growth curve can be developed when the ages of various individuals are plotted against their sizes on a graph. Tyrannosaurids grew throughout their lives, but underwent tremendous growth spurts for about four years, after an extended juvenile phase. Sexual maturity may have ended this rapid growth phase, after which growth slowed down considerably in adult animals. Examining five Gorgosaurus specimens of various sizes, Erickson calculated a maximum growth rate of about 50 kg (110 lb) per year during the rapid growth phase, slower than in tyrannosaurines like Daspletosaurus and Tyrannosaurus, but comparable to Albertosaurus.[39]

Gorgosaurus spent as much as half its life in the juvenile phase before ballooning up to near-maximum size in only a few years.[39] This, along with the complete lack of predators intermediate in size between huge adult tyrannosaurids and other small theropods, suggests that these niches may have been filled by juvenile tyrannosaurids. This pattern is seen in modern Komodo dragons, whose hatchlings start off as tree-dwelling insectivores and slowly mature into massive apex predators capable of taking down large vertebrates.[6] Other tyrannosaurids, including Albertosaurus, have been found in aggregations that some have suggested to represent mixed-age packs, but there is no evidence of gregarious behavior in Gorgosaurus.[40][41]

Restoration of a sub-adult

The discovery of two exceptionally preserved juvenile skulls from Gorgosaurus suggests that Gorgosaurus underwent the morphological shift from gracile juveniles to robust adults at an earlier age than Tyrannosaurus, to which it was compared in a study published by Jared Voris et al., suggests that the ontogenetic changes occurred at roughly 5-7 years of age in Gorgosaurus; much earlier than its larger and later relative. However, both tyrannosaur genera underwent these ontogenetic transformations at a similar percent of skull length relative to the large known adult individuals. The study's results likewise indicate that there is a dissociation between body size and cranial development in tyrannosaurs, while simultaneously allowing better identification of juvenile remains that may have been misidentified in museum fossil collections.[42] It is estimated that an ontogenetic dietary shift of Gorgosaurus and Albertosaurus occurs when the mandibular length reaches 58 cm (1.90 ft), indicating that this is the stage when their bite force increases exponentially and when they begin to pursuit large prey.[33]

Paleopathology

Main article: Paleopathology
Bob Bakker and a skeleton with several bone injuries, from the "Dinosaur Mummy: CSI" exhibit at the HMNS

Several pathologies have been documented in the Gorgosaurus libratus

exostoses both in the middle and at the far end. The third phalanx of the third right toe is deformed, as the claw on that digit has been described as "quite small and amorphous". The three pathologies may have been received in a single encounter with another dinosaur.[43]

Another specimen cataloged as

gastralium. Lesions from a bite received to the face were present and showed evidence that the wounds were healing before the animal died.[43]

death pose", Royal Tyrrell Museum of Palaeontology

TMP91.36.500 is another Gorgosaurus with preserved face bite injuries but also has a thoroughly healed fracture in the right fibula. Also present was a healed fracture in the dentary and what the authors describing the specimen referred to as "a mushroom-like

death pose.[44]

Another specimen has a poorly healed fracture of the right fibula, which left a large callus on the bone. In a 2001 study conducted by Bruce Rothschild and other paleontologists, 54 foot bones referred to Gorgosaurus were examined for signs of stress fracture, but none were found.[43][45]

Paleoenvironment

Restoration of Gorgosaurus chasing Corythosaurus and Chasmosaurus

Most specimens of Gorgosaurus libratus have been recovered from the

Bearpaw Shale.[49]

The Dinosaur Park Formation preserves a great wealth of vertebrate fossils. A wide variety of fish swam the rivers and

dentary has been discovered in the Dinosaur Park Formation that bore tooth marks left by the bite of a young tyrannosaur, possibly Gorgosaurus.[52]

Coexistence with Daspletosaurus

Dinosaur Park specimen (FMNH PR308) of Daspletosaurus, mounted at the Field Museum

In the middle stages of the Dinosaur Park Formation, Gorgosaurus lived alongside a rarer species of tyrannosaurid, Daspletosaurus. This is one of the few examples of two tyrannosaur genera coexisting. Similar-sized predators in modern predator

hadrosaurs, while the rarer and more troublesome ceratopsians and ankylosaurians (horned and heavily armoured dinosaurs) were left to the more heavy built Daspletosaurus.[7] However, a specimen of Daspletosaurus (OTM 200) from the contemporaneous Two Medicine Formation of Montana preserves the digested remains of a juvenile hadrosaur in its gut region,[54] and another bonebed contains the remains of three Daspletosaurus along with the remains of at least five hadrosaurs.[40]

Unlike some other groups of dinosaurs, neither genus was more common at higher or lower elevations than the other.[53] However, Gorgosaurus appears more common in northern formations like Dinosaur Park, with species of Daspletosaurus being more abundant to the south. The same pattern is seen in other groups of dinosaurs. Chasmosaurine ceratopsians and saurolophine hadrosaurs are also more common in the Two Medicine Formation of Montana and in southwestern North America during the Campanian, while centrosaurines and lambeosaurines dominate in northern latitudes. Holtz has suggested this pattern indicates shared ecological preferences between tyrannosaurines, chasmosaurines and saurolophines. At the end of the later Maastrichtian stage, tyrannosaurines like Tyrannosaurus rex, saurolophines like Edmontosaurus and Kritosaurus and chasmosaurines like Triceratops and Torosaurus were widespread throughout western North America, while lambeosaurines were rare, consisting of a few species like Hypacrosaurus, and albertosaurines and centrosaurines had gone extinct.[6] However, in the case of the centrosaurines, they had thrived in Asia with genera like Sinoceratops.[55] While albertosaurine remains have been found in the Hell Creek Formation, it is most likely these are indeterminate remains belonging to a species of Tyrannosaurus.[56]

See also

References

  1. ^ a b Lambe, Lawrence M. (1914). "On the fore-limb of a carnivorous dinosaur from the Belly River Formation of Alberta, and a new genus of Ceratopsia from the same horizon, with remarks on the integument of some Cretaceous herbivorous dinosaurs". Ottawa Naturalist. 27: 129–135.
  2. ^ a b Lambe, Lawrence M. (1914). "On a new genus and species of carnivorous dinosaur from the Belly River Formation of Alberta, with a description of Stephanosaurus marginatus from the same horizon". Ottawa Naturalist. 28: 13–20.
  3. ISBN 978-0-19-910207-5
    .
  4. ^
    Currie, Philip J. (2003). "Cranial anatomy of tyrannosaurids from the Late Cretaceous of Alberta"
    (PDF). Acta Palaeontologica Polonica. 48 (2): 191–226.
  5. ^
    hdl:2246/3207
    .
  6. ^
    ISBN 978-0-520-24209-8
    .
  7. ^ a b c d e f g Russell, Dale A. (1970). "Tyrannosaurs from the Late Cretaceous of western Canada". National Museum of Natural Sciences Publications in Paleontology. 1: 1–34.
  8. ^
    S2CID 83744433. Archived from the original
    on September 30, 2008. Retrieved February 27, 2008.
  9. ^ Leidy, Joseph (1856). "Notice of remains of extinct reptiles and fishes, discovered by Dr. F.V. Hayden in the badlands of the Judith River". Proceedings of the Academy of Sciences in Philadelphia. 8: 72–73.
  10. ^
    hdl:2246/1300
    .
  11. ^ Weishampel, D.B.; Dodson, P.; Osmólska, H., eds. (2004). The Dinosauria (2nd ed.). Berkeley, CA: University of California Press.
  12. ^ Pickrell, John (November 24, 2003). "First dinosaur brain tumor found, experts suggest". National Geographic News. Archived from the original on November 26, 2003. Retrieved February 7, 2008.
  13. ^ "Meet the Gorgosaur". The Children's Museum of Indianapolis. Archived from the original on January 30, 2008. Retrieved February 7, 2008.
  14. Gilmore, Charles W.
    (1946). "A new carnivorous dinosaur from the Lance Formation of Montana". Smithsonian Miscellaneous Collections. 106: 1–19.
  15. Currie, Philip J.
    (1988). "Nanotyrannus, a new genus of pygmy tyrannosaur, from the latest Cretaceous of Montana". Hunteria. 1 (5): 1–30.
  16. Doklady Akademii Nauk SSSR
    (in Russian). 104 (5): 779–783.
  17. ^ Carpenter, Ken. (1992). "Tyrannosaurids (Dinosauria) of Asia and North America". In Mateer, Niall J.; Chen Peiji (eds.). Aspects of Nonmarine Cretaceous Geology. Beijing: China Ocean Press. pp. 250–268.
  18. ^ Rozhdestvensky, Anatoly K. (1965). "Growth changes in Asian dinosaurs and some problems of their taxonomy". Paleontological Journal. 3: 95–109.
  19. OCLC 985402380
    .
  20. ISBN 9780253350879
    .
  21. S2CID 53446536
    .
  22. S2CID 84317234
    .
  23. ^
    Currie, Philip J.; Hurum, Jørn H; Sabath, Karol (2003). "Skull structure and evolution in tyrannosaurid phylogeny"
    (PDF). Acta Palaeontologica Polonica. 48 (2): 227–234.
  24. ^ Currie, P. (2001). 2001 A. Watson Armour Symposium: The Paleobiology and Phylogenetics of Large Theropods. Field Museum of Natural History, Chicago.
  25. ^ a b Holtz, T. 2001. Phil Currie celebration, tyrant skin, and other things. Dinosaur Mailing List post. http://dml.cmnh.org/2001Jul/msg00243.html Archived August 1, 2020, at the Wayback Machine. Accessed: March 15, 2014
  26. ISBN 978-0-12-226810-6
    .
  27. ^
    S2CID 86243316
    .
  28. ^ Holtz, Thomas R. (September 20, 2005). "RE: Burpee Conference (LONG)". Archived from the original on April 12, 2016. Retrieved June 18, 2007.
  29. doi:10.1139/e02-083
    .
  30. ISBN 978-0-671-61946-6
    .
  31. ^ Paul. G.S. The Princeton Field Guide to Dinosaurs, Princeton University Press, 2010. P. 105.
  32. PMID 24223179
    .
  33. ^
    S2CID 234026715
    .
  34. doi:10.2174/1874262901206010065
    .
  35. PMID 35846881
    .
  36. PMID 38064561
    .
  37. ^ Greshko, Michael (December 8, 2023). "A Tyrannosaur Was Found Fossilized, and So Was Its Last Meal - A 75-million-year-old Gorgosaurus fossil is the first tyrannosaur skeleton ever found with a filled stomach". The New York Times. Archived from the original on December 8, 2023. Retrieved December 9, 2023.
  38. ^ Johnson, Carolyn (December 8, 2023). "Young tyrannosaur died with a full stomach, remarkable fossil reveals". Washington Post. Retrieved January 6, 2024.
  39. ^
    S2CID 4404887
    .
  40. ^
    ISBN 978-0-253-34539-4
    .
  41. Currie, Philip J. (1998). "Head-biting behavior in theropod dinosaurs: paleopathological evidence" (PDF). Gaia. 15: 167–184. Archived from the original
    (PDF) on February 27, 2008. [not printed until 2000]
  42. S2CID 248197540
    .
  43. ^ a b c d Rothschild, B., Tanke, D. H., and Ford, T. L., 2001, Theropod stress fractures and tendon avulsions as a clue to activity: In: Mesozoic Vertebrate Life, edited by Tanke, D. H., and Carpenter, K., Indiana University Press, p. 331–336.
  44. S2CID 129785393
    .
  45. ^ Molnar, R. E., 2001, Theropod paleopathology: a literature survey: In: Mesozoic Vertebrate Life, edited by Tanke, D. H., and Carpenter, K., Indiana University Press, p. 337–363.
  46. ^ Eberth, D.A. (2005). "The geology." In: Currie, P.J., and Koppelhus, E.B. (eds), Dinosaur Provincial Park: A Spectacular Ancient Ecosystem Revealed. Indiana University Press: Bloomington and Indianapolis, 54–82.
  47. S2CID 85665879
    .
  48. S2CID 129901811. Archived from the original
    (PDF) on June 7, 2011. Retrieved November 11, 2010.
  49. ^
    ISBN 978-0-12-226810-6
    .
  50. ISBN 978-0-253-34595-0
    .
  51. JSTOR 2424244
    .
  52. ^ Jacobsen, A.R. 2001. Tooth-marked small theropod bone: An extremely rare trace. p. 58–63. In: Mesozoic Vertebrate Life. Ed.s Tanke, D. H., Carpenter, K., Skrepnick, M. W. Indiana University Press.
  53. ^
    S2CID 18114585
    .
  54. S2CID 86113170
    .
  55. S2CID 128972108
    .
  56. JSTOR 1304167
    .

External links

Retrieved from "https://en.wikipedia.org/w/index.php?title=Gorgosaurus&oldid=1218691498"