Gryposaurus

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Gryposaurus
Skeletal reconstruction of Gryposaurus incurvimanus

Skeletal reconstruction of Gryposaurus incurvimanus

Temporal occurrence
Upper Cretaceous ( Campanium )
83.6 to 72 million years
Locations
Systematics
Pelvic dinosaur (Ornithischia)
Ornithopoda
Iguanodontia
Hadrosaurs (Hadrosauridae)
Hadrosaurinae
Gryposaurus
Scientific name
Gryposaurus
Lambe , 1914
species
  • Gryposaurus notabilis
  • Gryposaurus latidens
  • Gryposaurus monumentensis

Gryposaurus is a genus of dinosaurs from the group of Hadrosauridae . Fossils were discovered in the North American continent and are dated to the sub-Campanium . Recognized species of Gryposaurus come from the Dinosaur Park Formation in Alberta , Canada , the Two Medicine Formation in Montana, and the Kaiparowits Formation in Utah .

Gryposaurus shows strong similarities with Kritosaurus , both genera were considered the same genus for many years. Gryposaurus is passed down through numerous skulls and various skeletons, some of which have even been preserved with skin prints. The genus can be distinguished from other hadrosaurids by the narrow, arched nasal hump, which is reminiscent of a humped nose . This hump could have been used for species recognition, sexual identification and / or in intra-species fights. Like other hadrosaurids, Gryposaurus could probably move both two-legged (biped) and four-legged (quadruped) and fed on plants (herbivorous). About 9 meters long, Gryposaurus was a medium-sized hadrosaurid that may have preferred habitats near rivers.

etymology

The name Gryposaurus is derived from the Greek words grypos for "hooked nose" and sauros for "lizard". The name points to the curved nose region as a characteristic of the genus. Sometimes the name is mistakenly translated as "griffin lizard" (from Latin : gryphus "griffin").

description

Live reconstruction of Gryposaurus notabilis
Skull of Gryposaurus in the Royal Tyrrell Museum; the nasal arch can be clearly seen here.

Gryposaurus showed the size and shape typical of hadrosaurids. One of the best preserved skeletons, the almost complete type specimen of Kritosaurus incurvimanus (now regarded as a synonym of Gryposaurus notabilis ), comes from an animal about 8.2 meters long. This skeleton also shows the best preserved skin prints known from Gryposaurus . They show that this dinosaur had different types of scales: On the tail and on the flanks, Gryposaurus had pyramidal, corrugated, limpet- shaped scales up to 3.8 cm long, while the neck and sides of the body had uniform, polygonal scales . Pyramid-shaped, laterally flattened and fluted structures were arranged in a row on the back along the center line of the body.

The three named species of Gryposaurus differ in subtleties in the skull and in the lower jaw. The distinctive nasal arch, characteristic of this genus, is formed by the pair of nasal bones . The arch culminates in a rounded hump in front of the eyes, which is as high as the highest point on the back of the skull. The skeleton is very well known and is therefore often used for interpretations and comparisons of other hadrosaurids.

Systematics

Gryposaurus is placed within the family Hadrosauridae to the subfamily Hadrosaurinae , the subfamily without hollow head crests. The general term "gryposaur" is sometimes used to refer to all hadrosaurs with a curved nose. The genus Tethyshadros was also assigned to this group before its description (then known under the nickname "Antonio"). A subfamily "Gryposaurinae" was established by Jack Horner (1992), but this is now considered to be discarded. The question of which representatives of the Hadrosaurinae Gryposaurus is most closely related cannot be clearly clarified, since a comprehensive comparison with Kritosaurus is not possible. The differences between the two genera are the locations ( Gryposaurus was found in Alberta and Montana , Kritosaurus in New Mexico ) and the age of the fossils ( Kritosaurus comes from somewhat younger rock layers such as Gryposaurus ). The skull of Kritosaurus is not fully known, most of the bones in the area of ​​the eyes are missing; however, the known part is very similar to the skull of the Gryposaurus .

The following cladogram is based on phylogenetic studies by Prieto-Márquez and Wagner (2012) and shows the relationships of Gryposaurus within the Kritosaurini , a group of derived representatives from the hadrosaur family:

  Kritosaurini 

Wulagasaurus


   

Kritosaurus


   


Gryposaurus latidens


   

Gryposaurus notabilis


   

Gryposaurus monumentensis




   

Unnamed genus from Big Bend National Park


   

Secernosaurus


   

Willinakaqe







Template: Klade / Maintenance / Style

Find and story of discovery

Gryposaurus notabilis fossils

Gryposaurus is based on the example NMC 2278 ( holotype ), a partial skeleton including a skull, which was discovered in 1913 by George F. Sternberg . The find comes from the Dinosaur Park Formation on the Red Deer River in Alberta ( Canada ). Shortly afterwards (1914) it was described and named by Lawrence Lambe ; Lambe pointed out the nasal arch as an unusual feature. A few years earlier, Barnum Brown had discovered a fragmentary skull in New Mexico and described it as a new genus, Kritosaurus . The snout of this skull has only survived in a few fragments and was reconstructed by Brown from the skull of the hadrosaurid known today as anatotitan , which shows a flat top. Brown believed that some oddly shaped snout fragments were the result of compressions that occurred during fossil formation. Lambe's description of Gryposaurus , however, showed that Kritosaurus probably did not have a flat snout, but possibly also had a curved nose. In 1916 the Kritosaurus skull was reconstructed, this time with a nasal arch analogous to that of the Gryposaurus . Both Brown and Charles Gilmore then suspected that Gryposaurus and Kritosaurus were the same genus. This hypothesis, although not universally supported, has met with support from other paleontologists; so William Parks named an almost complete skeleton from the Dinosaur Park formation as Kritosaurus incurvimanus , but not as Kritosaurus incurvimanus (interestingly, they left the species Gryposaurus notabilis in its own genus Gryposaurus ). However, the anterior part of the skull is missing from the skeleton described by Parks, so that no details of the nasal arch can be seen. The influential monograph on Hadrosaurids by Lull and Wright , published in 1942, cleared the Kritosaurus / Gryposaurus question in favor of Kritosaurus for nearly fifty years . However, more recent work published in the 1990s argued that the fossil material was insufficient to place Gryposaurus in the genus Kritosaurus ; thus Gryposaurus was again, at least temporarily, separated from Kritosaurus .

The assumption that Hadrosaurus was also a synonym for Gryposaurus , Kritosaurus, or even both, caused further confusion . This hypothesis was advocated by Jack Horner (1979) and others and was particularly popular in the late 1970s and early 1980s. It appeared in some popular science books of the time; a well-known book, The Illustrated Encyclopedia of Dinosaurs , uses the name Kritosaurus for the Canadian material (now attributed to Gryposaurus ), but irritably identifies K. incurvimanus as Hadrosaurus in a caption. Although Horner used the new name combination Hadrosaurus (Kritosaurus) notabilis for a partial skeleton with a fragmentary skull and for a less complete skeleton from the Bearpaw Shale of Montana in 1979 , he changed his mind again in 1990 and was one of the first to use the name again Gryposaurus used in his works. Currently, the view has prevailed that Hadrosaurus , although known only from fragmentary material, can be distinguished from Gryposaurus by differences in the humerus (upper arm bone) and in the ilium (iliac bone).

Advancing research revealed a third species, G. latidens , from rocks from Montana, which are somewhat older than the classic gryphosaur sites in Alberta. The new species is based on two parts of a skeleton that had already been collected for the American Museum of Natural History in 1916 ; In addition, bonebeds ("bones") with G. latidens fossils are known. Horner, who described the specimens, suspected that it was a less derived ("advanced") species.

Partly fossilized skeleton of a young Gryposaurus ; excavated and exhibited at Escalante-Grand Staircase National Monument in southern Utah

New material from the Kaiparowits formation in the Grand Staircase-Escalante National Monument in Utah consists of a skull and partial skeleton of the species G. monumentensis . The skull of this species was more robust than that of other species, and the predentals showed enlarged jaggies along the upper edge, where the beak of the lower jaw started. This new species significantly expands the geographic distribution of Gryposaurus , and a second, lighter species could be present. Several species of gryphosaurs are known from the Kaiparowits Formation by cranial and postcranial remains and were larger than their northern relatives.

species

Skull of Gryposaurus notabilis in Milan

Three species are recognized today: G. notabilis , G. latidens , and G. monumentensis . The type species G. notabilis comes from the late Campanium ( Upper Cretaceous of the Dinosaur Park Formation in Alberta ). Probably G. notabilis with G. incurvimanus identical, which comes from the same formation. Both species were differentiated from one another on the basis of the nasal arch (which is larger and closer to the eyes in G. notabilis ) and the shape of the humerus (which is longer and more robust in G. incurvimanus ). By G. notabilis are ten full and twelve fragmentary sustaining skull and numerous postcranial skeletons known; there are also two skeletons and skulls that were once assigned to G. incurvimanus . G. latidens is from the Two Medicine Formation (late Santonium to early Campanium) from Pondera County , Montana , and is known for having incomplete skulls and skeletons of various individuals. The nasal arch of this species is as pronounced as that of G. notabilis , but sits further forward on the snout; in addition, the teeth are less strongly derived and show features that are characteristic of basal iguanodontia . The informal name " Hadrosauravus " is an early, rarely used synonym for this species. The species G. monumentensis , which was only described in 2007, is known from Utah for its skull and partial skeleton . This species was listed at number two in the 2008 Top 10 New Species list by the International Institute for Species Exploration .

Poorly preserved fossils from Alberta, originally described as Trachodon ( Pteropelyx ) marginatus , have sometimes been imputed to Kritosaurus on the assumption that Kritosaurus and Gryposaurus are identical. This noun dubium could have been a synonym for G. notabilis ; the last review of the Hadrosauridae, however, kept the two species separate.

Paleobiology

Reconstructed head of Gryposaurus notabilis

Like other Hadrosauriden fed on gryposaurus of plants and could probably both bipedal and quadrupedal move. Special joints in the skull made it possible to chew the food effectively. The teeth were continuously replaced; so the jaws were equipped with hundreds of teeth arranged in tooth batteries, of which only a handful were ever in use. Plant material was cut from the broad beak and held in the mouth by a cheek-like organ while chewing. Gryposaurus could probably reach food sources up to 4 m high.

Like other pelvic dinosaurs in the Dinosaur Park Formation, Gryposaurus did not exist during the formation's entire deposition period. The upper and thus younger layers increasingly show marine influences. Gryposaurus is missing in the upper section of the formation, instead Prosaurolophus is present. Other dinosaurs found only in the lower portion of the formation include the horned dinosaur Centrosaurus and the hollow-crested hadrosaurid Corythosaurus . Gryposaurus may have preferred habitats near rivers.

The characteristic nasal arch of Gryposaurus presumably served various social functions. It could have indicated the gender, species, or social status of the individual. It could also have been used for pushing and pushing in intra-species fights. It is possible that the nasal arch housed inflatable air sacs for visual and acoustic communication. The surface of the arch is rough in some specimens, indicating either a covering of thick keratinous skin or a cartilaginous outgrowth.

Paleoecology

Argon-argon dating indicates that the Kaiparowits Formation in Utah was deposited about 76.6 and 74.5 million years ago during the Upper Cretaceous Campanian . The depository was located during the Upper Cretaceous near the west coast of the Western Interior Seaway , a large inland sea that divided North America into two land masses, Laramidia to the west and Appalachia to the east. The dinosaurs populated a river plain surrounded by the highlands, which was characterized by large rivers, swamps, ponds and lakes. The climate was warm and humid and enabled a diverse flora and fauna.

Gryposaurus shared its habitat in the Kaiparowits Formation with a variety of other dinosaurs. Among the theropods were dromaeosaurids , the troodontid Talos sampsoni , oviraptorosaurs such as Hagryphus giganteus , ornithomimosaurs such as Ornithomimus velox and tyrannosaurids such as Albertosaurus and Teratophoneus . Pelvis dinosaurs are represented by armored ankylosaurs and the horned ceratopsids Utahceratops gettyi , Nasutoceratops titusi and Kosmoceratops richardsoni as well as by Parasaurolophus cyrtocristatus , another representative of the Hadrosauridae. The palaeofauna of the Kaiparowits formation also included cartilaginous fish , frogs , salamanders , turtles , lizards and crocodiles or crurotarsi . A variety of early mammals were also present, including representatives of multituberculata , marsupials and insectivores .

The Dinosaur Park Formation and the Two Medicine Formation had similar fauna and flora and a similar climate to the Kaiparowits Formation. In the Dinosaur Park Formation, the fossils of Gryposaurs have been dated to approximately 76 million years ago. Gryposaurus lived with the hadrosaurids Corythosaurus and Parasaurolophus , the ceratopsians Centrosaurus and Chasmosaurus , ankylosaurs such as Euoplocephalus and Edmontonia and the tyrannosaurids Gorgosaurus . In the Two Medicine Formation, the Ceratopsia genus Cerasinops , the Deinonychosauria Dromaeosaurus , Saurornitholestes and Troodon and the tyrannosaurids Gorgosaurus and Albertosaurus were found in the same rock layers as Gryposaurus .

Individual evidence

  1. ^ Gregory S. Paul : The Princeton Field Guide To Dinosaurs. Princeton University Press, Princeton NJ et al. 2010, ISBN 978-0-691-13720-9 , pp. 304–305, online ( memento of the original from July 13, 2015 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. . @1@ 2Template: Webachiv / IABot / press.princeton.edu
  2. ^ A b Benjamin S. Creisler: Deciphering duckbills. In: Kenneth Carpenter (Ed.): Horns and Beaks. Ceratopsian and Ornithopod Dinosaurs. Indiana University Press, Bloomington IN 2007, ISBN 978-0-253-34817-3 , pp. 185-210.
  3. ↑ Gryposaurus on "The Dinosaur Omnipedia" ( Memento from July 10, 2011 in the Internet Archive )
  4. ↑ a b c d Donald F. Glut : Gryposaurus. Donald F. Glut: Dinosaurs. The Encyclopedia. McFarland & Co, Jefferson NC 1997, ISBN 0-89950-917-7 , pp. 445-448.
  5. ^ Richard S. Lull , Nelda E. Wright: Hadrosaurian Dinosaurs of North America (= The Geological Society of America. Special Papers. No. 40, ISSN  0072-1077 ). The Geological Society of America, New York NY 1942, p. 226.
  6. ^ Richard S. Lull, Nelda E. Wright: Hadrosaurian Dinosaurs of North America (= The Geological Society of America. Special Papers. No. 40). The Geological Society of America, New York NY 1942, pp. 110-117.
  7. ↑ a b Lawrence M. Lambe : On Gryposaurus notabilis, a new genus and species of trachodont dinosaur from the Belly River Formation of Alberta, with a description of the skull of Chasmosaurus belli. In: The Ottawa Naturalist. Vol. 27, No. 11, 1924, ISSN  0316-4411 , pp. 145-155, digitized .
  8. ^ William A. Parks : The Osteology of the Trachodont Dinosaur Kritosaurus incurvimanus (= University of Toronto Studies. Geological Series. No. 11. ISSN  0372-4913 ). University of Toronto - Univ. Library, Toronto 1920.
  9. ↑ a b c d e f John R. Horner , David B. Weishampel , Catherine A. Forster: Hadrosauridae. In: David B. Weishampel, Peter Dodson , Halszka Osmólska (eds.): The Dinosauria . 2nd edition. University of California Press, Berkeley CA et al. 2004, ISBN 0-520-24209-2 , pp. 438-463.
  10. ↑ a b c John R. Horner, David B. Weishampel: Hadrosauridae. In: David B. Weishampel, Peter Dodson, Halszka Osmólska (eds.): The Dinosauria . University of California Press, Berkeley CA et al. 1990, ISBN 0-520-06727-4 , pp. 534-561.
  11. ^ Donald F. Glut: Dinosaurs. The Encyclopedia. Supplement 2. McFarland & Co, Jefferson NC 2002, ISBN 0-7864-1166-X , pp. 79-80.
  12. ↑ a b c d e John R. Horner: Cranial morphology of Prosaurolophus (Ornithischia: Hadrosauridae). With descriptions of two new Hadrosaurid species and an evolution of Hadrosaurid phylogenetic relationships (= Museum of the Rockies Occasional Paper. No. 2). Museum of the Rockies et al., Bozeman MT et al. 1992, ISBN 1-56044-156-9 .
  13. ↑ a b James I. Kirkland , René Hernández-Rivera, Terry Gates, Gregory S. Paul, Sterling Nesbitt, Claudia Inés Serrano-Brañas, Juan Pablo Garcia de la Garza: Large hadrosaurine dinosaurs from the latest Campanian of Coahuila, Mexico. In: Spencer G. Lucas, Robert M. Sullivan: Late Cretaceous Vertebrates from the Western Interior (= New Mexico Museum of Natural History & Science. Bulletin. 35, ISSN  1524-4156 ). New Mexico Museum of Natural History and Science, Albuquerque NM 2006, pp. 299-315, digital version (PDF; 20.41 MB) .
  14. ^ Albert Prieto-Márquez, Jonathan R. Wagner: A new species of saurolophine hadrosaurid dinosaur from the Late Cretaceous of the Pacific coast of North America. In: Acta Palaeontologica Polonica. Vol. 58, No. 2, ISSN  0567-7920 , 2013, pp. 255-268, doi : 10.4202 / app.2011.0049 .
  15. ↑ Barnum Brown : The Cretaceous Ojo Alamo beds of New Mexico with description of the new dinosaur genus Kritosaurus. In: Bulletin of the American Museum of Natural History. Vol. 28, Article 24, 1910, ISSN  0003-0090 , pp. 267-274, online .
  16. ↑ Barnum Brown: Cretaceous Eocene correlation in New Mexico, Wyoming, Montana, Alberta. In: Bulletin of the Geological Society of America. Vol. 25, 1914, ISSN  0016-7606 , pp. 355-380, digitized .
  17. ^ Charles W. Gilmore : Contributions to the geology and paleontology of San Juan County, New Mexico; 2, Vertebrate faunas of the Ojo Alamo, Kirtland, and Fruitland formations. In: United States Geological Survey. Professional paper. Vol. 98, Article Q, 1917, ISSN  0096-0446 , pp. 279-302, digital version (PDF; 30.67 MB) .
  18. ^ William A. Parks: Preliminary description of a new species of trachodont dinosaur of the genus Kritosaurus. Kritosaurus incurvimanus. In: Proceedings and transactions of the Royal Society of Canada. Series 3, Vol. 13, Section 4, 1919, pp. 51-59, digitized .
  19. ^ A b John R. Horner: Upper Cretaceous dinosaurs from the Bearpaw Shale (marine) of South-central Montana with a checklist of Upper Cretaceous dinosaur remains from marine sediments in North America. In: Journal of Paleontology. Vol. 53, No. 3, 1979, ISSN  0022-3360 , pp. 566-577.
  20. ^ Donald F. Glut: The New Dinosaur Dictionary. Citadel Press, Secaucus NJ 1982, ISBN 0-8065-0782-9 , p. 158.
  21. ^ David Lambert and the Diagram Group: A Field Guide to Dinosaurs. The first complete Guide to every Dinosaur now known. Avon Books, New York NY 1983, ISBN 0-380-83519-3 , p. 161.
  22. ^ David B. Norman : Hadrosaurids I. In: David B. Norman: The Illustrated Encyclopedia of Dinosaurs. An Original and Compelling Insight into Life in the Dinosaur Kingdom. Crescent Books, New York NY 1985, ISBN 0-517-468905 , pp. 116-121.
  23. ↑ Albert Prieto-Márquez, David B. Weishampel, John R. Horner: The dinosaur Hadrosaurus foulkii, from the Campanian of the East Coast of North America, with a reevaluation of the genus. In: Acta Palaeontologica Polonica. Vol. 51, No. 1, 2006, pp. 77-98, online .
  24. ^ Richard S. Lull, Nelda E. Wright: Hadrosaurian Dinosaurs of North America (= The Geological Society of America. Special Papers. No. 40). The Geological Society of America, New York NY 1942, p. 226.
  25. ^ A b Terry A. Gates, Scott D. Sampson: A new species of Gryposaurus (Dinosauria: Hadrosauridae) from the late Campanian Kaiparowits Formation, southern Utah, USA. In: Zoological Journal of the Linnean Society. Vol. 151, No. 2, 2007, ISSN  0024-4082 , pp. 351-376, doi : 10.1111 / j.1096-3642.2007.00349.x .
  26. ↑ Terry A. Gates, Scott D. Sampson: A new species of Gryposaurus (Dinosauria: Hadrosauridae) from the Upper Campanian Kaiparowits Formation of Utah. In: Journal of Vertebrate Paleontology. Vol. 26, Supplement to No. 3 = Abstracts of Papers Sixty-Sixth Annual Meeting Society of Vertebrate Paleontology, Canadian Museum of Nature, Marriott Ottawa, Crowne Plaza Ottawa, Ottawa, Ontario, Canada, October 18-21, 2006 , 2006, ISSN  0272-4634 , p. 65A.
  27. ^ Albert Prieto-Marquez: The braincase and skull roof of Gryposaurus notabilis (Dinosauria, Hadrosauridae), with a taxonomic revision of the genus. In: Journal of Vertebrate Paleontology. Vol. 30, No. 3, 2010, pp. 838-854, doi : 10.1080 / 02724631003762971 .
  28. ↑ a b Michael J. Ryan, David C. Evans: Ornithischian Dinosaurs. In: Philip J. Currie , Eva B. Koppelhus (Eds.): Dinosaur Provincial Park. A Spectacular Ancient Ecosystem Revealed. Indiana University Press, Bloomington IN et al. 2005, ISBN 0-253-34595-2 , pp. 312-348.
  29. ^ David Lambert and the Diagram Group: Dinosaur Data Book. The definitive, fully illustrated Encyclopedia of Dinosaurs and other prehistoric Reptiles. Avon Books, New York NY 1990, ISBN 0-380-75896-2 , p. 64.
  30. ↑ George Olshevsky: Re: What are these dinosaurs? . November 16, 1999. Retrieved October 21, 2014.
  31. ^ Scientists Announce Top 10 New Species; Issue SOS . In: International Institute for Species Exploration . Newswise. May 23, 2008. Retrieved October 21, 2014.
  32. ^ Lawrence M. Lambe : New Genera and Species from the Belly River Series (Mid-Cretaceous). In: Lawrence M. Lambe: On Vertebrata of the mid-cretaceous of the North West Territory. 1) Distinctive characters of the mid-cretaceous fauna by Henry Fairfield Osborn. 2) New Genera and Species from the Belly River Series (Mid-Cretaceous) (= Survey of Canada. Contributions to Canadian Palaeontology. Vol. 3, Part 2, ZDB -ID 974450-2 ). Government Printing Bureau, Ottawa 1902, pp. 25-81.
  33. ^ Charles W. Gilmore: On the genus Stephanosaurus, with a description of the type specimen of Lambeosaurus lambei, Parks. In: Canada, Department of Mines, Geological Survey. Bulletin. Vol. 38, No. 43, 1924, ZDB -ID 429582-1 , pp. 29-48.
  34. ^ A b James A. Hopson: The evolution of cranial display structure in hadrosaurian dinosaurs. In: Paleobiology. Vol. 1, No. 1, 1975, ISSN  0094-8373 , pp. 21-43.
  35. ↑ Eric M. Roberts, Alan L. Deino, Marjorie A. Chan: 40 Ar / 39 Ar age of the Kaiparowits Formation, southern Utah, and correlation of contemporaneous Campanian strata and vertebrate faunas along the margin of the Western Interior Basin. In: Cretaceous Res. Vol. 26, No. 2, 2005, ISSN  0195-6671 , pp. 307-318, doi : 10.1016 / j.cretres.2005.01.002 .
  36. ↑ Jeffrey G. Eaton: Multituberculate mammals from the Wahweap (Campanian, Aquilan) and Kaiparowits (Campanian, Judithian) formations, within and near Grand Staircase-Escalante National Monument, southern Utah (= Utah Geological Survey. Miscellaneous Publication. 02-4) . Utah Geological Survey, Salt Lake City UT 2002, ISBN 1-55791-665-9 .
  37. ^ Alan L. Titus, Mark A. Loewen (eds.): At the Top of the Grand Staircase. The Late Cretaceous of Southern Utah. Indiana University Press, Bloomington IN 2013, ISBN 978-0-253-00883-1 .
  38. ↑ Lindsay E. Zanno, Scott D. Sampson: A new Oviraptorosaur (Theropoda, Maniraptora) from the Late Cretaceous (Campanian) of Utah. In: Journal of Vertebrate Paleontology. Vol. 25, No. 4, 2005, pp. 897-904, doi : 10.1671 / 0272-4634 (2005) 025 [0897: ANOTMF] 2.0.CO; 2 .
  39. ↑ Jeffrey G. Eaton, Richard L. Cifelli, J. Howard Hutchinson, James I. Kirkland, J. Michael Parrish: Cretaceous vertebrate faunas from the Kaiparowits Plateau, south-central Utah. In: David D. Gillette (Ed.): Vertebrate Paleontology in Utah (= Utah Geological Survey. Miscellaneous Publication. 99-1). Utah Geological Survey, Salt Lake City UT 1999, ISBN 1-55791-634-9 , pp. 345-353.
  40. ↑ Victoria M. Arbor, Michael E. Burns, Robin L. Sissons: A redescription of the ankylosaurid dinosaur Dyoplosaurus acutosquameus Parks, 1924 (Ornithischia: Ankylosauria) and a revision of the genus. In: Journal of Vertebrate Paleontology. Vol. 29, No. 4, 2009, pp. 1117-1135, doi : 10.1671 / 039.029.0405 .
  41. ^ Paul Penkalski: A new ankylosaurid from the late Cretaceous Two Medicine Formation of Montana, USA. In: Acta Palaeontologica Polonica. Vol. 59, No. 3, 2014, pp. 617-634, doi : 10.4202 / app.2012.0125 .
  42. ↑ 3.11 Montana, United States; 2. Lower Two Medicine Formation. In: David B. Weishampel, Peter Dodson, Halszka Osmólska (eds.): The Dinosauria . 2nd edition. University of California Press, Berkeley CA et al. 2004, ISBN 0-520-24209-2 .

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