Pachyrhinosaurus

Credit: Julio Lacerda.

*Pachyrhinosaurus* is an extinct genus of Centrosaurine Ceratopsian that lived in North America during the Late Cretaceous

## History

In 1945-1946, several skulls are discovered from the Horseshoe Canyon Formation. In 1947, Charles Sternberg published the abstract on a new Ceratopsian dinosaur representing a new family.  In 1950, Sternberg named this species *Pachyrhinosaurus canadensis*. In 1975, Langston, W. Jr. described more material of *P. canadensis* from the St. Mary River Formation's Scabby Butte. Al Lakusta (1974) found a large bonebed along Pipestone Creek, Alberta, being excavated between 1986 and 1989 by staff and volunteers of the Royal Tyrrell. They found a very large, dense selection of material - up to 100 bones/square meter, totaling to 3500 bones and 14 skulls. In the 1980s, a young Philip Currie and Darren Tanke were looking through the specimens in the TMP's collection when stumbling on the remains of a Ceratopsian from Al Lakusta's excavations, representing material from "numerous individuals, with virtually every bone in the skeleton represented." In 2008 *Currie, Langston & Tanke* formally described the bones as *Pachyrhinosaurus lakustai.* In 1998, a multitaxic bonebed in the Prince Creek Formation was discovered. Out of this, a multitude of Pachyrhinosaurus skeletons were perserved. In 2012, Fiorillo & Tykoski described the remains from the 2006 expedition as belonging to a new species: *Pachyrhinosaurus perotorum.* In 2015, Kruk published a thesis on Pachyrhinosaurus ontogeny and histology. In that thesis she named a fourth species of *Pachyrhinosaurus, P.* "youngi"*.* This specimen was collected in 2010. She says that, "This chapter will be submitted to PLoS ONE fo*r publication."* So far an official description hasn't been published, making *P.* "youngi" a nomen nudum. Finally, TMP 2002.76.1 was discovered in the Iddesleigh of the Dinosaur Park Formation in 1996, and was deposited and cataloged in the TMP in 2002. It was described by *Ryan et. al*. (2010) as a new Ceratopsian, but wasn't given a name.

## Description

*Pachyrhinosaurus* can be distinguished from Non-Pachyrostran Centrosaurs by the presence of a nasal boss instead of a nasal horn. Further, it can be distinguished from *Achelousaurus,* the other known Pachyrostran, by the more medially projected, curved P3 epiparietals, more pronounced P1 epiparietals, a shorter, rounder frill, by, "a relatively broader, longer, and typically thicker boss.", "the nasal rugosity extends posteriorly onto the frontals", and "Supraorbital boss is stouter and less rugose than in *Achelousaurus."*

### *P. canadensis*

*P. canadensis* is known from the Horsehoe Canyon Formation and the laterally equivalent St. Mary River Formation. It was estimated by to be 6 meters long, 2 meters tall, and weigh 3 metric tones. *P. canadensis* can be distinguished from the other species of *Pachyrhinosaurus* by: the lack of a small rostral comb dorsal to the rostral (shared with *P*. *"youngi"*); nasal boss and supraorbital bosses that contact each other on the skull roof (shared with *P. perotorum* and *P.* "youngi"); presence of a supranarial ossification on the lateral surface of the rostrum (shared with *P. perotorum*, not perserved in *P.* *"youngi"*); nasal boss and other anterior facial ornamentations (including "fist-sized knobs") are more hypertrophied than *P. lakustai*, but less so than *P. perotorum* and *P.* "youngi"; lack of a single transverse shelf of bone on the medial side of the premaxilla (shared with *P. perotorum* and *P.* "youngi")' "long slender, finger-like premaxillary process that extends forward and then curves 90° medially"; "irregularly developed and vertical fluting", a flat parietal bar in lateral view"; "lateral parietal spike twists dorsolaterally"; and the presence of a "Supranasal Boss" (not shared with any other species). In 1967/1968 a skull from Drumheller was discovered by the Drumheller Dinosaur and Fossil Museum, which is now the Badlands Historical Centre. A taxon number wasn't given to this skull, but Currie, Langston, and Tanke dub this specimen the "Drumheller Skull". It is a large *Pachyrhinosaurus canadensis*.

### *P. lakustai*

*P. lakustai* is known from the Wapiti Formation. It was around 5m long, and weigh 2 metric tons. *P. lakustai* can be distinguished from other known *Pachyrhinosaurus* species by: the "presence of a small rostral comb dorsal to the rostral" (shared with *P. perotorum*); the "presence of a supranarial ossification on the lateral surface of the rostrum" (shared with *P. canadensis*); nasal boss and other anterior facial ornamentations (including "fist-sized knobs") less hypertrophied than both *P. canadensis, P. perotorum, and P.* "youngi"*;* a single transverse shelf of bone on the medial side of the premaxilla (not shared by any other species); the "short robust premaxillary process projects straight forward into nares"; the parietal bar curves slightly upwards in lateral (possibly shared with *P.* "youngi"); "lateral parietal spike twists anteroventrally" (shared with *P.* *"youngi"* and to a lesser extent *P. perotorum* [more horizontal]); the lack of a "Supranasal Boss" (shared with *P. perotorum* and *P.* "youngi").

### *P. perotorum*

*P. perotorum* is known from the Prince Creek Formation. It was around 5m long, and weigh 2 metric tons *P. perotorum* can be distinguished from other species of *Pachyrhinosaurus* by: "rostrum anterior tip upturned with anteroventrally directed premaxillary oral margin, resulting in a rostral bone shifted to a level dorsal to the maxillary tooth row"; "rostral bone lacks the acute, ventrally downturned, parrot-like beak common to other ceratopsians"; "nasal boss dorsal surface with median ridge near posterior end of boss" (none of these feature is shared with another species of Centrosaur). Both "epiparietal 2 (P2) posterior margin excavated by enhanced, trough-like, mediolaterally oriented sulcus" and "epiparietal 2 (P2) horn base penetrated by canal passing dorsoventrally through body of horn." are tentative autapomorphies of *P. perotorum*. Further, these features can be used to better distinguish P. perotorum from its relatives. "small rostral comb dorsal to the rostral" (shared with *P. lakustai*); the "nasal boss and supraorbital bosses that contact each other on the skull roof" (shared with *P. canadensis* and *P.* "youngi"); "presence of a supranarial ossification on the lateral surface of the rostrum" (shared with *P. canadensis* and not perserved in *P.* "youngi"); nasal boss and other anterior facial ornamentations (including "fist-sized knobs") are more hypertrophied than *P. canadensis, P. lakustai,* and *P.* "youngi"; the lateral parietal spike twists anteroventrally (similar, but less pronounced than *P.* lakustai and *P.* "youngi"; the lack of a "supranasal boss (shared with *P. lakustai* and *P.* "youngi".

### *P.* "youngi"

*P.* "youngi" was found in the Wapiti Formation. Kruk didn't provide estimates on size of *P.* "youngi", however it can be assumed to be around 5-6m long and weighed 2-3 tons due to its phylogenetic position. *P.* "youngi" can be differentiated from other *Pachyrhinosaurus* species by: the lack of a "small rostral comb dorsal to the rostral" (shared with *P. canadensis*); the "nasal boss and supraorbital bosses that contact each other on the skull roof" (shared with *P. canadensis* and *P. perotorum*); "dorsolaterally curved parietal horns"; a "distinctive tall separation between supraorbital bosses"; an "anteriorly protruding “pommel"" (all 3 unique to *P.* "youngi"); lack of a "single transverse shelf of bone on the medial side of the premaxilla" (shared with *P. canadensis* and *P. perotorum*); the lack of "Supranasal Boss" (shared with *P. perotorum* and *P. lakustai*.)

### *P.* sp. nov.

TMP 2002.76.1 is known from the Dinosaur Park Formation. This specimen is known from a mostly complete skull missing the back of the frill, both radii and ulnae of the front feet, the right humerus, both scapulae, both scapulacoracoids, 3 complete feet, 2 tibiae (one partial one complete), a fibula, around 5 cervical vertebrae, around 14 dorsal vertebrae, and around 11 caudal vertebrae, and around 12 pairs of ribs, as well as a highly incomplete sacrum. If this taxon is *Pachyrhinosaurus* it would be the oldest species of the genus. Both Kruk (2015) and Tykoski et. al. (2019) recover this taxon as a taxon closer to Pachyrhinosaurus rather than *Achelousaurus.*However*,* Savhannah Carpenter's unpublished phylogeny from 2021 (labeled as *Achelousaurus* [Iddesleigh]) as well as *Ryan et. al.* (2010) places TMP 2002.76.1 in a polytomy with *Achelousaurus and Pachyrhinosaurus*. The reason why it's position within Pachyrostra hasn't been consistent is due to the preservation of TMP 2002.76.1. TMP 2002.76.1 is missing the top of its frill, which is a vital character that distinguished Ceratopsids in general and *Pachyrhinosaurus* in particular. Until further expeditions to the Dinosaur Park Formation uncover another specimen of this species, it is unlikely to receive a name (despite several characters that distinguish it from *Achelousaurus horneri* and the other known *Pachyrhinosaurus* species) due to the uncertainty of whether it is a new genus, a new species of *Achelousaurus,* or a new species of *Pachyrhinosaurus.*

In October 2013 a Darla Zelenitsky and her team discovered the skull of a "gargantuan pachyrhinosaur" within the limits of Drumheller, Alberta. The Pachyrhinosaur was unveiled at the University of Calgary in February of 2014. It was the largest skull of a Pachyrhinosaur discovered, over 6 meters in length. Zelenitsky estimates that the skull is 75-80% complete. She and her team planned on returning to the site in spring/summer of 2014 to determine if more of the "gargantuan pachyrhinosaur" is preserved, and to determine "if this specimen represents a new species.” So far, no more news of the Pachyrhinosaur has been publicized since the original unveiling.

## Species

* *P. canadensis*
* *P. lakustai*
* *P. perotorum*
* *P.* "youngi"
* P. sp. nov.? TMP 2002.76.1, possibly the U of C "Gargantuan Pachyrhinosaur"

## Paleobiology

Remains of *Pachyrhinosaurus* have been found in the Horseshoe Canyon Formation, St. Mary River Formation, Wapati Formation, and Prince Creek Formations.

## Phylogeny

This cladogram was recovered by Kruk (2015) in her thesis on *P. "youngi".*

## Paleoecology

### Horseshoe Canyon/St. Mary River Formation

*Pachyrhinosaurus canadensis* is known from both the Horseshoe Canyon Formation and the laterally equivalent St. Mary River Formation. It shared its environment with the Leptoceratopsid *Montanoceratops*, The Chasmosaurs *Regaliceratops**, Anchiceratops,* and *Arrhinoceratops.* It would have also coexisted with hadrosaur *Edmontosaurus regalis,* The Ornithomimosaurs *Ornithomimus* and *Struthiomimus,* the Tyrannosaur *Albertosaurus sarcophagus,* The Ankylosaurs *Anodontosaurus* and *Edmontonia longiceps.* It would have also coexisted with the *Troodontid Albertavenator,* the *Dromeosaur Atrociraptor**,* and the Caenagnathid Ovoraptorosaurs *Apatoraptor* and *Epichirostenotes**.* Among Non-Dinosaurians the mammal *Didelphodon coyi* from Drumheller*.* *Stangerochampsa* is from Horseshoe Canyon isn't clear in the article's description, but probably belongs to the Drumheller unit, making it coocurring*.* *Basilemys* is known from the Horseshoe Canyon Formation, but isn't given a locality, based on other formations it probably cooccurs with *P. canadensis.* The Choristoderan *Champsosaurus albertensis* and the plesiosaur *Leurospondylus* were found in Horseshoe Canyon, but no further locality information can be gathered*.*

### Wapiti Formation

*Pachyrhinosaurus lakustai* and *P.* "youngi" are known from the Wapiti Formation. It would have shared its environment with A large Tyrannosaur, possibly Albertosaurus (represented by teeth and *Bellatoripes* tracks), the Velociraptorine *Boreonykus certekorum**,* the Hadrosaur *Edmontosaurus*, and *Saurornitholestes sp.**.* "*Troodon*" and the morphotaxon *Richardoestesia*. are also present.

### Prince Creek Formation

*Pachyrhinosaurus perotorum* is known from the Prince Creek Formation. It would have shared its environment with an indeterminate Leptoceratopsid, The Hadrosaur *Edmontosaurus sp. (*previously within the junior synonym *"Ugrunaaluk")* , an indeterminate Lambeosaurine represented by the supraoccipital DMNH 2014-12-266. The Pachycephalosaur *Alaskacephale gangloffi* is also present. *Nanuqsaurus* was also present within this formation. *Dromaeosaurus cf. albertensis, Saurornitholestes cf. langstoni*, indeterminate Thescelosaurinae and indeterminate "Hypsilophodontid" teeth have been found within the formation.An indeterminate genus of saurornitholestinae, represented by the dentary fragment DMNH 21183 is present. A Distal metatarsal IV from an indeterminate Ornithomimosaur and the tracks of ichnogenus bird *Gruipeda* have also been reported. Of all the remains, only one non-dinosaurian faunal taxon is known, the metatherian mammal *Unnuakomys.*

### Dinosaur Park Formation

TMP 2002.76.1 is known from the Dinosaur Park Formation, specifically the Lethbridge Coal. Very little has been reported from the Lethbridge Coal, among the known remains from the Dinosaur Park Formation: *Centrosaurus*, *Chasmosaurus belli and C. russeli* are Ceratopsids it would have coexisted with. The Hadrosaurids *Corythosaurus, Gryposaurus,* and *Parasaurolophus walkeri.* The Tyrannosaur *Gorgosaurus* would have lived at the same time and possibly hunted this taxon.

## Notable Specimens

* CMN 8867: The holotype of *Pachyrhinosaurus canadensis* and by proxy *Pachyrhinosaurus* as a whole*.*
* CMN 8866: The paratype of *Pachyrhinosaurus canadensis.*
* TMP 1986.55.258: The holotype of *Pachyrhinosaurus lakustai.*
* DMNH 21200: The holotype of *Pachyrhinosaurus perotorum.*
* DMNH 22558: Paratype of *Pachyrhinosaurus perotorum.*
* DMNH 21201: Paratype of *Pachyrhinosaurus perotorum.*
* UALVP 53300: Holotype of *P*. "youngi".
* UALVP 54165: Paratype of *P*. "youngi"
* UALVP 50652: Paratype of *P*. "youngi"
* UALVP 55805 : Paratype of *P*. "youngi"
* TMP 2002.76.1: A new species that possibly belongs to *Pachyrhinosaurus,* if so, it is the oldest *Pachyrhinosaurus* known*.*
* "University of Calgary's Gargantuan Pachyrhinosaur": a taxon of Pachyrhinosaur, possibly belonging to the new species represented by TMP 2002.76.1. It is the largest Pachyrhinosaur discovered.
* "Cerabottoms": A site discovered and named by Riley Black (other paleontologists on the team including Evan Johnson-Ransom and Zack Perry) while hiking through Denali National Park during the filming of the PBS documentary Alaskan Dinosaurs. Te site preserves what are likely *P. perotorum* trackways, since other prints from Denali are identified as such and it, aside from another leptoceratopsid (which was much smaller), from the Prince Creek Formation. Hadrosaur prints were found at the same site. The rock had twisted the prints so that the bottoms were up, hence the name "Cerabottoms".

## References

1. ↑ Sternberg, C. M. (1947). "New dinosaur from southern Alberta, representing a new family of the Ceratopsia". Geological Society of America Bulletin. 58: 1230
2. ↑ 2.0 2.1 2.2 2.3 2.4 2.5 Sternberg C. M. (1950). "Pachyrhinosaurus canadensis, representing a new family of the Ceratopsia, from southern Alberta". *National Museum of Canada Bulletin. **118**: 109–120.*
3. ↑ Langston, W. Jr. (1975). "The Ceratopsian Dinosaurs and Associated Lower Vertebrates from the St. Mary River Formation (Maestrichtian) at Scabby Butte, Southern Alberta". Canadian Journal of Earth Sciences. 12 (9): 1576–1608. Bibcode:1975CaJES..12.1576L. doi:10.1139/e75-142
4. ↑ 4.0 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 #Currie, P.J., Langston, W., and Tanke, D.H. (2008). "A new species of *Pachyrhinosaurus* (Dinosauria, Ceratopsidae) from the Upper Cretaceous of Alberta, Canada." pp. 1-108. In: Currie, P.J., Langston, W., and Tanke, D.H. 2008. *A New Horned Dinosaur from an Upper Cretaceous Bone Bed in Alberta*. NRC Research Press, Ottawa, Ontario, Canada. 144 pp. ISBN 978-0-660-19819-4
5. ↑ https://search.museums.ualberta.ca/8-141323
6. ↑ 6.00 6.01 6.02 6.03 6.04 6.05 6.06 6.07 6.08 6.09 6.10 6.11 6.12 6.13 Kruk, E. A. Histology and ontogeny of pachyrhinosaurus... *ERA* (2015). Available at: https://era.library.ualberta.ca/items/1acc9f42-5e22-4e3c-a924-625d149100bd.
7. ↑ 7.0 7.1 7.2 7.3 Ryan, M.J. & Eberth, D.A. & Brinkman, Donald & Currie, Philip & Tanke, Darren. (2010). A new Pachyrhinosaurus-like ceratopsid from the upper Dinosaur Park Formation (Late Campanian) of southern Alberta, Canada. New Perspectives on Horned Dinosaurs: The Royal Tyrrell Museum Ceratopsian Symposium. 141-155.
8. ↑ Wilson John P., Ryan Michael J. and Evans David C. 2020A new, transitional centrosaurine ceratopsid from the Upper Cretaceous Two Medicine Formation of Montana and the evolution of the ‘Styracosaurus-line' dinosaursR. Soc. open sci.7200284200284 https://doi.org/10.1098/rsos.200284
9. ↑ Scott D. Sampson (1995) Two new horned dinosaurs from the upper Cretaceous Two Medicine Formation of Montana; with a phylogenetic analysis of the Centrosaurinae (Ornithischia: Ceratopsidae), Journal of Vertebrate Paleontology, 15:4, 743-760, https://doi.org/10.1080/02724634.1995.10011259
10. ↑ 10.0 10.1 1.4 Alberta, Canada; 13. St. Mary River Formation," in Weishampel, et al. (2004). Pages 577-578
11. ↑ https://commons.wikimedia.org/wiki/File:Pachyrhinosaurus\_Scale\_2.svg
12. ↑ 12.0 12.1 12.2 Paul, Gregory, S. *Princeton Field Guide to Dinosaurs, Princeton, NJ, Princeton University Press, 2010, pg. 292-293*
13. ↑ 13.0 13.1 13.2 13.3 13.4 13.5 13.6 13.7 13.8 Anthony R. Fiorillo and Ronald S. Tykoski (2012). "A new species of the centrosaurine ceratopsid *Pachyrhinosaurus* from the North Slope (Prince Creek Formation: Maastrichtian) of Alaska". *Acta Palaeontologica Polonica*. **57** (3): 561–573. doi:10.4202/app.2011.0033.
14. ↑ 14.0 14.1 14.2 14.3 14.4 14.5 Ronald S. Tykoski, Anthony R. Fiorillo & Kentaro Chiba (2019) New data and diagnosis for the Arctic ceratopsid dinosaur *Pachyrhinosaurus perotorum*, Journal of Systematic Palaeontology, 17:16, 1397-1416, https://doi.org/10.1080/14772019.2018.1532464
15. ↑ https://badlandsmuseum.wordpress.com/
16. ↑ https://www.researchgate.net/publication/284893179\_A\_new\_Pachyrhinosaurus-like\_ceratopsid\_from\_the\_upper\_Dinosaur\_Park\_Formation\_Late\_Campanian\_of\_southern\_Alberta\_Canada
17. ↑ https://www.flickr.com/photos/58554451@N00/4552995690/ (mount of TMP 2002.76.1 from RTMP)
18. ↑ https://youtu.be/Qr7u0U4u5bo?t=1488
19. ↑ 19.0 19.1 THE CANADIAN PRESS (2015, January 25). *'gargantuan' pachyrhinosaur skull found in Drumheller 72 million years after horned dinosaur roamed Alberta*. nationalpost. Retrieved May 8, 2022, from https://nationalpost.com/news/canada/gargantuan-pachyrhinosaur-skull-found-in-drumheller-72-million-years-after-horned-dinosaur-roamed-alberta
20. ↑ 20.0 20.1 CBC/Radio Canada. (2014, February 21). *'gargantuan' pachyrhinosaur skull found near Drumheller | CBC News*. CBCnews. Retrieved May 8, 2022, from https://www.cbc.ca/news/canada/calgary/gargantuan-pachyrhinosaur-skull-found-near-drumheller-1.2544925
21. ↑ 21.0 21.1 Ronald S. Tykoski, Anthony R. Fiorillo & Kentaro Chiba (2019) New data and diagnosis for the Arctic ceratopsid dinosaur *Pachyrhinosaurus perotorum*, Journal of Systematic Palaeontology, 17:16, 1397-1416, DOI: 10.1080/14772019.2018.1532464

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31. ↑ Brown, Barnum, 1913 "A new plesiosaur, Leurospondylus, from the Edmonton Cretaceous of Alberta". *Bulletin of the AMNH*; v. 32, article 40
32. ↑ Reid, Ian J. (2016). "A review of dinosaurian body fossils from British Columbia, Canada". PeerJ Preprints. doi:10.7287/peerj.preprints.1369v3.
33. ↑ McCrea, R. T.; Buckley, L. G.; Farlow, J. O.; Lockley, M. G.; Currie, P. J.; Matthews, N. A.; Pemberton, S. G. (2014). "A 'Terror of Tyrannosaurs': The First Trackways of Tyrannosaurids and Evidence of Gregariousness and Pathology in Tyrannosauridae". PLOS ONE. 9 (7): e103613. Bibcode:2014PLoSO...9j3613M. doi:10.1371/journal.pone.0103613. PMC 4108409. PMID 25054328.
34. ↑ Bell, P. R.; Currie, P. J. (2015). "A high-latitude dromaeosaurid, Boreonykus certekorum, gen. et sp. nov. (Theropoda), from the upper Campanian Wapiti Formation, west-central Alberta". Journal of Vertebrate Paleontology. 36 (1). doi:10.1080/02724634.2015.1034359.
35. ↑ Bell, Phil R.; Fanti, Federico; Acorn, John; Sissons, Robin S. (January 2013). "Fossil Mayfly Larvae (Ephemeroptera, cf. Heptageniidae) from the Late Cretaceous Wapiti Formation, Alberta, Canada" (PDF). Journal of Paleontology. 87 (1): 147–150. doi:10.1666/12-058R.1. ISSN 0022-3360. S2CID 128944375
36. ↑ 36.0 36.1 Fanti, Federico; Miyashita, Tetsuto (2009-05-01). "A high latitude vertebrate fossil assemblage from the Late Cretaceous of west-central Alberta, Canada: evidence for dinosaur nesting and vertebrate latitudinal gradient" (PDF). Palaeogeography, Palaeoclimatology, Palaeoecology. 275 (1): 37–53. Bibcode:2009PPP...275...37F. doi:10.1016/j.palaeo.2009.02.007. ISSN 0031-0182
37. ↑ Druckenmiller, Patrick S.; Erickson, Gregory M.; Brinkman, Donald; Brown, Caleb M.; Eberle, Jaelyn J. (June 2021). "Nesting at extreme polar latitudes by non-avian dinosaurs". Current Biology. 31 (16): 3469–3478.e5. doi:10.1016/j.cub.2021.05.041. ISSN 0960-9822. PMID 34171301.
38. ↑ Takasaki R, Fiorillo AR, Tykoski RS, Kobayashi Y (2020) Re-examination of the cranial osteology of the Arctic Alaskan hadrosaurine with implications for its taxonomic status. PLoS ONE 15(5): e0232410. https://doi.org/10.1371/journal.pone.0232410
39. ↑ Sullivan, RM (2006). "A taxonomic review of the Pachycephalosauridae (Dinosauria: Ornithischia)" (PDF). New Mexico Museum of Natural History and Science Bulletin (35): 347–365.
40. ↑ "3.33 Alaska, United States; 3. Prince Creek Formation," in Weishampel, et al. (2004). Page 587.
41. ↑ Brown, C.M.; Druckenmiller, P. (2011). "Basal ornithopod (Dinosauria: Ornithischia) teeth from the Prince Creek Formation (early Maastrichtian) of Alaska". Canadian Journal of Earth Sciences. 48 (9): 1342–1354. Bibcode:2011CaJES..48.1342B. doi:10.1139/e11-017
42. ↑ **Citation:** Chiarenza AA, Fiorillo AR, Tykoski RS, McCarthy PJ, Flaig PP, Contreras DL (2020) The first juvenile dromaeosaurid (Dinosauria: Theropoda) from Arctic Alaska. PLoS ONE 15(7): e0235078. https://doi.org/10.1371/journal.pone.0235078
43. ↑ Watanabe, Akinobu; Erickson, Gregory M.; Druckenmiller, Patrick S. (2013-09-01). "An ornithomimosaurian from the Upper Cretaceous Prince Creek Formation of Alaska". Journal of Vertebrate Paleontology. 33 (5): 1169–1175. doi:10.1080/02724634.2013.770750. ISSN 0272-4634. S2CID 130049294.
44. ↑ Fiorillo, A. R.; Hasiotis, S. T.; Kobayashi, Y.; Breithaupt, B. H.; McCarthy, P. J. (2011). "Bird tracks from the Upper Cretaceous Cantwell Formation of Denali National Park, Alaska, USA: a new perspective on ancient northern polar vertebrate biodiversity". Journal of Systematic Palaeontology. 9 (1): 33–49. doi:10.1080/14772019.2010.509356.
45. ↑ Eberle, Jaelyn J.; Clemens, William A.; McCarthy, Paul J.; Fiorillo, Anthony R.; Erickson, Gregory M.; Druckenmiller, Patrick S. (2019-02-14). "Northernmost record of the Metatheria: a new Late Cretaceous pediomyid from the North Slope of Alaska". Journal of Systematic Palaeontology. 17 (21): 1805–1824. doi:10.1080/14772019.2018.1560369. ISSN 1477-2019. S2CID 92613824.
46. ↑ 46.0 46.1 #Victoria M. Arbour, Michael E. Burns & Robin L. Sissons (2009) A redescription of the ankylosaurid dinosaur *Dyoplosaurus acutosquameus* Parks, 1924 (Ornithischia: Ankylosauria) and a revision of the genus, Journal of Vertebrate Paleontology, 29:4, 1117-1135, DOI: 10.1671/039.029.0405
47. ↑ Evans D.C.; Bavington R.; Campione N.E. (2009). "An unusual hadrosaurid braincase from the Dinosaur Park Formation and the biostratigraphy of Parasaurolophus (Ornithischia: Lambeosaurinae) from southern Alberta". Canadian Journal of Earth Sciences. 46 (11): 791–800. Bibcode:2009CaJES..46..791E. doi:10.1139/E09-050
48. ↑ https://twitter.com/EJR\_Paleo\_MSc/status/1484405976094629888
49. ↑ https://www.cell.com/current-biology/fulltext/S0960-9822(21)00739-9
50. ↑ https://twitter.com/Laelaps/status/1483803013948923908
51. ↑ https://www.nps.gov/dena/learn/nature/pachyrhinosaurus.htm
52. ↑ https://archive.org/details/g.s.paul2016theprincetonfieldguidetodinosaurs/page/n253/mode/1up