Anodontosaurus

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Anodontosaurus
Temporal range: Late Cretaceous, 75.6–67  Ma
Anodontosaurus.tif
A. lambei holotype skull CMN 8530
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Clade: Ornithischia
Clade: Thyreophora
Clade: Ankylosauria
Family: Ankylosauridae
Subfamily: Ankylosaurinae
Tribe: Ankylosaurini
Genus: Anodontosaurus
Sternberg, 1929
Type species
Anodontosaurus lambei
Sternberg, 1929
Other species
  • A. inceptus
    Penkalski, 2018

Anodontosaurus is an extinct genus of ankylosaurid dinosaurs within the subfamily Ankylosaurinae. It is known from the entire span of the Late Cretaceous Horseshoe Canyon Formation (mid Late Campanian to "middle" Maastrichtian stage, about 72.8-67 Ma ago) of southern Alberta, Canada, and is also known from the Dinosaur Park Formation (75.6 Ma ago). It contains two species, A. lambei and A. inceptus. [1] [2] [3]

Contents

Discovery

Cast of referred A. lambei tail club AMNH 5245 Schwanzkeule von Ankylosaurus.JPG
Cast of referred A. lambei tail club AMNH 5245

Anodontosaurus was named by Charles Mortram Sternberg in 1928, based on holotype CMN  8530, a partially preserved skeleton including the skull, half ring, armor and other postcranial remains. [4] The badly crushed [1] skeleton was collected by Sternberg in 1916 from a Canadian Museum of Nature quarry, 8 miles southwest of Morrin. [4] It was collected from the upper part of the Lower Horseshoe Canyon Formation (unit 2), dating to the latest Campanian to the earliest Maastrichtian stage of the Late Cretaceous period, about 71-70.2  million years ago. [1] [5] The generic name means "toothless lizard" in Ancient Greek. It was inspired by the fact that compression damage to the specimen had removed the teeth, at the same time shifting various flat round elements below the skull and on top of the left lower jaw, misleading Sternberg into assuming that large "trituration plates" had replaced the normal dentition. [6] The specific name, lambei, honours Lawrence Morris Lambe, the Canadian geologist and palaeontologist from the Geological Survey of Canada where the holotype was reposited. [4]

In 1986 Coombs examined specimen AMNH 5266, at the time by him referred to Euoplocephalus, and determined that it was a juvenile. It consists of five vertebral centra, a neural arch, one dorsal and two sacral ribs, the right ischium, the complete right hindlimb, the right pes, an incomplete left pes, and various other fragments. AMNH 5266 was discovered in 1912 at Red Deer River and was collected by Barnum Brown with assistance from Peter Kaisen, George Olsen, and Charles M Sternberg in the sediments from the Horseshoe Canyon Formation. [7]

Description

Holotype skull of A. inceptus, TMP 1997.132.1 Anodontosaurus lambei.tif
Holotype skull of A. inceptus, TMP 1997.132.1

Anodontosaurus was a medium-sized ankylosaurid, measuring up to 4–5 metres (13–16 ft) in length and 2 metric tons (2.2 short tons) in body mass. [8] [9] It was a quadrupedal, ground-dwelling herbivore. Like other ankylosaurs, Anodontosaurus has armor on a majority of the dorsal surfaces of its body. It has a wide, pointed tail club at the end of its armored tail. The skull features postocular caputegulae, which are small polygonal plates of bone that are present on the cranium and are situated to the immediate rear of the eye. [1]

Coombs supported the assertion that specimen AMNH 5266 represented a juvenile by citing that the vertebral centra were not fused to their neural arches, and that sacral ribs were likewise not fused to vertebrae and to the ilium. Other morphological characters supporting that this is a juvenile specimen include (a) long bones that feature smooth surfaces, which are not marked by the rugosities characteristic of adult bone; (b) the head of the femur is less spherical in shape and is clearly delimited from the adjacent part of the femoral shaft; (c) the distal ends of the tibia and the fibula are not fused to the astragalus and the calcaneum; and (d) the ungual phalanx of the manus is not widest at the proximal articular end as is observed in adults. [7]

Classification

Referred A. lambei skull Anodontosaurus lambei ROM 832.TIF
Referred A. lambei skull
Referred A. inceptus skull AMNH 5238 Anodontosaurus AMNH 5238.tif
Referred A. inceptus skull AMNH 5238

In 1971, Walter Coombs concluded that there was only one species of ankylosaurid during the Campanian age of the Late Cretaceous of North America. He synonymised the species Anodontosaurus lambei, Dyoplosaurus acutosquameus , and Scolosaurus cutleri with Euoplocephalus tutus . [10] The synonymisation of Anodontosaurus lambei and Euoplocephalus tutus was generally accepted and thus CMN 8530 was assigned to E. tutus. [6] However, following the redescription of Dyoplosaurus as a valid genus by Arbour et al. (2009), [5] In an abstract presented at the SVP 2010 conference, Victoria Arbour considered Anodontosaurus distinct from Euoplocephalus in distinctive skull and cervical half ring ornamentation, as well as tail club morphology, including the presence of pointed, triangular knob osteoderms in Anodontosaurus. She therefore reassigned all Horseshoe Canyon Formation ankylosaurine specimens previously referred to Euoplocephalus to Anodontosaurus. [2]

The validity of Anodontosaurus was formalized in three studies. The first, published by Paul Penkalski and William T. Blows in 2013, re-validated Scolosaurus as well. [11] The second study, by Penkalski (2013), named and described Oohkotokia from Montana on the basis of remains that were originally thought to be referable to Euoplocephalus. Penkalski (2013) performed a small phylogenetic analysis of some ankylosaurine specimens. The only Anodontosaurus specimen that was included in this analysis was its holotype. Anodontosaurus was placed in a polytomy with the holotype of Euoplocephalus and some specimens that are referred to it, while Oohkotokia was placed in a clade with Dyoplosaurus, and specimens that are thought to represent either Dyoplosaurus or Scolosaurus. [1] In a study based on the results of her 2010 SVP abstract, Arbour along with Philip Currie formalized the revalidation of Anodontosaurus, and one specimen from the Dinosaur Park Formation, TMP 1997.132.1, was referred to Anodontosaurus extending the stratigraphic range of the genus back a few million years. [12] The DPF specimen, however, was later made the holotype of a new species, A. inceptus. [3] The following cladogram is based on a 2015 phylogenetic analysis of the Ankylosaurinae conducted by Arbour and Currie: [13]

Ankylosaurinae

See also

Related Research Articles

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<i>Euoplocephalus</i> Genus of ankylosaurid dinosaur from the Late Cretaceous period

Euoplocephalus is a genus of large herbivorous ankylosaurid dinosaurs, living during the Late Cretaceous of Canada. It has only one named species, Euoplocephalus tutus.

<i>Zuul</i> Genus of armored ankylosaurine dinosaurs

Zuul is a genus of herbivorous ankylosaurine dinosaur from the Campanian Judith River Formation of Montana. The type species is Zuul crurivastator. It is known from a complete skull and tail, which represents the first ankylosaurin known from a complete skull and tail club, as well as the most complete ankylosaurid specimen thus far recovered from North America. The specimen also preserved in situ osteoderms, keratin, and skin remains.

<i>Edmontonia</i> Extinct genus of dinosaurs

Edmontonia is a genus of panoplosaurin nodosaurid dinosaur from the Late Cretaceous Period. It is part of the Nodosauridae, a family within Ankylosauria. It is named after the Edmonton Formation, the unit of rock where it was found.

<i>Montanoceratops</i> Extinct genus of dinosaurs

Montanoceratops is an extinct genus of small ceratopsian dinosaur that lived approximately 70 million years ago during the latter part of the Cretaceous Period in what is now Montana and Alberta. Montanoceratops was a small sized, moderately-built, ground-dwelling, quadrupedal herbivore, that could grow up to an estimated 2.5 m (8.2 ft) in length and 170 kg (370 lb) in body mass.

<span class="mw-page-title-main">Ankylosauridae</span> Extinct family of dinosaurs

Ankylosauridae is a family of armored dinosaurs within Ankylosauria, and is the sister group to Nodosauridae. The oldest known Ankylosaurids date to around 122 million years ago and went extinct 66 million years ago during the Cretaceous–Paleogene extinction event. These animals were mainly herbivorous and were obligate quadrupeds, with leaf-shaped teeth and robust, scute-covered bodies. Ankylosaurids possess a distinctly domed and short snout, wedge-shaped osteoderms on their skull, scutes along their torso, and a tail club.

<i>Aletopelta</i> Extinct genus of dinosaurs

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<i>Dyoplosaurus</i> Extinct genus of dinosaurs

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<i>Scolosaurus</i> Extinct genus of dinosaurs

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<i>Panoplosaurus</i> Extinct genus of dinosaurs

Panoplosaurus is a genus of armoured dinosaur from the Late Cretaceous of Alberta, Canada. Few specimens of the genus are known, all from the middle Campanian of the Dinosaur Park Formation, roughly 76 to 75 million years ago. It was first discovered in 1917, and named in 1919 by Lawrence Lambe, named for its extensive armour, meaning "well-armoured lizard". Panoplosaurus has at times been considered the proper name for material otherwise referred to as Edmontonia, complicating its phylogenetic and ecological interpretations, at one point being considered to have existed across Alberta, New Mexico and Texas, with specimens in institutions from Canada and the United States. The skull and skeleton of Panoplosaurus are similar to its relatives, but have a few significant differences, such as the lumpy form of the skull osteoderms, a completely fused shoulder blade, and regularly shaped plates on its neck and body lacking prominent spines. It was a quadrupedal animal, roughly 5 m (16 ft) long and 1,600 kg (3,500 lb) in weight. The skull has a short snout, with a very domed surface, and bony plates directly covering the cheek. The neck had circular groups of plates arranged around the top surface, both the forelimb and hindlimb were about the same length, and the hand may have only included three fingers. Almost the entire surface of the body was covered in plates, osteoderms and scutes of varying sizes, ranging from large elements along the skull and neck, to smaller, round bones underneath the chin and body, to small ossicles that filled in the spaces between other, larger osteoderms.

<i>Tarchia</i> Extinct genus of dinosaurs

Tarchia is a genus of herbivorous ankylosaurid dinosaur from the late Cretaceous of Mongolia.

<i>Nodocephalosaurus</i> Extinct genus of dinosaurs

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<span class="mw-page-title-main">Horseshoe Canyon Formation</span> Geological formation in Canada

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<i>Oohkotokia</i> Extinct genus of dinosaurs

Oohkotokia is a genus of ankylosaurid dinosaur within the subfamily Ankylosaurinae. It is known from the upper levels of the Two Medicine Formation of Montana, United States. The discovery of Oohkotokia supports that Ankylosaurine dinosaurs existed and flourished continuously in Montana and/or Alberta throughout the late Campanian and early Maastrichtian stages in the Late Cretaceous period. It was a large, heavily built, quadrupedal, herbivore, that could grow up to 5 metres (16 ft) long and weigh up to 2 metric tons.

<i>Ziapelta</i> Genus of ankylosaurid dinosaur from the Late Cretaceous period

Ziapelta is an extinct genus of ankylosaurid. Its fossils have been found in the Hunter Wash and De-na-zin members of the Kirtland Formation of Upper Cretaceous (Campanian) New Mexico. It was named in 2014, in a research paper led by ankylosaur researcher Victoria Arbour. There is a single species in the genus, Ziapelta sanjuanensis. The genus is named after the Zia sun symbol, a stylized sun with four groups of rays, having religious significance to the Zia people of New Mexico, and the iconic symbol on the state flag of New Mexico, and pelta (Latin), a small shield, in reference to the osteoderms found on all ankylosaurids. The specific name is in reference to San Juan County and the San Juan basin, where the fossils were found. Multiple specimens have been described to date, though the fossils are mostly from the front part of the animal. Its closest relative appears to be either Scolosaurus or Nodocephalosaurus, depending on what cladistic model is used.

<span class="mw-page-title-main">Timeline of ankylosaur research</span>

This timeline of ankylosaur research is a chronological listing of events in the history of paleontology focused on the ankylosaurs, quadrupedal herbivorous dinosaurs who were protected by a covering bony plates and spikes and sometimes by a clubbed tail. Although formally trained scientists did not begin documenting ankylosaur fossils until the early 19th century, Native Americans had a long history of contact with these remains, which were generally interpreted through a mythological lens. The Delaware people have stories about smoking the bones of ancient monsters in a magic ritual to have wishes granted and ankylosaur fossils are among the local fossils that may have been used like this. The Native Americans of the modern southwestern United States tell stories about an armored monster named Yeitso that may have been influenced by local ankylosaur fossils. Likewise, ankylosaur remains are among the dinosaur bones found along the Red Deer River of Alberta, Canada where the Piegan people believe that the Grandfather of the Buffalo once lived.

<i>Platypelta</i> Extinct genus of dinosaurs

Platypelta is an extinct genus of herbivorous ankylosaurid dinosaurs within the subfamily Ankylosaurinae. It is known from the Late Cretaceous Dinosaur Park Formation of southern Alberta, Canada. The type species is Platypelta coombsi.

References

  1. 1 2 3 4 5 Penkalski, P. (2013). "A new ankylosaurid from the late Cretaceous Two Medicine Formation of Montana, USA". Acta Palaeontologica Polonica. doi: 10.4202/app.2012.0125 .
  2. 1 2 Arbour, Victoria (2010). "A Cretaceous armoury: Multiple ankylosaurid taxa in the Late Cretaceous of Alberta, Canada and Montana, USA". Journal of Vertebrate Paleontology. 30 (Supplement 2): 55A. doi:10.1080/02724634.2010.10411819. S2CID   220429286.
  3. 1 2 Paul Penkalski (2018). Revised systematics of the armoured dinosaur Euoplocephalus and its allies. Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen 287(3): 261-306. doi: https://doi.org/10.1127/njgpa/2018/0717
  4. 1 2 3 C. M. Sternberg (1929) "A toothless armoured dinosaur from the Upper Cretaceous of Alberta." Canada Department of Mines Geological Survey Bulletin (Geological Series) 54(49):28-33
  5. 1 2 Arbour, V. M.; Burns, M. E.; Sissons, R. L. (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. Bibcode:2009JVPal..29.1117A. doi:10.1671/039.029.0405. S2CID   85665879.
  6. 1 2 Vickaryous, M.K. and Russell, A.P., 2003, "A redescription of the skull of Euoplocephalus tutus (Archosauria: Ornithischia): a foundation for comparative and systematic studies of ankylosaurian dinosaurs", Zoological Journal of the Linnean Society137: 157–186
  7. 1 2 Coombs, W.P., Jr. (1986, June). A Juvenile Ankylosaur Referable to the Genus Euoplocephalus (Reptilia, Ornithischia). Journal of Vertebrate Paleontology, 6(2), 162-173.
  8. Paul, Gregory S. (2016). The Princeton Field Guide to Dinosaurs. Princeton University Press. p. 264. ISBN   978-1-78684-190-2. OCLC   985402380.
  9. Arbour, V.M.; Mallon, J.C. (2017). "Unusual cranial and postcranial anatomy in the archetypal ankylosaur Ankylosaurus magniventris". FACETS. 2 (2): 764–794. doi: 10.1139/facets-2017-0063 .
  10. Coombs W. (1971) The Ankylosauridae. Ph.D. thesis, Columbia University, New York, NY, 487 p.
  11. Penkalski, P.; Blows, W. T. (2013). "Scolosaurus cutleri (Ornithischia: Ankylosauria) from the Upper Cretaceous Dinosaur Park Formation of Alberta, Canada". Canadian Journal of Earth Sciences. 50 (2): 171–182. Bibcode:2013CaJES..50..171P. doi:10.1139/cjes-2012-0098.
  12. Arbour VM, Currie PJ (2013) Euoplocephalus tutus and the Diversity of Ankylosaurid Dinosaurs in the Late Cretaceous of Alberta, Canada, and Montana, USA. PLoS ONE 8(5): e62421. https://doi.org/10.1371/journal.pone.0062421
  13. Arbour, V. M.; Currie, P. J. (2015). "Systematics, phylogeny and palaeobiogeography of the ankylosaurid dinosaurs". Journal of Systematic Palaeontology. 14 (5): 1–60. Bibcode:2016JSPal..14..385A. doi:10.1080/14772019.2015.1059985. S2CID   214625754.