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Anodontosaurus

Sternberg, 1929 an-o-DONT-o-SOR-us

From Ancient Greek 'an' meaning 'without', 'odon' meaning 'tooth', and 'sauros' meaning 'lizard', meaning 'toothless lizard', inspired by compression damage to the specimen that removed the teeth and misled the describer into assuming large trituration plates had replaced the normal dentition.

83.6–66.0 million years ago Campanian–Maastrichtian, Late Cretaceous
Late Cretaceous stages

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.

Diagnosis

  1. Skull very much depressed; completely covered with moderate-sized, irregular dermal ossifications
  2. Teeth entirely absent; broad flat bony plates developed on maxillae and dentaries for masticating food
  3. Mandible greatly reduced and without coronoid process
  4. External nares transversely elongate and terminally placed, facing almost directly forward
  5. Pterygoids small and meeting on midline; palatines not fused on midline and not uniting with pterygoids
  6. Dermal scutes uniformly thin and concave inferiorly, even in long high-keeled forms

Species (2)

Anodontosaurus lambei Sternberg, 1929

Type species

Named for Lawrence Morris Lambe, the Canadian geologist and paleontologist from the Geological Survey of Canada where the holotype was reposited.

Holotype
CMN 8530 , Canadian Museum of Nature
Material
Skull, left mandibular ramus, one caudal vertebra with co-ossified chevron, one phalanx, and many dermal scutes.
Horizon
upper Horsethief Member, Horseshoe Canyon Formation, Campanian–Maastrichtian, Late Cretaceous , 83.6–66.0 million years ago
Locality
8 miles southwest of Morrin, along the Red Deer River, Alberta, Canada

Anodontosaurus inceptus Penkalski, 2018

Latin inceptus, beginning or incipient, reflecting its early/transitional stratigraphic position

Holotype
TMP 1997.132.0001 , Royal Tyrrell Museum of Paleontology
Material
Skull with teeth, mandible, a partially prepared skeleton, both cervical half-rings, and osteoderms
Horizon
middle Dinosaur Park Formation, Campanian, Late Cretaceous , 83.6–72.2 million years ago
Locality
Near Hilda, Alberta, Canada
Diagnosis
  1. Broader-based squamosal horns
  2. Fan-shaped nasal plate (bell-shaped in A. lambei)
  3. Lacks the four symmetric postnasal scales present in A. lambei
  4. More prominent coronoid process
  5. Possibly triangular manual unguals
  6. Relatively flat, subcircular medial osteoderms on the first cervical half-ring with a low caudal prominence, and complex pyramidal lateral osteoderms on the same half-ring

References

  1. Sternberg, C. M. (1929). A toothless armoured dinosaur from the Upper Cretaceous of Alberta. Annual Report of the National Museum of Canada. Natural Resources Canada/CMSS/Information Management. doi:10.4095/306008 sternberg1929a
  2. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Ornithischians. Princeton University Press.

    Source of the hip height estimate, and the appearance features.

    jones2026a
  3. Penkalski, P. (2018). Revised systematics of the armoured dinosaur Euoplocephalus and its allies. Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen 287(3): 261-306. Schweizerbart. doi:10.1127/njgpa/2018/0717 penkalski2018a