Anodontosaurus was an armored dinosaur in the ankylosaurid family that lived in what is now Western Canada, between 74 and 67 million years ago. From snout to tail it measured about 20 feet long, and would have eaten plants when alive. The genus name translates to "Toothless Lizard/Reptile" because it was originally thought to have been toothless. (but it wasn't). There are two named species within the genus. The first discovered of the two was Anodontosaurus lambei, which lived later, while earlier-living species by a few million years was named Anodontosaurus inceptus.
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| My life reconstruction of Anodontosaurus lambei in watercolors. |
Anodontosaurus, like most ankylosaurids was covered on the top side of its body with bony armor, called osteoderms. These chunks of bone grew out from the skin, and many were keeled, and slightly triangular in shape. Over its hips it possessed a sacral shield, a sheet of bone studded with osteoderms, growing over its hips. Its skull was adorned with short broad horns above the eyes and lining the back of the head, as well as longer, broader horns growing out from under its eyes. It had a wide beak at the front of the mouth and its jaws were lined with small teeth ideal for processing plants. At the time of its discovery, however, because the skull as crushed in such a way after the animal's death, causing the teeth to fall out, scientists initially believed it was toothless in life.
After its initial discovery and naming Anodontosaurus was later lumped into the genus with another ankylosaurid relative, Euoplocephalus, thus losing its genus name. However, in 2010, it was re-examined more closely and once again deemed different enough for its own genus, in a study led by paleontologist, Victoria Arbour. The main reasons why the genus was split was because Anodontosaurus' horn arrangement, neck armor, and tail club were different from those of Euoplocephalus, and a few other ankylosaurids, which were also given their own genus from the study. Anodontosaurus' tail club was unique in that it was elongated and pointed on either end, while Eouplocephalus' club is a smoother oval shape.
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| Cast of Anodontosaurus tail club on display at the American Museum of Natural History in New York. |
Like all ankylosaurids, Anodontosaurus would have relied on its armor and tail club, which could be swung from side to side very powerfully, for defense against predators, like tyrannosaurids. It is also very possible that ankylosaurids engaged in combat within the species, possibly smashing each other with their clubs, as well. Anodontosaurus' tail club looks particularly wicked, since it comes to a point on either side, concentrating all the force onto a smaller surface when swung. I'd imagine getting hit by Anodontosaurus would be more like being pummeled with a hammer than a club. Ouch.
References
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.
Arbour, V. M.; Currie, P. J. (2015). "Systematics, phylogeny and palaeobiogeography of the ankylosaurid dinosaurs". Journal of Systematic Palaeontology. 14 (5): 1–60.
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
Coombs, W.P., Jr. (1986, June). A Juvenile ankylosaur referable to the genus euoplocephalus (reptilia, ornithischia). Journal of Vertebrate Paleontology, 6(2), 162-173.
Penkalski, P. (2013). "A new ankylosaurid from the late Cretaceous Two Medicine Formation of Montana, USA". Acta Palaeontologica Polonica.
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