Anodontosaurus

AnodontosaurusNo Tooth Lizard
Classification
Domain	Eukaryota
Kingdom	Animalia
Phylum	Chordata
Subphylum	Vertebrata
Superclass	Tetrapoda
Clade	Sauropsida
Class	Reptilia
Clade	Archosauria Avemetatarsalia Ornithodira Dinosauria Ornithischia Thyreophora Ankylosauria Euankylosauria
Family	Ankylosauridae
Subfamily	Ankylosaurinae
Tribe	Ankylosaurini
Species	Anodontosaurus lambei
Presence
Location	Horseshoe Canyon Formation, Alberta, Canada
Temporal Range	73 - 67 million years ago, Campanian - Maastrichtian Stage, Late Cretaceous Period
Episodes	Forests (Segment 5) How Did Ankylosaurs Use Their Tail? (Cameo, Fossil and Diagram only)
Characteristics
Length	4 - 5 meters (13 - 16 feet)
Mass	2 metric tons (2.2 short tons)
Diet	Herbivorous
Tail Club Mass of around 17 - 20 kilograms (37.5 - 44.1 pounds) Tail Club Strike Impact Force of around 7,281 - 14,360 newtons or 742 - 1,464 kilograms (1,636 - 3,228 pounds) Tail Club Strike Impact Stress of around 36,400 – 71,810 newtons (3,712 - 7,323 kilograms) per square centimeter (52,800 - 104,152 pounds per square inch), or 364 - 718 megapascals Has a uniquely-shaped tail club that is wide and pointed on both sides

Anodontosaurus (No Tooth Lizard, a misconception made due to compression damage removing the holotype's teeth, making it appear toothless), simply referred to as "a two-tonne ankylosaur" on the show, is a genus of ankylosaurid dinosaur that lived in the Horseshoe Canyon Formation in southwestern Alberta, Canada, 73 - 67 million years ago, during the Maastrichtian stage of the Late Cretaceous Period. The species depicted on Prehistoric Planet is Anodontosaurus lambei, the type species, given how the other species, Anodontosaurus inceptus, lived at least 1 - 4 million years prior in the Dinosaur Park Formation, which underlies the Bearpaw Formation (which is, in turn, buried under the Horseshoe Canyon Formation).

Paleobiology

Size, Physique, and Armor

As an ankylosaurid, Anodontosaurus is a large, heavily-armored animal, around 4 - 5 meters (13 - 16 feet) in length and 2 metric tons (2.2 short tons) in mass. Its tail club is unique in shape compared to those of other ankylosaurids, being wide and pointed on both sides. As with most ankylosaurs, this tail club likely served as an excellent weapon in intraspecific combat and self-defense against predators. Several clubs found in the Horseshoe Canyon Formation (all of which are now believed to be those of Anodontosaurus) appear to be worn down and more rounded, likely due to constant usage.

In 2009, a study about the impact forces of ankylosaur tail clubs was published. The species involved in the paper include Anodontosaurus lambei (with one of the specimens used in the study, AMNH 5245, considered to be a Euoplocephalus by that time) and Dyoplosaurus acutosquameus, a smaller ankylosaur measuring around 4 - 4.5 meters (13 - 15 feet) in length and 1.2 metric tons (1.32 short tons) in mass. Composites of their tail clubs are estimated to weigh around 17 - 20 kilograms (37.5 - 44.1 pounds). Given this mass, the average ankylosaurid club is capable of delivering a bone-shattering impact force of 7,281 - 14,360 newtons or 742 - 1,464 kilograms (1,636 - 3,228 pounds), and an impact stress of 36,400 – 71,810 newtons (3,712 - 7,323 kilograms) per square centimeter (52,800 - 104,152 pounds per square inch), or 364 - 718 megapascals. Larger specimens with bigger clubs can likely strike with a force that exceeds the calculated results of the study. Even so, the paper clarifies that these tail clubs would not have been hard for the ankylosaurids to wield. The knobs that compose a tail club are predominantly cancellous (spongy and porous bone), and, while the tails have limited vertical flexibility, they can be swung approximately 100 degrees horizontally. This is demonstrated in the fourth segment of Badlands, where the Tarchia have to put slightly more effort in brandishing their tail clubs up and down, but need less windup when swinging their tails from side to side, during which their weapons can be moved with a wider range of freedom.

Prehistoric Planet's Portrayal

Prehistoric Planet depicts Anodontosaurus with an emerald-colored body and a creamy yellow underside. It is also portrayed with black, shiny nictitating membranes, perhaps to help protect the eyes from the heat of the forest fires that constantly occur in the area. It shares this trait with the show's depiction of the abelisaurid Rajasaurus, which lived in the hostile volcanic environment of the Lameta Formation in India.

Paleoecology

Paleoenvironment

Main: Horseshoe Canyon Formation

Main: Horseshoe Canyon Formation

“ In the forests of North America, there is an additional annual hazard for forest-dwellers. Fire, started by a strike of lightning. As it spreads, temperatures rise to over 2000 degrees Fahrenheit. The flames rise several hundred feet into the air. ”

― David Attenborough, Forests

Anodontosaurus lived 73 - 67 million years ago in the Horseshoe Canyon Formation in southern Alberta, Canada, which by that time was an area of floodplains and estuaries. Coal swamps in the region indicated that riparian (waterside) forests thrived in such environments, though, as the show depicts, these places were vulnerable to the threat of fires started by factors like dry seasons or thunderstorms. Even so, in the aftermath of such disasters, several plants and animals can take advantage of the scorched land and what remains within.

Paleofauna

Anodontosaurus coexisted with several animals in the Horseshoe Canyon Formation. Smaller fauna include the caegnathid oviraptorosaurs Apatoraptor and Epichirostenotes, the mononykin alvarezsaurid Albertonykus, three ornithomimids including Ornithomimus edmontonicus, the pachycephalosaur Sphaerotholus, and the thescelosaurid Parksosaurus. Larger animals include the saurolophines Edmontosaurus regalis and Saurolophus osborni, the lambeosaurine Hypacrosaurus, and at least five ceratopsians including Pachyrhinosaurus canadensis (the type species, larger than the Alaskan Pachyrhinosaurus perotorum). The Horseshoe Canyon Formation is also home to mammals like Didelphodon, the crocodile-like choristodere Champsosaurus, actual crocodilians, the plesiosaur Leurospondylus, fish, and turtles.

Ankylosaurs are believed to have evolved their armor because they are too large to run or hide (hence why some, like the Early Cretaceous nodosaurid Borealopelta, had countershaded skin for camouflage), yet too small to deter predators the same way sauropods do. Given its size and formidable, pointed tail club, an adult Anodontosaurus would have likely never been bothered by small predators like the troodontid Albertavenator and the saurornitholestine dromaeosaur Atrociraptor. Albertosaurus, the largest predator in the Horseshoe Canyon Formation, would have also likely avoided Anodontosaurus (though not at all times), since albertosaurines, being lighter and sleeker than their tyrannosaurine cousins, were believed to better adapted to chasing fleet-footed, less-armored prey like hadrosaurs.

Only one other ankylosaur, the nodosaurid Edmontonia, lived alongside Anodontosaurus. Both animals likely avoided competition with each other via niche partitioning. Another ankylosaurid, Euoplocephalus, was once thought to have lived in the formation, since Anodontosaurus was considered to be a junior synonym of it in the past. However, subsequent studies since then have determined that Anodontosaurus is distinct from Euoplocephalus, and all Euoplocephalus fossils found in the Horseshoe Canyon Formation are therefore suggested to be Anodontosaurus fossils instead.

Social Behavior

Generally, adult ankylosaurs are found alone, supporting the idea that they are solitary animals, just like Prehistoric Planet's portrayal of Anodontosaurus. But some bonebeds suggest that some ankylosaurs lived gregariously at some point in their lives, with several Pinacosaurus mass-burial sites indicating that they were more likely to group up as juveniles. However, such mass death assemblages may also be caused by other factors, like natural disasters (e.g. floods) forcing animals together, consequently killing or depositing them in the same place. Furthermore, when fully grown, ankylosaurs were capable of fending for themselves alone. Hence, a two-tonne Anodontosaurus would not have received any significant aid from companionship in events like the forest fires of the Horseshoe Canyon Formation, and traveling alone has the benefit of allowing it to take advantage of resources (especially in the wake of a forest fire) without having to share with potential competitors, in contrast with the pair of juvenile Tarchia in the fourth segment of Badlands, which were portrayed competing over a single patch of dry vegetation.

Feeding Preferences and Adaptations

“ A two-tonne ankylosaur. It also finds something worth eating after a fire. Charcoal. It will bind with many of the plant toxins in its stomach, and neutralize them. ”

― David Attenborough, Forests

In its brief appearance, Anodontosaurus is shown to be a solitary animal. It also appears to be one of the first animals to return to the forest just hours after it burned, perhaps feeling more secure due to its armored hide and fearsome weaponry. Much like the Triceratops which appeared earlier in the same episode, Anodontosaurus seems to be smart enough to recognize the poison-neutralizing properties of some substances, except rather than feed on certain mineral-infused clay to bind away many of the toxic plants within its stomach, Anodontosaurus instead consumes charcoal, which has similarly-helpful protective effects. This may be based on the cololite (gastrointestinal cast) of the Early Cretaceous Canadian nodosaurid Borealopelta, 6% of which is comprised of fusinite (fossilized charcoal), relatively more significant compared to non-burnt wood, which only made up 4% of its preserved stomach contents. It is unknown if Borealopelta ingested these large amounts of charcoal accidentally or intentionally, but it nevertheless indicates that, much like the show's depiction of Anodontosaurus, Borealopelta also fed on plants (both normal and burnt) soon after a forest fire.

Appearances

Forests

In the fifth segment of the episode, in the ruins of a forest ravaged by fire just hours before, animals begin to return. Beetles arrive to lay their eggs (for their larvae would feast on the near-limitless supply of dead wood). An Atrociraptor, taking advantage of the situation, feeds on one of the beetles, and picks up a smoking twig to rid itself of parasites. Sensing a large animal coming close, the Atrociraptor flees the scene as a two-tonne Anodontosaurus arrives to feed on a newly-burned tree stump to help aid digestion by purifying its stomach, the toxins of the many plants it ate neutralized by the charcoal it consumes.

Uncovered: How Did Ankylosaurs Use Their Tail?

	How Did Ankylosaurs Use Their Tail?
	Subject The anatomical features, strength, and purpose of ankylosaur tails as weapons for various combat-related purposes. Experts Dr. Susannah Maidment, Professor Paul Barrett, Dr. Darren Naish

How Did Ankylosaurs Use Their Tail?

Subject
The anatomical features, strength, and purpose of ankylosaur tails as weapons for various combat-related purposes.

Experts
Dr. Susannah Maidment, Professor Paul Barrett, Dr. Darren Naish

“ When they were first discovered, they were interpreted as a weapon of some kind. This one belonged to a kind of ankylosaur known as 'Anodontosaur'. But what makes us think that this was ever wielded like a club? Comparing ankylosaurs with animals alive today suggests that it was. ”

― David Attenborough, How Did Ankylosaurs Use Their Tail?

During this Uncovered segment, which was dedicated to discussing the purpose of ankylosaur tail clubs, six examples (including repetitions of the same club) were shown in a diagram. The ones on the upper left and upper right belong to indeterminate species. The club in the top center is a top view of a club that belongs to Anodontosaurus specimen AMNH 5245, the club in the actual center is a frontal view of that same club, the club in the lower left belongs to Anodontosaurus specimen AMNH 5216, and the club in the lower right is that of Anodontosaurus specimen USNM 10753. In the following scene, a fossil replica of an Anodontosaurus club is shown, with it being suggested that, when compared to modern-day animals, these clubs were likely wielded as weapons.

Gallery

Anodontosaurus concept art by Jama Jurabaev

Top view of the tail club of Anodontosaurus specimen AMNH 5245

Sir David Attenborough introducing an Anodontosaurus tail club

Trivia

• Anodontosaurus is the third animal featured on Prehistoric Planet that was named outside of the actual show. It was only referred to as "a two-tonne ankylosaur" in its sole appearance in the fifth segment of Forests.
  • It was predeced by Dromaeosaurus and Cimolodon, and followed by Prognathodon and Pachycephalosaurus.
  • While it was named as the owner of a tail club fossil shown in the Uncovered segment "How Did Ankylosaurs Use Their Tail?", this does not count, as the naming is associated with the tail club fossil rather than its depiction on Prehistoric Planet, and the animal's identity was already revealed by Dr. Darren Naish, Prehistoric Planet's lead consultant, prior to the second season of the series.

References

General

Dr. Darren Naish

Prehistoric Planet