Aftoktoniasaurus
Taxonomic Classification
Domain: Eukarya
Kingdom: Animalia
Phylum: Chordata
Class: Sauropsida
Clade: Dinosauria
Order: Saurischia
Suborder: Theropoda
Family: †Carcharodontosauridae
Subfamily: †Aftoktoniasaurinae
Genus: †Afoktoniasaurus (Morrison et al, 2007)
Species: †Aftoktoniasaurus morrisunis (Morrison et al, 2007)
Synonyms: †Ceratosaurus maximus? (Dalman, 2012)
Basic Information
Height: 4.2 meters
Length: 12.8 meters
Weight: 7.5 tons
Temporal Range: Mid-Jurassic - Early Cretaceous (169.5 MYA - 100.5 MYA)
Region: North America (Oklahoma, United States)
Formation: Morrison Formation
Diet: Carnivore
Prey: Sauropoda, Stegosauria, Allosaurinae
Predators: None
Discovery
Aftoktoniasaurus morrisunis (quad modo (q.m) “Suicide Lizard of Morrison”) is an extinct species of large carnivorous theropod from Jurassic-Cretaceous Oklahoma. It was found in 2002 but was only considered a valid species in 2007. It is identifiable by the large horn on its muzzle.
While in the Dead Zone of the Oklahoman panhandle, Morrison and his group searched for Allosaurus fossils to further research for the Morrison Museum of Natural History. Morrison eventually found a fragment of a maxilla, which he classified as an Allosaurus fragilis. However, when he dug deeper into the Earth, he found a nearly preserved theropod skull, aside from small dents and cracks. At first, Morrison thought it was a specimen of Allosaurus jimmadseni, but it had a horn. Not a horn-like Ceratosaurus or the now-inaccurate reconstruction of Ornitholestes, but a full, five-foot-long, forward-facing, separated horn. It puzzled him until he concluded that it was the thagomizer spike of a Stegosaurid, likely Stegosaurus. Morrison’s claim was challenged when one of the paleontologists on the team, Matthew Sachar, pointed out that the horn was flat, and showed no signs of forced entry. Morrison then came up with the idea that this dinosaur had a horn used to hunt. As he and his team dug around the skull, they eventually struck gold. 12 meters away, Morrison found a small clutch of tail vertebrae. He used the tail vertebrae and skull size, ratioed them to other theropods that shared similarities, and found the animal was likely around 12-14 meters long. This claim was backed up by the discovery of another specimen only 58 meters away. It was a nearly complete specimen.
This specimen showed large claws, and two, barbed canines, and the skull had a thick layer of hardened osteoderms, coined as the “Boss”. Morrison reexamined the specimen’s head he found, and the remnants of the osteoderms were there; the same species. The cervical vertebrae showed points for thick muscles, meaning two things, the reptile had thick neck fat and a powerful neck. It had curved brows, similar to that of the Albertosaurus sarcophagus. Morrison released a press report detailing the discoveries, which was where he first coined the term “The Suicide Lizard of Morrison”, which, after many misconceptions, he clarified as being named after the Morrison Formation, not the discoverer.
In 2012, Brandon Dalman found a nasal of a theropod skull, which showed signs of a horn. Dalman immediately thought it was a Ceratosaurus, and its ratio compared to other specimens made him publish his findings as Ceratosaurus maximus. Other paleontologists, such as Matthew Sachar and Steven Janiski pointed out Dalman’s errors, correctly classifying the specimen as a male Aftoktoniasaurus.
Paleobiology
Aftoktoniasaurus morrisunis was a large species of apex predator in its home. While it was found in Oklahoma, other specimens showed it went as far southwest as Arizona and New Mexico. Its most famous feature, the horn, measured a heavy 5 feet. It’s likely the horn caused the adaptation of a stronger neck to support its large horn. Additionally, some specimens have been found with no horn. While some associated this with a new subspecies or even a new species, it’s now thought that this was likely sexual dimorphism, with males being horned. It had a deep skull, similar to that of Teratophoneus curriei and Tyrannosaurus rex, which meant it could deliver powerful bites, reinforced by their thick neck. The ribcage is smooth and elongated, which suggests a speed-based build, similar to that of Giganotosaurus carolinii or Carcharodontosaurus saharicus, which resulted in its classification under Carcharodontosauridae.
Male specimens measured at an average of 4.2 meters tall, and 12.8 meters long, with females being slightly smaller, at 4.1 meters tall and 11.3 meters long. Thanks to their build, weights have been estimated around 7.5 tons for males, and 5.6 tons for females. A unique feature in the arms showed a thumb. Or, at least, a way smaller finger off the side of the index finger, which had a larger claw than the rest of the fingers. The initial thought was that Aftoktoniasaurus was partially piscivorous, but the claw was shaped to slice, not impale. Its arms were long and robust, comparable to that of Spinosaurinae. Its muzzle was shaped oddly, with the maxilla rising in the middle slightly, and the premaxilla being at this height. This proved the animal was a mix of a wrestler and a chaser. This helped identify its prey. One specimen of Allosaurus jimmadseni showed bite marks in the ribs, and a large tooth stuck in the neck, which matched the upscaled barbed canine found in Aftoktoniasaurus. It also was shown to directly live in packs, with a fossil site showing a specimen of Diplodocus carnegii being killed by 4 specimens of male Aftoktoniasaurus.
Due to its similarity to Allosaurus and Carcharodontosaurus, it was seen as the missing link. Allosaurus and any genera under Allosauridea were put under Allosaurinae, which was classed under Carcharodontosauridae, along with Carcharodontosaurinae, Aftoktoniasaurinae, and Concavenatinae, the latter containing genera such as Concavenator and Altispinax.
Trivia
