Achillobator

Live reconstruction of Achillobator giganticus

• Mongolia, Gobi Aimag Dorno ( Bayan- Shireh Formation)

• Achillobator giganticus

Achillobator was a genus of carnivorous dinosaur from the group of Dromaeosauridae. The only way is Achillobator giganticus.

So far, a fragmentary skeleton is known, which dates from the Upper Cretaceous of Mongolia. With a length of about five meters Achillobator owned by the American Utahraptor the biggest representatives of Dromaeosauridae.

Features

Achillobator is estimated to have a length of less than 5 meters and a weight of about 350 kg. The large upper jaw ( maxilla ) indicates a relatively large head, similar in size was proportional to that of the Carnosauria. On each side of the upper jaw were 11 teeth, the total number of teeth is unknown. Both the front and the rear edge of the cutting teeth were cut, the denticles ( teeth ) were, however, as with other Dromaeosauriden on the rear cutting edge is greater than at the front.

The hind legs were relatively short and stocky. In contrast to all other Dromaeosauriden the thigh bone ( femur) was longer than the shinbone ( tibia). The arms were long. As with most other Dromaeosauriden the caudal vertebrae were connected by long, rod- like spinous processes, prolonged post and prezygapophyses and chevron bones. The second toe of the foot shows the typical for Dromaeosauriden, curved and greatly enlarged sickle claw. From other Dromaeosauriden Achillobator to be distinguished by some primitive features in the construction of the pool: So the pubic bone ( pubis ) was proportionally shorter and not birdlike backwards oriented as in other Dromaeosauriden, but pointed towards the abdomen down. In addition, the enlarged lower end of the pubic bone was ( Pubic boot) very large.

Systematics and chimera hypothesis

Achillobator was related probably closest with Utahraptor and Dromaeosaurus. Together these genera form the Dromaeosaurinae, a subgroup of the Dromaeosauridae.

Burnham and colleagues ( 2000) suggest that it could be found in the skeleton of a chimera, which means that the bones belonged to more than one kind. These researchers argue that the upper jaw, the ischium, the pubic bone and the caudal vertebrae do not share any common features with other Dromaeosauriden and thus likely to originate from a different animal. The Fußkrallen found, however, would actually belong to a Dromaeosauriden, the researchers said. Norell and Makovicky (2004) argue that the bones were found partially associated, indicating that they belonged to the same individual. Nevertheless, these researchers noted that especially the vertically oriented pubis and its strongly widened lower end are very atypical for Dromaeosauriden.

Fund, history of discovery and naming

The only known skeleton was discovered in 1989 by Namsarai, an assistant paleontologist of the Mongolian Natural History Museum, during a Russian -Mongolian expedition. The site, which Burkhant -locality, located 28.8 km south west of the village Dzun Bayan in the Mongolian Gobi Aimag Dorno. The Burkhant -locality is only 100 m2 with a small reference; Achillobator the skeleton is so far the only Fund. The sedimentary rocks that hid the skeleton belong stratigraphically to Bayan- Shireh lineup. For other references to this formation remains of Hadrosauriden, ankylosauruses, sauropods and crocodiles have been found. The sediments are from the Upper Cretaceous and are probably 89-84 million years old ( Conicium to Santonian ). This age is, however, uncertain.

The skeleton ( holotype, specimen number FR.MNUFR -15) was found articulated; However, the bones were no longer in the anatomical network. The find includes a left upper jaw bone ( maxilla ), nine teeth, some cervical, dorsal and caudal vertebrae, three V-shaped chevron bones, rib fragments, some isolated hand and foot bones, the right ilium, pubis and ischium, the left femur and tibia as well as the left metatarsal 3 and 4

Achillobator giganticus was described in 1999 by Altangerel pearl, Mark Norell and James Clark in a Mongol Journal for the first time scientifically. However, the description is based on a preliminary manuscript and was published without the knowledge of Clark and Norell. The name Achillobator giganticus means " gigantic Achilles Hero " and consists of " Achilles ", a hero of Greek mythology, and " bator ", which means as much as hero together. The name suggests a suspected very strong tendon that was sitting on the second toe and allowed powerful movements of the sickle claw.