Named By: Altangerel Perle, Mark A. Norell & Jim Clark - 1999.
Classification: Chordata, Reptilia, Dinosauria, Saurischia, Theropoda, Dromaeosauridae, Eudromaeosauria, Dromaeosaurinae.
Species: A. giganticus (type).
Size: Estimated 6 meters long.
Known locations: Mongolia, Dornogovi Province - Bayan Shireh Formation.
Time period: Turonian to Campanian of the Cretaceous, although further study of the formation that Achillobator came from suggests it may actually date between the Santonian and Cenomanian of the Cretaceous.
Fossil representation: Partial remains including vertebrae, hindlimbs, forelimbs, shoulder, ribs, as well as an upper jaw fragment of the premaxilla with teeth.
discovered in a joint Mongolian and Russian dig in 1989,
Achillobator did not get named until 1999.
These remains are very
fragmentary but do suggest that Achillobator was a
dromaeosaurid dinosaur. The achilles tendons seem to have been
particularly well developed, probably to account for the extra size
and weight of the body, and were referenced in the naming of the
Achillobator has in the past been accused of being a fossil chimera, which in the simplest terms means that the fossil material attributed to the genus actually represents more than one kind of dinosaur. The main support for this theory is that the pubis (most forward bone of the hips) points vertically down. In all other known dromaeosaurids the pubis points backwards similar to birds, something that often leads to the pubis pointing in the same direction as the ischium (the bone at the rear of the hips). Despite this claim however some of the skeletal remains of Achillobator were found partially articulated, and the other bones all show dromaeosaurid characteristics. General opinion today points to Achillobator being a dromaeosaurid, but one with a unique hip structure.
Additional study of Achillobator has yielded the conclusion that it was most closely related to the dromaeosaurids Dromaeosaurus and Utahraptor, the latter being a particularly large dromaeosaurid.