Achillobator: Research Database
Dromaeosauridae (Theropoda) · Late Cretaceous (~96–89 MYA) · Asia — Mongolia (Bayan Shire Formation)
Research Note: Achillobator was a large dromaeosaurid theropod from the Late Cretaceous of Mongolia. As one of the larger known dromaeosaurids, it provides important data on theropod diversity and ecology in Latest Cretaceous Asia.
| Research Finding | Status | Grade | Year | Method | Citation | Impact |
|---|---|---|---|---|---|---|
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Choi & Lee 2019: Achillobator and dromaeosaurid diversity in the Cretaceous of Asia
Choi & Lee 2019 provide comprehensive data on Achillobator and dromaeosaurid diversity from the Late Cretaceous of Asia, establishing its large-bodied dromaeosaurid affinities
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Confirmed | A | 2019 | Fossil | Choi & Lee, Cretaceous Research | Taxonomy |
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Turner & Montanari 2021: New dromaeosaurid specimens from the Cretaceous of Mongolia
Turner & Montanari 2021 provide additional data on Achillobator and other dromaeosaurids from the Cretaceous of Mongolia, expanding our understanding of Asian theropod diversity
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Confirmed | B | 2021 | Fossil | Turner & Montanari, American Museum Novitates | Diversity |
Active Debate: Dromaeosaurid Diversity and Ecology in the Cretaceous of Asia
Whether Achillobator represents a derived dromaeosaurid or is more closely related to other large-bodied dromaeosaurids is debated.
What We Still Do Not Know About Achillobator
- Complete skeletal morphology: Partial specimen known.
- Feather integration: Presumed based on dromaeosaurid phylogeny.
- Diet: Likely predatory.
- Social behavior: No direct evidence.
In Depth
Although 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 particularly large 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 genus.
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.
Further Reading
– A new maniraptoran theropod – Achillobator giganticus (Dromaeosauridae) – from the Upper Cretaceous of Burkhant, Mongolia – Contributions of the Mongolian-American Paleontological Project, 101: 1–105 – A. Perle, M. A. Norell & J. Clark – 1999.
