Achillesaurus is a genus of alvarezsaurid theropod dinosaur from the Santonian-aged (Late Cretaceous) Bajo de la Carpa Formation of Rio Negro, Argentina. It contains one species, Achillesaurus manazzonei.
Discovery and naming
The holotype specimen of
Achillesaurus, MACN-PV-RN 1116, was discovered in 1995 by a team of the Museo Argentino de Ciencias Naturales “Bernardino Rivadavia” led by Dr. José F. Bonaparte. It was found in the Paso Córdova Locality, Río Negro Province, northern
Patagonia, where the Santonian-aged Bajo de la Carpa Formation outcrops.
Its genus name was chosen in reference to Achilles' heel, because diagnostic features are found there for these animals, while the species name honors Professor Rafael Manazzone, an amateur paleontologist whose knowledge of Patagonian fossils and localities assisted the researchers on their field trips.
Description
The genus was a relatively large, basal alvarezsaurid, and a contemporary of
Alvarezsaurus. It is only known from MACN-PV-RN 1116, a partial
skeleton including a
sacrum vertebra, four tail vertebrae, part of the left
femur,
tibia and foot, and the left ilium. Agustín Martinelli and Ezequiel Vera, who described the specimen, performed a
phylogenetics and found their new genus to be an alvarezsaurid with an unresolved relationship to
Alvarezsaurus and more
Synapomorphy alvarezsaurids.
However, Makovicky, Apesteguía & Gianechini (2012) argued that Achillesaurus might actually be a junior synonym of Alvarezsaurus, which, according to the authors, "is known from the same formation and from which it i.e. differs trivially."
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