Ilokelesia is a primitive abelisaur

Abelisaur

Abelisaurs were a group of ceratosaurian dinosaurs which lived in the Southern hemisphere during the Cretaceous period. Some well-known dinosaurs of this group include Abelisaurus, Carnotaurus, and Majungasaurus. They are known for their small arms...

 found in 1991, preserved in the layers of the earliest

Cenomanian

The Cenomanian is, in the ICS' geological timescale the oldest or earliest age of the Late Cretaceous epoch or the lowest stage of the Upper Cretaceous series. An age is a unit of geochronology: it is a unit of time; the stage is a unit in the stratigraphic column deposited during the corresponding...

 Late Cretaceous

Late Cretaceous

The Late Cretaceous is the younger of two epochs into which the Cretaceous period is divided in the geologic timescale. Rock strata from this epoch form the Upper Cretaceous series...

 of the Río Limay Formation, Neuquén Group, located near Plaza Huincul, Neuquén Province

Neuquén Province

Neuquén is a province of Argentina, located in the west of the country, at the northern end of Patagonia. It borders Mendoza Province to the north, Rio Negro Province to the southeast, and Chile to the west...

, Argentina

Argentina

Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...

. The specimen, consisting of very fragmentary elements of the skull, the axial and the appendicular skeletons, was described by Coria et al. in late 1998.

The generic name’s etymology is derived from the Mapuche

Mapuche

The Mapuche are a group of indigenous inhabitants of south-central Chile and southwestern Argentina. They constitute a wide-ranging ethnicity composed of various groups who shared a common social, religious and economic structure, as well as a common linguistic heritage. Their influence extended...

 language, ilo meaning “flesh” and kelesio, “lizard”; while the specific descriptor reflects the name of the locality where the fossil was found, Aguada Grande.

Ilokelesia, a medium sized theropod, is characterized by features of the skull, namely of its quadrate and postorbital bones. The vertebral series also has distinctive characters setting it apart from other abelisaurs, such as reduced processes on the cervical vertebrae and dorsal vertebrae lacking pleurocoels.

I. aguadagrandensis was the most basal abelisaur described at the time, sharing characters, such as an expansion of the postorbital bone above the orbit and a flange of the same bone inside the orbit, with Abelisauridae

Abelisauridae

Abelisauridae is a family of ceratosaurian theropod dinosaurs. Abelisaurids thrived during the Cretaceous Period, on the ancient southern supercontinent of Gondwana, and today their fossil remains are found on the modern continents of Africa and South America, as well as on the Indian...

 and Noasauridae

Noasauridae

Noasaurids were a group of theropod dinosaurs from the Cretaceous Period . They were generally small in size...

; it retained, however, primitive features for Abelisauria as are an opening in the quadrate bone and a T-shaped postorbital.