Description and Classification

Ilokelesia was a medium-sized carnivorous dinosaur, typical of the abelisaurid group. Scientists estimate it grew to be about 5 to 6 meters (16 to 20 feet) long. Like other abelisaurids, such as Carnotaurus and Abelisaurus, Ilokelesia walked on two powerful hind legs and had very short, almost vestigial, front limbs. It possessed a relatively large head with a short snout, and its skull bones may have had a roughened texture, a common trait in its family.

Ilokelesia belongs to the theropod group known as Ceratosauria, and more specifically to the Abelisauroidea. Within this larger group, it is classified as an abelisaurid. Some studies suggest Ilokelesia is a relatively basal, or early-evolving, member of the Abelisauridae family. This means it might show some features that are more primitive compared to later, more specialized abelisaurids. Its classification helps scientists understand how this diverse group of southern hemisphere predators evolved and spread.

Distinguishing Features

Ilokelesia can be distinguished from other abelisaurids by a combination of specific features found in its skeleton, particularly in its vertebrae (backbones) and pelvis. Some of these include:

• The absence of pleurocoels (hollow openings, often for air sacs) on the sides of its back vertebrae, which is an unusual trait for many abelisauroids.
• Specific characteristics in the structure of its sacrum (the fused vertebrae that connect to the pelvis) and ilium (the largest pelvic bone).
• Details in the vertebral processes, such as the shape and orientation of the epipophyses (small bony projections) on the neck vertebrae.

These anatomical details, when studied together, help paleontologists place Ilokelesia within the abelisaur family tree and differentiate it from its close relatives.

Paleoenvironment and Diet

Ilokelesia lived in the Patagonia region of Argentina during the early part of the Late Cretaceous period. At that time, the environment, recorded in the rocks of the Rio Limay Formation, was characterized by a warm climate with extensive river systems, floodplains, and vegetated areas. This ecosystem supported a diverse range of dinosaurs and other prehistoric life.

Ilokelesia shared its habitat with giant long-necked sauropods like Argentinosaurus, one of the largest land animals known. Other dinosaurs in the area included different types of theropods, various herbivorous dinosaurs, and possibly early birds. As a carnivore, Ilokelesia was a predator. It likely hunted smaller herbivorous dinosaurs, the young of larger species, or may have scavenged carcasses. Its teeth, similar to those of other abelisaurids, were suited for slicing flesh from its prey.

Significance and Ongoing Research

The discovery of Ilokelesia is significant because it provides valuable information about the early evolution and diversity of abelisaurid dinosaurs in South America. As one of the more primitive known abelisaurids, its fossils offer important clues about the ancestral characteristics of this major group of predators that became dominant in the southern continents (Gondwana) during the Cretaceous period.

Ongoing research involving Ilokelesia focuses on further clarifying its exact evolutionary relationships within the Abelisauridae family. This is often done by comparing its anatomy in detail with newly discovered fossils of other abelisaurids and related theropods. Scientists also continue to study the paleoecology of the Rio Limay Formation to better understand the interactions between Ilokelesia and other species that lived alongside it, painting a more complete picture of life in ancient Patagonia.