Anabisetia

Anabisetia is a genus of small, bipedal herbivorous dinosaurs that inhabited Patagonia, South America, during the Late Cretaceous Period. Estimated to be around two meters in length and weighing approximately twenty kilograms, this dinosaur adds to our understanding of ornithopod diversity in the Southern Hemisphere.

Discovery and Naming

The genus Anabisetia was formally named in 2002 by Argentine paleontologists Rodolfo Coria and Jorge Orlando Calvo. The generic name, Anabisetia, serves as an honorific for the late Ana Maria Biset, a significant archaeologist from Neuquén Province, Argentina, which is the region where the dinosaur's remains were unearthed. The single named species, A. saldiviai, commemorates Roberto Saldivia Blanco, a local farmer who discovered the fossils in 1985 and subsequently brought them to the attention of the scientific community in 1993. The findings had been noted in scientific literature as early as 1996.

Fossil Evidence

Four specimens of Anabisetia are currently known, all detailed in the original 2002 description. The holotype specimen, MCF-PVPH 74, is the most complete. It includes fragmentary skull material, a complete forelimb and hindlimb, and vertebral elements from across the spinal column. Other specimens, while less complete, provide additional anatomical information, such as a complete pelvis and an articulated tail. Collectively, these specimens offer a nearly complete skeletal reconstruction, with the exception of the skull.

Paleontological Context

All four Anabisetia specimens were recovered from the Cerro Bayo Mesa locality in Neuquén Province, Argentina. This area is part of the Cerro Lisandro Formation, which preserves evidence of a swamp environment that existed from the late Cenomanian to the early Turonian stages of the Late Cretaceous, approximately 95 to 92 million years ago.

Description and Classification

Anabisetia is characterized as a small, bipedal herbivore. Distinctive anatomical features include the occipital condyle at the back of the skull, which pointed downwards, and a notably large acromial process on the shoulder blade among euornithopods. In the hand, the fifth metatarsal was flattened with straight edges, unlike the rounded cross-section seen in many other dinosaurs. The pelvis features an ilium with a front blade exceeding half its total length, extending forward of the prepubis, and an ischium with a triangular upper shaft and a quadrangular lower shaft. In the ankle, the fibula made contact with the astragalus. Phylogenetically, Anabisetia is considered closely related to other ornithopods from Patagonia and Antarctica, belonging to the clade Elasmaria. Its exact placement within Iguanodontia remains a subject of discussion, with some analyses suggesting it lies just outside the clade.