''Llukalkan'' (

Mapuche The Mapuche ( (Mapuche & Spanish: )) are a group of indigenous inhabitants of south-central Chile and southwestern Argentina, including parts of Patagonia. The collective term refers to a wide-ranging ethnicity composed of various groups who sha ...

for "one who causes fear") is a genus of

abelisaurid Abelisauridae (meaning "Abel's lizards") is a family (or clade) of ceratosaurian theropod dinosaurs. Abelisaurids thrived during the Cretaceous period, on the ancient southern supercontinent of Gondwana, and today their fossil remains are found ...

theropod Theropoda (; ), whose members are known as theropods, is a dinosaur clade that is characterized by hollow bones and three toes and claws on each limb. Theropods are generally classed as a group of saurischian dinosaurs. They were ancestrally c ...

dinosaur from the

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''creta'', the ...

Bajo de la Carpa Formation The Bajo de la Carpa Formation is a geologic formation of the Neuquén Basin that crops out in northern Patagonia, in the provinces of Río Negro and Neuquén, Argentina. It is the oldest of two formations belonging to the Río Colorado Subgroup ...

Argentina Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the second-largest country in South America after Brazil, th ...

. The type species is ''Llukalkan aliocranianus''.

Discovery and naming

The

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of several ...

of ''Llukalkan'', MAU-Pv-LI-581, consisting of a partial skull, was discovered during 2015 in the La Invernada site in

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. It also meets La Pampa Province a ...

, in the rocks of the Bajo de la Carpa Formation. It was discovered only away from the remains of the contemporary abelisaurid '' Viavenator''. It was described as belonging to the new taxon ''Llukalkan aliocranianus'' in 2021; the generic name is Mapuche for "one who scares" or "one who causes fear", and the specific name is Latin for "different skull".

Description

''Llukalkan'' is very similar to ''Viavenator'', except that it is smaller and the holes in the skull through which the veins pass are larger and more widely separated from the supraoccipital crest, among other differences. It also has a small posterior air-filled sinus in the middle ear zone, a ''recessus tympanicus caudalis'', that has not been found in any other abelisaurids and thus is an

autapomorphy In phylogenetics, an autapomorphy is a distinctive feature, known as a derived trait, that is unique to a given taxon. That is, it is found only in one taxon, but not found in any others or outgroup taxa, not even those most closely related to t ...

Paleobiology

On account of its unusual ear, it has been theorized than ''Llukalkan'' had a keener sense of hearing than other abelisaurids, almost like a crocodile's.

Classification

Gianechini ''et al.'' place ''Llukalkan'' as a derived abelisaurid, in the clade Furileusauria. Their cladogram is shown below.

References

{{Taxonbar, from=Q106297191 Abelisaurids Santonian life Late Cretaceous dinosaurs of South America Cretaceous Argentina Bajo de la Carpa Formation Fossil taxa described in 2021