''Llukalkan'' (

Mapuche The Mapuche ( , ) also known as Araucanians are a group of Indigenous peoples of the Americas, Indigenous inhabitants of south-central Chile and southwestern Argentina, including parts of Patagonia. The collective term refers to a wide-ranging e ...

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 foun ...

theropod Theropoda (; from ancient Greek , (''therion'') "wild beast"; , (''pous, podos'') "foot"">wiktionary:ποδός"> (''pous, podos'') "foot" is one of the three major groups (clades) of dinosaurs, alongside Ornithischia and Sauropodom ...

dinosaur from the

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the more recent 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 ''cre ...

Bajo de la Carpa Formation The Bajo de la Carpa Formation is a geologic formation of the Neuquén Basin that outcrop, crops out in northern Patagonia, in the provinces of Río Negro Province, Río Negro and Neuquén Province, Neuquén, Argentina. It is the oldest of two for ...

Argentina Argentina, officially the Argentine Republic, is a country in the southern half of South America. It covers an area of , making it the List of South American countries by area, second-largest country in South America after Brazil, the fourt ...

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

Discovery and naming

The

holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...

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 Provinces of Argentina, 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 me ...

, in the rocks of the Bajo de la Carpa Formation. It was discovered only away from the remains of the contemporary abelisaurid ''

Viavenator ''Viavenator'' (meaning "road hunter") is a genus of carnivorous abelisaurid theropod dinosaur discovered in Argentina's Bajo de la Carpa Formation. It coexisted with the megaraptoran '' Tratayenia rosalesi''. Classification Filippi classifi ...

''. 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 a small abelisaurid with an estimated body length of . Refer Table 2, Supplementary data 1 ''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 Synapomorphy, 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 (cladistics), outgroup taxa, not ...

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 Brachyrostra (meaning "short snouts") is a clade within the theropod dinosaur family Abelisauridae. It includes the famous genera ''Carnotaurus'', '' Aucasaurus'', potentially ''Abelisaurus'' as well as their close relatives from the Cretaceous P ...

. Their cladogram is shown below.

References

{{Taxonbar, from=Q106297191 Abelisauridae Dinosaur genera Santonian dinosaurs Bajo de la Carpa Formation Fossil taxa described in 2021 Dinosaurs of Argentina