Gualicho NT Small

''Gualicho'' (named in reference to the gualichu) is an enigmatic genus of theropod dinosaurs. The type species is ''Gualicho shinyae''. It lived in what is now northern Patagonia, on what was then a South American island continent split off from the supercontinent Gondwana. The fossils were found in the Huincul Formation, dating to the late Cenomanian-early Turonian age of the upper Cretaceous Period, around 91 million years ago.

Discovery

On 13 February 2007, Akiko Shinya, preparator of the Field Museum of Natural History, east of the Ezequiel Ramos Mexía Reservoir at the Rancho Violante, discovered the skeleton of a theropod new to science. In 2016, the specimen was named and described by Sebastián Apesteguía, Nathan D. Smith, Rubén Juárez Valieri and Peter J. Makovicky. The generic name is derived from the ''gualichu'', a demon of local folklore. The specific name honours Shinya as the animal's discoverer.

The holotype, MPCN PV 0001, consists of a partial skeleton lacking the skull. It contains four vertebrae of the back, three vertebrae of the middle tail, ribs, a basket of belly-ribs, the left shoulder girdle, the left forelimb, the right lower arm, the lower ends of both pubic bones, the right thighbone, the lower end of the left thighbone, the upper ends of the right shinbone and calf bone, elements of both metatarsi and three toes of the right foot. Most bones were uncovered in their original anatomical position but much of the skeleton had been destroyed by erosion.

''Gualicho'' has been informally suggested on blogs to be synonymous with the megaraptoran ''Aoniraptor'', also known from Huincul Formation and uncovered at the Violante site in view of similarities in their caudal vertebrae. If this were supported, the name ''Gualicho'' would have precedent. Aranciaga Rolando et al. in 2020 performed a comparative analysis between the pneumatic structures of ''Aoniraptor'' and ''Gualicho,'' and found many differences between the two.

Description

Like the well-known ''Tyrannosaurus'', to which it has been compared, the ''Gualicho'' possesses reduced arms and possibly two fingered hands, although a 2020 study suggests enough of the third metacarpal is present for a third finger. If it is an allosauroid, this finding indicates that carnosaurs may have been subject to the same evolution of limb-reduction as tyrannosaurids and abelisaurids.

Classification

''Gualicho'' has been interpreted as presenting two evolutionary scenarios: that megaraptorans and neovenatorids were allosauroids, or that megaraptorans and neovenatorids were a grade of theropods more closely related to coelurosaurs than to carnosaurs. The cladogram below follows a 2016 analysis by Apesteguía et al., with ''Gualicho'' within Carcharodontosauria:

The cladogram below follows the strict consensus (average result) of the twelve most parsimonious trees (the simplest evolutionary paths, in terms of the total amount of sampled features evolved or lost between sampled taxa) found by Porfiri et al. (2018)'s phylogenetic analysis. Although the results are different, with ''Gualicho'' within Coelurosauria, the methodology analysis was practically identical to that of Apesteguia et al. (2016), only differing in the fact that it incorporated ''Tratayenia'' and ''Murusraptor'', two megaraptorans not sampled in the analysis of Apesteguia et al.

In 2025, Calvo and colleagues compared the humerus of ''Gualicho'' to that of other megaraptorans including a specimen of adult ''Megaraptor'', and concluded that this taxon is not closely related to them due to significant morphological differences. They also noted that the features of its humerus shares many similarities to various groups of coelurosaurs, so a confident referral within a specific clade of theropods cannot be made.

See also

*2016 in paleontology

References

{{Taxonbar, from=Q25859335

Tetanurae
Dinosaur genera
Turonian dinosaurs
Huincul Formation
Fossil taxa described in 2016
Dinosaurs of Argentina