Gualicho
Temporal range: Late Cretaceous, 93 Ma
Gualicho.PNG
Skeletal reconstruction, with known elements in white
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Order: Saurischia
Suborder: Theropoda
Clade: Orionides
Clade: Avetheropoda
Genus: Gualicho
Apesteguía et al., 2016
Type species
Gualicho shinyae
Apesteguía et al., 2016

Gualicho (named in reference to the gualichu) is a genus of theropod dinosaur. The type species is Gualicho shinyae. Gualicho 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 93 million years ago.

Description

Restoration
Estimated size compared to a human

Like the well-known Tyrannosaurus, to which it has been compared, the 6–7 m (20–23 ft) Gualicho possesses reduced arms and two fingered hands. This finding indicates that carnosaurs may have been subject to the same evolution of limb-reduction as tyrannosaurids and abelisaurids, provided that Gualicho is a carnosaur in the first place.[1]

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.[2]

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.[2]

Gualicho has been suggested 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.[3][4] However, Aoniraptor does not meet the requirements of ICZN Article 8.5.3, meaning it is an invalid nomen nudum.[5]

Classification

Digits of the left hand
Life restoration

Phylogenetically, Gualicho presents two possibilities; that megaraptorans and neovenatorids were carnosaurs, or that megaraptorans and neovenatorids were a grade of theropods more closely related to coelurosaurs than to carnosaurs.[2]

The cladogram below follows a 2016 analysis by Sebastián Apesteguía, Nathan D. Smith, Rubén Juarez Valieri, and Peter J. Makovicky.[2]

Allosauroidea 

Metriacanthosauridae Metriacanthosaurus.jpg

Allosauria

Allosauridae Allosaurus Revised.jpg

Carcharodontosauria

Carcharodontosauridae Giganotos Db.jpg

Neovenatoridae

Deltadromeus Deltadromeus silhouette.svg

Gualicho Gualicho shinyae restoration.jpg

Neovenator Neovenator.png

ChilantaisaurusChilantaisaurus.jpg

Megaraptora Australovenator.jpg

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.[6] Although the results are different, 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.[2]

Avetheropoda

Eocarcharia

Neovenator

Concavenator

Acrocanthosaurus

Allosaurus

Sinraptor

Monolophosaurus

Shaochilong

Carcharodontosaurus

Tyrannotitan

Mapusaurus

Giganotosaurus

Coelurosauria

Gualicho

Chilantaisaurus

Megaraptora

Fukuiraptor

Megaraptoridae

Murusraptor

Tratayenia

Megaraptor

Aerosteon

Australovenator

Orkoraptor

Tyrannoraptora

See also

References

  1. ^ Davis N (13 July 2016). "Meet Gualico shinyae, the puny armed distant relative of T-rex". The Guardian. Retrieved 13 July 2016.
  2. ^ a b c d e Apesteguía S, Smith ND, Juárez Valieri R, Makovicky PJ (2016). "An Unusual New Theropod with a Didactyl Manus from the Upper Cretaceous of Patagonia, Argentina". PLOS One. 11 (7): e0157793. Bibcode:2016PLoSO..1157793A. doi:10.1371/journal.pone.0157793. PMC 4943716. PMID 27410683.
  3. ^ Mortimer M (2016-07-13). "Is Gualicho Aoniraptor?". The Theropod Database Blog. Retrieved 14 July 2016.
  4. ^ Cau A. "Nuovi resti di Aoniraptor? Ehm... Benvenuto Gualicho!". Theropoda. Retrieved 14 July 2016.
  5. ^ Mortimer M (July 2016). "Is Gualicho Aoniraptor?". The Theropod Database Blog.
  6. ^ Porfiri JD, Juárez Valieri RD, Santos DD, Lamanna MC (March 2018). "A new megaraptoran theropod dinosaur from the Upper Cretaceous Bajo de la Carpa Formation of northwestern Patagonia". Cretaceous Research. 89: 302–319. doi:10.1016/j.cretres.2018.03.014.