[Paleontology • 2016] Gualicho shinyae • An Unusual New Theropod with a Didactyl Manus from the Upper Cretaceous of Patagonia, Argentina

Gualicho shinyae 

Apesteguía, Smith, Valieri & Makovicky, 2016   DOI: 10.1371/journal.pone.0157793 

Abstract

Background

Late Cretaceous terrestrial strata of the Neuquén Basin, northern Patagonia, Argentina have yielded a rich fauna of dinosaurs and other vertebrates. The diversity of saurischian dinosaurs is particularly high, especially in the late Cenomanian-early Turonian Huincul Formation, which has yielded specimens of rebacchisaurid and titanosaurian sauropods, and abelisaurid and carcharodontosaurid theropods. Continued sampling is adding to the known vertebrate diversity of this unit.

Methodology/ Principal Findings

A new, partially articulated mid-sized theropod was found in rocks from the Huincul Formation. It exhibits a unique combination of traits that distinguish it from other known theropods justifying erection of a new taxon, Gualicho shinyae gen. et sp. nov. Gualicho possesses a didactyl manus with the third digit reduced to a metacarpal splint reminiscent of tyrannosaurids, but both phylogenetic and multivariate analyses indicate that didactyly is convergent in these groups. Derived characters of the scapula, femur, and fibula supports the new theropod as the sister taxon of the nearly coeval African theropod Deltadromeus and as a neovenatorid carcharodontosaurian. A number of these features are independently present in ceratosaurs, and Gualicho exhibits an unusual mosaic of ceratosaurian and tetanuran synapomorphies distributed throughout the skeleton.

Conclusions/ Significance

Gualicho shinyae gen. et sp. nov. increases the known theropod diversity of the Huincul Formation and also represents the first likely neovenatorid from this unit. It is the most basal tetatanuran to exhibit common patterns of digit III reduction that evolved independently in a number of other tetanuran lineages. A close relationship with Deltadromaeus from the Kem Kem beds of Niger adds to the already considerable biogeographic similarity between the Huincul Formation and coeval rock units in North Africa.

a pair of Gualicho dinosaurs pursuing prey.

illustration: Jorge Gonzalez and Pablo Lara 

Systematic paleontology

Dinosauria

Theropoda

Tetanurae

Avetheropoda

Gualicho shinyae gen. et sp. nov. 

(replaces Nototyrannus violantei Anonymous, 2011, nomen nudum)

Holotype: MPCN PV 0001, comprising four articulated centra from the dorsal vertebral column, an articulated gastral basket, a section of the tail distal to the transition point, the left scapulocoracoid and forelimb, the distal end of both pubes including the pubic boot, and parts of both hind limbs (Fig 1A). Much of the specimen had been lost to erosion when discovered, but the preserved parts including the forelimb, dorsal vertebrae, gastralia, and feet were articulated. Specimen measurements are provided in Table 1.

 Skeletal reconstruction of Gualicho shinyae showing recovered elements in white and missing elements in grey shading.

Artwork by J. González. 

Etymology: Gualicho, a Spanish name derived from the Gennaken (günün-a-künna or northern Tehuelche language) watsiltsüm, for a goddess who was considered the owner of animals and later, following the introduction of Christianity, reinterpreted as a demonic entity. She is now considered a source of misfortune by rural settlers (gauchos) of the Southern Cone. The name was chosen to reflect the difficult circumstances surrounding the discovery and study of the specimen, and its contentious history following excavation. The specific name honors Ms. Akiko Shinya, Chief Fossil Preparator at the Field Museum, for her many contributions to paleontology including discovery of the holotype of Gualicho on February 13th, 2007 (see S1 Fig).

Sebastián Apesteguía, Nathan D. Smith, Rubén Juárez Valieri and Peter J. Makovicky. 2016. An Unusual New Theropod with a Didactyl Manus from the Upper Cretaceous of Patagonia, Argentina. PLoS ONE. 11(7): e0157793.   DOI: 10.1371/journal.pone.0157793

Meet Gualicho shinyae, the puny-armed distant relative of T. rex https://www.theguardian.com/science/2016/jul/13/meet-gualicho-shinyae-the-puny-armed-distant-relative-of-t-rex

[Paleontology • 2013] Siats meekerorum • Neovenatorid theropods are Apex Predators in the Late Cretaceous of North America

Siats meekerorum 

Zanno & Makovicky 2013

Allosauroid theropods were a diverse and widespread radiation of Jurassic–Cretaceous megapredators. Achieving some of the largest body sizes among theropod dinosaurs, these colossal hunters dominated terrestrial ecosystems until a faunal turnover redefined apex predator guild occupancy during the final 20 million years of the Cretaceous. Here we describe a giant new species of allosauroid – Siats meekerorum gen. et sp. nov. – providing the first evidence for the cosmopolitan clade Neovenatoridae in North America. Siats is the youngest allosauroid yet discovered from the continent and demonstrates that the clade endured there into the Late Cretaceous. The discovery provides new evidence for ecologic sympatry of large allosauroids and small-bodied tyrannosauroids. These data support the hypothesis that extinction of Allosauroidea in terrestrial ecosystems of North America permitted ecological release of tyrannosauroids, which went on to dominate end-Cretaceous food webs.

This illustration shows Siats within its ecosystem,
eating an Eolambia and intimidating early, small-bodied tyrannosauroids.

Illustration: Julio Lacerda

Siats meekerorum

Illustration: Jorge Gonzales

Zanno, L. E.; Makovicky, P. J. 2013. Neovenatorid theropods are Apex Predators in the Late Cretaceous of North America. Nature Communications. 4. doi: dx.doi.org/10.1038/ncomms3827

Colossal new predatory dino terrorized early tyrannosaurs

A new species of carnivorous dinosaur – one of the three largest ever discovered in North America – lived alongside and competed with small-bodied tyrannosaurs 98 million years ago. This newly discovered species, Siats meekerorum, (pronounced see-atch) was the apex predator of its time, and kept tyrannosaurs from assuming top predator roles for millions of years.

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http://phys.org/news/2013-11-colossal-predatory-dino-terrorized-early.html

http://www.sci-news.com/paleontology/science-siats-meekerorum-dinosaur-utah-01567.html