Zupaysaurus (; "ZOO-pay-SAWR-us") is an extinct genus of early theropod dinosaur living during the Norian stage of the Late Triassic in what is now Argentina. Fossils of the dinosaur were found in the Los Colorados Formation of the Ischigualasto-Villa Unión Basin in northwestern Argentina. Although a full skeleton has not yet been discovered, Zupaysaurus can be considered a predator, up to long. It may have had two parallel crests running the length of its snout.
Discovery
Discovered in May 1997 by Santiago Reuil ("Vultur"), part of the crew of Guillermo Rougier, it was later described by Arcucci and Coria and published in 2003. The name
Zupaysaurus is composed of the
Quechua language word
supay meaning "devil" and the
Greek language word
sauros (σαυρος) meaning "lizard"; thus "devil lizard". In Incan mythology,
supay was both the god of death and ruler of the
ukhu pacha, the Incan underworld. The
type species was named
Z. rougieri in the honor of Guillermo Rougier, the scientist who led the expedition which discovered and collected the
holotype (original specimen) PULR-076.
Zupaysaurus was first described and named in the scientific journal
Ameghiniana by
Argentina Andrea Arcucci and
Rodolfo Coria in 2003.
Description
Zupaysaurus was a medium-sized theropod. An adult
skull, measured approximately in length, suggesting a body length of approximately from its snout to the tip of its tail. In 2010 Gregory S. Paul gave a length of 6 meters (20 ft) and a weight of 250 kg (550 lbs).
In 2016 it was given a much smaller size of 4.2 meters (14 ft) and 70 kg (154 lbs).
Like all theropods,
Zupaysaurus walked only on its hindlegs, leaving its forelimbs free to grasp its
prey. The length of the neck bones recovered suggests that this genus has a rather long neck. Like the
coelophysoids,
Zupaysaurus has a kink in its snout, between the
and
bones of the upper jaw. It is estimated that
Zupaysaurus had 24 teeth and an intermandibular hinge is present in the lower jaw.
[Arcucci, A.B. & Coria R.A. 2003. A new Triassic carnivorous dinosaur from Argentina. Ameghiniana 40(2):217-228.] Only one specimen of
Zupaysaurus is known to science. The
holotype specimen was designated PULR-076, which consists of a nearly complete skull which was very well preserved, the right
shoulder girdle, the lower right leg and
ankle, and twelve
from the neck, back, and hips. Additional material of a smaller individual found at the same site may or may not belong to
Zupaysaurus.
As
Zupaysaurus was originally described, the head bore two thin parallel crests on top of the skull, similar to theropods like
Dilophosaurus and
Coelophysis kayentakatae. These crests are thought to have been formed by the
nasal bone bones solely, unlike those of many other theropods which also incorporated the
lacrimal bone bones. Crests on the skull were pervasive among theropods and may have been used for communicative purposes such as species or gender recognition.
[Currie, P.J. & Zhao X. 1993. A new carnosaur (Dinosauria, Theropoda) from the Jurassic of Xinjiang, People's Republic of China. Canadian Journal of Earth Sciences 30: 2037-2081.] However, more recent analysis of the skull has cast doubt on the presence of these crests in
Zupaysaurus. An unpublished abstract presented at a recent conference indicated the structures initially identified as crests were in fact the lacrimal bones displaced upwards during the process of
.
[Ezcurra, M.D. & Novas, F.E. 2005. Phylogenetic relationships of the Triassic theropod Zupaysaurus rougieri from NW Argentina. Presented in August 2005 during the II Latin American Congress of Vertebrate Paleontology in Rio de Janeiro, Brazil. This analysis will be published in peer-reviewed print form later in 2006. A summary of the talk can be seen here.] Other cranial ornamentation included a rugose laterally-projecting lacrimal ridge on the top of the skull.
A diagnosis is a statement of the anatomical features of an organism (or group) that collectively distinguish it from all other organisms. Some, but not all, of the features in a diagnosis are also autapomorphies. An autapomorphy is a distinctive anatomical feature that is unique to a given organism or group. According to Ezcurra (2006) and Ezcurra and Novas (2006),
Zupaysaurus can be distinguished based on the following characteristics: the maxillary fenestra is within the antorbital fossa (according to Ezcurra, 2006), the rostral process of the lacrimal is ventrally bowed (according to Ezcurra, 2006), the ventral process of the
Squamosal bone is kinked (according to Ezcurra, 2006), wide contact between squamosal and
quadratojugal (according to Ezcurra, 2006). The maxillary-jugal ventral margin describes an obtuse angle in lateral view (according to Ezcurra and Novas, 2006), a notch on the dorsal margin of the ascending process of the maxilla, relating to horizontal ramus of the lacrimal is rostrally tapering onto the forked caudal tip of the ascending process of the
maxilla; (according to Ezcurra and Novas, 2006), a lacrimal with a highly pneumatized antorbital recess (according to Ezcurra and Novas, 2006), a short and square-shaped retroarticular process of the
mandible (according to Ezcurra and Novas, 2006), the
cnemial crest is poorly developed (according to Ezcurra and Novas, 2006).
Classification
Zupaysaurus was classified as the earliest known
tetanuran theropod due to several features of its skull, dentition, and hindlimb. However, several features typical of more basal theropods were also noted by the original authors.
Analyses by Carano (2005), Tykoski (2005), and Ezcurra and Novas (2005) have classified
Zupaysaurus as a
coelophysoid related to
Segisaurus and probably
Liliensternus, though more basal than
Coelophysis.
[Carrano, M.T., Hutchinson, J.R., & Sampson, S.D. 2005. New information on Segisaurus halli, a small theropod dinosaur from the Early Jurassic of Arizona. Journal of Vertebrate Paleontology 25(4): 835-849.][Tykoski, 2005. Anatomy, ontogeny and phylogeny of coelophysoid theropods. PhD Dissertation. University of Texas at Austin. 553 pp.] Yates (2006) found
Zupaysaurus to form a group with
Dilophosaurus and
Dracovenator, placing it in a monophyletic
Dilophosauridae.
[Yates, A.M., 2006 (for 2005). "A new theropod dinosaur from the Early Jurassic of South Africa and its implications for the early evolution of theropods." Palaeontologia Africana, 41: 105-122.] But later studies found
Zupaysaurus to be a sister taxon sister to a clade containing
Dilophosauridae,
ceratosaurs and
Tetanurae.
[Smith N.D., Makovicky P. J., Hammer W. R. & Currie P. J. 2007 Osteology of Cryolophosaurus ellioti (Dinosauria: Theropoda) from the Early Jurassic of Antarctica and implications for early theropod evolution. Zool. J. Linn. Soc. 151, 377–421.][Nesbitt, S. J., Smith, N. D., Irmis, R. B., Turner, A. H., Downs, A., & M. A. Norell. 2009. A complete skeleton of a Late Triassic saurischian and the early evolution of dinosaurs. Science 326:1530-1533.]
Below is a cladogram based on the phylogenetic analysis conducted by Sues et al. in 2011, showing the relationships of Zupaysaurus:[Hans-Dieter Sues, Sterling J. Nesbitt, David S. Berman and Amy C. Henrici (2011). "A late-surviving basal theropod dinosaur from the latest Triassic of North America". Proceedings of the Royal Society B 278 (1723): 3459–3464]
Paleoecology
Zupaysaurus was discovered in red siliciclastic sediments at the "Quebrada de los Jachaleros" locality within the Los Colorados Formation of the La Rioja province in Argentina. This formation has been shown by magnetostratigraphy to date to the
Norian stage of the
Late Triassic period, approximately 228 to 208 million years ago.
[Weishampel, D.B., Barrett, P.M., Coria, R.A., Le Loueff, J., Xu X., Zhao X., Sahni, A., Gomani, E.M.P., & Noto, C.R. 2004. Dinosaur distribution. In: Weishampel, D.B., Dodson, P., & Osmólska, H. (Eds.). The Dinosauria (2nd Edition). Berkeley: University of California Press. Pp. 517-606.] but has also been assigned to the slightly younger
Rhaetian stage, which was approximately 208 to 201 million years ago.
[Heckert, A.B. & Lucas, S.G. 1998. Global correlation of the Triassic theropod record. Gaia 15: 63-74. not] Both specimens assigned to this genus are housed in the collection of the National University of La Rioja in La Rioja, Argentina.
The Los Colorados Formation was interpreted as an ancient floodplain and it was home to several types of early sauropodomorph dinosaurs (including Riojasaurus, Coloradisaurus , and Lessemsaurus), all of which shared the same paleoenvironment with Zupaysaurus.
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