AMEGHINIANA (Rev. Asoc. Paleontol. Argent.) - 40 (2): 217-228. Buenos Aires, 30-06-2003 ISSN0002-7014 A new Triassic carnivorous dinosaur from Argentina Andrea B. ARCUCCI1and Rodolfo A. CORIA2 Abstract.A new Triassic theropod, Zupaysaurusrougieriis described from La Rioja Province and its phy- logenetic relationships amongst Theropoda are discussed. Zupaysaurusshares with Tetanurae several fea- tures that include the presence of a tooth row that is anterior to the orbit, a pneumatized lacrimal, and a tibia with a posterolaterally concave and transversely expanded distal end. Features shared with some cer- atosaurs, like the presence of a longitudinal alveolar ridge on the maxilla, a large antorbital fenestra, and a fused astragalus-calcaneum, are either homoplasies with some ceratosaurs or plesiomorphic features within Neotheropoda. Based on relative stratigraphical position, Zupaysaurusis regarded as Late Triassic in age, which makes it the oldest record of Tetanurae. Zupaysaurusprovides data about the early evolution of theropods, strengthening the assumption about the origin of tetanurans in the Late Triassic, and indi- cating their simultaneous record with the oldest coelophysids (i.e. Coelophysisand Liliensternus) Resumen.NUEVODINOSAURIOCARNÍVOROTRIÁSICODEARGENTINA.Se describe un nuevo terópodo triásico de la provincia de La Rioja, Zupaysaurusrougieri, y se discuten sus relaciones filogenéticas dentro de los Theropoda. Zupaysauruscomparte con Tetanurae varios caracteres que incluyen la presencia de una hilera dental por delante de la órbita, un lagrimal pneumatizado y una tibia con extremo distal posterolateral- mente cóncavo y expandido lateralmente. Caracteres compartidos con algunos ceratosaurios, tales como la presencia de una cresta alveolar longitudinal en el maxilar, una fenestra antorbital grande, y astrágalo y calcáneo fusionados, son considerados homoplásicos o caracteres plesiomórficos dentro de los Neotheropoda. En base a la posición estratigráfica relativa de los niveles en donde se encontró el holotipo, se considera que Zupaysauruses de edad Triásica tardía, lo que lo convierte en el registro más antiguo de Tetanurae. Zupaysaurusprovee información acerca de la evolución temprana de los terópodos, fortale- ciendo la hipótesis del origen de los tetanuros en el Triásico Superior, e indicando su registro simultáneo con los celofísidos más antiguos (p.e. Coelophysisy Liliensternus). Key words. Theropoda. Triassic. Los Colorados Formation. Phylogeny. Palabras clave.Theropoda. Triásico. Formación Los Colorados. Filogenia. Introduction abundant fossil record throughout the Mesozoic (Gauthier, 1986; Novas, 1989; Holtz, 1994; Sereno, Late Triassic theropod dinosaurs are scarce 1997). Interestingly, Triassic theropods have not yet worldwide, with a few reports from South America, included forms that could be assigned to tetanurans, North America and Europe (Huene, 1934; Bonaparte, whose earliest record is from the Early Jurassic 1971; Colbert, 1989; Carpenter, 1997; Heckert and (Cryolophosaurus; Hammer and Hickerson, 1994). Lucas, 2000; Rauhut and Hungerbühler, 1998). These A new carnivorous dinosaur, Zupaysaurusrougieri records include primitive carnivorous forms, such as gen. et sp. nov., is described here, which contributes Eoraptor(Sereno et al.1993), Herrerasaurus(Reig, significantly to the theropod record of the 1964) and coelophysids (Rowe and Gauthier, 1990), Argentinian Late Triassic Los Colorados Formation that show important stages in the origin and evolu- (Arcucci and Coria, 1997, 1998), from which only a tion of theropods. These genera allow workers to poorly preserved small specimen of uncertain affini- build a phylogenetic scenario of the evolution of the ties was formerly known (Bonaparte, 1971). This new Theropoda. Moreover, they have been useful as suc- taxon increases information about the oldest di- cessive outgroups to polarize the character states nosaurs in one of the most diverse Triassic terrestrial within the more derived and diversified Tetanurae vertebrate assemblages from South America (including Allosaurus, Tyrannosaurusand birds; (Bonaparte, 1971, 1982; Marsicano et al., 2001), and Gauthier, 1986), which have a significantly more shows that tetanuran theropods were already pre- sent during the Late Triassic. It is represented by one 1Universidad Nacional de San Luis, Area de Zoología. Chacabuco skeleton that includes an almost complete skull with 914, 5700 San Luis, Argentina. 2Dirección Provincial de Cultura, Museo Carmen Funes, Av. articulated mandibles, the neck, anterior dorsal ver- Córdoba 55, 8318 Plaza Huincul, Neuquén, Argentina. tebrae, and other associated postcranial remains. ©Asociación Paleontológica Argentina AMGHB2-0002-7014/03$00.00+.50 218 A.B. Arcucci and R.A. Coria Figure 1. Location map showing the area where the holotype of Zupaysaurus rougieriwas found (modified from Caselli, 1998 and Caselli et al., 2001)./ Mapa de ubicación mostrando el área donde se encontró el holotipo de Zupaysaurus rougieri (modificado de Caselli, 1998 y Caselli et al., 2001). AMEGHINIANA40 (2), 2003 New Triassic dinosaur from Argentina 219 With an estimated total skull length of 45 cm Description (figure 2), Zupaysaurus rougierigen. et sp. nov. is a larger animal than other Triassic theropods such as Skull.The skull of Zupaysaurus(PULR-076) is almost Coelophysis(Colbert, 1989), Liliensternus(Huene, complete, lacking only the premaxillae (figure 2). The 1934), Eoraptor(Sereno et al.1993) and Herrerasaurus specimen has a long, narrow and low skull. The pre- (Reig, 1964), but is similar in size to Goijirasaurus served skull length, from the anterior end of the max- (Carpenter, 1997). Zupaysaurusalso adds to the poor- illa up to the quadrate distal articulation is 38 cm. Its ly-known diversity of Triassic theropods. In spite of height from the top of the supraoccipital crest to the the high number of individuals of Coelophysisand ventral border of the quadratojugal is 13.5 cm (fi- Syntarsus(Colbert, 1989; Raath, 1990) collected, there gures 2.A, 2.E) and the width between the postor- is limited anatomical information due to either the bitals is 12.5 cm (figures 2.C-D). The skull has suf- preservation of the fossils or the low number of other fered some distortion, mainly on its left side where taxa recorded from the same age. there are indications of weathering (figure 2.B). Institutional abbreviations: BPI, Bernard Price This contribution is focused on the rostral, orbital Institute, Johannesburg, South Africa; MUNC-CH, and temporal regions of the skull, and does not in- Museo de la Universidad Nacional del Comahue, clude the description of bones that are part of the Colección El Chocón, Neuquén, Argentina; PULR, braincase (e.g.skull roof and occiput), which are be- Paleontología, Universidad Nacional de La Rioja. ing described elsewhere. The maxilla, lacrimal and jugal have been dis- Systematic paleontology placed anteriorly. The left nasal seems to have col- lapsed into the skull and it was also exposed on the SAURISCHIA right side after preparation (figures 2.A and 2.B). The THEROPODA orbit is oval, unlike the round orbit of Coelophysis TETANURAE (Colbert, 1989) and Syntarsus(Rowe, 1989), and lacks Zupaysaurus rougierigen. et sp. nov. the intraorbital projection of the postorbital recorded Figures 2 and 3 in some large theropods like Giganotosaurus(Coria Etymology.Zupaysaurus, from Quechua native lan- and Salgado, 1995), some tyrannosaurids (Molnar et guage zupay, devil, and saurus (Greek), lizard; al., 1990) and Carnotaurus(Bonaparte, 1991). rougieri, in acknowledgment of Dr. Guillermo The maxilla is long (26 cm) and low (3 cm at level Rougier, under whose direction the specimen was of the horizontal process). Laterally, it has an alveolar found and collected. ridge that extends from the anterior edge of the an- Holotype.PULR-076 (Paleontología, Universidad de torbital fossa to the distal end of the bone at its con- La Rioja). The specimen includes the skull, which tact with the jugal, resembling the condition reported lacks only the premaxillae, articulated posterior cer- for Eoraptor(Sereno et al., 1993, fig. 1), Coelophysis, vical and anterior dorsal vertebrae, two incomplete, Syntarsusand Liliensternus(Rowe and Gauthier, fused sacral vertebrae, the proximal end of the right 1990) (figure 2). The well-defined antorbital fossa has scapula and coracoid, the distal ends of the right tib- a tall internal lamina that is widely exposed in front ia and fibula, the fused right astragalus and calca- of the anterior margin of the antorbital fenestra, and neum, and proximal parts of two pedal unguals. extends up onto the wide ascending process of the Locality and horizon.Quebrada de los Jachaleros, 7 maxilla (figures 2.A and 2.E). The anterior end of the km West of National Route 126, La Rioja Province, maxilla has a conspicuous step, with a vertical edge Argentina (figure 1). Upper levels of Los Colorados that anteriorly encloses the antorbital fossa. Both Formation, Upper Triassic (Caselli et al., 2001). maxillary fenestra and promaxillary fenestra are pre- Diagnosis.Zupaysaurusrougieriis distinguished by sent (figures 2.A and 2.E). The base of the ascending having an oval, anteroventrally oriented antorbital process is anteroposteriorly broad above the maxil- fenestra; two parasagittal crests on the snout formed lary fenestra. It projects posterodorsally, thinning by the nasals; anterior process of lacrimal longer than and forking distally. The dorsal edge is angular, un- the ventral; main