Anais da Academia Brasileira de Ciências ISSN: 0001-3765 [email protected] Academia Brasileira de Ciências Brasil KELLNER, ALEXANDER W.A.; RUBILAR-ROGERS, DAVID; VARGAS, ALEXANDER; SUÁREZ, MARIO A new titanosaur sauropod from the Atacama Desert, Chile Anais da Academia Brasileira de Ciências, vol. 83, núm. 1, marzo, 2011, pp. 211-219 Academia Brasileira de Ciências Rio de Janeiro, Brasil Available in: http://www.redalyc.org/articulo.oa?id=32717681010 How to cite Complete issue Scientific Information System More information about this article Network of Scientific Journals from Latin America, the Caribbean, Spain and Portugal Journal's homepage in redalyc.org Non-profit academic project, developed under the open access initiative “main” — 2011/2/10 — 15:28 — page 211 — #1 Anais da Academia Brasileira de Ciências (2011) 83(1): 211-219 (Annals of the Brazilian Academy of Sciences) Printed version ISSN 0001-3765 / Online version ISSN 1678-2690 www.scielo.br/aabc A new titanosaur sauropod from the Atacama Desert, Chile ALEXANDER W.A. KELLNER1, DAVID RUBILAR-ROGERS2, ALEXANDER VARGAS3 and MARIO SUÁREZ4 1Setor de Paleovertebrados, Departamento de Geologia e Paleontologia, Museu Nacional/Universidade Federal do Rio de Janeiro, Quinta da Boa Vista s/n, São Cristóvão, 20940-040 Rio de Janeiro, RJ, Brasil 2Área Paleontología, Museo Nacional de Historia Natural, Casilla 787, Santiago, Chile 3Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Las Palmeras 3425, Ñuñoa, Casilla 653, Santiago, Chile 4Museo Paleontológico de Caldera, Av. Wheelwrigth 001, Caldera, Chile Manuscript received on December 22, 2010; accepted for publication on January 12, 2011 ABSTRACT Partial remains of a titanosaur sauropod collected in the Tolar Formation (Upper Cretaceous) at the Atacama Desert (Antofagasta Region), northern Chile, is described, and a new species, Atacamatitan chilensis gen. et sp. nov., is erected. The material consists mainly of dorsal and caudal vertebrae, part of a humerus and a femur. The presence of a titanosaur confirms the Cretaceous age for the outcrops of red sandstone of the Tolar Formation whose agewas previously uncertain, ranging from the Upper Cretaceous to the Paleocene. The new specimen represents the most complete dinosaur reported for this region and one of the most complete titanosaur known from Chile and the pacific margin of South America so far. Key words: Dinosauria, Titanosauria, Atacamatitan, Atacama Desert, Cretaceous, Chile. INTRODUCTION tiago) and the Museu Nacional/UFRJ (Rio de Janeiro) to the Antofagasta region. During this field activity, a The record of continental fossil vertebrates in Meso- site located about 150 km north of Calama town and zoic deposits of Chile is very rare. From these, although some 50 km east from El Abra cooper mine was dis- scarce, titanosaur sauropods are the best documented, covered (Vargas et al. 2000). The deposits in this area mostly limited to incomplete and isolated remains re- represent the Tolar Formation that consists of a sequence covered from only four localities, all from the north- of sedimentary clastic red rocks with intercalations of ern part of the country (Rubilar-Rogers 2003, 2005). conglomerates of the same color and brechas at the base They include the first report of non-avian dinosaur bones, (Maksaev 1978). Up to that time, the age inferred for consisting of an incomplete left scapula and coracoid, this formation had not been defined with precision, rang- and the distal end of a right humerus that were regarded ing from the Upper Cretaceous to the Paleocene. The as cf. Antarctosaurs wichmannianus and as Titanosauri- dinosaur specimen supports a Cretaceous age at least for dae indet., respectively (Casamiquela et al. 1969). the outcrops of the Tolar Formation near Conchi Viejo In order to prospect for continental Mesozoic tetra- town, where the dinosaur site is located. pod fossils in Chile, contacts between Chilean and The year thereafter (July, 2001), a second expedi- Brazilian researchers were established in 1998 and a tion continued to excavate the site. This activity resulted preliminary expedition during February 2000 was orga- in what is the second most complete titanosaur dinosaur nized by the Museo Nacional de Historia Natural (San- recovered from Chile so far (a more complete specimen Proceedings of the Third Gondwanan Dinosaur Symposium is known from III Región de Copiapó, D. Rubilar-Rogers Correspondence to: Alexander Wilhelm Armin Kellner et al., unpublished data.). The material was collected in E-mail: [email protected] An Acad Bras Cienc (2011) 83 (1) “main” — 2011/2/10 — 15:28 — page 212 — #2 212 ALEXANDER W.A. KELLNER, DAVID RUBILAR-ROGERS, ALEXANDER VARGAS and MARIO SUÁREZ a surface of 2 m2 and is regarded as representing one acuminate posteriorly*; ventral surface of the dorsal ver- individual, which is described here. tebra strongly concave*; posterior caudals with a lat- erally compressed neural spine that bears a blade-like SYSTEMATIC PALEONTOLOGY anterior margin*; femur with the shaft getting gradually Dinosauria Owen, 1842 narrower until two thirds of its length*. Sauropoda Marsh, 1878 Titanosauria Bonaparte & Coria, 1993 DESCRIPTION AND COMPARISONS Titanosauriformes Salgado et al., 1997 When the site was found, the first specimen of Ataca- Titanosauridae Lydekker, 1893 matitan chilensis gen. et sp. nov. to be recognized was Atacamatitan gen. nov. the femur, which was eroding on the surface. Subse- quently, other bones were excavated, including several Etymology: Atacama, from the desert where the spec- fragments. Some are slightly distorted due to taphon- imen was found, and Titan, which relates to a group of omy, but their original shape can be established without Greek divinities. difficulty. The bones have a reddish color and are quite Type species: Atacamatitan chilensis sp. nov., type by heavy, a result of extensive permineralization. monotypy. Only two dorsal vertebrae were recovered. They are incomplete, with the neural arches only partially pre- Recorded temporal and stratigraphic range: Upper served. Both are opisthocoelic, lacking hyposphene- Cretaceous, Tolar Formation. hypantrum as in several members of the Titanosauridae Diagnosis: As for the type and only known species. (e.g., Salgado et al. 1997). In SGO-PV-961a (Figs. 1A, B) the centrum is remarkably opisthocoelic, with the an- Atacamatitan chilensis sp. nov. terior articulation more convex in lateral view than in SGO-PV-961b. Also, in the former, the centrum is more Etymology: In allusion to Chile, the country where the elongated. It bears on the lateral side developed pleu- specimen was found. rocoels that are more rounded and less elongated com- Holotype: The material includes a right femur, the pared with other titanosaurids. These pleurocoels do proximal end of a humerus, two dorsal vertebrae, pos- not acuminate posteriorly in the preserved elements of terior caudal vertebrae, dorsal ribs and a fragmentary the new species, contrary to what is observed in several element regarded as part of the sternum, besides other other members of this clade (e.g., Trigonosaurus, see incomplete bones, all housed at the Sección Paleonto- also Calvo et al. 2007b). The main axis of the pleuro- logía, Museo Nacional de Historia Natural, under the coel has 83 mm and occupies a dorsal position in the number SGO-PV-961 (Figs. 1-4). A cast of one caudal centrum. The neural arch is broken and only part of the vertebra (MN 7232-V) is deposited in the Museu Na- peduncles is preserved. Their attachment to the centrum cional/UFRJ (Rio de Janeiro). is longer than the total length of the pleurocoels. The Occurrence: The material comes from an outcrop near centrodiapophyseal lamina is undivided. Together with Conchi Viejo town, Atacama Desert, Antofagasta Re- the peduncles, this lamina is inclined anteriorly. gion, and was collected in a surface of 2 m2. Judging from the preserved portion, the neural arch is wider than high. There is no evidence of the para- Recorded temporal and stratigraphic range: Upper pophyses at the centrum or at the lower portion of the Cretaceous, Tolar Formation. neural arch indicating that this is a middle or posterior Diagnosis: Titanosaurid dinosaur with the following dorsal vertebra. The ventral margin of the centrum is combination of characters that distinguishes it from other concave. Posteriorly, the centrum bears a pronounced members of this clade (autapomorphies are marked with excavation. an asterisk): centrum of dorsal vertebrae pierced by The second preserved dorsal vertebra of Atacama- pleurocoels, which are rounded or elliptical but do not titan chilensis (SGO-PV-961b, Figs. 1C, D) is antero- An Acad Bras Cienc (2011) 83 (1) “main” — 2011/2/10 — 15:28 — page 213 — #3 A NEW TITANOSAUR SAUROPOD FROM THE ATACAMA DESERT, CHILE 213 Fig. 1 – Atacamatitan chilensis gen. et sp. nov., lateral and anterior views of dorsal vertebrae of SGO.PV. 961a (A, B) and SGO-PV-961b (C,D). Scale bars: 50 mm. posteriorly compressed. The neural arch is not complete in the preserved base of the neural arch. The pleuro- and only the peduncles, the prezygapophyses and part coel is circular and deep. The most proximal part of the of the left diapophysis are preserved. The base of the diapophyses presents an inclination of 30◦. The poste- peduncles is long and covers almost the total length of rior face of the centrum is less excavated than in SGO- the centrum. There is little distance between both prezy- PV-961a. The short inter-prezygapophyseal distance, the gapophyses, forming, in anterior view, an angle of ap- reduced excavation of the posterior centrum face, the proximately 35◦. Part of the prezygapophyseal lamina dorsolaterally projected transverse process and the ab- is preserved in the left prezygapophysis. There is no sence of the parapophyses suggest that this vertebra evidence of parapophyses situated on the centrum or belongs to the posterior part of the dorsal series. An Acad Bras Cienc (2011) 83 (1) “main” — 2011/2/10 — 15:28 — page 214 — #4 214 ALEXANDER W.A.