Relict duck-billed dinosaurs survived into the last age of the dinosaurs in subantarctic Chile (original) (raw)
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Boletín Museo Nacional de Historia Natural
Documentamos nueva evidencia de huellas tridáctilas de dinosaurios, las que comprenden nueve huellas aisladas en una nueva localidad de la Región de Atacama, norte de Chile. Los afloramientos que portan las marcas están localizados principalmente en la quebrada La Descubridora, hallándose además una traza aislada cerca de la intersección entre las quebradas La Descubridora y Carrizalillo, aproximadamente 11 km al sudeste del pueblo de Tierra Amarilla. Los niveles estudiados son asignados a la Formación Pabellón (Cretácico Inferior). Estas trazas corresponden al menos a dos formas pertenecientes a ornitópodos (con afinidades a dinosaurios Hadrosauriformes) y terópodos. Este registro expande el conocimiento de huellas de ornitópodos cretácicos en el país, las cuales sólo eran conocidas más al norte, en las formaciones Chacarilla y Quehuita, Región de Tarapacá, Formación Baños del Flaco en la Región de O'Higgins y en la Formación Dorotea en la Región de Magallanes.
A HISTORICAL AND BIOGEOGRAPHICAL EXAMINATION OF HADROSAURIAN DINOSAURS
2006
Duck-billed dinosaurs, or hadrosaurs, rank among the most unique, specialized, and successful dinosaur groups. They are known from localities throughout the Northern Hemisphere, predominately in North America and Asia, as well as from South America and Antarctica. During their Cretaceous tenure, hadrosaurs diversified into an array of crested and non-crested forms. This paper reviews the history of hadrosaur discoveries, placing them into geographic context, noting 27 valid taxa from North America, 16 from Asia, two from South America, two from Europe, and one occurrence from Antarctica.
NEW TRIDACTYL DINOSAUR FOOTPRINTS FROM THE LOWER CRETACEOUS OF THE ATACAMA REGION, NORTHERN CHILE
We report here new evidence of tridactyl dinosaur footprints, comprising nine isolated footprints from a new locality in the Atacama Region, northern Chile. The track-bearing levels are located mainly at La Descubridora ravine and one isolated track near the intersection between La Descubridora and Carrizalillo ravines, approximately 11 km southeast from Tierra Amarilla town; the studied levels are assigned to the Pabellon Formation (Lower Cretaceous). The icnites correspond at least to two dinosaur forms, mainly ornithopods (with affinities to Hadrosauriformes dinosaurs) and theropod footprints. These are the first well-documented dinosaur icnites and the first record of ornithopod footprints from the Atacama Region. This record expands the knowledge of ornithopods in Chile, which previously were only known from the Chacarilla Formation, Tarapacá Region, the Baños del Flaco Formation in O'Higgins Region and the Dorotea Formation in Magallanes Region.
First Late Jurassic dinosaur bones from Chile
Journal of Vertebrate Paleontology, 2008
Skeletal remains of dinosaurs from Chile are rare, unlike the ichnological record, which includes sauropods, theropods, and ornithopods, mostly from the Upper Jurassic-Lower Cretaceous (Moreno and Pino, 2002; Moreno et al., 2004). The first record of dinosaur bone in this country-a few remains of a titanosaur sauropod from the Upper Cretaceous of the Fourth (IV) Región-was reported by Casamiquela et al. (1969). Since then, the reported materials have been very scarce: only some titanosaur bones collected in the Upper Cretaceous of the Third (III) Región (Iriarte et al., 1999). Concerning their geographic distribution, most of the Chilean dinosaur remains occur north of 39°S Lat. (Salinas et al., 1991; Rubilar, 2003). In this paper, an assemblage of dinosaur bones from the Central Patagonian Cordillera at Aysén (southern Chile; ca. 46°S.), south of Lago General Carrera, is reported. Previous records of Jurassic dinosaurs of Chile consisted of footprints (Chong and Gasparini, 1976; Moreno and Rubilar, 1999). Thus, the remains from southern Chile are the first undoubted Jurassic dinosaurs found in this country, and the first significant remains of carnivorous dinosaurs, which previously were known only from isolated teeth found in the Upper Cretaceous Viñita Formation at the Monumento Natural Pichasca, in the Fourth (IV) Región (Rubilar, 2003).
Several Upper Cretaceous plesiosaur specimens recovered from southernmost Chile are described here. These were collected from upper levels of the Dorotea Formation exposed on three different localities (Sierra Baguales, Cerro Castillo, and Dumestre). The new material includes the first record of Aristonectes (Plesiosauria, Elasmosauridae), previously recorded from Argentina, central Chile, and Antarctica. Additional specimens include associated postcranial skeletons as well as isolated elements. Among these, we recognize the presence of aristonectines in the three studied localities, while non-aristonectine elasmosaurids were only collected from Cerro Castillo. The specimen from Dumestre is remarkable by being a small-sized adult, indeterminate aristonectine, and could be related to known representatives from Antarctica. These new finds prove the abundance of aristonectines as well as intermediate elasmosaurids along the Magallanes Basin during the uppermost Cretaceous, while extreme long-necked elasmosaurids as well as polycotylids seems to be completely absent during this time span. This key record from southernmost Chile and its strategic placement in the middle part of the Weddellian Province gives the chance for complementing the paleobiogeography of Upper Cretaceous plesiosaurs from the Southern Hemisphere. As a first result, a faunal turnover is observed during the early Maastrichtian, when extreme (very-long necked) elasmosaurids and polycotylids disappeared from the austral record. Since the early Maastrichtian and towards the late Maastrichtian, aristonectines became differentially abundant along the southeastern Pacific and Antarctica, but moderately represented in the southwestern Atlantic. On contrary, intermediate elasmosaurids were scarce in the Antarctic-Pacific realm, but abundant in the Atlantic. The updated record of austral plesiosaurs suggest a first stage of interchange from the Northern into the Southern Hemisphere, and through the Atlantic seaway, at least since the Coniacian to the late Campanian-early Maastrichtian. During the early Maastrichtian, aristonectines were relatively frequent in the New Zealand-Antarctica archipelago, becoming abundant along southern South America during the late Maastrichtian
Evolution of the carnivorous dinosaurs during the Cretaceous The evidence from Patagonia
Patagonia has yielded the most comprehensive fossil record of Cretaceous theropods from Gondwana, consisting of 31 nominal species belonging to singleton taxa and six families: Abelisauridae, Noasauridae, Carcharodontosauridae, Megaraptoridae nov. fam., Alvarezsauridae, and Unenlagiidae. They provide anatomical information that allows improved interpretation of theropods discovered in other regions of Gondwana. Abelisauroids are the best represented theropods in Patagonia. They underwent an evolutionary radiation documented fromthe Early Cretaceous through to the latest Cretaceous, and are represented by the clades Abelisauridae and Noasauridae. Patagonian carcharodontosaurids are known from three taxa (Tyrannotitan, Giganotosaurus and Mapusaurus), as well as from isolated teeth, collected from Aptian to Cenomanian beds. These allosauroids constituted the top predators during the mid-Cretaceous, during which gigantic titanosaur sauropodswere the largest herbivores. Megaraptorans have become better documented in recent years with the discovery of more complete remains. Megaraptor, Aerosteon and Orkoraptor have been described from Cretaceous beds from Argentina, and these taxa exhibit close relationships with the Aptian genera Australovenator, from Australia, and Fukuiraptor, from Japan. The Gondwanan megaraptorans are gathered into the newfamily Megaraptoridae, and the Asiatic Fukuiraptor is recovered as the immediate sister taxon of this clade. Although megaraptorans have been recently interpreted as members of Allosauroidea, we present evidence that they are deeply nested within Coelurosauria. Moreover, anatomical information supports Megaraptora as more closely related to the Asiamerican Tyrannosauridae than thought. Megaraptorans improve our knowledge about the scarcely documented basal radiation of Gondwanan coelurosaurs and tyrannosauroids as awhole. Information at hand indicates that SouthAmericawas a cradle for the evolutionary radiation for different coelurosaurian lineages, including some basal forms (e.g., Bicentenaria, Aniksosaurus), megaraptorans, alvarezsaurids less derived than those of Laurasia, and unenlagiids, revealing that Gondwanan coelurosaurs played sharply differing ecological roles, and that theywere taxonomically as diverse as in the northern continents. The unenlagiids represent an endemic South American clade that has been recently found to be more closely related to birds than to dromaeosaurid theropods. Analysis of the theropod fossil record from Gondwana shows the highest peak of origination index occurred during the AptianeAlbian and a less intense one in the Campanian time spans. Additionally, peaks of extinction index are recognized for the Cenomanian and TuronianeConiacian time spans. In comparison, the Laurasianpattern differs fromthat of Gondwana in the presence of an older extinction event during the AptianeAlbian time-span and a high origination rate during the Cenomanian time-bin. Both Laurasian and Gondwanan theropod records show a peak of origination rates during the Campanian.
Several Upper Cretaceous plesiosaur specimens recovered from southernmost Chile are described here. These were collected from upper levels of the Dorotea Formation exposed on three different localities (Sierra Baguales, Cerro Castillo, and Dumestre). The new material includes the first record of Aristonectes (Plesiosauria, Elasmosauridae), previously recorded from Argentina, central Chile, and Antarctica. Additional specimens include associated postcranial skeletons as well as isolated elements. Among these, we recognize the presence of aristonectines in the three studied localities, while non-aristonectine elasmosaurids were only collected from Cerro Castillo. The specimen from Dumestre is remarkable by being a small-sized adult, indeterminate aristonectine, and could be related with known representatives from Antarctica. These new finds prove the abundance of aristonectines as well as intermediate elasmosaurids along the Magallanes Basin during the uppermost Cretaceous, while extreme long-necked elasmosaurids as well as polycotylids seems to be completely absent during this time span. This key record from southernmost Chile and its strategic placement in the middle part of the Weddellian Province gives the chance for complementing the paleobiogeography of the Upper Cretaceous plesiosaurs from the Southern Hemisphere. As a first result, a faunal turnover is observed during the early Maastrichtian, when extreme (very-long necked) elasmosaurids and polycotylids disappeared from the austral record. Since the early Maastrichtian and towards the late Maastrichtian, aristonectines became differentially abundant along the southeastern Pacific and Antarctica, but moderately represented in the southwestern Atlantic. On contrary, intermediate elasmosaurids were scarce in the Antarctic-Pacific realm, but abundant in the Atlantic. The updated record of austral plesiosaurs suggest a first stage of interchange from the Northern into the Southern Hemisphere, and through the Atlantic seaway, at least since the Coniacian to the late Campanian-early Maastrichtian. During the early Maastrichtian, aristonectines were relatively frequent in the New Zealand-Antarctica archipelago, becoming abundant along southern South America during the late Maastrichtian.