Bicentenaria (meaning "two hundred year anniversary"; named after the 200th anniversary of the 1810 May Revolution in Argentina) is an extinct genus of carnivorous coelurosaurian theropods which lived during the early Late Cretaceous (Cenomanian) Candeleros Formation of Argentina. It contains the type species, B. argentina.
Discovery and naming
In 1998, after a drop in the water level at the Ezequiel Ramos Mexía Reservoir had exposed rocks from the Candeleros Formation, Rauel Spedale and his two friends went on a fishing trip and discovered several bones and claws sticking out of the ground, which were several specimens of Bicentenaria, including the holotype. Spedale excavated the fossils using a pocket knife along with his bare hands, and he believed that he had discovered the remains of a machairodontine.
In 1999 and 2000, Spedale returned to the site, and he subsequently uncovered more bones on an area of only 30 by 40 centimeters with hammer and chisel to a depth of no more than , and he exhibited these remains in a display case in his home. The subsequent rise in water level made further excavations impossible, and because Spedale was enthusiastic about the find, he always carried photographs of it in his pocket to show to others. After he showed the photographs to a teacher from a local school, they understood that it was a unique discovery and put Spedale in touch with the paleontologist Raúl Ortiz. Ortiz concluded that it was an unknown dinosaur species and had the finds examined by a team from the Museo Argentino de Ciencias Naturales.
The fossils were determined to have belonged to a new genus of dinosaur, and the name Bicentenaria argentina was first reported in news articles in June 2012, and the paper describing it was formally published in August 2012 by Novas et al. (2012).
The holotype, MPCA 865, consists of the back of a skull and attached to it the back of the lower jaws. The paratype, MPCA 866, is a collection of loose bones from at least four individuals, including parts of the postcrania. It includes: fragments of two premaxillae with three pairs of teeth; a piece of upper right jawbone with a tooth; pieces of seventeen vertebrae; fourteen sacral vertebrae; twenty caudal vertebrae; pieces of two shoulder blades; an upper back corner of a right raven's jawbone; the tops of three ulna; the end of a spoke bone; eight hand claws; pieces of a left femur; five upper shafts of pubic bones; five partial femurs; the tops of two left tibia; the underside of a right tibia; a right tibia; pieces of five metatarsals; fifteen phalanges, separately eight foot claws and pieces of rib.
Description
General construction, size and distinctive features
Bicentenaria is a rather small bipedal predatory saurian whose body length is estimated at in length.
The describers were able to identify some distinguishing features. The praemaxillary teeth of the anterior upper jaw have only serrations at the base of the tooth crown. The quadratojugal has an anterior branch that is twice as long as the ascending branch. The quadratum has an outer articular nodule at the bottom that is much larger than the inner one. In the lower jaw, the surangulare has a raised upper edge that is trapezoidal in lateral view. The retroarticular protrusion at the back of the mandible is flattened, widened transversely, and spoon-shaped. The humerus has a top that is flattened from front to back and a bottom that shows a deep groove at the front. The hand claws of the outer fingers have posteriorly overhanging leg edges on their posterior top.