estimated length of . Extrapolating from that skull, they estimated the skull of Giganotosaurus to have been long, making it one of the largest known theropod skulls. Description Giganotosaurus is thought to have been one of the largest theropod dinosaurs, but the incompleteness of its remains have made it difficult to estimate its size reliably. It is therefore impossible to determine with certainty whether it was larger than Tyrannosaurus, for example, which has been considered the largest theropod historically. Different size estimates have been reached by several researchers, based on various methods, and depending on how the missing parts of the skeleton have been reconstructed. Length estimates for the holotype specimen have varied between , with a skull between long, a femur (thigh bone) between long, and a weight between . Fusion of sutures (joints) in the braincase indicates the holotype specimen was a mature individual. A second specimen, consisting of a dentary bone from a supposedly larger individual, has been used to extrapolate a length of , a skull long, and a weight of . Some writers have considered the largest size estimates for both specimens exaggerated. Giganotosaurus has been compared to an oversized version of the well-known genus Allosaurus. Skull Though incompletely known, the skull of Giganotosaurus appears to have been low. The maxilla of the upper jaw had a long tooth row, was deep from top to bottom, and its upper and lower edges were almost parallel. The maxilla had a pronounced process (projection) under the nostril, and a small, ellipse-shaped fenestra (opening), as in Allosaurus and Tyrannosaurus. The nasal bone was very rugose (rough and wrinkled), and these rugosities continued backwards, covering the entire upper surface of this bone. The lacrimal bone in front of the eye had a prominent, rugose crest (or horn) that pointed up at a backwards angle. The crest was ridge-like, and had deep grooves. The postorbital bone behind the eye had a down and backwards directed jugal process that projected into the orbit (eye opening), as seen in Tyrannosaurus, Abelisaurus, and Carnotaurus. The supraorbital bone above the eye that contacted between the lacrimal and postorbital bones was eave-like, and similar to that of Abelisaurus. The quadrate bone at the back of the skull was long, and had two pneumatic (air-filled) foramina (holes) on the inner side. The skull roof (formed by the frontal and parietal bones) was broad and formed a