Saurophaganax ("lord of lizard-eaters") is a genus of large allosaurid dinosaur from the Morrison Formation of Late Jurassic (latest Kimmeridgian age, about 151 million years ago) Oklahoma, United States.[1] Some paleontologists consider it to be a junior synonym and species of Allosaurus (as A. maximus). Saurophaganax represents a very large Morrison allosaurid characterized by horizontal laminae at the bases of the dorsal neural spines above the transverse processes, and "meat-chopper" chevrons.[2] The maximum size of S. maximus has been estimated at anywhere from 10.5 meters (34 ft)[3] to 13 meters (43 ft) in length,[4] and 3 metric tons (3.3 short tons)[3] to 4.5 metric tons (5.0 short tons) in weight.[5] In 2020, it was estimated at 3.5-3.8 tons, with a minimum average weight of 2.6 tons and a maximum average weight of 4.7 tons.[6]
In 1931 and 1932, John Willis Stovall uncovered remains of a large theropod near Kenton in Cimarron County, Oklahoma in layers of the late Kimmeridgian. In 1941, these were named Saurophagus maximus by Stovall in an article by journalist Grace Ernestine Ray.[7] The generic name is derived from Greek σαυρος, sauros, "lizard", φάγειν, phagein, "to eat", with the compound meaning of "lizard eater". The specific epithet maximus means "the largest" in Latin. Because the naming article did not contain a description, the name remained a nomen nudum. In 1987, Spencer George Lucas erroneously made OMNH 4666, a tibia, the lectotype, unaware that Saurophagus was a nomen nudum.[8]
Later, it was discovered that the name Saurophagus was preoccupied: in 1831, it had already been given by William Swainson to a tyrant-flycatcher, an extant eater of taxonomically true lizards.[9] In 1995, Daniel Chure named a new genus: Saurophaganax, adding Greek suffix -άναξ, anax, meaning "ruler", to the earlier name. Chure also found OMNH 4666 undiagnostic in relation to Allosaurus, so he chose OMNH 01123, a neural arch, as the holotype for Saurophaganax.[10] — and Saurophaganax is not a renaming of "Saurophagus".[11] Much of the material informally named "Saurophagus maximus", namely those diagnostic elements that could be distinguished from Allosaurus, were referred to Saurophaganax maximus by Chure. They contain disarticulated bones of at least four individuals.[11]
Saurophaganax is the official state fossil of Oklahoma,[12] and a large skeleton of Saurophaganax can be seen in the Jurassic hall in the Sam Noble Oklahoma Museum of Natural History. Although the best known Saurophaganax material was found in the panhandle of Oklahoma, possible Saurophaganax material, NMMNH P-26083, a partial skeleton including a femur, several tail vertebrae, and a hip bone, has been found in northern New Mexico.[13]
The identification of Saurophaganax is a matter of dispute. It has been described as its own genus,[11] or as a species of Allosaurus: Allosaurus maximus.[14] The most recent[when?] review of basal tetanurans accepted Saurophaganax as a distinct genus.[15] New possible Saurophaganax material from New Mexico may clear up the status of the genus.[13]
Saurophaganax was one of the largest carnivores of Late Jurassic North America. Chure even gave an estimate of 14 m (46 ft),[11] though other estimations have been lower. The fossils known of Saurophaganax (both the possible New Mexican material and the Oklahoma material) are known from the Brushy Basin Member, which is the latest part of the Morrison Formation, suggesting that this genus was either always uncommon or that it first appeared rather late in the Jurassic. Saurophaganax was large for an allosaurid, and bigger than both its contemporaries Torvosaurus tanneri and Allosaurus fragilis. Being much rarer than its contemporaries, making up one percent or less of the Morrison theropod fauna, not much about its behavior is known.