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Saurophaganax ("lord of lizard-eaters") is a nomen dubium, chimeric genus of large saurischian dinosaur, possibly a sauropod, from the Late Jurassic (Kimmeridgian) Morrison Formation of Oklahoma, United States. This taxon was historically considered to represent a species of Allosaurus or very large allosaurid. However, re-examinations of the attributed specimens suggested that it is a chimera of multiple dinosaur genera, since some specimens most likely belong to a diplodocid sauropod, while the other referred specimens could be reassigned to a novel species of Allosaurus.
Later, it was discovered that the name Saurophagus was preoccupied: in 1831, it had already been given by William Swainson to Great kiskadee, an extant eater of taxonomically true lizards.W. Swainson and J. Richardson, 1831, Fauna boreali-americana, or, The zoology of the northern parts of British America: containing descriptions of the objects of natural history collected on the late northern land expeditions under command of Captain Sir John Franklin, R.N. Part 2, Birds, London, J. Murray In 1995, Daniel Chure named a new genus Saurophaganax, adding Greek suffix -άναξ, anax which means "ruler", replacing the earlier informal name "Saurophagus"; he also found OMNH 4666 undiagnostic in relation to Allosaurus, so he chose OMNH 1123, a neural arch, as the holotype for Saurophaganax.Chure, D., 2000, A new species of Allosaurus from the Morrison Formation of Dinosaur National Monument (Utah-Colorado) and a revision of the theropod family Allosauridae. Ph.D. dissertation, Columbia University, pp. 1–964 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.
In 2024, Danison and colleagues revised the referral of various specimens assigned to Saurophaganax maximus including the fragmentary holotype neural arch (OMNH 1123) based on their comparative analysis. They suggested that the holotype could not confidently be regarded as a theropod or sauropod, although the complex accessory laminae are more comparable to those of sauropods, especially some juvenile specimens of Apatosaurus. Some referred specimens more likely belong to diplodocids than the large Kenton 1 Quarry allosaurid. Since the holotype neural arch is so fragmentary, the researchers could not confidently refer it to a theropod or sauropod, so they considered Saurophaganax maximus to be a nomen dubium.
The Morrison Formation records an environment and time dominated by gigantic sauropod dinosaurs such as Barosaurus, Apatosaurus, Brontosaurus, Camarasaurus, Diplodocus, and Brachiosaurus. Dinosaurs that lived alongside Saurophaganax included the herbivorous ornithischians Camptosaurus, Dryosaurus, Stegosaurus, and Nanosaurus. Predators in this paleoenvironment included the theropods Torvosaurus, Ceratosaurus, Marshosaurus, Stokesosaurus, Ornitholestes, andFoster, J. (2007). "Appendix." Jurassic West: The Dinosaurs of the Morrison Formation and Their World. Indiana University Press. pp. 327–329. Allosaurus, which accounted for 70 to 75% of theropod specimens and was at the top trophic level of the Morrison food chain. Other vertebrates that shared this paleoenvironment included actinopterygii, such as Eobatrachus, , , sphenodontia, , terrestrial and aquatic crocodylomorpha like Goniopholis, and several species of pterosaur like Kepodactylus. Early mammals were present in this region, such as Fruitafossor, docodonts, multituberculates, symmetrodonts, and triconodonts. The flora of the period has been revealed by fossils of chlorophyta, fungi, , equisetum, , , and several families of . Vegetation varied from river-lining forests of , and (), to fern with occasional trees such as the Araucaria-like conifer Brachyphyllum.
Previously assigned allosaurid specimens
The identification of the allosaurid elements referred to Saurophaganax was a matter of dispute. It has been described as its own genus, or as a species of Allosaurus: Allosaurus maximus. A review of basal tetanurans in 2004 and Carrano et al.'s comprehensive 2012 analysis of Tetanurae accepted Saurophaganax as a distinct genus. Possible Saurophaganax material from New Mexico may clear up the status of the genus. In 2019, Rauhut and colleagues noted that the definitive taxonomic placement of Saurophaganax within Allosauroidea is unstable, being recovered as a sister taxon of Metriacanthosauridae or Allosauria, or even as a basalmost carcharodontosaurian. Supplementary information Re-evaluation of the assigned specimens in a 2024 reassessment suggested that the referred allosaurid specimens belong to a novel species of Allosaurus, named as Allosaurus anax.
Paleoenvironment
The Morrison Formation is a sequence of shallow marine and alluvial sediments which, according to radiometric dating, ranges between 156.3 million years old (Mega-annum) at its base, to 146.8 million years old at the top, which places it in the late Oxfordian stage, Kimmeridgian, and early Tithonian faunal stages of the Late Jurassic period. This formation is interpreted as a semiarid environment with distinct wet season and . The Morrison Basin where dinosaurs lived, stretched from New Mexico to Alberta and Saskatchewan, and was formed when the precursors to the Front Range of the Rocky Mountains started pushing up to the west. The deposits from their east-facing were carried by streams and and deposited in lowlands, lakes, river channels and . This formation is similar in age to the Solnhofen Limestone Formation in Germany and the Tendaguru in Tanzania. The fossils known of Saurophaganax (both the possible material from New Mexico 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. Because of the rarity of discovered remains, not much about its behavior is known. (2025). 9780253051578, Indiana University Press. ISBN 9780253051578
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