Saurophaganax

Credit: Mario Lanzas on the Wikimedia Commons.

*Saurophaganax* is a genus of theropod dinosaur that lived in North America during the Late Jurassic, 151 million years ago.

## History

John Willis Stovall in 1931 and 1932 discovered large theropod material near Kenton, Cimarron County, Oklahoma in Late Kimmeridgian-aged layers. In 1941, they were named Saurophagus maximus by Stovall in an article by Grace Ernestine Ray from the Greek σαυρος (sauros), "lizard" and φάγειν (phagein), "to eat", fully meaning of "lizard eater". Maximus means "the largest" in Latin. Since the article did not contain a description, it was a nomen nudum. Lucas assigned OMNH 4666, a fossil tibia, as the lectotype, and was unaware it was informally named.

However, in 1831, William Swainson had given the name to a tyrant-flycatcher. In 1995, Daniel Chure erected *Saurophaganax*. In relation, to *Allosaurus*, Chure found OMNH 4666 was undiagnostic, so he used OMNH 01123, a neural arch, as a holotype. Most of the elements referred to the nomen nudum can be differentiated from *Allosaurus*. At least four disarticulated individuals were attributed by Chure.

*Saurophaganax* is the state fossil of Oklahoma, with a large skeleton mounted in the Jurassic hall of the San Noble Oklahoma Museum of Natural History. NMMNH P-26083 is a partial skeleton (femur, tail vertebrae and a hip) and was found in New Mexico.

The name *Saurophaganax* is from the Greek "sauros", meaning reptile or lizard, "phagos," meaning eater, and "anax", meaning master, ruler or king. The meaning of the generic name according to Chure (1995) is "king of the reptile-eaters".

## Description

*Saurophaganax* is known from fragmentary remains. The holotype specimen consists of the fifth dorsal neural arch, though the paratypes consist of metatarsi, teeth, chevrons, a pubis, two quadrates, a humerus, tibia, a femur, an ischium, a partial ilium, and an ungual. Referred specimens include phalanges and additional femora, among other things.

*Saurophaganax* can be distinguished from other theropods by horizontal laminae, protruding from the bases of the dorsal neural spines, and unusual "meat-chopper" chevrons. While generally accepted as a distinct taxon, Saurophaganax is represented by at least four individuals, and it is difficult to refer fossils to specific ones.

## Classification

It is difficult to ascertain the classification of *Saurophaganax*. Some believe it to be a distinct taxon, while others believe it to be a species of *Allosaurus*, or even a large *A. fragilis*. It must be noted, though, that the authors of the 2020 paper describing *Allosaurus jimmadseni* chose to list *Saurophaganax* as its own genus. New material from New Mexico may clear up if *Saurophaganax* is distinct or not.

## Paleoecology

*Saurophaganax* was one of the largest Late Jurassic, North American predators. Chure estimated a length of 14 meters (46 feet), but other estimations are lower. All *Saurophaganax* are known ffrom the Brushy Basin Member, Morrison Formation, where it was likely uncommon or appeared late in the Jurassic. *Saurophaganax* was a large allosauroid, larger than contemporaneous genera *Torvosaurus tanneri* and *Allosaurus fragilis*, and was much rarer, making 1% or less of Morrison theropod fauna. Little behaviour is known.

The Morrison is a sequence of shallow marine and alluvial sediment, which is 156.3 million years old at the base and 146.8 million years old at the top, according to radiometric dating. This places the formation as Late Oxfordian, Kimmeridgian and Early Tithonian (Late Jurassic). It was semiarid, with wet and dry seasons. The Morrison Basin stretched from New Mexico to Saskatchewan, forming when the Front Range of the Rocky Mountains precursors pushed upwards and to the west. Deposits, from an eastward drainage, were carried by streams and rivers, depositing in swampy lowlands, lakes, river channels and floodplains. It is similar in age to the Solnhofen Formation and Tendaguru Formation. It was the center of the Bone Wars in 1877.

The fauna was dominated by sauropods, including: *Barosaurus*, *Apatosaurus*, *Brontosaurus*, *Camarasaurus*, *Diplodocus* and *Brachiosaurus*. Contemporaneous with *Saurophaganax*, and may have been prey, include *Camptosaurus*, *Dryosaurus*, *Stegosaurus* and *Nanosaurus*. Other predators include *Torvosaurus*, *Ceratosaurus*, *Marshosaurus*, *Stokesosaurus*, *Ornitholestes* and *Allosaurus*, who made 70-75% of theropods and the highest level in the trophic food web. Other vertebrates include ry-finned fish, frogs (like *Eobatrachus*), salamanders, turtles, sphenodonts, lizards, crocodylomorphs (like *Goniopholis*) and pterosaurs (like *Kepodactylus*). *Fruitafossor*, docodonts, multituberculates, symmetrodonts and triconodonts make up the mammal populations. Green algae, fungi, mosses, horsetails, cycads, ginkgoes and conifers make the flora. River-lining forests made of tree ferns, gallery forests, fern savannas with trees (*Brachyphyllum*) were all present environments. Stovall found *Apatosaurus* in Oklahoma, which could have been prey for *Saurophaganax*.

*Allosaurus* bites on *Mymoorapelta* were found (among other remains) in the Late Jurassic Mygatt-Moore Quarry. These left striations that, when measured to find the denticle width, produced a body size greater than any *Allosaurus* or *Ceratosaurus*, being the only like these found. It was either a large *Allosaurus*, or a separate taxon from *Torvosaurus* and *Saurophaganax* (which were not known from the quarry.. This increases the diversity of the site and produces great evidence for *Allosaurus* cannibalism. Based on the position and nutrient value of associated elements, the *Mymoorapelta* was predated or scavenged after death, with *Allosaurus* scavenging some time after death.

## References

* https://www.theropoddatabase.com/Carnosauria.htm#Saurophaganaxmaximus

* Ray, 1941. Big for his day. Natural History. 48, 36-39.

* Camp, Welles and Green, 1953. Bibliography of fossil vertebrates 1944-1948. Geological Society of America Memoir. 57, 465 pp.

* https://www.researchgate.net/profile/Daniel-Chure/publication/230892243\_A\_reassessment\_of\_the\_gigantic\_theropod\_Saurophagus\_maximus\_from\_the\_Morrison\_Formation\_Upper\_Jurassic\_of\_Oklahoma\_USA/links/54808f3f0cf22525dcb5f4a1/A-reassessment-of-the-gigantic-theropod-Saurophagus-maximus-from-the-Morrison-Formation-Upper-Jurassic-of-Oklahoma-USA.pdf

* Glut, Donald F. (1997). "Saurophagus". *Dinosaurs: The Encyclopedia*. Jefferson, North Carolina: McFarland & Co. pp. 793–794.
* Smith, 1998. A morphometric analysis of *Allosaurus*. Journal of Vertebrate Paleontology. 18(1), 126-142.

* Chure, 2000. A new species of *Allosaurus* from the Morrison Formation of Dinosaur National Monument (Utah-Colorado) and a revision of the theropod family Allosauridae. PhD thesis. Columbia University. 964 pp.

* Chure & Loewen, 2020 "Cranial anatomy of *Allosaurus jimmadseni*, a new species from the lower part of the Morrison Formation (Upper Jurassic) of Western North America." *PeerJ*.
* https://www.nhm.ac.uk/discover/dino-directory/saurophaganax.html
* https://www.researchgate.net/figure/Skeleton-of-Saurophaganax-with-bones-known-from-Peterson-quarry-darker-shade-and\_fig9\_284450467
* https://www.researchgate.net/publication/272151969\_A\_morphometric\_analysis\_of\_Allosaurus
* https://www.researchgate.net/publication/296022663\_A\_NEW\_LARGE-BODIED\_THEROPOD\_DINOSAUR\_FROM\_THE\_UPPER\_MORRISON\_FORMATION\_LATE\_JURASSIC\_TITHONIAN\_OF\_COLORADO
* https://www.researchgate.net/publication/341693059\_High\_frequencies\_of\_theropod\_bite\_marks\_provide\_evidence\_for\_feeding\_scavenging\_and\_possible\_cannibalism\_in\_a\_stressed\_Late\_Jurassic\_ecosystem
* https://www.mindat.org/taxon-4967061.html
* https://www.smithsonianmag.com/science-nature/a-comedy-of-dinosaur-errors-8396256/
* https://www.tandfonline.com/doi/abs/10.1080/02724634.1998.10011039