Acrocanthosaurus atokensis

Acrocanthosaurus atokensis was the dominant known giant theropod of parts of Early Cretaceous North America. Its most conspicuous feature is a continuous series of tall neural spines over the neck, trunk, hips and front of the tail. These bones probably anchored substantial muscles and other soft tissues, producing a thick ridge whose precise external shape is unknown. A deep skull with blade-like serrated teeth, robust hind limbs and unusually strong forelimbs made Acrocanthosaurus a formidable macropredator. Anatomical studies place it within Carcharodontosauridae, linking it more closely to giant African and South American allosauroids than to the later tyrannosaurids.

Its fossils occur between approximately 113 and 110 million years ago. Values shown here are approximate and reflect the current curated seed dataset.

The skull was deep and narrow from above, with large openings and strongly textured bones around the snout and eyes. Laterally compressed teeth carried serrated cutting edges. Each hand retained three clawed fingers, and the muscular forelimb could flex strongly toward the body. Neural spines up to about two and a half times the height of their vertebral centra ran from the neck onto the tail. Their roughened surfaces suggest strong ligament and muscle attachment, favouring a thick muscular ridge over the unsupported thin sail common in older artwork. The body was balanced over powerful hind limbs by a long, deep tail.

• Tall neural spines extending from the neck along the back and onto the tail
• Deep narrow skull with large antorbital and temporal openings
• Laterally compressed teeth with serrated cutting edges
• Powerful forelimbs ending in three clawed fingers
• Robust hind limbs supporting a large bipedal body
• Long muscular tail balancing the head and torso

J. Willis Stovall's University of Oklahoma crews collected two partial skeletons in Atoka County, Oklahoma, during the early 1940s. Stovall and Wann Langston Jr. named Acrocanthosaurus atokensis in 1950, combining the Greek for high, spine and lizard with a reference to Atoka County. The holotype OMNH 10146 includes a partial skull and skeleton; paratype OMNH 10147 preserves complementary anatomy. Later Texas material, especially the much more complete NCSM 14345 nicknamed Fran, shaped modern mounts and body estimates. Fran has historically been referred to this species, but detailed differences from the Oklahoma type make renewed comparison worthwhile.

Discovery credit: University of Oklahoma field crews, J. Willis Stovall.

Naming authors: J. Willis Stovall, Wann Langston Jr..

The Antlers and Twin Mountains formations record river channels, floodplains, forests and seasonally wet lowlands near the ancient Gulf of Mexico. Acrocanthosaurus lived in ecosystems containing large sauropods, the herbivore Tenontosaurus, smaller theropods, crocodile-line reptiles, turtles and fish. The famous Paluxy trackways come from broadly comparable Texas rocks, but an individual track maker cannot securely be identified as Acrocanthosaurus from footprint shape alone.

Its teeth and reinforced skull identify Acrocanthosaurus as a flesh eater, while the forelimbs were capable of strongly drawing objects toward the chest. Large sauropods and ornithopods were potential prey or carrion sources, but no particular attack sequence is fossilized. The back ridge may have contributed to display, heat exchange, fat storage or mechanical support; the bones alone do not select one function. No nest, bonebed or securely assigned trackway demonstrates pack hunting or other social behaviour.

• Acrocanthosaurus lived roughly 45 million years before Tyrannosaurus rex.
• Its name refers to the tall vertebral spines running far beyond the shoulders and down the tail.
• CT study of the holotype skull reconstructed spaces for the brain, inner ear, nerves and blood vessels.
• The exceptionally complete Texas skeleton Fran underpins many familiar mounts but is not the Oklahoma holotype.

A research repository is not necessarily a public exhibit. Loan and display status can change, so check with the institution before visiting.

1. 01
   Acrocanthosaurus atokensis, a new genus and species of Lower Cretaceous Theropoda from Oklahoma

   J. Willis Stovall, Wann Langston Jr. · American Midland Naturalist 43 · 1950

   Open source
2. 02
   New information on the cranial anatomy of Acrocanthosaurus atokensis and its implications for the phylogeny of Allosauroidea

   Drew R. Eddy, Julia A. Clarke · PLoS ONE 6(3) · 2011

   Open source
3. 03
   Acrocanthosaurus atokensis holotype endocast

   Digital Morphology, University of Texas at Austin

   Open source
4. 04
   Estimating mass properties of dinosaurs using laser imaging and 3D computer modelling

   Karl T. Bates, Peter L. Manning, David Hodgetts, William I. Sellers · PLoS ONE 4(2) · 2009

   Open source