Torvosaurus tanneri

Torvosaurus tanneri was among the largest theropods in the Late Jurassic Morrison ecosystem of western North America. It belonged to Megalosauridae, an older radiation of large predators distinct from the allosaurids that shared its environment. Fossils from the Dry Mesa Dinosaur Quarry include the type forelimbs and referred skull, vertebral, pelvic and hind-limb bones. Together they indicate a deep-bodied, heavy-headed carnivore with massive arms and a large claw on the inner finger. No single complete skeleton is known, so the familiar whole-animal reconstruction combines multiple individuals.

Its fossils occur between approximately 153 and 148 million years ago. Values shown here are approximate and reflect the current curated seed dataset.

Torvosaurus had a large, deep skull armed with thick, laterally compressed and serrated teeth. The forelimbs were unusually robust for a giant theropod: the humerus was massive, the ulna short, and the hand retained three functional clawed fingers with an enlarged first claw. A broad pelvis and powerful hind limbs supported a heavy bipedal body. Megalosaurid features in the jaws, vertebrae and pelvis distinguish it from Allosaurus. Preserved elements imply a long muscular tail, but much of the skull and skeleton remains reconstructed from related taxa.

• Large, deep skull with thick serrated teeth
• Massive straight humerus and short robust ulna
• Three functional fingers with an enlarged first claw
• Broad, strongly joined pelvic bones
• Powerful hind limbs supporting obligate bipedal movement
• Megalosaurid vertebral and jaw features distinct from Allosaurus

Vivian and Eddie Jones discovered a large theropod toe bone in the Dry Mesa area in 1971, prompting James Jensen's Brigham Young University excavations. Peter Galton and Jensen named Torvosaurus tanneri in 1979 from paired forelimb bones catalogued as BYU 2002, with other Dry Mesa bones referred to the species. Brooks Britt's 1991 monograph described additional cranial and postcranial material and clarified its osteology. The genus means savage lizard; the species honours Nathan Eldon Tanner, a counsellor in the First Presidency of the Church of Jesus Christ of Latter-day Saints.

Discovery credit: Vivian Jones, Eddie Jones, James A. Jensen.

Naming authors: Peter M. Galton, James A. Jensen.

The Morrison Formation records seasonally dry river floodplains, wetlands and gallery forests across western North America. At Dry Mesa, Torvosaurus occurred in an exceptionally diverse dinosaur assemblage that included Allosaurus, Ceratosaurus, several sauropods, Stegosaurus and smaller ornithischians. Its rarity relative to Allosaurus makes its precise ecological role difficult to quantify.

Large serrated teeth, a deep skull and powerful grasping forelimbs identify Torvosaurus as a macropredator and carcass feeder. It could probably attack large herbivores, but no specific prey choice is demonstrated by gut contents or an associated kill site. Coexistence with Allosaurus and Ceratosaurus may reflect ecological partitioning, yet direct evidence for how these predators divided food or habitat is limited. No fossil association supports pack hunting.

• Its type specimen consists primarily of paired forelimb bones rather than a complete skeleton.
• The arms were large and muscular, with three useful fingers and an enlarged thumb claw.
• It shared the Morrison ecosystem with the more abundant predators Allosaurus and Ceratosaurus.
• The Portuguese species Torvosaurus gurneyi is distinct from the North American T. tanneri shown here.

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1. 01
   A new large theropod dinosaur from the Upper Jurassic of Colorado

   Peter M. Galton, James A. Jensen · Brigham Young University Geology Studies 26(1), 1–12 · 1979

   Open source
2. 02
   Theropods of Dry Mesa Quarry (Morrison Formation, Late Jurassic), Colorado, with emphasis on the osteology of Torvosaurus tanneri

   Brooks B. Britt · Brigham Young University Geology Studies 37, 1–72 · 1991

   Open source
3. 03
   Museum of Paleontology

   Brigham Young University

   Open source