Photos: Newfound Tyrannosaur Had Nearly 3-Inch-Long Teeth

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Fearsome beast

<em>D. horneri</em> had large, flat scales and portions of armor-like skin on its snout, jaws and horns. The large horn behind its eye was covered by keratin, the same material found in human fingernails.

(Image credit: Copyright Dino Pulerà)

The skull

New tyrannosaur skull

(Image credit: Copyright Dino Pulerà)

The first D. horneri skull ever found, next to an illustration of what the dinosaur may have looked like in real life. The skull is about 32 inches (89.5 cm) long.

Rawr

<em>D. horneri</em> had large, flat scales and portions of armor-like skin on its snout, jaws and horns. The large horn behind its eye was covered by keratin, the same material found in human fingernails.

(Image credit: Copyright Dino Pulerà)

D. horneri had large, flat scales and portions of armor-like skin on its snout, jaws and horns. The large horn behind its eye was covered by keratin, the same material found in human fingernails.

The small bumps on its flat scales are called integumentary sensory organs (ISOs), which are also seen in crocodilians. These ISOs provide tactile sensitivity. The skull is 895 millimeters long.

Evolution

tyrannosaur anagenesis

(Image credit: Copyright Thomas D. Carr)

Evolution through anagenesis (above) is much rarer than cladogenesis (below).

Super skull

tyrannosaur skull anatomy

(Image credit: Copyright Thomas D. Carr)

The anatomy of a D. horneri skull.

Direct descendant?

tyrannosaur descendant

(Image credit: Copyright Thomas D. Carr)

Different anatomical clues suggest that D. horneri is a direct descendant of another tyrannosaur called Daspletosaurus torosus. This likely happened through anagenesis, the researchers said.

Size matters

tyrannosaur skulls

(Image credit: Copyright Thomas D. Carr)

A comparison of D. horneri skulls, a T. rex skull and a D. torosus skull.

Timeline

tyrannosaur timeline

(Image credit: Copyright Thomas D. Carr)

D. horneri lived from about 75.1 million to 74.4 million years ago, after D. torosus, which lived from about 76.7 million to 75.2 million years ago.

Dinosaur differences

tyrannosaur differences

(Image credit: Copyright Thomas D. Carr)

D. horneri and D. torosus have several differences.

Excavation

tyrannosaur excavation

(Image credit: Provided by David Varricchio)

Researchers enlisted the help of mules to excavate the field jackets containing the bones of an adult D. horneri specimen in Montana in August 2001.

[ Read the Full Story on the New Tyrannosaur Finding ]

Laura Geggel
Laura Geggel
Managing Editor

Laura is the managing editor at Live Science. She also runs the archaeology section and the Life's Little Mysteries series. Her work has appeared in The New York Times, Scholastic, Popular Science and Spectrum, a site on autism research. She has won multiple awards from the Society of Professional Journalists and the Washington Newspaper Publishers Association for her reporting at a weekly newspaper near Seattle. Laura holds a bachelor's degree in English literature and psychology from Washington University in St. Louis and a master's degree in science writing from NYU.