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

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)

After nearly 30 years since its discovery in Montana, a new species of tyrannosaur is finally making its debut. During its lifetime about 75 million years ago, Daspletosaurus horneri measured almost 30 feet (9 meters) long and stood 7.2 feet (2.2 m) tall at its hipbone. Its longest tooth measured 2.7 inches (70 centimeters) long.The D. horneri finding also helped settle a recent debate about whether tyrannosaurs, such as Tyrannosaurus rex, had lips. A number of well-preserved D. horneri skulls reveal that the dinosaur did not have lips, and instead sported large, flat scales that were likely extremely sensitive to touch. [ Read the Full Story on the New Tyrannosaur Finding ]

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 ]