Tuesday, 31 January 2012

Tyrannosaurus Teeth - The crowns of a king

The teeth of Tyrannosaurus are unlike any other, they are highly specialized for killing and eating other Dinosaurs. They are not only famously large and recurved (or "banana-shaped"), but they are also placed for maximum effect.
Teeth of Tyrannosaurus Rex
Allosaurus and T. rex (not to scale)
Tyrannosaurus did not have the hatched-shaped head common to most Theropods, rather the head of a T. rex was comparatively wide ending in a blunt snout.
The teeth of a Tyrannosaur were also different in shape from those of other Theropods. Where almost all Theropods had flat blade-like teeth for slicing through meat, Tyrannosaurs had teeth that were decidedly more rounded (in some teeth almost circular) for punching through flesh and crushing bone. Tyrannosaurus in fact had three distinct types of teeth in it's jaws.

The upper front jaw of a T. rex was U-shaped and densely packed with smaller teeth. Small, curved backward and with flat tips these closely spaced teeth were ideal for shearing pieces of meat from an animal, living or dead, and for scraping the meat of the bones once the prey is down.

The middle teeth of Tyrannosaurus were actually the largest, with some being as tall as 30 centimetres total length. That does however include the massive root, which was disproportionally large in Tyrannosaurs (as much as two-thirds of the total length of the tooth!).
A good sized T-Rex tooth might have a crown of over 10 centimetres, but it should be noted that T. rex teeth differ extremely in size, even within the middle part of the jaw. The longest teeth would initially have the full pressure of the bite behind them, helping them to sink deeply into the flesh of the prey, and even crushing bones that happened to get in their way. These teeth were recurved and reinforced with ridges to withstand the extreme pressure of a bite, and they had serrations to even better cut through flesh.
The middle teeth would not only have inflicted massive puncture wounds to it's victims, but with their massive roots they would have been ideal for coping with the stresses of holding on to a struggling prey as well.

Differently-sized teeth of Tyrannosaurus, note the clearly visible line marking the crown

At the rear of it's jaw T. rex had smaller even more robust teeth, these could be clamped together to deliver particularly crushing bites. This would have been used to deliver devastating bite/forces (in one famous case even biting the horn of a Triceratops in two) and to crush the bones of smaller prey so it could swallow them along with the rest of the animal. As attested by the crushed bones of a young Dinosaur found in a Tyrannosaurus coprolite,

That Tyrannosaurus could deliver a bone-crushing bite didn't mean that it deliberately crushed bones to get at the marrow (as seen in modern scavengers, like Hyena's). The existing evidence  for Tyrannosaur scavenging shows that the Tyrannosaur in question deliberately ate around the bones, leaving the bone undamaged except from where it grazed them while scarping of the flesh.

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