Long Limbs Helped Propel T. Rex Up the Dinosaur Food Chain - The New York Times

The apex predator wasn’t a quick runner because of its heft, but its lanky limbs ensured it could amble efficiently for hours.

A study published earlier this month in PLOS One showed that some dinosaurs were particularly efficient walkers because of their long hind limbs.

Dececchi and his colleagues amassed measurements of hind limbs and published body mass estimates for 34 dinosaur specimens.

Dececchi and his collaborators compared calculations of running speed.

The researchers determined that dinosaurs weighing less than a few hundred pounds were actually faster according to the calculations that used their body mass compared with the calculations that didn’t.

But the situation changed for animals larger than about 2,000 pounds — those dinosaurs moved considerably slower, according to the equations that included their mass compared with those that just included stride length and hip height.

For behemoths like Tyrannosaurus, that difference was significant: 18 miles per hour versus 45 miles per hour.

Dececchi and his colleagues wondering about the evolutionary advantage of lanky limbs for a massive dinosaur.

Dinosaurs like Tyrannosaurus walked about 10 miles per day, previous research has suggested.

They found that Tyrannosaurus used between 1 and 35 percent less energy than other related dinosaurs.