Some kangaroos were not hopping mad

What word springs to mind when you think of a kangaroo? "Hop" would probably be on the list. Hopping is an efficient way for today's kangaroos to move along speedily, but a study in the open-access journal Plos One suggests that some giant kangaroos used to get around by striding.

Sthenurines lived tens of thousands of years ago, and some species of the short-faced kangaroos could grow large; the biggest, Procoptodon goliah, topped the scales at an estimated 240kg.

That bulk has called into question "their biomechanical abilities for a hopping gait", say authors of the paper, Locomotion in Extinct Giant Kangaroos: Were Sthenurines Hop-Less Monsters?

The paper discusses the anatomy of the extinct giant kangaroos in detail, including features that would indicate they bore weight on one foot at a time, and it suggests that sthenurine kangaroos were able to stride bipedally with a relatively upright trunk.

“We propose that this gait would have been used only at slow speeds in the smaller sthenurines, with hopping employed at faster speeds, but in the very large sthenurine species this may have been their sole mode of locomotion,” write the researchers.

Study author Christine Janis, from Brown University in Rhode Island in the US, notes: “People often interpret the behaviour of extinct animals as resembling that of the ones known today, but how would we interpret a giraffe or an elephant known only from the fossil record? We need to consider that extinct animals may have been doing something different from any of the living forms, and the bony anatomy provides great clues.”