|Two baby Stegosaurus models on display at the Morrison Natural History Museum. Stegosaurus individuals of all sizes would have been able to switch between walking on two and four legs, facultative bipedalism, which is the topic of this post.|
|Several gerenuk at Walt Disney World in Florida using their hind legs to eat some food off of the higher branches. Photo Credit: Julie Neher|
|A little golden-mantled ground squirrel (Callospermophilus lateralis) using its forepaws to manipulate its meal at the Cheyenne Mountain Zoo in Colorado Springs. Forepaw manipulation is something that many rodents can do.|
|A meerkat at the Cheyenne Mountain Zoo, using part of its termite mound as a lookout area. It'll stand on its hind legs, but runs around on all fours.|
|A Jefferson's ground sloth (Megalonyx jeffersoni) exaggerates the size of the fish it caught last summer at the Rocky Mountain Dinosaur Resource Center (RMDRC) in Woodland Park, Colorado. Just like the gerenuk, the ground sloths would have reared up on their hind legs to consume vegetation off of a higher level.|
|A Glossotherium skeleton on display at the American Museum of Natural History in New York, walking quadrupedally.|
|An Anatotitan skeleton on display at the American Museum of Natural History in New York. You can see this skeleton is moving around on all fours....|
|....but the animal could also walk bipedally.|
|Baby Stegosaurus model on display at the Morrison Natural History Museum, right next to the very first baby Stegosaurus track ever discovered by museum director Matthew Mossbrucker in 2007.|
|Two trackways made by infant apatosaur dinosaurs, on display at the Morrison Natural History Museum. The lower trackway has tracks from both the front and back feet, while the upper trackway has only hind foot tracks, and are spaced two to three times further apart than the ones in the lower trackway. This shows that these baby dinosaurs would have been capable of running around on their hind legs!|
|A Parma wallaby at the Cheyenne Mountain Zoo, moving around on its hind limbs.|
|Here, you can see the same Parma wallaby, moving on all four legs.|
|A mounted skeleton of the Pleistocene kangaroo Simosthenurus at the American Museum of Natural History in New York. As you can see, even though it looks like its twerking, it is on its hind legs, grabbing some vegetation.|
Alexander, R. (n.d.). Bipedal animals, and their differences from humans. J Anatomy Journal of Anatomy, 321-330.
Weinbaum, J. (2013). Postcranial skeleton of Postosuchus kirkpatricki (Archosauria: Paracrocodylomorpha), from the Upper Triassic of the United States. Geological Society, London, Special Publications, 525-553.