Jurassic World: Facultative Bipedalism

In the new Jurassic World movie, the main movie monster is a critter that the movie characters called Indominus rex.  The dinosaur is a big guy, and its forearms are especially large, especially when compared to the tiny arms of Tyrannosaurus rex.  There were a few funky things going on with the Jurassic World dinosaur hands, but we can talk about that in a later post.  Today, we are going to talk about an interesting type of behavior exhibited by Indominus: facultative bipedalism.

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.

Facultative bipedalism is an animal that can walk on both two or four legs, at least for a little bit.  For example, the gerenuk (Litocranius walleri), a type of African antelope, can rear up on their hind legs to nab plants off of some higher branches.  But they can't really walk on their hind legs, so they wouldn't really be considered facultative bipeds.  My little Djungarian hamster (Phodopus sungorus) will lean back on his hind limbs to manipulate food with his forepaws, as do many other types of rodents.  Meerkats (Suricata suricatta) often sit on their hind legs to observe their surroundings.  The extinct giant ground sloths would have reclined on their haunches to browse from the higher branches of trees.  But none of them would have moved around on their hind limbs, and therefore would not be classified as bipeds, facultative or otherwise.

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. 

Another rodent manipulating an object with its forepaws. This North American porcupine (Erethizon dorsatum), also at the Cheyenne Mountain Zoo, is holding a primitive slingshot weapon.  Zookeepers have had a very difficult time controlling these animals.

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.

The duck-billed hadrosaur dinosaurs and the iguanodonts are good examples of facultative bipeds.  They would have been capable of moving around on both two or four legs, depending on whether they were grazing lazily (quadrupedal) or moving more quickly (bipedal).

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.

Stegosaurus was initially thought to be bipedal, and although most modern reconstructions show the armored dinosaur as a quadruped, fossil trackways at the Morrison Natural History Museum (MNHM) in Colorado demonstrate quite clearly that the baby Stegosaurus, tiny little six pound hatchlings, were entirely capable of moving around on their back legs!

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.

For stegosaur and hadrosaur dinosaurs, most of their weight was centered over their hips, and the same is true of some of the long-necked dinosaurs, such as Apatosaurus and Brontosaurus.  Fossil trackways of baby Apatosaurus at the MNHM show that the babies could run around on their hind legs, to keep up with their parents, and probably keep out of their way as well!  The little baby Apatosaurus tracks at the MNHM show the animal scooting along on its back legs, sort of like the modern basilisk lizard from South America.

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!

Very few mammals are facultative bipeds, or even bipeds at all, with exceptions such as pangolins, jerboas, and kangaroo rats, as well as the regular old kangaroos.  Apparently, even cockroaches in the genus Periplaneta can run on their hind legs as well, if they get going fast enough!

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.

Although Indominus was never shown really running on all four legs, and most of the time seemed like a biped, there were a few times where the beast would drop down to all four legs.  At those times, Indominus looked a bit like some of the earliest dinosaurs might have, as well as their close cousins.  Poposaurus and Postosuchus are both dinosaur cousins for whom the possibility of facultative bipedalism, or just regular bipedalism, has been suggested in the past.  Even if those specific critters weren't facultative bipeds, there were definitely cousins of theirs that were.


Works Cited:

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.

Drive to Dinosaur: Dinosaur Road Trip With Grace Part 1

Last Sunday, my girlfriend Grace Albers and I drove down for a few nights to Dinosaur National Monument in north western Colorado and north eastern Utah!  We saw a TON of awesome things, and I am going to share it all with you over the course of numerous posts!  First off, here are some pictures from our drive down there!

First off, we nabbed a few pics of my cat, Chimney, and dog, Daisy, before we left!

Pyg stops for a rest break at Lake Dillon near Frisco and Silverthorne!

Some pretty scenery on the road again!

A nice lunch of home made pasta salad, thank you mother!

Around Rifle I believe, Grace spotted a bald eagle!  We were moving pretty fast (but not over the speed limit, of course), so we didn't get any good pictures, but it's still enough to tell that it's a bald eagle!

A bit after the bald eagle, we saw some pronghorn, one of my most favorite animals of all time!  We will be talking about the evolution of the pronghorns speed sometime within the next few weeks!

After the pronghorn stopped to look at us in the picture above, the pair took off, and we got some great action shots!

We kept driving, and got some more awesome shots of the surrounding landscape!

It wasn't too long before we saw our second group of pronghorn, this one much larger!  Pyg tried to spot them, but you really need a zoomed in picture to see them.  Actual eyes and a brain don't hurt, either.

Here are some closer pictures of the pronghorn!  Below is a picture of a female.

Next, we have several shots of several pronghorn, with the male being the individual on the far right (or the only individual in the shot).  While female pronghorn have horns just like the males, they are much smaller, and are rarely pronged.

This looks like a female and a calf grazing!

Several shots of the sagebrush shrublands: Grace really enjoyed the landscape, as did I!

Finally, we were getting close to Dinosaur National Monument!  We first reached the Canyon Visitor Center, which is situated right next to the beginning of the Harper's Corner scenic drive, which we will most definitely talk about later on!  While we were at the visitor center, Pyg desperately wanted her picture taken next to this pre-rennaisance, old school Allosaurus model!

Utah, at last!  More state signs need to have dinosaurs on them, in my opinion.

Some more landscape shots!

We reached the small town of Jensen, and then turned north on the final leg of our journey!  Right after the right turn however, we spotted some funky looking deer, and went back a little ways to check it out!  On someones private property was a group of several fallow deer, a species of deer that, although it has its origins in Europe and Asia, has been introduced on every continent except for Antarctica!  There were several small and cute fawns in the mix, as well!  Notice that all of the deer, regardless of age, are spotted.  Unlike the mule and white-tailed deer fawns that live here in Colorado, the adults do not grow out of their white spots, and instead keep them their entire lives!  We actually saw several of these critters at the drive through animal park near my Gramma Roo's house in Texas, click HERE to check out that post, too!

At last, we reached the national park!

We stopped just inside the park to consult the map, and to check out the Green River!  While our side of the river was National Park, the boundary of the park traced the rivers course for aways, as you can see in the picture of the map below.  Right on the other side of the river was actually cultivated farmland, whose green pastures was a stark contrast to the arid sagebrush shrubland and desert right on the other side of the river.  I wonder just how much water they use to keep all those plants green?  We will actually talk more about water related issues in future posts of this series, including a fascinating fact that I learned about a dam!  But that comes later....

There were several Canada geese on one of the sandbars.  It was weird for me to see them out here in the middle of nowhere: usually when I see them, they are pooping all over the green grasses of the schools near my house!

The scenery in the park is pretty spectacular, and here are just a few shots of some of the rocky outcrops that we saw right away!

We finally got to our campground, the Green River Campground (consult the map above), which, as you might have already guessed, is a campground right along the banks of the Green River.  (If you didn't get that one, don't worry about it, it was supposed to be a tough one, most people don't get it the first time, either.)  Here is a shot of some more gorgeous outcrops between the trunks of two cottonwood trees at our campsite, followed by a picture of our tent!

Immediately upon arrival, we were plagued by several golden mantled ground squirrels who were positively itching for food scraps from us humans.

After we'd settled in, we decided to walk down to the river for a few minutes.  It was really gorgeous there, and we saw a ton of what I think are frog eggs in the water!

It was getting late in the day, but before the sun set, we wanted to go exploring.  Grace is super into Archaeology (Grace:Archaeology::Zack:Paleontology), so we decided to go check out: some petroglyphs.

Join us for our next installment, coming shortly: In Which We Check Out Some Petroglyphs!