Sunday, March 17, 2013

Were Dinosaurs "Lounge Lizards"?

Painting by Steve Kirk.
A question I have often asked myself during my renewed interest in dinosaurs and paleontography is "what is a proper dinosaur resting posture?" I have seen many different artists portray dinosaur resting much like what you see in the Steve Kirk painting to the left, and John Conway's sleeping tyrannosaur painting in the book "All Yesterdays" - on their sides, lounging like lions, or in this case, like a tuckered-out kangaroo. But is this necessarily accurate? Could dinosaurs, in fact, lounge in this way?

I am skeptical of this -"lounging," as is depicted here, is something that I've found in my studies (admittedly limited in comparison to some of my readers) to be a distinctly mammalian trait. Crocodiles, birds, and squamates do not, in my experience, exhibit this kind of resting behavior where they lay upon their sides, with the majority of their weight upon their ribcage, hip, and tucked-under leg.

Birds have a variety of sleeping postures and habits ranging from snoozing standing up (sometimes on one leg!), to nesting with both legs folded up under the body, to perching - or, in the case of some hummingbird species, hanging upside-down like little, feathery bats. Their heads are either tucked behind the wing, or pulled into their bodies with their beaks resting on their chests.

...or like this.
(Photo by Rinaldo Santos de Almeida)
Crocodiles and squamates "lounge" in a different fashion from birds, but still do not have the same kind of world-class lounging skills that a mammal, like a dog or cat, does. Both clades typically rest flat on their bellies, with legs splayed out to the sides, sometimes with their bodies looping around upon itself to conserve heat.
Photo removed at the request of the image distributor.

I am curious as to what my readers think - based on the behaviors of these dinosaur kin and cousins, is it still possible that dinosaurs could still lounge in the fashion of leopards, lions, and lemurs? Feel free to leave comments below.


Craig Dylke said...

Good question.

I don't pretend to know.

Curious to see what people say myself.

Julio Lacerda said...

I think the key is on dinosaur anatomy. Crocodiles' bodies are wider than they are tall, and their legs stick out sideways, so that kind of resting position would be rather unconfortable and unnatural for them. Birds on the other hand also have very specialized anatomies, most need to be careful with theirs wings and feathers so as not to damage them, and are all bipedal. So in terms of body plan and general behaviour, non-avian dinosaurs could well have some mammalian-looking activities, like louging on their sides.

Marko Bosscher said...

Would a sleeping position like that of Mei long work for larger, unfeathered, Dinosaurs?

qilong said...

I think that for the most part, dinos wer elikely belly-squaters. However, if elephants can lay and get up, one wonders if, if the mobility of the limbs is sufficient, a giant ornithischians could. I have my doubts about tyrannosaurs, though; the issue is not of mass or delicacy, but leverage, and whether or how a tyrannosaur would ascend from a prone and side-ways posture into one in which it could stand up. Quadrupeds, even sauropods, have it easier, because the forelimb assists the hind in providing leverage: Forelimb sprawls, lifting forequarters up, which twists body up and over, allowing hindlimb position and leverage to push it over onto a quadrupedal stance, at which point the animal just "stands up." This is all hypothetical, but its how elephants do it. Mobility, weight, and leverage are issues for giant quadrupeds, but likely more favorable than giant bipeds. It seems squatting is a better model for them.

Thomas Holtz said...

At least some theropods sat on their belly, large bird-style:

quarksparrow said...

Ground-feeding birds like turkeys or peafowl can adopt a lounge-like posture when dust bathing or sun bathing. I suspect that tree-dweller anatomy and a fused backbone are probably pretty significant when explaining why most birds don't lounge like a mammal, so one need not necessarily assume that dinosaurs would follow suit.

Raven Amos said...

I've seen some great comments here that made me take another look at my initial hypothesis. After observing chickens and turkeys a bit more closely, I've observed them not only sunbathing in a very "mammalian lounging" position, but also falling asleep in that position. I am therefore obliged to discard my preconceived notions and conclude that, yes, larger non-avian dinosaurs were probably capable of lounging like lions, or kicking back like kangaroos.

Thanks, guys, for the great feedback!