>In a related vein, is anyone aware of any extant birds that lie on their
sides like a cat or dog? If they do, it might indicate that dinosaurs
were capable of the same behavior.
wrote Roger Compton<
Many birds lie on their sides like a cat or dog, occasionally . Chicken often practice this pose when sunbathing and dusting. It is quite probable that bipedal dinosaurs of smaller up to the size of one ton or so, behaved in a similar way. Heavier dinosaurs might have avoided this position on dry ground and used it only when wallowing.
Beri's Dinosaur World