The old way of restoring theropods was with their bodies reared in an upnght human-like pose. Life size animatronic dinosaur But such a body posture is unusual even for bipeds, and a few artists dissented by showing them horizontal-backed like ground birds or kangaroos. Newman’s 1970 restudy of IJnannosourus made this the generally accepted standard. But the recl reason theropods moved with level spinal columns is still not widely understood. walking dinosaur costume It is that muscles operate best when they are not stretched more than 1.3 times their length during a working rycle. In theropods, important hind limb retractors were anchored on the base of the ischium, the back one of the two lower hip bones. When the hips were horizontal, these muscles were set behind the hind limb, and could pull back on the femur while staying within their stretch limits. Dinosaur model When the hips tilted up, the ischial retractors were then between the hind limbs. Not only would they end up being badly overstretched if they tried to work from this position, but they would not even be able to pull back on the femur.
The theropod hip socket confirms this arrangement. The hip joint was fully articulated together only as long as the femur remained perpendicular to the hips, or forward of that. As the body reared up and the femur retracted well behind perpendicular, then the femoral head lost its complete articulation with the hip joint’s posterior articulating surface. A theropod. or paleodinosaur that reared to scan the landscape or intimidate a foe was alright only as long as it stood still or moved slowly. Moving fast with a reared body would be injurious. The exact horizontal positioning of the theropod body when in normal motion is uncertain. Some think it was fully horizontal, while others think it was tilted up twenty or so degrees.te Actually, we cannot reconstruct muscle stretch patterns precisely enough to tell, and posture may have varied among and within species, or even within individuals from time to time.