>>213769933
We can discern a lot of things from bones, from how the animal moved, and where the muscles were attached, to how strong various muscles would be, how much pressure would specific body parts regularily endure, as well as what other animals that specimen could be related to. Based on all that info, and comparing it to similar animals we know more of, you can somewhat reliably guess. Of course it could all turn out to be false, but it's just the best guess we have based on the bones we have found so far.
>"Both genera had large, well-developed, and relatively strong arms; the pelvic girdle was robust and suited for a sitting behavior; and the hindlimb (particularly the foot) structure was robust and shortened. They considered these adaptations to represent an example of convergent evolution—a condition where organisms evolve similar traits without necessarily being related—between extinct mammal and dinosaur genera. Moreover, the body plan is somewhat exhibited by the modern-day gorillas. Because the animals with this type of body plan are known to represent herbivores, the authors suggested this lifestyle for Therizinosaurus."
