Regarding prehistoric beds, I cannot resist passing on this story from a visit to the National Zoo in Washington, DC. Be forewarned: it is slightly risque.

A crowd gathered at the orangutan enclosure as a young male appeared to be busy preparing a bed. First he bunched up some hay in a mound slightly larger than himself. Then he took a light sheet and, holding on to one edge, tossed it out across the hay. The first atempt was less than satisfactory, so he tried again. On the third try, he was satified ... almost. There were two straws of hay on top of the sheet, which he proceeded to delicately remove one at a time. At this point everyone gathered around was going, "Aaaww!"

He then gingerly clambered aboard his bed, lay back and -- with his audience about to burst in applause -- began playing wth himself! Parents immediately shielded their childrens eyes and beat a hasty retreat to other spectacles the zoo had to offer.