I'm guessing from the identical pose on most of the elephants, that these are similar to the ones you can find new on ebay for a couple bucks (at least I only buy them when they're that cheap), usually from China - type in "carved elephant" for example, to see. Probably not petrified wood, maybe jasper? The grey is maybe snowflake obsidian? (can't tell from picture, but if you google it, that will help you.) They're cute, and many people collect dophins and elephants, so that's good. The one with the knot is a rat? mouse? rabbit? - search "carved jade" on ebay and see what you can find.