These are goatheads...My town of Alamogordo, NM is full of them including my rock filled yard here in the God forsaken desert...lol.
These things are tire assasins...lol...The reason that I run nothing but Kevlar tires and self sealing tubes.
They come off my shoes on my parlor carpeting, when I walk around in my socks, I find them again...lol...Not a fun time, I think the cats even laugh at me when I hit one since they never step on them...lol.
My dog will step on them sometimes. Sometimes she'll just pull them out, but most of the time she just limps around and it falls out. But when it falls out she just keep limping