The description of a long stem makes me think that it's not a buttercup. We have had creeping buttercup bad over most of east Texas the last few years. It is more of a vine, that is dense growing in low, wet areas. Spreads like Bama said. If you decide that's what you've got, get on top of it quick!
I think we also have some of the weeds you're talking about, 9 ER. We've had them for years, but they seem to be worse this year than ever. If it's what I'm thinking about, they are a winter annual that are really more of an aggravation than something of economic importance. Pretty shallow rooted and they will die out soon and be gone quickly. Only problem is they are prolific seeders and you will have more of them next year. If it is what I'm thinking about, the seedheads mature into a puffball similar to a dandelion. They are just starting to mature now at my place.
Although I'm not positive, I
suspect that this is the plant:
http://www.weedalert.com/weed_pages/wa_groundsel.htm
The picture of the flowers isn't very good, though. The flowers that I am talking about open up to about quarter sized or slightly larger. Still possible that this is what you have, 9 ER. Maybe you can look around and find a better groundsel picture. I've never been real concerned about the true identity of something as long as I can figure out what to kill it with.
On control, I sprayed about 30 acres of them in a hay meadow two or three weeks ago just to see what would happen. I used a real low rate of 2,4-D and only suppressed them. Will probably take at least 3 or 4 pints to kill them this late. Maybe more. And depending on where you're located south of Houston, you might just have to live with them instead of spraying them. Some of those farmers down there can smell 2,4-D from 40 miles away when you unscrew the lid.