identify gecko type

Question
We found 2 geckos (appears male & female) in our yard (Dallas) we have several typical ones but these two are different; they change from brown to green, skin not too rough, no spots or stipes apparant, have a turtle like head, neck blows up to/pink/white type sack, has a peaked ridge along top of backside, 4-6" long, not slim/straight, wider mid section, they were not afraid of us, kind of personable.  They look like a "very old, 1000s of years" small reptile.  Any clues?  

Answer
Hello,
thank you for your question.
I think you have two Anolis carolinesis, Green Anoles. Your description fits well enough: A. carolinesis can change from green to brown when stressed, cold, angry or frightened, they often have a crest, the males have a pink dewlap and they do look ancient :) They are very common as pets and native to the US (Virginia, Florida, Oklahoma and the east of Texas).
Here are some pictures:
http://www.rainwaterreptileranch.org/scr/images/anole.jpg
http://www.agamen.de/reptilien/leguane/fotos/Anolis5.jpg
and here's an excellent website with more anole info
http://www.kingsnake.com/anolecare/index.htm

If your lizards are not anoles, please let me know!
Jennifer