I think you have a Malus with yellow fruits. Tiny yellow crab apples. Possibly Malus transitoria. I believe the thorns you mention are just short spurs ( twigs) http://www.plantpress.com/plant-encyclopedia/plantdb.php?plant=740
Ditto to a crabapple. Numerous cultivars with yellow fruit available (the commonest here is 'Golden Hornet', but yours is likely some other cultivar).
Silver Surfer, That seems to fit. The yellow color threw me--my crab apple experiences have always been red ones. The tree is located on a piece of land that is slowly reverting to natural prairie. It is going to be fun when Spring arrives--I will be asking lots of questions about the strange plants that seem to grow there. Thanks much for your reply PS--are you far from Tregaron? My family came from there in 1847... Regards, Pilot Dave n295vv@aol.com
Michael, Thanks for your opinion. This is getting very interesting to me. As I mentioned, the 75 acres is reverting to natural prairie. This tree has popped up in the last few years--it must have been wild-sown by some bird. I haven't cultivated the farm since 1984. Regards, Pilot Dave
Pilot Dave, I thought you might like to see a pic, to show the extreme variation that you can get with yellow apples. Malus Golden Hornet to the left. Malus transitoria to the right. ( Malus transitoria is about the size of a pea.) (P.S. Private e mail sent re Tregaron in Wales )
Silver Surfer, Thanks for the photos. Very definitely, that is the tree--most likely the M Transitoria. I look forward to Tregaron info. Regards, Pilot Dave
Michael F is right, there are others with yellow apples, such as Malus toringo. Pics were just to show size difference!
