It's Lantana montevidensis, and the parent plant was Lantana montevidensis. This trailing species can have flowers in different colors including yellow. The yellow color attracts thrips, their pollinators.

"The inflorescence is a circular head of several purple to lavender to white funnel-shaped flowers with lobed corollas each nearly a centimeter wide. Yellow-flowered montevidensis are a case of misidentification and most often relate to the "New Gold" lantana Lantana × hybrida, a hybrid between camara and montevidensis. Occasionally these yellow-flowered plants are misidentified Lantana depressa var. depressa, a Florida endemic taxon more closely related to Lantana camara with smaller, less robust flowers."

Lantana camera can also trail easily and often comes in a solid yellow form as well.

Gardengal is correct. Sorry for the misinformation. That's what I get for trusting google photos.

Thank you. This may be a Lantana I don't want in our yard. I'll study photos of L. camara and see if it matches the one I have. The roots are VERY thick, like a man's thumb.