Ask Mr. Smarty Plants

Without seeing your Lantana urticoides (Texas lantana) I can't be absolutely sure, but it sounds like a case of fasciation.  This is a plant developmental anomaly that occurs in a wide variety of plants and especially affects the flowers or stems.  In a fasciated plant it appears that the stems, flowers leaves and/or fruits have been fused and broadened.  It is uncertain whether it is genetically determined or caused by disease or some other sort of trauma to the plant. It does appear that there may be an inheritable tendency toward fasciation that may be triggered by environmental conditions such as temperature, crowding, insect attack, disease or wounding of the plant.  Sophora secundiflora (Texas mountain laurel) seem to be affected frequently but other plants are also susceptible.   I wasn't able to find a record of a fasciation associated with Lantana urticoides (Texas lantana), but I feel pretty sure it does occasionally happen.  Here are photos photos of fasciated plants and more information from Purdue University Extension and some photos of fasciated, or cristated, cactus (cristation is a synonym for fasciation).

Below are photos of fasciation on the stem of a Texas mountain laurel and a fasciated blossom of Lupinus texensis (Texas bluebonnet).