Itis does not even list Opuntia anahuacensis and the Plant List considers it a synonym of Opuntia stricta. There are four species of Opuntia that are recorded in Chambers County where Anahuac NWR is located, O. engelmannii, O. humifusa, O. macrorhiza, and O. stricta. Not sure which one is in the picture, except that it is not O. humifusa.