 The Sierra Madre Oriental range to the west separates the Tamaulipan mezquital from the drier Chihuahuan Desert.The Tamaulipan matorral is a transitional ecoregion between the mezquital and the Sierra Madre Oriental pine-oak forests to the west and the Veracruz moist forests to the south.The Western Gulf coastal grasslands, known as the Tamaulipan pastizal south of the border, fringe the Gulf of Mexico.