Fig. 2. Four biotic provinces: 1 Tamaulipan; 2 Potosian; 3 Chihuahuan; 4 Veracruzian.
Around the Sierra de Tamaulipas and in the area between it and the Sierra San Carlos the vegetation is Thorn Forest (Tropical Thorn Forest of Martin et al., 1954), in which the dominant plants are Acacia, Ichthyomethia, Ipomea, Prosopis, and Cassia. Another type of vegetation in the Sierra de Tamaulipas is the Tropical Deciduous Forest at 300 to 700 meters elevation, the trees of which are 20 meters high with a canopy averaging eight meters high (Martin et al., op. cit.). The common species of trees belong to the genera Tabebuia, Ipomea, Bombax, and Conzattia. Species of Bursera, Acacia, and Cassia are less abundant. In the low canyons Bursera, Ceiba, and Psidium, draped with lianas and various epiphytes, can be found.
The Pine-oak Formation grows above an elevation of 800 meters in the Sierra de Tamaulipas and is characterized by Pinus cembroides, P. nelsonii, P. teocote, and Quercus arizonica. Martin et al. (op. cit.) recorded Montane Scrub from the dry areas, between elevations of 600 and 900 meters. That scrub is formed by huisaches (Acacia farnesiana) along with a few oaks and some trees of the Tropical Deciduous Forest.
The vegetation of the Sierra San Carlos was studied by Dice (1937) and divided into three life belts, each with several associations. For more information about the plants of each association and their related mammals see the publication of the mentioned author.
Endemic mammals of the Tamaulipan Biotic Province, in the part of it that is in Tamaulipas, are the following: Scalopus inflatus; Lepus californicus curti; Spermophilus spilosoma oricolus; Cratogeomys castanops tamaulipensis; Dipodomys ordii parvabullatus; and Sigmodon hispidus solus. Other characteristic mammals of this Province in the state of Tamaulipas are: Sylvilagus floridanus connectens; S. audubonii parvulus; Lepus californicus merriami; Perognathus merriami merriami; Dipodomys ordii compactus; Orzomys melanotis carrorum; Reithrodontomys fulvescens intermedius; Peromyscus boylii ambiguus; Canis latrans texensis; C. l. microdon; C. lupus monstrabilis; Taxidea taxus berlandieri; Mephitis mephitis varians; Felis pardalis albescens; Trichechus manatus latirostris; and Odocoileus virginianus texanus.
Many other kinds of mammals occur mainly in the Tamaulipan Province but are not listed above because they occur also in one or more of the other provinces.
The Sierra de Tamaulipas is placed in the Tamaulipan Biotic Province because the fauna, especially of non-flying mammals, is closely related to that of the rest of the Province. Nevertheless, many mammals found in this Sierra are tropical in relationship. This is especially true of the bats. Therefore, most of the tropical bats that occur in Tamaulipas occur in the Veracruzian Biotic Province and in the Sierra de Tamaulipas.