This Province is recognized by most authors who have written about the
zoogeography of Mexico. It is the most extensive in the state and
includes the northern part of the Coastal Plain (see Fig. 2).
The vegetation of the Tamaulipan Biotic Province is in general
Mesquite-grassland but in the Sierra San Carlos and Sierra de
Tamaulipas other types of vegetation are found.
Two formations occur in the Mesquite-grassland. The first is
the Mesquite Scrub, in which the dominant plant is the
mesquite (_Prosopis juliflora_), associated with _Cordia
boissieri_, several species of _Acacia_, and in some areas
with _Opuntia_ and _Yucca treculeana_. The dominant grasses
are of the genera _Bouteloua_ and _Andropogon_. The second
formation is the Gulf Bluestem Prairie, where species of
_Andropogon_ are the dominants on the well-drained sites.
Sloughs and depressions are occupied by cordgrass, _Spartina
spartinae_. Many areas have been invaded by mesquite and
other shrubs.
[Illustration: 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.