No endemic mammals of the Chihuahuan Province are known in Tamaulipas. Mammals that occur princ.i.p.ally in this Province are: _Dipodomys merriami atronasus_; _D. ordii durranti_; _Peromyscus melanophrys consobrinus_; _P. difficilis petricola_; _Onychomys torridus subrufus_; and _Neotoma albigula subsolana_.
Veracruzian Biotic Province
This Province includes the southern part of the Coastal Plain physiographic region, south of the Sierra de Tamaulipas and Soto la Marina. But the exact line between this Province and the Tamaulipan Province to the north is difficult to draw. The northern boundary of the Veracruzian Province is the line between the Nearctic and Neotropical regions in eastern Mexico.
Vegetation of most of the Veracruzian Biotic Province is Tropical Deciduous Forest. This Forest is made up of _Tabebuia_, _Ipomea_, _Bombax_, and _Conzattia_, along with some _Ceiba_, _Bursera_, and _Psidium_.
The mammalia fauna of the Veracruzian Biotic Province is tropical in nature. This is especially true of the bats.
Representatives of the tropical genera _Micronycteris_, _Sturnira_, _Artibeus_, _Enchistenes_, _Desmodus_, _Diphylla_, and _Molossus_ have their northern distributional limits in this Province. The non-flying mammals characteristic of the Province in Tamaulipas are: _Philander opossum pallidus_; _Marmosa mexicana_; _Ateles geoffroyi velerosus_; _Geomys tropicalis_; _Oryzomys melanotis rostratus_; _O. alfaroi huastecae_; _O. fulvescens engracie_ (endemic to this Province in Tamaulipas); _O. f.
fulvescens_; _Reithrodontomys mexica.n.u.s_; _Peromyscus orchraventer_ (endemic); _Neotoma micropus angustapalata_; _Eira barbara senex_; _Felis wiedii oaxacensis_; and _Mazama americana temama_.
BARRIERS AND ROUTES OF MOVEMENT
The distributional patterns and affinities of the mammalian fauna of Tamaulipas suggest possible routes of migration and barriers that limited or controlled movements of the mammals.
Mammals may have reached Tamaulipas by way of a Northern route, a Trans-plateau route, a Montane route, or a Tropical route (Fig 3).
The Northern route permitted species of mammals from the temperate region to the north to enter the Tamaulipan Biotic Province from or via Texas. Several came from the Great Plains, and a few came from the eastern part of the United States. Also, a few mammals that may have originated in the Tamaulipan Province moved northwards. Some of these, according to Dice (1937:267) were _Liomys irroratus texensis_, _Peromyscus leucopus texensis_, and _Lepus californicus merriami_.
Other mammals thought to have moved north by this route are _Didelphis marsupialis_, _Dasypus novemcinctus_, _Oryzomys pal.u.s.tris_, _Nasua narica_, and _Taya.s.su tajacu_. Some mammals that pa.s.sed through Tamaulipas into Texas have extended their geographic ranges far north of Texas.
Mammals that came _via_ the Trans-plateau route (name proposed by Baker, 1956:146) came no farther into Tamaulipas than the Chihuahuan Biotic Province. They encountered the barrier formed by the Sierra Madre Oriental. These mammals were listed in the account of the Chihuahuan Biotic Province.
The route that Baker (1956:146) termed the "Southern Route" I here term the Montane route because I think it was used for movement southward as well as northward.
[Ill.u.s.tration: FIG. 3. Routes of movement: 1 Northern; 2 Trans-Plateau; 3 Montane; 4 Tropical.]
The Montane route was used by mammals of boreal affinities (_Microtus_ and _Neotoma_), that moved into Tamaulipas from the north; also in this category are bats of the family Vespertilionidae. For movement from south to north, the route was used by several species native to Mexico, for example, _Cratogeomys castanops_. The seaward slope of the montane area has enabled some tropical mammals to move farther north than they have done at higher and lower elevations. _Philander opossum_ seems to be an example.
The fourth route, the Tropical one, was used by mammals of tropical origin. Most moved into Tamaulipas only as far as the Veracruzian Biotic Province. The princ.i.p.al mammals that have used this route are the bats and marsupials, but _Sylvilagus brasiliensis_, _Ateles geoffroyi_, _Heterogeomys hispidus_, _Eira barbara_, and _Mazama americana_ also can be included here. Some tropical mammals, as was pointed out previously, not only reached Tamaulipas but have moved through the state and far northward.
The major barriers to dispersal of mammals in Tamaulipas are three (see Fig. 2). Two of them, the Rio Grande Barrier and the Sierra Madre Barrier, are physiographical, but the Tropical Barrier is maintained by a combination of environmental factors. The three barriers separate the four Biotic Provinces in Tamaulipas. The Sierra Madre Oriental, which forms the Potosian Biotic Province, lies between the Tamaulipan and Chihuahuan provinces. The Tropical barrier separates the Tamaulipan and Veracruzian biotic provinces.
The Rio Grande, as was pointed out by R. H. Baker (1956:146), has low banks, is relatively shallow, and does not form an effective barrier for most mammals. For only two species, insofar as I know, has the Rio Grande const.i.tuted a barrier. _Cratogeomys castanops_ has not entered southeastern Texas from Mexico, and _Spermophilus spilosoma_ has not entered Mexico from southeastern Texas except on the coastal barrier beach. Alvarez (1962:124) postulated that the beach was the route by which _S. spilosoma_ arrived at La Pesca where the barrier beach meets the mainland.
The Sierra Madre Barrier is a good filter for some small mammals, especially for those that occur on the Mexican Plateau and those of tropical origin. The mammals that occur on each side of the Sierra are listed in accounts of the Chihuahuan (west side), Veracruzian and Tamaulipan (east side) biotic provinces.
The Tropical Barrier is formed mainly by a climatic complex (probably a change in temperature and rainfall) in the coastal region at or about the lat.i.tude of Soto la Marina, where no geographic barrier is found.
In the western and central part of the Tropical Barrier, the climatic factor is supported by a geographic factor. The Sierra Madre Oriental is in the west and the Sierra de Tamaulipas is in the center. The several mammals that are affected by this barrier are listed in the accounts of the Veracruzian and Tamaulipan biotic provinces.
A peculiar pattern of distribution is that presented by _Scalopus inflatus_ and _Geomys tropicalis_. Both are the only known species of their genera in northeastern Mexico. Each is isolated from other species of its genus. The nearest known record of _Scalopus_ is 45 miles northward and the nearest record of _Geomys_ is approximately 165 miles northward. A possible explanation for the distribution of these two kinds is that each was widely distributed in one of the glacial periods and when the glacier receded to the north these animals remained in Tamaulipas, where they evolved and formed distinct species.
The two species, _G. tropicalis_ and _S. inflatus_, are fossorial and for this reason probably were able to resist inhospitable climates better than non-burrowing species.
HISTORY OF MAMMALOGY
In Tamaulipas the first exploration directed in substantial measure toward finding out about the mammalian fauna, at least as far as I know, was made by Dr. L. Berlandier, who traveled mainly in the northern half of the state. His collections provided specimens of several previously unknown mammals, which were described by Baird (1858). The original ma.n.u.script of Berlandier never has been published.
About 1880 Dr. E. Palmer collected mammals in the southern part of Tamaulipas, in the area around Tampico. The results of his exploration were reported by J. A. Allen (1881). E. W. Nelson and E. A. Goldman twice collected in Tamaulipas (Goldman, 1951). In 1898 they visited and collected mammals in the southern part of the state, around Tampico, Altamira, Victoria, Forlon, and Miquihuana. In 1901-1902 they visited the area between Nuevo Laredo and Bagdad, then went south to Soto la Marina and Victoria. From their collections several species and subspecies have been described. Between 1910 and the early 1920"s little was done in the way of scientific exploration because of the Mexican Revolution.
From 1930 on, several expeditions yielded new information about the native mammals. In that year L. B. Kellum visited the Sierra San Carlos. The results were reported by Dice (1937). Another important collection from Tamaulipas was made by Marian Martin in the area of Gomez Farias. Mammals collected by her were reported by Goodwin (1954).
Hooper (1953) also reported specimens from Gomez Farias but included in his report records of mammals collected in other areas as well. In 1950 E. R. Hall and C. von Wedel made a trip to the barrier beach in the northeastern part of the state and collected several kinds of mammals among which three were described as new by Hall (1951).
The report here presented is based upon specimens in the Museum of Natural History of The University of Kansas that were collected mainly by the persons named beyond. Gerd H. Heinrich and his wife Hilda collected in 1952 and 1953 in the areas around Miquihuana, Ciudad Victoria, Soto la Marina, Sierra de Tamaulipas, and Altamira. W. J.
Schaldach collected in 1949 and 1950 in the Sierra Madre Oriental south of Ciudad Victoria; he returned to Tamaulipas in 1954 in company with V. Grissino and worked in the Sierra Madre Oriental south and north of Ciudad Victoria. In 1961 P. L. Clifton and J. H. Bodley collected in the northwestern part of the state and in the western part, around Tula, Nicolas, and Tajada. Some students and staff members of the Museum have occasionally collected in Tamaulipas.
As a result of all the mentioned expeditions and others, 32 species and subspecies have been described with type localities in Tamaulipas. They are:
Altamira
_Lepus californicus altamirae_ Nelson _Sciurus aureogaster aureogaster_ (Cuvier) (by restriction) _Sciurus deppei negligens_ Nelson _Geomys tropicalis_ Goldman
Antiguo Morelos, 8 mi. N of
_Tadarida laticaudata ferruginea_ Goodwin
Brownsville (Texas), 45 mi. from
_Scalopus inflatus_ Jackson
Charco Escondido
_Perognathus hispidus hispidus_ Baird _Neotoma micropus micropus_ Baird
El Carrizo
_Peromyscus ochraventer_ Baker
Gomez Farias
_Heterogeomys hispidus negatus_ Goodwin
Hacienda Santa Engracia
_Oryzomys fulvescens engracia_ Osgood
Jaumave
_Dipodomys ordii durranti_ Setzer
La Pesca, 1 mi. E of