The Tamaulipan mezquital (), also known as the Brush Country, is a

deserts and xeric shrublands Deserts and xeric shrublands are a biome defined by the World Wide Fund for Nature. Deserts and xeric (Ancient Greek 'dry') shrublands form the largest terrestrial biome, covering 19% of Earth's land surface area. Ecoregions in this habitat ...

ecoregion An ecoregion (ecological region) is an ecological and geographic area that exists on multiple different levels, defined by type, quality, and quantity of environmental resources. Ecoregions cover relatively large areas of land or water, and c ...

in the

Southern United States The Southern United States (sometimes Dixie, also referred to as the Southern States, the American South, the Southland, Dixieland, or simply the South) is List of regions of the United States, census regions defined by the United States Cens ...

and northeastern

Mexico Mexico, officially the United Mexican States, is a country in North America. It is the northernmost country in Latin America, and borders the United States to the north, and Guatemala and Belize to the southeast; while having maritime boundar ...

. It covers an area of , encompassing a portion of the

Gulf Coastal Plain The Gulf Coastal Plain extends around the Gulf of Mexico in the Southern United States and eastern Mexico. This coastal plain reaches from the Florida Panhandle, southwest Georgia (U.S. state), Georgia, the southern two-thirds of Alabama, over m ...

in southern

Texas Texas ( , ; or ) is the most populous U.S. state, state in the South Central United States, South Central region of the United States. It borders Louisiana to the east, Arkansas to the northeast, Oklahoma to the north, New Mexico to the we ...

, northern

Tamaulipas Tamaulipas, officially the Free and Sovereign State of Tamaulipas, is a state in Mexico; one of the 31 states which, along with Mexico City, comprise the 32 federal entities of Mexico. It is divided into 43 municipalities. It is located in nor ...

, northeastern

Coahuila Coahuila, formally Coahuila de Zaragoza, officially the Free and Sovereign State of Coahuila de Zaragoza, is one of the 31 states of Mexico. The largest city and State Capital is the city of Saltillo; the second largest is Torreón and the thi ...

, and part of

Nuevo León Nuevo León, officially the Free and Sovereign State of Nuevo León, is a Administrative divisions of Mexico, state in northeastern Mexico. The state borders the Mexican states of Tamaulipas, Coahuila, Zacatecas, and San Luis Potosí, San Luis ...

Distribution

The

Sierra Madre Oriental The Sierra Madre Oriental () is a mountain range in northeastern Mexico. The Sierra Madre Oriental is part of the American Cordillera, a chain of mountain ranges (cordillera) that consists of an almost continuous sequence of mountain ranges that ...

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 The Veracruz moist forests () is a tropical moist broadleaf forests ecoregion in eastern Mexico. Geography The Veracruz moist forests cover an area of , occupying a portion of Mexico's Gulf Coastal Plain between the Sierra Madre Oriental and t ...

to the south. The

Western Gulf coastal grasslands The Western Gulf coastal grasslands () are a tropical and subtropical grasslands, savannas, and shrublands, subtropical grassland ecoregion of the southern United States and northeastern Mexico. It is known in Louisiana as the "Cajun Prairie", T ...

, known as the Tamaulipan pastizal south of the border, fringe the

Gulf of Mexico The Gulf of Mexico () is an oceanic basin and a marginal sea of the Atlantic Ocean, mostly surrounded by the North American continent. It is bounded on the northeast, north, and northwest by the Gulf Coast of the United States; on the southw ...

. The

Edwards Plateau The Edwards Plateau is a geographic region forming the crossroads of Central, South and West Texas, United States. It is named in honor of Haden Edwards. It is bounded by the Balcones Fault to the south and east; the Llano Uplift and the Lla ...

savannas lie to the north, and the East Central Texas forests and Texas blackland prairies to the northeast.

Geography

The Bordas Escarpment transects this ecoregion, running from near the southern limit northwest to the vicinity of

Rio Grande City, Texas Rio Grande City is a city in and the county seat of Starr County, Texas, United States. The population was 15,317 at the time of the 2020 census. The city is west of McAllen. It is connected to Camargo, Tamaulipas, via the Rio Grande City� ...

, arching back northeast to the vicinity of Choke Canyon Reservoir in Texas. The region east of the Bordas Escarpment is flat with deep, sandy soils, of which vast areas both north and south of the border have been converted to agricultural use. West of the Bordas Escarpment the topography changes to gently rolling hills with a thin layer of high calcium soil over a thick layer of

caliche Caliche () is a soil accumulation of soluble calcium carbonate at depth, where it precipitates and binds other materials—such as gravel, sand, clay, and silt. It occurs worldwide, in aridisol and mollisol soil orders—generally in arid or se ...

. Some large portions of the west are poorly suited for cultivation but good for ranching and excellent wildlife habitat.Fulbright, Timothy E., and Fred C. Bryant (2004).The Last Great Habitat. A Special Publication of the Caesar Kleberg Wildlife Research Institute, Texas A&M University-Kingsville. Special Publication No. 1, 1-32 pp. A series of

Cenozoic The Cenozoic Era ( ; ) is Earth's current geological era, representing the last 66million years of Earth's history. It is characterized by the dominance of mammals, insects, birds and angiosperms (flowering plants). It is the latest of three g ...

strata In geology and related fields, a stratum (: strata) is a layer of Rock (geology), rock or sediment characterized by certain Lithology, lithologic properties or attributes that distinguish it from adjacent layers from which it is separated by v ...

limestone Limestone is a type of carbonate rock, carbonate sedimentary rock which is the main source of the material Lime (material), lime. It is composed mostly of the minerals calcite and aragonite, which are different Polymorphism (materials science) ...

sandstone Sandstone is a Clastic rock#Sedimentary clastic rocks, clastic sedimentary rock composed mainly of grain size, sand-sized (0.0625 to 2 mm) silicate mineral, silicate grains, Cementation (geology), cemented together by another mineral. Sand ...

siltstone Siltstone, also known as aleurolite, is a clastic sedimentary rock that is composed mostly of silt. It is a form of mudrock with a low clay mineral content, which can be distinguished from shale by its lack of fissility. Although its permeabil ...

, and

claystone Mudrocks are a class of fine-grained siliciclastic sedimentary rocks. The varying types of mudrocks include siltstone, claystone, mudstone and shale. Most of the particles of which the stone is composed are less than and are too small to ...

occur throughout most of the region. These strata are slightly tilted, gently slanting seaward, with increasingly recent exposures to the east, including some

Quaternary The Quaternary ( ) is the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy (ICS), as well as the current and most recent of the twelve periods of the ...

bodies at the coast transitioning into the sea, and a few older

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 143.1 to 66 mya (unit), million years ago (Mya). It is the third and final period of the Mesozoic Era (geology), Era, as well as the longest. At around 77.1 million years, it is the ...

exposures and outcrops appearing in some far western interior areas. Elevations generally range from near sea level to 300 meters, transitioning at ca. 300–500 meters into the Sierra Madres,

, and Chihuahua Desert in western areas. A series of small mountain ranges occur in the region, isolated on the coastal plain between the Sierra Madre Oriental and the Gulf of Mexico. These ranges are not part of the strata of the Gulf Coast Plain or the complexly folded and faulted

Jurassic The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately 143.1 Mya. ...

and

formations of the Sierra Madre Oriental. The Sierra de San Carlos, (and Sierra de Tamaulipas just beyond the southern limit of this ecoregion) are plutons,

igneous rock Igneous rock ( ), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rocks are formed through the cooling and solidification of magma or lava. The magma can be derived from partial ...

intrusions of

nepheline syenite Nepheline syenite is a holocrystalline Intrusion, plutonic rock that consists largely of nepheline and alkali feldspar. The rocks are mostly pale colored, grey or pink, and in general appearance they are not unlike granites, but dark green varie ...

to gabbroic composition, emplaced during the Mid-

Tertiary Tertiary (from Latin, meaning 'third' or 'of the third degree/order..') may refer to: * Tertiary period, an obsolete geologic period spanning from 66 to 2.6 million years ago * Tertiary (chemistry), a term describing bonding patterns in organic ch ...

with a few minor sierras of alkaline basalt flows occurring locally (e.g. in the vicinity of Llera, Tamaulipas).Ferrusquía-Villafranca, Ismael. 1993. ''Geology of Mexico: A Synopsis'', pages 3-107. In. T. P. Ramamoorthy, Robert Bye, Antonio Lot, and John Fa (Eds.). ''Biological Diversity of Mexico: Origins and Distribution.'' Oxford University Press, Inc. New York. The Coastal Sand Plain, sometimes referred to as the "Wild Horse Desert", is a region of

sand deposits extending about 60 miles inland from the

Laguna Madre The Laguna Madre is a long, shallow, hypersaline lagoon along the western coast of the Gulf of Mexico in Nueces County, Texas, Nueces, Kenedy County, Texas, Kenedy, Kleberg County, Texas, Kleberg, Willacy County, Texas, Willacy and Cameron Coun ...

. It is bordered by

Baffin Bay Baffin Bay (Inuktitut: ''Saknirutiak Imanga''; ; ; ), located between Baffin Island and the west coast of Greenland, is defined by the International Hydrographic Organization as a marginal sea of the Arctic Ocean. It is sometimes considered a s ...

to the north and the Lower Rio Grande Valley to the south. Quaternary to Tertiary marine sedimentary strata, which may be exposed in western areas, underlie the sand sheet. The sand sheet is six feet deep in many places with maximum dune elevations reaching 30 feet. Although the area is generally flat, the unstable sands often form a dune and swale topography where vegetated dunes are interspersed with active, unstable, wind-blow dunes. The active dunes attain areas as large as 250 acres, predominantly in the eastern third. Grasslands cover much of the sand plain where seacoast bluestem ('' Schizachyrium littorale'') is dominant in all but the wettest areas. These grasslands are banded with live oak (''

Quercus virginiana ''Quercus virginiana'', also known as the southern live oak, is an evergreen oak tree endemic to the Southeastern United States. Though many other species are loosely called live oak, the southern live oak is particularly iconic of the Old South. ...

'') groves, forming dense forest in spots, and smaller honey mesquite ('' Prosopis glandulosa'') mottes in discontinuous belts which are sometimes connected with one another and collectively cover at least a quarter of the sand sheet. Numerous ephemeral, internally drained ponds form where subsidence and blow-outs occur.Fuibright, Timothy E., David D. Diamond, John Rappoie, and Jim Norwine. 1990. Coastal Sand Plain of Southern Texas. Rangelands 12(6): 337-340. Hydrology: The region is generally semi-arid however, various

wetlands A wetland is a distinct semi-aquatic ecosystem whose groundcovers are flooded or saturated in water, either permanently, for years or decades, or only seasonally. Flooding results in oxygen-poor ( anoxic) processes taking place, especially ...

are present. The

is one of only five hypersaline coastal lagoons (or negative estuaries) in the world and a significant

ecosystem An ecosystem (or ecological system) is a system formed by Organism, organisms in interaction with their Biophysical environment, environment. The Biotic material, biotic and abiotic components are linked together through nutrient cycles and en ...

in itself, laying between the Gulf of Mexico and the Tamaulipan mezquital ecoregion.Tunnell, Jr. John W. and Frank W. Judd. editors. (2002). The Laguna Madre of Texas and Tamaulipas. Texas A&M University Press, College Station, Texas. xxi, 346 pp. As one moves inland from the hypersaline lagoon, a relatively narrow band of freshwater marshlands are encountered running north to south, albeit occurring fragmented and irregularly. These marshes are dynamic, fluctuating with rainfall and tropical storm activity, and alternating with wet and dry periods. When and where present, these marshlands can be locally, surprisingly extensive with deep marshes and both permanent and ephemeral freshwater ponds that support populations of salamanders (''

Siren intermedia The lesser siren (''Siren intermedia'') is a species of aquatic salamander native to the eastern United States and northern Mexico. They are referred to by numerous common names, including two-legged eel, dwarf siren, and mud eel. The specific ep ...

''), turtles (''

Trachemys ''Trachemys'' is a genus of turtles belonging to the family Emydidae. Members of this genus are native to the Americas, ranging from the Midwestern United States south to northern Argentina, but one subspecies, the red-eared slider (''T. scripta ...

''), and millions of migrating

waterfowl Anseriformes is an order of birds also known as waterfowl that comprises about 180 living species of birds in three families: Anhimidae (three species of screamers), Anseranatidae (the magpie goose), and Anatidae, the largest family, which i ...

, such as redheads ('' Aythya americana'') in the winter.Smith, Elizabeth H. (2002). Redheads and Other Wintering Waterfowl. 169-181 pp. In Tunnell, Jr. John W. and Frank W. Judd. (editors). ''The Laguna Madre of Texas and Tamaulipas''. Texas A&M University Press, College Station, Texas. xxi, 346 pp. Farr, William L. (2015). Herpetofauna of Tamaulipas. 101-121 pp. In. Lemos Espinal, J. A. (Editor). ''Amphibians and Reptiles of the US-Border States''. Texas A&M University Press. College Station, Texas. x, 614 pp. Several rivers cross the region, all flowing eastward to the

. Many of these river have created innumerable

oxbow lakes An oxbow lake is a U-shaped lake or stream pool, pool that forms when a wide meander of a river is meander cutoff, cut off, creating a free-standing body of water. The word "oxbow" can also refer to a U-shaped bend in a river or stream, whether ...

, resacas, and abandoned channels with associated marshes and swamps as they meander across the flat coastal plain east of the Bordas Escarpment. The few remaining riparian zones in this region that have not been cleared for agriculture, housing, and industry, can support unexpectedly lush tropical jungle vegetation, particularly in the south. The

San Antonio River The San Antonio River is a major waterway that originates in central Texas in a cluster of springs in midtown San Antonio, about 4 miles north of downtown, and follows a roughly southeastern path through the state. It eventually feeds into the ...

(a major tributary of the Guadalupe River) runs at the approximate northeastern border of this region. Other major rivers (north to south) include: the

Nueces River The Nueces River ( ; , ) is a river in the U.S. state of Texas, about long. It drains a region in central and southern Texas southeastward into the Gulf of Mexico. It is the southernmost major river in Texas northeast of the Rio Grande. ''Nu ...

and its tributary the Frio River;

Rio Grande The Rio Grande ( or ) in the United States or the Río Bravo (del Norte) in Mexico (), also known as Tó Ba'áadi in Navajo language, Navajo, is one of the principal rivers (along with the Colorado River) in the Southwestern United States a ...

(referred to as Rio Bravo in Mexico) and its tributaries Rio Salado, Rio San Juan; the Rio San Fernando (sometimes called the Rio Conchos and not to be confused with the major drainage Rio Conchos of Chihuahua); the Rio Soto La Marina and its tributaries Rio San Carlos, Rio Pilón, San Antonio, Rio Purificacion, Rio Corona, Rio Santa Ana, form the approximate southern border.Texas Water Development Board, TWDB Maps:
Major Surface Water Features
'.Agustin Palacios Roji Grcía and Joaquin Palacios Roji Grcía. (2007). Por Las Carreteras de México. Guia Roji, S.A. de C. V. México, D. F., Mexico. 151 pp. A number of large lakes occur in the region, but they were all constructed in the decades fallowing the Second World War in the 20th century. These include: Choke Canyon Reservoir and

Lake Corpus Christi Lake Corpus Christi is a reservoir in coastal southern Texas. The lake was created by impoundment of the Nueces River by the Wesley E. Seale Dam opened in 1958. The lake and the dam that creates it are managed by the City of Corpus Christi. La ...

in the Nueces River drainage in the USA; Amistad International Reservoir and

Falcon International Reservoir Falcon International Reservoir (), commonly called Falcon Lake, is a reservoir on the Rio Grande 40 miles (64 km) southeast of Laredo, Texas, United States, and Nuevo Laredo, Tamaulipas, Mexico. The huge lake is bounded by Starr County, Texa ...

on the Rio Grande; Presa Venustiano Carranza in Coahuila on the Rio Salado, Presa El Cuchillo in Nuevo Leon and Presa Marte R. Gómez in Tamaulipas on the Rio San Juan, and Presa Vicente Guerrero in Tamaulipas on the Rio Soto La Marina drainage in Mexico.

Gallery

File:Wild Olive (Cordia boissieri), FM 1017, Jim Hogg County, Texas, USA (10 April 2016).jpg, Grasslands with Wild Olive (''

Cordia boissieri ''Cordia boissieri'' is a white-flowered, evergreen shrub or small tree in the borage family (Boraginaceae). Its native range extends from southern Texas in the United States south to central Mexico. Common names include anacahuita, Mexican olive ...

''), Jim Hogg County, Texas (10 April 2016) File:Sabal Palm Sanctuary, Cameron Co. TX, 11 April 2016.jpg, Mesquite woodlands, Sabal Palm Sanctuary,

Cameron County, Texas Cameron County is the southernmost county in the U.S. state of Texas. As of the 2020 census, its population was 421,017. Its county seat is Brownsville. The county was founded in 1848 and is named for Captain Ewen Cameron, a soldier durin ...

(11 April 2016). File:Bentsen-Rio Grande Valley State Park, Hidalgo County, Texas, USA (15 April 2016).jpg, Bentsen-Rio Grande Valley State Park,

Hidalgo County, Texas Hidalgo County (; ) is located in the U.S. state of Texas. As of the 2020 census, its population was 870,781, making it the ninth-most populous county in Texas, and the most populous county outside of the counties in the Texas Triangle. The ...

(15 April 2016) File:State Highway 16, Duval County, Texas, USA. (16 April 2016).jpg, State Highway 16, Duval County, Texas (16 April 2016) File:Tamaulipan thornscrub habitat, private ranchland, Webb Co. TX; 10 June 2016.jpg, Tamaulipan thornscrub, private ranchland,

Webb County, Texas Webb County is a county located in the U.S. state of Texas. As of the 2020 census, its population was 267,114. Its county seat is Laredo. The county was named after James Webb (1792–1856), who served as secretary of the treasury, secre ...

(10 June 2016). File:Sabal Palm Sanctuary, Cameron Co. TX; 11 Apr 2016.jpg, Old growth sabal palm grove, Sabal Palm Sanctuary, Cameron County, Texas (11 April 2016). File:Tamaulipan thornscrub, State Highway 4, Cameron Cameron County, Texas, USA (11 April 2016).jpg, Tamaulipan thornscrub, State Highway 4, Cameron County, Texas (11 April 2016) File:Trail in Santa Ana National Wildlife Refuge, Hidalgo County, Texas, USA (14 April 2016).jpg, Trail through mature thornscrub forest in Santa Ana National Wildlife Refuge, Hidalgo County, Texas (14 April 2016). File:Yturria Brush National Wildlife Refuge, Hidalgo County, Texas, USA (15 April 2016).jpg, Road in thornscrub vegetation, Yturria Brush National Wildlife Refuge, Hidalgo County, Texas (15 April 2016) File:Rio Grande SE of Falcon Reservoir, Municipality of Mier, Tamaulipas, Mexico (12 August 2007).jpg, Rio Grande southeast of Falcon Reservoir, Municipality of Mier, Tamaulipas, Mexico (12 August 2007) File:Thornscrub south of Reynosa, Municipality of Reynosa, Tamaulipas, Mexico (13 August 2007).jpg, Thornscrub south of Reynosa, Municipality of Reynosa, Tamaulipas, Mexico (13 August 2007) File:Sierra San Carlos, Municipality of San Carlos, Tamaulipas, Mexico (14 July 2007).jpg, Sierra San Carlos, Municipality of San Carlos, Tamaulipas, Mexico (14 July 2007) File:Sierra San Carlos, with Pinus teocote (left), Municipality of San Carlos, Tamaulipas, Mexico (12 July 2007).jpg, Sierra San Carlos, with a pine tree ('' Pinus teocote'') on left, Municipality of San Carlos, Tamaulipas, Mexico (12 July 2007) File:Thornscrub ranchland west of Tepehuajes, Municipio Soto La Marina, Tamaulipas, Mexico (20 May 2002).jpg, Thornscrub ranchland west of Tepehuajes, Municipio Soto La Marina, Tamaulipas, Mexico (20 May 2002)

Flora

This semi-arid region is dominated by Mezquital (Spanish for a mesquite groveGooch, Anthony, and Angel García de Paredes. 1978. ''Cassell's Spanish-English Dictionary''. Cassell Ltd. London and Macmillan Publishing Co. Inc. New York. xxv, 1109 pp. ), thorny brush, and chaparral vegetation referred to as Tamaulipan thornscrub. In this

subtropical The subtropical zones or subtropics are geographical zone, geographical and Köppen climate classification, climate zones immediately to the Northern Hemisphere, north and Southern Hemisphere, south of the tropics. Geographically part of the Ge ...

environment some plant growth continues through most of the year, particularly in the south. Years with droughts or tropical storms and hurricanes can dramatically affect vegetation at any given locality, particularly the herbaceous ground layer, which may be sparse with patches of bare earth in a dry year, or thick and verdant in a wet year. Thornscrub vegetation tends to grow taller and thicker in the east, benefited by coastal moisture where it can be impenetrable in places, and it is often shorter and more open in interior areas of the region, although soils also influence this throughout the region.Blair, W. Frank. (1950). ''The Biotic Provinces of Texas''. Texas Journal of Science. 2(1): 93-117.Martin, Paul S., C. Richard Robins, and William B. Heed. 1954. ''Birds and Biogeography of the Sierra de Tamaulipas, an Isolated Pine-Oak Habitat''.The Wilson Bulletin.Vol. 66, No. 1: 38-57. Mixtures of sand and clay make up much of the soils with pockets of near pure sand and near pure clay occurring locally.Richardson, Alfred and Ken King. 2011. ''Plants of Deep South Texas, A Field Guide to the Woody and Flowering Species''. Texas A&M University Press. College Station, Texas. xii, 457 pp. Sandy soils in this region tend to support more open vegetation with widely spaced trees and shrubs in grasslands, while clay soils tend to support a greater diversity and denser, sometimes even canopied areas of trees and shrubs. Past land usage can also have a significant influence, where recently cleared areas may have a near monoculture of honey mesquite ('' Prosopis glandulosa''), with pricklypear ('' Opuntia engelmannii'' var. ''lindheimeri''), and non-native grasses in the understory.Texas Parks and Wildlife (& Nature Serve Explorer), Ecological Mapping Systems of Texas:
Tamaulipan Savanna Grassland
' (Accessed: 18 August 2020). Some species of are nearly ubiquitous, occurring in most of the soils and vegetation communities, although varying in levels of dominance, some of these include honey mesquite, spiny hackberry (''

Celtis ehrenbergiana ''Celtis ehrenbergiana'', called the desert hackberry or spiny hackberry, is a plant species that has long been called ''C. pallida'' by many authors, including in the "Flora of North America" database. It is native to Arizona, Florida, New Mexic ...

''), desert Christmas cholla ('' Cylindropuntia leptocaulis''), Texas persimmon ('' Diospyros texana''), Texas prickly pear ('' Opuntia engelmannii'' var. ''lindheimeri''), and black brush ('' Vachellia rigidula''). Other common trees and shrubs more often found on clay soils include white bush ('' Aloysia gratissima''), goat bush ('' Castela erecta''), brasil ('' Condalia hookeri''), knackaway ('' Ehretia anacua''). Texas lignum-vitae ('' Guaiacum angustifolium''), Texas purple sage (''

Leucophyllum frutescens ''Leucophyllum frutescens'' is an evergreen shrub in the Scrophularia, figwort family, Scrophulariaceae, native to the U.S. state of Texas, where it is the official "State Native Shrub of Texas", and to the states of Coahuila, Nuevo León, and Ta ...

''), retama ('' Parkinsonia aculeata''), Berlandier acacia ('' Senegalia berlandieri''), and huisache (''

Vachellia farnesiana ''Vachellia farnesiana'', also known as ''Acacia farnesiana'', and previously ''Mimosa farnesiana'', commonly known as sweet acacia, huisache, casha tree, or needle bush, is a species of shrub or small tree in the legume family, Fabaceae. Its flo ...

'' var. ''farnesiana'').Texas Parks and Wildlife (& Nature Serve Explorer), Ecological Mapping Systems of Texas:
Tamaulipan Calcareous Thornscrub
' (Accessed: 18 August 2020). Grasslands with sparsely scattered trees and shrubs occur on level to gently rolling sites with sandy soils. These are dominated by dense graminoids such as Texas grama ('' Bouteloua rigidiseta''), little bluestem ('' Schizachyrium scoparium''), sand dropseed ('' Sporobolus cryptandrus''), and many others. Wildflowers include bull-nettle ('' Cnidoscolus texanus''), shrubby blue sage ('' Salvia ballotiflora''), hairy tubetongue ('' Justicia pilosella''), Texas palafoxia ('' Palafoxia texana''), and hairy zexmania ('' Wedelia texana''). Shrub-dominated patches may develop within these grassy sites where tighter, clay soils occur, reaching six meters or higher, often dominated by several of the ubiquitous species noted above. Woodlands occur in places with a well-developed canopy over an understory of grasses. The grasses in these communities contain a layer of taller species such as hooded windmill grass ('' Chloris cucullata'') and four-flower trichloris ('' Trichloris pluriflora''), and a layer of shorter species such as grama (''

Bouteloua ''Bouteloua'' is a genus of plants in the grass family Poaceae. Members of the genus are commonly known as grama grass. Description ''Bouteloua'' includes both annual and perennial grasses, which frequently form stolons. Species have an inflo ...

'' spp.) and curly mesquite grass ('' Hilaria belangeri''). In some places dense stands of Texas prickly pear occur instead of shrubs and grasses. Canopy species include many ubiquitous trees along with huisache (''

Acacia farnesiana ''Vachellia farnesiana'', also known as ''Acacia farnesiana'', and previously ''Mimosa farnesiana'', commonly known as sweet acacia, huisache, casha tree, or needle bush, is a species of shrub or small tree in the legume family, Fabaceae. Its flo ...

''), desert hackberry ('' Celtis pallida''), brasil ('' Condalia hookeri''), Texas hogplum ('' Colubrina texensis''), colima (''

Zanthoxylum fagara ''Zanthoxylum fagara'' or wild lime, is a species of flowering plant that—despite its name—is not part of the genus ''Citrus'' with real limes and other fruit, but is a close cousin in the larger citrus family, Rutaceae. It is more closely ...

''), and others. Other shrubs include desert yaupon ('' Schaefferia cuneifolia''), desert olive (''

Forestiera angustifolia ''Forestiera'' is a genus of flowering plants in the olive family, Oleaceae. Members of the genus are often called swampprivets. Most are shrubs. Species There are about 20 species, native to Mexico, Central America, the West Indies, Ecuador an ...

''), and lotebush ('' Ziziphus obtusifolia''). Xeric rocky uplands with shallow calcareous soils on

and gravel substrates support shrublands one half to two meters high. Species such as cenizo (''

''), guajillo ('' Acacia berlandieri''), Texas kidneywood ('' Eysenhardtia texana''), twisted acacia ('' Vachellia schaffneri''), Spanish dagger ('' Yucca treculeana''), and baretta ('' Helietta parvifolia'') and others grow with ubiquitous trees and shrubs. The creosote bush (''

Larrea tridentata ''Larrea tridentata'', called creosote bush, greasewood, and chaparral is a medicinal herb. In Sonora, it is more commonly called ''hediondilla''; Spanish ''hediondo'' = "smelly". It is a flowering plant in the family Zygophyllaceae. The specific ...

'') grows in western areas. The herbaceous layer may be sparse in places where rocky exposures occur. Forbs and wildflowers can be conspicuous in rocky areas, including narrowleaf thryallis ('' Galphimia angustifolia''), peonia ('' Acourtia runcinata''), Gregg's senna ('' Chamaecrista greggii''), plateau rocktrumpet ('' Macrosiphonia macrosiphon''), and hairy zexmania ('' Wedelia hispida'').Texas Parks and Wildlife (& Nature Serve Explorer), Ecological Mapping Systems of Texas:
Tamaulipan Mixed Deciduous Thornscrub
' (Accessed: 18 August 2020). Saline lakes and saline thornscrub occur in some interior, low-lying areas with interior draining basins, created by runoff and evaporation. Lakebeds (often dry) may lack vegetation or have sparse

halophytic A halophyte is a salt-tolerant plant that grows in soil or waters of high salinity, coming into contact with saline water through its roots or by salt spray, such as in saline semi-deserts, mangrove swamps, marshes and sloughs, and seashores. ...

grasses and forbs like alkali sacaton (''

Sporobolus airoides ''Sporobolus airoides'' is a species of grass known by the common name alkali sacaton. It is native to western North America, including the Western United States west of the Mississippi River, British Columbia and Alberta in Canada, and northern ...

''), sea ox-eye daisy ('' Borrichia frutescens''), and saltwort ('' Batis maritima''). Surrounding saline thornscrub is semi-open with ubiquitous shrubs under 5 m., growing with species like saladillo ('' Varilla texana''), knifeleaf condalia ('' Condalia spathulata''), Johnston's seaheath ('' Frankenia johnstonii''), and screw bean mesquite ('' Prosopis reptans'') among others. Soils may have a thin layer of gravel over clay with patchy grasses and cacti such as Fitch's hedgehog cactus ('' Echinocereus reichenbachii'' var. ''fitchii'') and horse crippler ('' Homalocephala texensis'').Texas Parks and Wildlife (& Nature Serve Explorer), Ecological Mapping Systems of Texas:
Tamaulipan Saline Lake
' (Accessed: 18 August 2020).Texas Parks and Wildlife (& Nature Serve Explorer), Ecological Mapping Systems of Texas:
Tamaulipan Saline Thornscrub
' (Accessed: 18 August 2020).Cram, Silke, Irene Sommer, Luis-Miguel Morales, Oralia Oropeza, Estela Carmona, and Francisco Gonzalez-Medrano. 2006. ''Suitability of the vegetation types in Mexico's Tamaulipas state for the siting of hazardous waste treatment plants''. Journal of Environmental Management. 80 (2006): 13-24. Internally drained basins with non-salin, or freshwater also occur on clay lined or clay loam soils that hinder drainage. Sometimes called potholes, lagunas, lagunitas, ponds, or copitas, these are ephemeral wetlands but may remain moist over extended periods of time.Texas Parks and Wildlife (& Nature Serve Explorer), Ecological Mapping Systems of Texas:
Tamaulipan Closed Depression Wetland
' (Accessed: 18 August 2020). Riparian zones and floodplains can support luxuriant forest on the

alluvial Alluvium (, ) is loose clay, silt, sand, or gravel that has been deposited by running water in a stream bed, on a floodplain, in an alluvial fan or beach, or in similar settings. Alluvium is also sometimes called alluvial deposit. Alluvium is ...

soils of the major rivers. These can sometimes have a dense canopy up to 15 meters high. Dominant canopy species may include many of the ubiquitous and common species noted above, as well as granjeno (''

''), sugar hackberry ('' Celtis laevigata''), Texas ebony ('' Ebenopsis ebano''), anacua ('' Ehretia anacua''), Mexican ash ('' Fraxinus berlandierana''), tepeguaje ('' Leucaena pulverulenta''), and cedar elm ('' Ulmus crassifolia''). Riverbanks may have a reduced over-story with black mimosa ('' Mimosa asperata''), black willow (''

Salix nigra ''Salix nigra'', or the black willow, is a species of willow native to a large portion of North America, from New Brunswick and southern Ontario west to Arizona and California, and south to northern Florida and Texas. Description ''Salix nigr ...

''), and giant reed (''

Arundo donax ''Arundo donax'' is a tall perennial cane. It is one of several so-called reed species. It has several common names including giant cane, elephant grass, carrizo, arundo, Spanish cane, Colorado river reed, wild cane, and giant reed. ''Arundo'' a ...

'') an

invasive species An invasive species is an introduced species that harms its new environment. Invasive species adversely affect habitats and bioregions, causing ecological, environmental, and/or economic damage. The term can also be used for native spec ...

. Numerous species of vines and epiphytes like Spanish moss (''

Tillandsia usneoides Spanish moss (''Tillandsia usneoides'') is an epiphytic flowering plant that often grows upon large trees in tropical and subtropical climates. It is native to much of Mexico, Bermuda, the Bahamas, Central America, South America (as far south as ...

'') are frequently encountered as well as rarer Bailey's ballmoss ('' Tillandsia baileyi''). The herbaceous layer is often not well developed. In the

drainage and northward, pecan ('' Carya illinoinensis'') and plateau live oak (''

Quercus fusiformis ''Quercus fusiformis'' (also often referred to as ''Q. virginiana'' var. ''fusiformis''), commonly known as escarpment live oak, plateau live oak, plateau oak, or Texas live oak, is an evergreen or nearly evergreen tree. Its native range inc ...

'') may be common. Diversity increases southward and the Rio Grande Delta has a denser understory with a sub-canopy layer at 4 to 5 meters including Sierra Madre torchwood ('' Amyris madrensis''), Texas torchwood ('' Amyris texana''), Barbados cherry ('' Malpighia glabra''), catclaw acacia ('' Senegalia wrightii''), brushholly ('' Xylosma flexuosa''), and others. Monumental Montezuma cypresses (''

Taxodium mucronatum ''Taxodium mucronatum'', commonly known as Montezuma bald cypress, Montezuma cypress, or ahuehuete, is a species of ''Taxodium'' that is primarily native to Mexico and Guatemala, with a few populations in the southwestern United States. Ahuehue ...

'') once lined portions of the Rio Grande and other southern rivers, but few remain today. Parque Nacional El Sabinal in the town of Ciudad Cerraivo, Nuevo Leon preserves some fine examples of old Montezuma cypress in an urban environment.Gobierno El México
Parque Nacional El Sabinal
/ref> Only a few, small groves of Mexican sabal palm ('' Sabal mexicana'') remain on the Rio Grande Delta, but it is believed they once occurred as far as 120 km. inland. Palms may dominate the canopy or share dominance with other floodplain species reaching 15 meters. The herbaceous layer may include bunch cutgrass ('' Leersia monandra''), tropical sage ('' Salvia coccinea''), and blue boneset ('' Tamaulipa azurea''), or dead palm fronds may restrict the development of the ground layer.Texas Parks and Wildlife (& Nature Serve Explorer), Ecological Mapping Systems of Texas:
Tamaulipan Floodplain
' (Accessed: 18 August 2020).Texas Parks and Wildlife (& Nature Serve Explorer), Ecological Mapping Systems of Texas:
Rio Grande Delta Thorn Woodland and Shrubland
' (Accessed: 18 August 2020).Texas Parks and Wildlife (& Nature Serve Explorer), Ecological Mapping Systems of Texas:
Tamaulipan Palm Grove Riparian Forest
' (Accessed: 18 August 2020). Cacti: This region is rich in cacti diversity. In addition to wide-ranging species like lace cactus ('' Echinocereus reichenbachii''), and horse-crippler cactus ('' Homalocephala texensis''), other species found in the province include: root cactus ('' Sclerocactus scheeri''), triangle or barbed wire cactus ('' Acanthocereus tetragonus''), star cactus ('' Astrophytum asterias''), Runyon's beehive cactus ('' Coryphantha macromeris'' var. ''runyonii''), Berlandier's hedgehog ('' Echinocereus berlandieri''), pitaya ('' Echinocereus enneacanthus'' var. ''brevispinus''), Allicoche hedgehog cactus ('' Echinocereus papillosus''), ladyfinger hedgehog ('' Echinocereus pentalophus''), Dahlia cactus ('' Echinocereus poselgeri''), Junior Tom Thumb cactus ('' Escobari emskoetteraana''), Turk's head barrel cactus ('' Ferocactus hamatacanthus'' var. ''sinuatus''), peyote (''

Lophophora williamsii The peyote (; ''Lophophora williamsii'' ) is a small, spineless cactus which contains Psychoactive cactus, psychoactive alkaloids, particularly mescaline. is a Spanish word derived from the Nahuatl (), meaning "caterpillar Pupa#Cocoon, cocoon" ...

''), Heyder's pincushion cactus ('' Mammillaria heyderi''), hair-covered cactus or Texas pincushion ('' Mammillaria prolifera'' var. ''texana''), pale mammillaria (''

Mammillaria sphaerica ''Mammillaria sphaerica'', the longmamma nipple cactus or pale mammillaria is a species of flowering plant in the cactus family Cactaceae, native to south eastern Texas in the USA and north eastern Mexico, where it occurs in scattered patches at ...

''), twisted rib cactus ('' Thelocactus setispinus'') and several others.Loflin, Brian and Shirley Loflin. (2009). ''Texas Cacti''. Texas A&M University Press, College Station. xv, 291. Some of these species have very limited distributions and are endemic to the region such as '' Astrophytum caput-medusae'' from Nuevo Leon, Mexico.Hernández, Héctor M. and Carlos Gómez-Hinostrosa. 2011. Mapping the Cacti of Mexico, Their geographical distribution and based on referenced records. DH Books, Milborne Port, England with CONABIO, Succulent Plant Research, Vol. 7: 128 pp.

Fauna

Mammals: This region once hosted an impressive number of carnivores but, most were very rare, or entirely

extirpated Local extinction, also extirpation, is the termination of a species (or other taxon) in a chosen geographic area of study, though it still exists elsewhere. Local extinctions are contrasted with global extinctions. Local extinctions mark a chan ...

by the early to mid 20th century. The gray wolf (''

Canis lupus The wolf (''Canis lupus''; : wolves), also known as the grey wolf or gray wolf, is a canine native to Eurasia and North America. More than thirty subspecies of ''Canis lupus'' have been recognized, including the dog and dingo, though gr ...

'') is extirpated and black bears (''

Ursus americanus The American black bear (''Ursus americanus''), or simply black bear, is a species of medium-sized bear which is endemic to North America. It is the continent's smallest and most widely distributed bear species. It is an omnivore, with a diet v ...

'') are now largely restricted to the Sierra de Picachos in

Nuevo Leon Nuevo is the Spanish word for "new". It may refer to: * Nuevology, California, a town in California, United States * Nuevo (band), featuring singer and musician Peter Godwin * Nuevo (Bayamón), a settlement in Puerto Rico * "Nuevo", Spanish-langu ...

, Mexico. The most recent records of the jaguar (''

Panthera onca The jaguar (''Panthera onca'') is a large cat species and the only living member of the genus ''Panthera'' that is native to the Americas. With a body length of up to and a weight of up to , it is the biggest cat species in the Americas a ...

'') in Texas, USA are from the early 1950s, but the species still lingers, although at risk of extinction in Mexico. Similarly, jaguarondi ('' Herpailurus yaguarondi''), ocelot (''

Leopardus pardalis The ocelot (''Leopardus pardalis'') is a medium-sized spotted Felidae, wild cat that reaches at the shoulders and weighs between on average. It is native to the southwestern United States, Mexico, Central America, Central and South America, ...

''), and margay ('' Leopardus wiedii'') are all threatened or endangered in the US and Mexico. Some puma or mountain lion (''

Puma concolor The cougar (''Puma concolor'') (, '' KOO-gər''), also called puma, mountain lion, catamount and panther is a large small cat native to the Americas. It inhabits North, Central and South America, making it the most widely distributed wil ...

''), White-nosed coati ('' Nasua narica''), and American Badger ('' Taxidea taxus'') populations still persist, apparently in stable numbers in some remote areas, although the latter is considered a threatened species in Mexico. A few other species such as the Northern Raccoon ('' Procyon lotor''), Coyote (''

Canis latrans The coyote (''Canis latrans''), also known as the American jackal, prairie wolf, or brush wolf, is a species of canine native to North America. It is smaller than its close relative, the gray wolf, and slightly smaller than the closely relat ...

''), and to a lesser extent Bobcats ('' Lynx rufus'') have adapted to human encroachment and development.Schmidly, D. J. (2004). ''The Mammals of Texas''. ixth Edition University of Texas Press, Austin, Texas. xviii, 501 pp. Ceballos, G. Ed. (2014). ''Mammals of Mexico''. Johns Hopkins University Press. Baltimore, Maryland. xiii, 957 pp. Other mammals found in the region include the collared peccary ('' Pecari tajacu''), white-tailed deer ('' Odocoileus virginianus''), black-tailed jackrabbit ('' Lepus californicus''), nine-banded armadillo ('' Dasypus novemcinctus''), Mexican long-tongued bat ('' Choeronycteris mexicana''), and the southern yellow bat ('' Lasiurus ega''). Rodents include the predatory northern grasshopper mouse (''

Onychomys leucogaster The northern grasshopper mouse (''Onychomys leucogaster'') is a North American carnivorous rodent of the family Cricetidae. It ranges over much of the western part of the continent, from southern Saskatchewan and central Washington to Tamaulipas ...

''), the Mexican prairie dog ('' Cynomys mexicanus''), Rio Grande ground squirrel ('' Ictidomys parvidens'') and others such as Coue's rice rat (''

Oryzomys couesi ''Oryzomys couesi'', also known as Coues's rice rat, is a semiaquatic rodent in the family Cricetidae occurring from southernmost Texas through Mexico and Central America into northwestern Colombia. It is usually found in wet habitats, such as m ...

''), southern plains woodrat (''

Neotoma micropus The Southern Plains woodrat (''Neotoma micropus'') is a species of rodent in the family Cricetidae. It is found in northwest Mexico and in Colorado, Kansas, New Mexico, Oklahoma, and Texas in the United States. The subspecies ''Neotoma micropus l ...

''), Mexican spiny pocket mouse ('' Liomys irroratus''), and Merriam's pocket mouse ('' Perognathus merriami''). File:Collared peccary (Pecari tajacu), Bentsen-Rio Grande Valley State Park, Hidalgo Co. Texas (4 Feb 2010). A.jpg, Collared peccary ('' Pecari tajacu''), Hidalgo Co. Texas (4 Feb 2010). File:Mexican ground squirrel (Ictidomys mexicanus) Cameron Co. Texas (12 April 2016).jpg, Rio Grande ground squirrel ('' Ictidomys parvidens'') Cameron Co. Texas (12 April 2016). File:Btjackrabbit.jpg, Black-tailed jackrabbit ('' Lepus californicus''), Texas (13 June 2006). File:Ocelot (Leopardus pardalis) Laguna Atascosa National Wildlife Refuge, Texas.jpg, Ocelot (''

'') with tracking collar, Laguna Atascosa National Wildlife Refuge, Cameron Co. Texas. File:MexicanCoati2.jpg, White-nosed coati ('' Nasua narica''), Mexico (5 Sept 2009). File:Taxidea taxus (Point Reyes, 2007) cropped.jpg, American badger ('' Taxidea taxus''), Marin Co., California (25 Nov 2007). Birds: The southern part of the ecoregion is an Endemic Bird Area and is home to the red-crowned amazon ('' Amazona viridigenalis''), tawny-collared nightjar ('' Caprimulgus salvini''), Tamaulipas crow ('' Corvus imparatus''), long-billed thrasher ('' Toxostoma longirostre''), Altamira yellowthroat ('' Geothlypis flavovelata''), and crimson-collared grosbeak ('' Rhodothraupis celaeno''). Other species occurring in this region include the white-tailed hawk ('' Buteo albicaudatus''), plain chachalaca ('' Ortalis vetula''), green parakeet ('' Psittacara holochlorus''), buff-bellied hummingbird ('' Amazilia yucatanensis''), Couch's kingbird ('' Tyrannus couchii''), and Audubon's oriole ('' Icterus graduacauda'') as well as wide-ranging tropical species such as the green jay ('' Cyanocorax yncas''), least grebe ('' Tachybaptus dominicus''), Ferruginous pygmy owl ('' Glaucidium brasilianum''), ringed kingfisher ('' Megaceryle torquata''), and the great kiskadee ('' Pitangus sulphuratus'').Howell, S. N. G. and S. Webb. (1995). A Guide to the Birds of Mexico and Northern Cantral America. Oxford University Press. Oxford. xvi, 851 pp. Terres, J. K. (1996). The Audubon Society Encyclopedia of North American Birds. Wings Books, a division of Random House Value Publishing, Inc.. New York. N. Y. 1109 pp. File:Ortalis vetula Linares.jpg, Plain chachalaca ('' Ortalis vetula''), Municipality of Montemorelos, Nuevo León (9 April 2009). File:Red-crowned Parrots (26460808665).jpg, Red-crowned Amazon ('' Amazona viridigenalis''), Cameron Co. Texas (15 Mar 2016). File:Ferruginous Pygny-Owl (26113203405).jpg, Ferruginous pygmy owl ('' Glaucidium brasilianum''), King Ranch, TX (15 Mar 2016). File:Buff-bellied Hummingbird (Amazilia yucatanensis) Sabal Palm C.jpg, Buff-bellied hummingbird ('' Amazilia yucatanensis''), Sabal Palm Sanctuary, Cameron Co. Texas (21 Sept. 2015). File:Great Kiskadee South Texas July 2011.jpg, Great kiskadee ('' Pitangus sulphuratus''). Bee Co., Texas (3 July 2011). File:Long-billed Thrasher (34153001873).jpg, Long-billed thrasher ('' Toxostoma longirostre''), Texas, USA (20 Feb. 2017). File:Audubon's Oriole (12626811374).jpg, Audubon's oriole ('' Icterus graduacauda''), Starr Co. Texas (1 Feb 2014). Reptiles: The American alligator ('' Alligator mississippiensis'') and the red-eared slider (''

Trachemys scripta The pond slider (''Trachemys scripta'') is a species of common, medium-sized, semiaquatic turtle. Three subspecies are described, the most recognizable of which is the red-eared slider (''T. s. elegans''), which is popular in the pet trade and ha ...

'') occur in the north of this region and the Morelet's crocodile ('' Crocodylus moreletii'') and Mesoamerican slider ('' Trachemys venusta'') in the south. Other turtles such as the Mexican box turtle ('' Terrapene mexicana''), Rio Grande cooter ('' Pseudemys gorzugi''), spiny softshell ('' Apalone spinifera''), and the yellow mud turtle ('' Kinosternon flavescens'') occur there. The geographic distribution of the Texas tortoise ('' Gopherus berlandieri'') nearly matches that of the Tamaulipan mezquital ecoregion. The Laredo striped whiptail ('' Aspidoscelis laredoensis'') is a

species complex In biology, a species complex is a group of closely related organisms that are so similar in appearance and other features that the boundaries between them are often unclear. The taxa in the complex may be able to hybridize readily with each oth ...

of all female lizards that reproduce by

parthenogenesis Parthenogenesis (; from the Greek + ) is a natural form of asexual reproduction in which the embryo develops directly from an egg without need for fertilization. In animals, parthenogenesis means the development of an embryo from an unfertiliz ...

that is

endemic Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also foun ...

to this region. The reticulate collared lizard ('' Crotaphytus reticulatus'') is also endemic. Other representative lizards include the Texas banded gecko (''

Coleonyx brevis The Texas banded gecko (''Coleonyx brevis'') is a species of small gecko native to the southwestern United States and northern Mexico. Description Texas banded geckos are small, terrestrial lizards, rarely exceeding in length. They have alte ...

''), four-lined skink ('' Plestiodon tetragrammus''), common spotted whiptail ('' Aspidoscelis gularis''), keeled earless lizard ('' Holbrookia propinqua''), Texas horned lizard ('' Phrynosoma cornutum''), blue spiny lizard ('' Sceloporus cyanogenys''), and the northern rose-belly lizard ('' Sceloporus variabilis marmoratus''), regarded by some as a full species (''Sceloporus marmoratus''). Some representative snakes of the Tamaulipan mezquital include the Tamaulipan hook-nose snake ('' Ficimia streckeri''), Mexican milksnake ('' Lampropeltis annulata''), and Schott's whipsnake ('' Masticophis schotti''). More wide-ranging species include the Great Plains ratsnake ('' Pantherophis emoryi''), gopher snake ('' Pituophis catenifer''), long-nose snake ('' Rhinocheilus lecontei''), and eastern patch-nose snake ('' Salvadora grahamiae''). Some tropical species reaching the northern margin of their ranges including the regal black-striped snake ('' Coniophanes imperialis''), Central American indigo snake ('' Drymarchon melanurus''), speckled racer ('' Drymobius margaritiferus''), northern cat-eyed Snake ('' Leptodeira septentrionalis''). Venoumous snakes include the Texas coralsnake ('' Micrurus tener'') and western diamond-back rattlesnake ('' Crotalus atrox''), with the western massasauga rattlesnake ('' Sistrurus tergeminus'') occurring in the north and the Totonacan rattlesnake ('' Crotalus totonacus'') occurring in the south.Lemos Espinal, J. A., Editor. (2015). ''Amphibians and Reptiles of the US-Mexico Border States''. Texas A&M University Press. College Station, Texas. x, 614 pp. Werler, J. E. and J. R. Dixon. (2000). Texas Snakes, Identification, Distribution, and Natural History. University of Texas Press, Austin, Texas. xv, 437 pp. File:Sceloporus variabilis marmoratus, Northern Rose-bellied Lizard, Texas.jpg, Rose-bellied lizard ('' Sceloporus variabilis marmoratus''), Hidalgo County, Texas, USA (14 April 2016). File:Holbrookia propinqua, keeled earless lizard, Tamaulipas.jpg, Keeled earless lizard ('' Holbrookia propinqua''), municipality of Soto La Marina, Tamaulipas, Mexico (20 May 2002). File:Coleonyx brevis, Texas Banded Gecko, Webb Co. Texas.jpg, Texas banded gecko (''

''), Webb County Texas, USA (10 June 2016). File:Gopherus berlandieri, Texas Tortoise, Tamaulipas.jpg, Texas Tortoise ('' Gopherus berlandieri''), northern Tamaulipas, Mexico (9 July 2007). File:Leptodeira septentrionalis, Northern Cat-eyed Snake, Tamaulipas.jpg, Northern cat-eyed snake ('' Leptodeira septentrionalis''), Municipality of Victoria, Tamaulipas, Mexico (7 Aug 2003). File:Mexican Milksnake (Lampropeltis annulata), Municipality of Victoria, Tamaulipas (30 Oct 2003).jpg, Mexican milksnake ('' Lampropeltis annulata''), Municipality of Victoria, Tamaulipas (30 Oct 2003). File:Crotalus atrox, Western Diamondback Rattlesnake, Tamaulipas.jpg, Western diamondback rattlesnake ('' Crotalus atrox''), Municipality of Padilla, Tamaulipas, Mexico (29 May 2004). Amphibians: In spite of the semi-arid environment, enough wetlands are present to support salamanders such as the black-spotted newt ('' Notophthalmus meridionalis'') and the lesser siren (''

''). A second species of siren is known to occur in the lower Rio Grande, thought to be a distant and isolated population of the greater siren ('' Siren lacertina'') by some, or an undescribed species by others. The Rio Grande leopard frog ('' Lithobates berlandieri'') and western narrow-mouthed toad ('' Gastrophryne olivacea'') occur in the region along with several toads (

Bufonidae {{Cat main, Toad This category Category, plural categories, may refer to: General uses *Classification, the general act of allocating things to classes/categories Philosophy * Category of being * ''Categories'' (Aristotle) * Category (Kant) * C ...

) inhabiting the thorn scrub and grasslands including the green toad ('' Anaxyrus debilis''), Texas toad ('' Anaxyrus speciosus''), Gulf Coast toad ('' Incilius nebulifer''), and cane toad ('' Rhinella horribilis''). Many tropical species reach the northern limits of their distributions there such as the Mexican treefrog ('' Smilisca baudinii''), white-lipped frog ('' Leptodactylus fragilis''), sheep frog ('' Hypopachus variolosus''), and the unusual burrowing toad (''

Rhinophrynus dorsalis The Mexican burrowing toad (''Rhinophrynus dorsalis'') is the single living representative of the family Rhinophrynidae. It is a unique species in its taxonomy and morphology, with special adaptations to assist them in digging burrows where they ...

''), so unique it is classified in a family (

Rhinophrynidae The Rhinophrynidae are a family of frogs containing one extant genus, the monotypic ''Rhinophrynus'', and a number of fossil genera. The family is sometimes known as the Mexican burrowing toads or simply burrowing toads. ''Rhinophrynus'' occurs ...

) by itself. File:Smilisca baudinii WLF-17-14A, Municipio Abasolo; 18 May 2002.jpg, Mexican Treefrog ('' Smilisca baudinii''), Municipality of Abasolo, Tamaulipas, Mexico (18 May 2002). File:Leptodactylus fragilis WLF-152-1A, Municipio Victoria; 12 Aug 2003.jpg, White-lipped Frog ('' Leptodactylus fragilis'') Municipality of Victoria, Tamaulipas, Mexico (12 August 2003). File:Scaphiopus couchii, Couch’s Spadefoot, Cameron County, Texas.jpg, Couch's Spadefoot ('' Scaphiopus couchii''), Cameron County, Texas, USA (11 April 2016). File:Black-spotted Newt (Notophthalmus meridionalis), Santa Ana NWR, Hidalgo Co, TX, USA, (26.0821°N, 98.1354°W), 14 April 2016.jpg, Black-spotted Newt ('' Notophthalmus meridionalis''), Santa Ana NWR, Hidalgo Co, Texas (14 April 2016). File:Rhinella horribilis, Cane Toad, Tamaulipas.jpg, Cane Toad ('' Rhinella horribilis''), Municipality of Soto La Marina, Tamaulipas, Mexico (17 May 2002). File:Hypopachus variolosus WLF-148-10A, Municipio Victoria; 12 Aug 2003.jpg, Sheep Frog ('' Hypopachus variolosus''), Municipality of Victoria, Tamaulipas, Mex (12 August 2003). File:Rhinophrynus dorsalis, Burrowing Toad, Tamaulipas.jpg, Burrowing Toad (''

''), Municipality of Reynosa, Tamaulipas, Mexico (8 October 2007). Fishes: Two species, the San Ignacio pupfish ('' Cyprinodon bobmilleri'') from the upper Rio San Fernando basin near Linares and the swordtail platyfish ('' Xiphophourus xiphidium'') occurring in the upper parts of the Rio Soto La Maria, in Tamaulipas are

to this region. The Amazon molly ('' Poecilia formosa''), is a unisexual (all female) species that reproduces through

gynogenesis Gynogenesis, a form of parthenogenesis, is a system of asexual reproduction that requires the presence of sperm without the actual contribution of its DNA for completion. The paternal DNA dissolves or is destroyed before it can fuse with the egg. T ...

, a form of a form of

. Other fishes found in the area are alligator gar ('' Atractosteus spatula''), longnose gar (''

Lepisosteus osseus The longnose gar (''Lepisosteus osseus''), also known as longnose garpike or billy gar, is a ray-finned fish in the family Lepisosteidae. The genus may have been present in North America for about 100 million years. References are made to gar ...

''), Rio Grande cichlid ('' Herichthys cyanoguttatus''), sailfin molly ('' Poecilia latipinna''), Rio Grande silvery minnow ('' Hybognathus amarus''), San Juan minnow ('' Dionda couchi''), Tamaulipas shiner ('' Notropis braytoni''), Rio Grande shinner ('' Notropis jemezanus''), Gulf killifish ('' Fundulus grandis''), and Rio Grande darter ('' Etheostoma grahami''). Two endemic species from this region, the phantom shinner ('' Notropis orca'') and the Salado shinner ('' Notropis saladonis''), are believed to be extinct.García de León, Francisco J., Delladira Gutiérrez Tirado, Dean A. Hendrickson, and Héctor Espinosa Pérez (2005). ''Fishes of the Continental Waters of Tamaulipas: Diversity and Conservation Status''. ''In'' Jean-Luc E. Cartron, Gerardo Ceballos, and Richard S. Felger (eds.). ''Biodiversity, Ecosystems, and Conservation in Northern Mexico''. Oxford University Press, Inc. New York, N. Y. xvi, 496 pp. Miller, R. R., W. L. Minckley, and S. M. Norris. (2005). ''Freshwater Fishes of Mexico''. University of Chicago Press. Chicago, Illinois. xxv, 490 pp. Thomas, Chad, Timothy H. Bonner, & Bobby G. Whiteside. (2007). ''Freshwater Fishes of Texas: A Field Guide''. Texas A&M University Press. College Station, Texas. xiv, 202 pp. File:Molly.jpg, Sailfin molly ('' Poecilia latipinna'') File:Etheostoma grahami.jpg, Rio Grande darter ('' Etheostoma grahami''), Val Verde Co., Texas (22 June 2006). File:Gulf killifish (Fundulus grandis), male, Dixie Co, Florida (27 Dec 2013).jpg, Gulf killifish ('' Fundulus grandis''), male, Dixie Co., Florida. File:Rio Grande silvery minnow 2.jpg, Rio Grande silvery minnow ('' Hybognathus amarus'') File:Herichthys cyanoguttatus (Rio Grande Cichlid) II.jpg, Rio Grande cichlid ('' Herichthys cyanoguttatus''), Texas File:Ybgar 2b (8379903165).jpg, Longnose gar (''

'') File:Alligator gar (Atractosteus spatula) I.jpg, Alligator gar ('' Atractosteus spatula'')

Protected areas

Nature preserves are numerous in the region, however many are relatively small tracts of land concentrated on the north side of the

Lower Rio Grande Valley Lower Rio Grande Valley (), often referred to as the Rio Grande Valley (RGV) of South Texas, is a region located in the southernmost part of Texas, along the northern bank of the Rio Grande. It is also known locally as the Valley or the 956 (the ...

. The state of Texas administers the following lands in the Lower Rio Grande Valley: Lake Casa Blanca International State Park (525-acres); Falcon State Park (576 acres); Bentsen-Rio Grande Valley State Park (764 acres); Estero Llano Grande State Park (230 acres); Resaca de la Palma State Park (1,200 acres); and the Las Palomas Wildlife Management Area comprised 18 units with tracts ranging from two to 604 acres (3,311 acres total). The U. S. Federal Government also administers lands in the

including the Santa Ana National Wildlife Refuge (2,088 acres) and western and higher elevation areas of the Laguna Atascosa National Wildlife Refuge on the Gulf Coast (>97, 000 acres). The multi-unit Lower Rio Grande Valley National Wildlife Refuge has nearly 40,000 acres open to the public .g. the Boca Chica tract (10,680-acres), East Lake unit (1,700 acres), La Puerta unit (4,000 acres), Teniente Lake unit (5,600 acres), Yturria Brush unit (1,800 acres)and an additional 6,000 acres open to hunting s of 2020 Also of note is the Sabal Palm Sanctuary (557-acres), cooperatively manage by the Gorgas Science Foundation and the

National Audubon Society The National Audubon Society (Audubon; ) is an American non-profit environmental organization dedicated to conservation of birds and their habitats. Located in the United States and incorporated in 1905, Audubon is one of the oldest of such orga ...

, preserving some of the finest old growth riparian zones and sabal palm groves ('' Sabal mexicana'') remaining. Beyond the Lower Rio Grande Valley of Texas protected lands include the Chaparral Wildlife Management Area (15,200 acres), Lake Corpus Christi State Park (356 acres), and Choke Canyon State Park: including the Calliham unit (1,100 acres), the South Shore unit (385-acres), and the adjoining James E. Daughtrey Wildlife Management Area (34,000 acres). In

, Mexico protected areas include western portions of the Laguna Madre y Delta del Rio Bravo and Parras de la Fuente, Reserva de la Paloma de Ala Blanca (ca. 23.8888°N, 98.5000°W), and in

, Mexico the Parque Nacional Los Novillos. Many of the protected lands in Mexico are actually "paper parks" owned and administer by local

ejido An ''ejido'' (, from Latin ''exitum'') is an area of communal land used for agriculture in which community members have usufruct rights, which in Mexico is not held by the Mexican state. People awarded ejidos in the modern era farm them indiv ...

s and municipalities, with few resources devoted to their management, no accommodations, no facilities or trails for visitors, and little management or enforcement of wildlife regulations. Nonetheless, such parks do limit land usage and development, and thus provide a significant degree of protection for habitat and the flora and fauna within.Gobierno del México
76 aniversario del Parque Nacional Los Novillos
/ref>

References

{{reflist Deserts and xeric shrublands in the United States Nearctic ecoregions Ecoregions of the United States Deserts and xeric shrublands Ecoregions of Mexico Deserts of Mexico Deserts of Texas Gulf Coast of Mexico Gulf Coast of the United States Geography of Texas Sierra Madre Oriental Natural history of Nuevo León Natural history of Tamaulipas