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Most Texas limestone caves were carved out between 2 and 15 million years ago. In the Panhandle and in Culberson County, gypsum, a chemically different, non-carbonate rock type, plays host to significant karst areas that include some unusual fast-growing sinkholes like the famous Wink Sink. However, the Edwards is a karst aquifer, meaning that spaces were dissolved out of the bedrock for water to move through and be stored in underground streams. The Edwards Aquifer traces a mile course beneath the Balcones Fault Zone from Brackettville to Austin and provides drinking water to 1.

Surface water originating as rain freely enters the Edwards Aquifer via stream beds, sinkholes and fractures.

MAMMALS | The Handbook of Texas Online| Texas State Historical Association (TSHA)

The vast majority of the water, however, moves rapidly, through conduits that are finger-sized or larger. It is about feet thick, exposed at the surface throughout the fault zone and Edwards Plateau and buried more than 2, feet deep where faulting drops it underground toward the Gulf Coast. Its water table averages an elevation of 1, feet above sea level near Brackettville and gradually descends to an average feet near Barton Springs in Austin.

Artesian springs, such as those in Austin, San Marcos, New Braunfels, and San Antonio, occur where the water table extends above the land surface. Where the land rises above the water table, water must be pumped from the ground. In , workers drilling an artesian well in San Marcos came across an unusual salamander. Eyeless and translucent, with feathery red external gills, the spindly-legged 5-inch-long creature was a breeding adult stalled at a juvenile stage of development, like a tadpole that never grew up. Scientists have found many more biological curiosities since the Texas blind salamander was first described.

Bats, the best-known denizens, roost by day and at night emerge to feed, often on insect pests: The colony of 20 million Mexican freetails at Bracken Cave near San Antonio consumes some tons of moths and beetles nightly.

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But within the subterranean depths dwells another, very different kind of life, one that few of us have had occasion to encounter. These denizens of the dark are called troglobites: fish, salamanders, shrimp, beetles, spiders, harvestmen daddy longlegs , centipedes, millipedes and other less-familiar species.


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Evolved in isolation, they can live nowhere else. But they are exquisitely adapted to life in their circumscribed environment. The karst systems of Central Texas are extraordinarily rich in troglobites. Species barriers are geographical features such as streams and mountains that prevent two previously connected populations from reaching each other to interbreed.

These previously similar populations begin to diverge, to evolve at their separate rates, over many years, in different directions. In the case of exclusive cave dwellers, eyes gradually disappear, pigment fades, and appendages lengthen. Some surprising inhabitants are found underground. Its closest relative, genetic studies show, lives at the bottom of the ocean, in marine vents.

So how did it end up in a Central Texas cave? The answer goes back to 60 million years ago, when Texas was still under a shallow sea. Troglobites share their underground world with other species less completely dark-adapted. Then there are the trogloxenes: creatures that must spend part, but not all, of their life cycle within a cave, like a cave cricket, which has tan coloring and elongated antennae but normal eyes. Crickets play an important role in cave ecology. Like bats, they leave the cave at night to forage. These crickets are largely herbivorous.

They, in turn, contribute nutrients to the cave community by becoming a food source for many of its inhabitants. Certain beetles, in fact, are adapted to eating cricket eggs, with long, narrow heads that have evolved to reach into the tiny holes in mud or clay where the crickets deposit their eggs. Today, some Texas troglobites are in trouble, through both the introduction of non-native species like fire ants and the activities of man. Over 20 species, including the Texas blind salamander and several cave beetles, are listed as endangered. Habitat necessary to the survival of endangered species, designated critical habitat, is regulated by the U.

Fish and Wildlife Service, and property owners — be they private developers, military bases or state parks — are charged with devising acceptable plans for land management.

Consultants like Zara are kept busy providing a wide range of services, from species population inventories to drafting management plans. Development poses the greatest threat to sensitive cave communities. Toxic spills and fertilizer residue make their way to the water table.

Impervious cover replaces important topside vegetation and alters drainage patterns.

Cave crickets need a healthy plant community. It used to be a big field, somewhere crickets could live. Cave communities have major ecological contributions to make. They are composters, returning nutrients to the soil crickets, harvestmen, beetles and many others.

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ISBN 13: 9780890961711

They are pest exterminators bats. And, with their sensitivity to pollution and other environmental disruptions, they are bellwethers of conditions outside. They thrive where the surrounding land thrives. Likewise, healthy aquifer communities point toward safe, uncontaminated water. Since , Texas has required landowners to contain their flowing artesian wells for conservation purposes.

By placing nets over selected artesian wellheads when the wells are opened, the researchers hope to answer those questions. Schindel has a hunch the fish might not be all that rare, just difficult to spot. Then again, three years of monitoring 50 wells on public and private land — each at least twice and some up to 25 times — will provide a lot of windows and, hopefully, a lot of answers. Caves have held an attraction for man since prehistoric times, with a wide range of human activities taking place within their depths.

In the lower Pecos River region of Texas, hunter-gatherer residents of 6,, years ago used caves for burials and left a vivid record of their presence in paintings on rock shelters in the area. For modern-day cavers, the lure remains. Sundry motives fuel their passion for exploring underground: the love of adventure, natural beauty, scientific discovery, physical challenge and more. Texas caves are as diverse as the cavers who roam their passages, offering something to suit everyone. For sheer beauty, the Caverns of Sonora in Sutton County rival caves worldwide, with their sparkling chambers of pure white or mineral-tinted formations.

Enchanted Rock Cave, a granite cave in Llano County, is an example of pseudokarst, in which caves are formed in non-soluble rocks by processes other than dissolution. From three-dimensional mazes to steep drops to stunning decorations, the charms of Texas caves have cavers coming back again and again. Sometimes, for decades. But in at age 11, accompanied by an adult friend, he gingerly descended feet down a ladder made of sheep-wire fencing to the top of the guano mountain that rises from the depths of the enormous pit.

Soon he was caving regularly. Dinosaur remains were often heavily surface weathered before burial, but Figure Each 'X'represents the predator disturbance. Arched necks, tightly coiled occurrence of a signficant vertebrate specimen or group of tails, and retracted digits in hands and feet of some specimens.

Contour interval is four feet. The distribution of bones and sedimentary struc- The derived elongate, rod-like prepubic process, tures a t Proctor Lake demonstrate hypsilophodontid narrow frontal, and hypaxial ossified tendon develop- habitation and bone accumulation over hundreds or ment on the caudals clearly ally this taxon with the thousands of years. This situation is similar to that Hypsilophodontidae Sereno, The Proctor hyp- seen in hypsilophodontid nesting sites in Montana silophodontid i s similar to, but distinct from, Horner, The relative numerical dominance of Hypsilophodon foxii from the Isle of Wight Winkler this one taxon is similar to the Hypsilophodon bed on and others, Derived characters of the Proctor the Isle of Wight Galton, , and the hypsilopho- Lake taxon with respect to Hypsilophodon foxii in- dontids a t Dinosaur Cove, Australia Rich and Rich, clude greater reduction of manus digit V and possibly No eggs have been found at Proctor Lake to the greater development of the anterior intercondylar corroborate the hypothesis that this locality repre- groove of the femur Galton, ; Dodson, The sents a hypsilophodontid nesting site Winkler and pes of the new hypsilophodontid appears more primi- Murry, Good skull material and articulated skeletons are found at the site in a three meter thick fossiliferous interval that spans a n outcrop nearly one kilometer long Figs.

Two modes of skeletal occurrence are evident in addition to scattered isolated elements Winkler and Murry, Articulated remains of adults are distributed a s isolated skeletons through- out the productive zone. Juveniles appear to occur in skeletal concentrations, a t least three of which have been identified. Based on size, the juvenile individu- als within each concentration appear to be of similar SC. A representative femur from one such con- centration Branch Microquarry is 45 mm in length.

Figure Each 'X' represents the occurrence of a femur length near mm. The largest and presumed signficant vertebrate specimen or group of specimens. The specimen is an articulated adult animal preserved lying on its abdomen on a root-mottled, mudcracked, paleosol surface.


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Block with specimen 1. Compared with other sites in the Comanchean by Langston from Greenwood Canyon, the where dinosaurs a r e known from tracks or bones shallowly pitted, slightly keeled osteoscutes from Proctor Lake i s unique in its low faunal diversity. Proctor Lake show affinities to Theriosuchus Joffe, Usually, faunas with a large terrestrial and fresh- Although some of the small crocodiles in the water component contain many fishes and crocodiles, Purbeck Formation Late Jurassic, England are juve- and abundant theropod dinosaur teeth.

On the other niles, the short-snouted Theriosuchus and its rela- hand, small hypsilophodontids were represented pre- tives are not known to have reached large size Joffe, viously in the Trinity Group by only two teeth from The lack of "adult-size" crocodiles in many Butler Farm Langston, ; Thurmond, As others have cially in more calcareous facies, are small specimens suggested see Joffe, , some small crocodiles Langston, Most of the terrestrial or aquatic animals.


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  • At Proctor Lake the specimens from Proctor Lake areisolated fragmentsof lack of other vertebrate prey items, especially fishes, jaw or postcrania. One associated specimen is known in this upland i. It may also be several partial limb bones. Lime mudstonel wackestone: massive. This is the "Paluxy lent to the fossil-bearing interval at Paluxy Church, 0.

    Here the lowest kilometers to the southwest , and the completesection of the unit exposed is four meters above the level of the Glen Rose Formation. The Glen Fig. Rose Formation is exposed in its entirety in the road At Paluxy Church the Twin Mountains Formation cut and is overlain by the heavily vegetated lower is the lateral landward equivalent of the Lower Paluxy Formation. The Glen Rose contains a diverse Member of the Glen Rose Formation Rodgers, ; bivalve, gastropod, and trace fossil assemblage, but Perkins, that can be seen a t Cedar Brake Camp many open marine forms e.