December 1, 1978. Harry and Sharla Lord walked into McKittrick Canyon at dusk in a light shower of snowflakes. By the time they reached their home, Pratt Lodge, half-way up the canyon, there was an inch of unmarked new snow in the yard. A little later, Harry went out to check his thermometer and saw a line of big wet pawprints just beyond the porch. A cougar had padded by, headed down the trail, passing within fifteen feet of the house.
--Guadalupe Mountains National Park Wildlife File: Mammals
Along U.S. 180 some ten miles northeast of Guadalupe Mountains National Park, there is a singular sight for this country. A lone Arizona ash stands by the pavement, one of only three or four trees along the highway for forty miles in either direction. It is no more than fifteen feet high, with a seven-inch trunk, but the presence of any tree at all in this bleak terrain stirs a need for outlines softer than the hard vistas of rock and sage stretching across the plains. The tree has also stirred the merchandising imperative of the KOA company, which has erected two garish signs next to it. They promise, twenty miles hence, "Grass for [picture of tent]" and "400 Trees [two pictured]." The vegetation-hungry travelers at whom this message is aimed are within eight miles of dense stands of Douglas fir, aspen, ponderosa pine, and bigtooth maple, but the forest is high above them, unsuspected, beyond the lip of the Guadalupe escarpment. From the highway, a thin frieze of trees is visible along the rimrock, but from these few wind-warped stragglers, it is impossible to imagine that the valleys beyond hide a Rocky Mountain forest, living in the cool moisture of the Pacific clouds rolling past, a mile above the spare Chihuahuan brush.
***
When Continental Airlines pilots knock back the throttles on their 727's for the hundred-mile glide into El Paso International, they are just under fourteen thousand feet, some five miles east of the Guadalupe Mountains. The rumpled brown rug two miles below is a northern loop of the Chihuahuan Desert. As I watch this strip of barren earth slide past my porthole, suddenly there are trees up close, seemingly just under the wings. A dark, wooded island thrusts upward, occupying nearly half of what was airspace an instant before. We are passing over the Guadalupe escarpment, jutting far up out of the desert floor. For less than a minute, the forest and meadow of the high plateau are close below. Then the sharp edge of the western scarp slices across the conifers with two thousand feet of sheer precipice, and the earth again drops away from our aluminum floor. It is a wonderful moment, reminding me of Amazon bush pilots winging over a remote crater of remnant dinosaurs hidden in the depths of the Mato Grosso.
Dramatic as the Guadalupes' topography is from the air, however, from the desert itself--where one would imagine the cliffs to be overwhelming--there is little visual impact. In most places, the palisades are so far away from the highway that they look no larger than the myriad smaller bluffs, a hundred feet high, that fill the foreground between scarp and road. For the most part, the Guadalupe cliffs' dramatic plunge from montane conifer forest to bleached salt flat goes unperceived. Only El Capitan stands out, looking a tenth its true size.
Thousands of cars climb through the pass that notches the mountains' spine just below this mile-high headland, but few passengers realize that they are threading their way across the disjunct, south ernmost tip of the Rocky Mountains. Like the bowsprit of a broadbeamed ship, El Capitan's stark monolith joins the southern ends of the two long Guadalupe escarpments, whose sheer rock faces have sealed off the high country from the surrounding desert since the mountains' birth. On top, the montane plateau is flat only in relation to its sheer sides, for the high country is so wrinkled with dozens of crenellated canyons that, from the air, the peaks look like a wedge of giant green molars. Both east and west scarps angle northward into New Mexico, the western side stretching fifty-six miles to Cleaver County, while the somewhat shorter eastern scarp peters out in the rolling hills below Carlsbad Caverns.
Originally, the Guadalupe Mountains were the hills surrounding the upper Guadalupe River near Kerrville, but an eighteenth-century map copier's error shifted the name four hundred miles northwest to the front range of the Rockies, whose lower end fingers southward from Colorado and New Mexico. Most of the Guadalupe Mountains are in New Mexico, in fact, and Guadalupe Mountains National Park includes only the highest and driest tip of the range, where it crosses the state line into Texas. The New Mexico portion of the Guadalupes, including some of the mountains' best deciduous woodland, is Lincoln National Forest.
Although its vertical palisades suggest violent seismic upheaval, only in the most gradual geological sense was the Guadalupe cordillera ever actually lifted. The peaks look and feel like the Rockies, sharing much of their flora and fauna, but the two ranges are not structurally related, since the Rockies are the buckled-up edges of colliding continental plates, while the Guadalupes are the product of erosion nibbling away at elevated tableland. During the Permian period, most of West Texas was sea floor, while northern South America filled the Caribbean, with Venezuela and Honduras-Guatemala beached along the Gulf Coast. Then, starting 165 million years ago, a slow balancing of the continental masses, sliding inexorably across the lithic putty beneath, made an adjustment to the buildup of dense sediments then flowing into both the Gulf of Mexico and the nearby Rio Grande rift by squeezing the lighter rock of the old West Texas seabed upward to form a high inland plateau. Conifer forests covered the uplands at first, during both late Permian and early Triassic time, but real mountains were created out of the new plateau only when the mud and sand that encased the reef during the latter part of its ocean-floor tenure weathered away. The Guadalupes did not join the surrounding sedimentary matrix in sliding off, down drainage channels into the alluvial soils of Central Texas and northern Mexico, because the peaks are harder.
They are harder because they were made by living creatures. The first were lime-secreting algae, filtering down an eons-long rain of fine calcareous dust. Then, building on the precipitated remains of the algae, tiny shelled brachiopods and coral polyps, steadily cementing together their intricate shell homes, eventually built a narrow reef thirty miles long, whose builders died when the reef was smothered with the detritus of erosion from the ancestral Rocky Mountains. Left untended by the lime-secreting polyps, the lacy avenues of their empty coral apartments gradually dissolved into a diagenetic solution of lime and magnesium carbonates that remained sealed within the surrounding sedimentary fill. Eventually, the solution recrystallized into a hard limestone bar, thousands of feet thick, the remnant of which now looms a mile above the eroded Trans-Pecos plain.
A little of this sedimentary covering remains as a coarse shell sand of mollusk fragments, still visible in thin sections of the limestone, while imprints of the animals themselves--crinoids, fusulinids, clams, and brachiopods--pock a stony matrix known as micrite. Deeper in the reef, where diagenetic solution has not melted away the limestone's original capillary structure, traces of its ancient coral filigree remain. Almost all of the gray crusty limestone which makes up the Guadalupe peaks once had this structure, but the lower layers formed by earlier coral colonies have been so thoroughly dissolved and redeposited by the interstitial drainage of rainwater that the stenciled lines of the polyps' walled homes were obliterated long ago. Pieces of more recent reefs, however, especially those of the caprock, are cut and polished to show the network of interlacing coral pores--each cell now filled with hardened dust--that lie hidden beneath the rocks' ordinary chalky exteriors. In other dry enclaves that escaped the fluid-homogenization process, chunks of the dark limestone are traced with lighter outlines left by the skeletons of calcareous sponges, whose remains also make up much of the periphery of Capitan reef.
A mile beyond its palisades, I stand on the old abyssal plain. Sharks were the only animals that lived in the depths here, for the first leviathans--reptilian marine plesiosaurs--were still seventy million years away in the future, the first whales nearly a hundred million years after that, when these scarps first breathed as a living coral wall. It is not easy to visualize, even after seeing the beautiful model of this community of tubular corals, sponges, and serpentine worms that is sandwiched between exhibits of Model-T era oilfield technology and petrochemical public relations displays at the Petroleum Museum in Midland. Later, from the end of the Leonardian to the Chidruan Epoch, taller reefs flowered here and covered the arid bluffs with the fleshy strainer flanges of the polyps that lived in the sunlit shallows, looking much the same as their descendants in today's tropic seas, for the coral community is the earth's oldest complex ecosystem. Although the rock faces seem lifeless now, dry and crumbly, in places miniature wildflowers-purplish rock-crevice milkworts (Polygala rimulicola) and mat dwarf daisies (Chaetoppa hersheyi) with white-petalled blossoms less than a quarter-inch across-push right out of the limestone.
***
Ninety million years after Capitan reef flourished here, shallow lagoons and marshes again covered West Texas, and in them lived dinosaurs. Some were pterosaurs, or pterodactyls, and one species, Titan opteryx, was the largest animal that ever flew. Although almost certainly warm blooded, and possibly covered with fur, it was a reptile, and it was as large as a jet fighter. Its remains were discovered in the Javelina deposits of Big Bend National Park in 1971 and immediately set off worldwide headlines, both because of the size of the creature-vindicating a dozen Japanese monster movies-and because everyone's fancy was caught by the intriguing theory of its finder, University of Texas graduate student Douglas Lawson (who, with characteristic paleontological flair, named the animal Quetzalcoatlus after the Aztec plumed serpent god, only to have it revised to Titanopteryx some eight years later), that his big flying reptile was a sort of saurian vulture, using its nine-foot neck to probe the innards of dinosaur carcasses. Dr. Warm Langston, leader of the expedition, told me how that theory came about.
"We had found a very large brontosaurus skeleton, which was holding up a small hill. In the course of excavating it, I had crawled inside the rib cage to scoop away more dirt and was still in there looking out through the ribs when Lawson came trotting up. This pterosaur discovery was fresh in his mind, and it just popped into his head that that long neck would be just the thing to reach in and take a bite of me."
Dr. Langston is strongly inclined toward debunking fanciful theories, and he thinks that the giant-scavenger hypothesis is one of them. From a row of cabinets at the University of Texas Balcones Research Center, he withdrew a pair of pterosaur mandibles, three feet long and very slender, with flattened, spoonlike tips. "See if you could eat a dinosaur with those," he challenged. There were plenty of fossilized carcasses at hand, but I decided not to try to dismember any of them with the spindly chopsticks. Langston believes the 65-million-year-old reptile was an aquatic, possibly marine, predator which fed on small, live prey. It may have probed the banks of those shallow West Texas marshes for the big burrowing worms and arthropods that lived there, but its long neck would have seen better service, and brought in larger prey for the creature's high-powered metabolism, if Titanopteryx had glided along just above the waves, periodically stabbing downward, like a black skimmer with an anhinga's extendable neck, to snatch mackerel-sized fish from beneath the surface. The aerial dexterity required for this would have been considerable, though, and the way in which Titanopteryx may have managed it is part of an ongoing controversy over how pterosaurs were able to fly at all.
The first three-foot shoulder bone that Lawson scraped out of the side of a crumbly Big Bend arroyo was so massive that he had no idea it could have belonged to a flying creature until analysis at the Vertebrate Paleontology Laboratory in Austin revealed that the huge bone had once been hollow, with paper-shell walls less than an eighth of an inch thick. "Only four kinds of animals have extremely hollow bones," Langston wrote, "'ostrich' dinosaurs, birds.... pterosaurs, and some fish. Fish this bone was not, nor could it have belonged to an 'ostrich' dinosaur whose bones had somewhat thicker walls." Birds use a different flight mechanism--hence different joint articulation--so Lawson's humerus had to belong to a pterosaur, although it was probably connected to the animal's respiratory system, as are the tubular flight bones of birds.
The world comes at you a lot faster when you fly, and processing so much new visual data quickly enough to make flight corrections in time required a brain more complex than any that had evolved so far, relatively larger than other dinosaurs, and nearly proportionate in size to modern birds. (Despite their big brains and similar hollow-bone respiratory structure, pterosaurs were not ancestral to birds. Birds evolved instead from a much earlier group of chicken-sized Jurassic dinosaurs that ran around on long, slender hind legs like small ostriches. Their forelimbs had extended fingers with flattened scales that they used like fans to scoop insects toward their hooked beaks. Today, hawks use a similar maneuver. They mantle, or cup, their fanned-out wings and tail into a stiff little tent that they droop over their prey. If the mouse wriggles free of the talons, it is fenced in by a picket of feathers in every direction except forward, under the hooked beak. Eventually, those flat finger scales thinned and faceted into primary feathers, which the little dinosaurs could flail rapidly enough to take off on short, Wright Brothers hops. Like tailless kites, they had no directional stability, though, until the scales along the sides of their tails also spread out into the thin, flexible flanges that eventually became feathers. At this point, the creature was Archaeopteryx, the first bird.)
Forty million years later, Titanopteryx also had trouble getting off the ground. It is generally accepted that, as advanced, warm-blooded reptiles, the smaller pterosaurs had high enough metabolisms to fly away from their perches like bats, but Titanopteryx's size and chunky build may have limited it to gravity-assisted take-off plunges from tall bluffs. There were no tall bluffs anywhere near the lowland estuarine setting of the Javelina Formation, however, although the tall redwood trees that grew there may have afforded high enough perches for a glide out over the water. But what if Titanopteryx forgot about its subsequent take-off and happened to land on flat ground? To get its three-hundred-pound bulk into the air required more energy than the big reptile's metabolism should have been capable of expending, and to keep it there took fifty-foot wings that aviation engineers doubt could have withstood the flight stresses. Little of the creature's structural anatomy fits the models of either paleontologists or aircraft designers. But, then, bumblebees are theoretically unable to fly, too.
Somehow, it must have been managed. The puzzle intrigues Wann Langston and has inspired him to become an amateur aviation theorist. Tracks preserved in Arizona sandstones indicate that pterosaurs were able to scramble along on all fours like grounded bats, and on flat terrain Titanopteryx probably used that technique, giving everything it had to attain a lumbering lift-off speed. Langston imagines this as a Brobdingnagian version of the paddling charge of the albatross, which also must run desperately into the wind to get aloft. Once airborne, by flexing its enormously elongated fingers, Titanopteryx could vary the tension of its wing membranes enough to increase lift or lose it, like hauling or luffing a sail into the wind. Before flight stresses built to0 high, it could simply spill some wind from its wings and give up a little altitude. Using this variable-membrane-tension approach to skim low over the water, the big reptile could surf on the billows of wind thrown up by surface rollers, stretching and loosening the leathery sheets between its long fingers to take just the right purchase on every upward surge and maintain an ideal fishing altitude three or four feet above the water.
Titanopteryx
The succession of seas that battered the ocean side of Capitan reef, and later fringed its estuarine marshes, have been gone as long as the dinosaurs, drained away to the east into the Atlantic basin. In their place, after the assault of eighty million winters of ice and rain against its earthen shroud, the reef has appeared again, reaching up to tap the cloud-borne moisture hanging above the desert. It is the Guadalupes' second time around as an oasis, but its evergreen forest--which harbors Texas' only chipmunks (gray-footed), elk, cougars, and even black bears--is slowly dying. It has done this many times since the Miocene, however, as successive ice sheets advanced and retreated, drawing their moisture away to the north and shrinking the suddenly dessicated conifer woodlands into disjunct island stands atop the highest plateaus, separated by expanses of new desert grassland.
Because the current dry spell is of recent origin, at least in biological terms, the prevailing plants and animals here are still primarily moist-environment forms that flourished when the Trans-Pecos was a wetter, cooler place and that lately have been forced to alter their ecological strategies as the land dried out around them.
Among the plants, the most successful adaptors to desert life have been the cacti, although most Chihuahuan vegetation has developed similarly thorny characteristics. "Everything that grows west of the Pecos either sticks, stings, or stinks," the cowhands' saying went; and many do worse than that. Despite Gene Autrey's theme, the lowly jimson weed seldom served as feed for the Longhorns, because it is a highly toxic member of the nightshade family. Datura wrightii, the species found in the Guadalupes, has tubular white flowers that bloom from late spring through the fall, when it produces large, deadly green fruits covered with spikes and called thornapples. All parts of the jimson weed are poisonous, but today its victims are usually backpackers trying to hallucinate on the seeds.
In contrast, and in spite of the hostile, spiny prospect they offer, cacti have directed more evolutionary effort toward dealing with the desert climate than toward resisting foragers: the thorns that cover every inch of most kinds are there only partly to protect the plant from being eaten. Before cacti adapted to desert life, their spines were leaves, lavishly transpiring water into a more humid atmosphere. Since all plants lose most of their water in this way, shaping their leaves into hardened spikes served both to ward off grazing animals and, more importantly, to cut evaporation to a minimum. But closing off their transpiration surfaces also meant giving up the leaves' wide, photosynthetic layers, and the cacti were forced to make their food in the skin of their green stems--which evolved a waxy, watertight armor and enlarged to hold the maximum amount of water (often in expandable accordion folds like those of the Sonoran saguaro, organ, and barrel cacti), as well as to offer more chlorophyll-enriched stalk surface to the sun. Only New World plants made these adaptations, and (except for a single distant cousin, Rhipsalis, found in Madagascar and Ceylon) cacti do not live in the older deserts of Asia, Africa, and Australia.
Far above the plains, now, the conifer forest--a remnant of the dense Pleistocene woodland that once stretched northward to the Arctic treeline--hangs on still, cool and green for the most part but also dry. West Texas is still drying out, and even above seven thousand feet, the clouds carry less moisture every year-too little for the woodland to replenish itself. Already, the aspens are confined to well-shaded valleys deep in the mountains and an arid juniper scrub may soon fill the highland bowl where Douglas fir now stand.
While the old forest flourished here, sometimes spreading out across the savannah below the escarpment, the age of mammals reached its peak. Broad evergreen forests grew everywhere across the great plains in the chill, moist path of the advancing glaciers, spreading hundreds of miles ahead of the ice. The ice never reached Texas, but the conifer woodland it pushed southward brought Arctic animals, including musk oxen, to the Guadalupe high country, where their remains are still occasionally found in Williams Cave, probably carried there by saber-toothed cats (smilodon), along with the remains of the cats themselves, zebras, ground sloths, and the scavenging hyenas and dire wolves (Canis dirus) that ultimately fed on all of them. Although it is surrounded by desert now, just below the western face of El Capitan, during the Pleistocene, the cave opened onto a mesic forest-and-savannah countryside that supported some wonderfully exotic herbivores: the North American rhinocerous, mammoths, and strange chalicotheres with their great defensive hooked claws instead of hooves. Herds of long-horned Bison attenuatus and B. occidentalis, ancestors of the animals that fed the plains Indians, grazed across a veldlike Trans-Pecos, preyed upon by dire wolves and Arctodus, the two-thousand-pound Pleistocene grizzly. Horses also first reached their present form on these western plains before migrating to Europe across an early land bridge linking a warmer Greenland to Scotland, not to be seen again in North America for fifty million years. (They returned with the Spaniards during the sixteenth and seventeeth centuries, but camels--llamas, really, that also evolved here later than the horses and then departed from the opposite corner of North America, over the dry Bering straits to Asia--didn't make their re-entry until two hundred years later, when the U.S. Army Camel Corps was set up at Camp Verde in Kerr County during the 1850's. The camels were farmed out to West Texas as desert freighters and performed well in the Trans-Pecos, ferrying supplies along the big bend of the Rio Grande between the army posts at Castolon and Presidio, where they exhibited only slightly worse temperaments than the most obnoxious mules. In spite of their great endurance and ability to get by on marginal fodder, however, within a few years the railroads rendered their overland, heavy-cargo-hauling capabilities obsolete, and several bunches were released or escaped into the desert, where they were the cause of sensational sightings for years. The Arabian handlers imported with the camels fared somewhat better: they learned Spanish and blended homogeneously into the border community.)
With the nearly simultaneous coming of man and the desert, the herds withered away, and with them went the predators and scavengers. The white-winged eagle-vultures that lived here for thirty million years are extinct, and the last condors are dying in southern California, hemmed in by freeways and housing developments, although once both were plentiful on these cliffs and from their rimrock eyries rode the morning thermals out over the prairie herds, spiraling down to blanket the previous night's kills in croaking flocks. In 1910, at the end of his first day on the African veld, Teddy Roosevelt is supposed to have bellowed, "A Pleistocene day! By God, it's still here." Now, even golden eagles--recent victims of shotgunning from light planes--are rare along the Guadalupe scarps.
