The Natural World
Dinosaurs in the Desert
Looking for the real Jurassic Park? Start in New Mexico.
Between 225 and 65 million years ago, the Land of Enchantment was the land of the dinosaurs. New Mexico is unique in that it preserves both body fossils and trace elements of Triassic, Jurassic and Cretaceous creatures. Body fossils are actual pieces of an animal, such as fossil bones and teeth. Trace elements are "fossilized behavior" and can include footprints, skin impressions and egg shells. Dinosaur fossils have been found across all of New Mexico except for the extreme southeastern corner of the state.
Why are dinosaurs called "dinosaurs"? Paleontologist Richard Owen coined the word "dinosaur" (meaning "fearful great lizard") in 1842. Over time, the term was simplified to "terrible lizard"; however, not all dinosaurs were terrible. Nor were they all lizards.
Long before Steven Spielberg depicted dinosaurs as "objects de tourism" in the Jurassic Park movies, prehistoric creatures already were in service as marketing tools for tourists. Musician Ray Price, comedian Jerry Seinfeld and many writers and photographers from a variety of publications have pulled off interstate highways in New Mexico to inspect dinosaur-related exhibits.
Among the questions New Mexicans and New Mexico visitors may have about the "terrible lizards" is: Why were dinosaurs so big? Most dinosaurs weren't giants, but no one knows for certain why some of the creatures were huge. The smallest dinosaur is named Compsognathus.
How long were dinosaurs around? The creatures evolved 228 million years ago (during the Triassic Period, toward the beginning of the Mesozoic Era) and became extinct some 65 million years ago at the end of the Cretaceous Period. Eoraptor is the earliest-known dinosaur. But because Eoraptor's skeleton shows genetically advanced skeletal features, it's possible that even older dinosaur fossils may be found somewhere.
Did all dinosaurs live together, and at the same time? No and no. Both time and geography separated dinosaur communities. The "Age of Dinosaurs" (the Mesozoic Era) included three consecutive geologic time periods. Distinct dinosaur species lived during each of these periods. For example, the principal Jurassic dinosaur — Stegosaurus — already had been extinct for some 80 million years before the appearance of the well-known Cretaceous dino known as Tyrannosaurus.
At the beginning of dinosaur history (the Triassic Period), there was one hypothesized super-continent on Earth, now known as Pangaea. Many dinosaur types were widespread across it. As Pangaea broke apart with continental drift, however, dinosaurs became scattered across the globe on separate continents. Distinctive dinosaur types evolved in specific geographical areas, including the desert Southwest.
Are all fossil animals dinosaurs? No. Dinos were a distinct group of ancient animals that had particular skeletal features. Their hips, hind legs and ankles were specialized and allowed the legs to move directly under the body, rather than extending out from the side of the body, as with modern lizards. This arrangement enabled dinosaurs to bring their knees and ankles directly below their hips and provided the necessary attachments for super-strong leg muscles.
Dinosaur bone structures were well-designed for supporting a large body, for standing upright and for running. The front legs were expertly adapted for grasping prey. These skeletal features separated dinosaurs from other ancient reptiles, such as the plesiosaurs and pterosaurs. Fossil mammals, such as mammoths and "saber-toothed tigers," are also sometimes incorrectly referred to as dinosaurs.
The fastest dinosaurs probably weren't any quicker than some modern-day land animals, such as giraffes. Dinosaur speeds are deduced from fossilized trackway finds, and from inspecting the dinosaurs' shape and structure. The speediest dinosaurs more than likely were bird-like bipedal carnivores called theropods, which had long, slim hind limbs and light bodies.
Where are most dinosaur fossils found? Fossils have been found all over the world and on every continent (except for Antarctica). Large concentrations have been found where it is easiest to recover fossils; that is, where Mesozoic Era sediment is exposed, such as badlands. In North America, dinosaur fossils have been found at many places, including New Mexico.
Dinosaurs lived in a violent world where volcanic eruptions continuously shook the land, darkening the sky with ash and sending steaming mudflows surging through canyons. It was among majestic volcanoes, in a world that harbored a fascinating array of plants and animals, that dinosaurs flourished.
Late Cretaceous dinosaurs from the New Mexico area were some of the last to live on Earth. They are well-known because of the information they provide scientists about the cause(s) of dinosaur extinction.
New Mexico's record of Triassic dinosaurs includes skeletons of Coelophysis, teeth of Revueltosaurus, bones of Eucoelophysis, fragmentary skeletons of other dinosaurs and tracks of many other prehistoric creatures. The New Mexico fossil record is particularly significant because some of these dinosaurs are among the oldest ever recorded. Additionally, Coelophysis, the official state fossil, is one of the best-preserved dinosaurs with regard to both completeness and abundance.
New Mexico's best-known dinosaur fossils come from rocks found in the San Juan Basin of the northwestern part of the state. Late Cretaceous fossils are particularly abundant in the Bisti-De-na-zin Federal Wilderness Area south of Farmington. Late Cretaceous dinosaurs from the San Juan Basin lived in river floodplains and jungles located near an ancient seacoast.
What color were dinosaurs? Direct fossil evidence for dinosaur skin color is not available. Some dinosaurs likely had protective coloration, such as pale undersides to reduce shadows, as well as irregular color patterns to make the creatures less visible in vegetation. Some dinosaurs probably were as brightly colored as modern-day lizards, snakes and birds.
Trackways Through Time
Evidence of creatures predating even the dinosaurs can be found at the Prehistoric Trackways National Monument, northwest of Las Cruces. The monument was established in 2009 to conserve, protect and enhance the unique and nationally important paleontological, scientific, educational, scenic and recreational resources and values of the Robledo Mountains in southern New Mexico. The monument includes a major deposit of Paleozoic Era fossilized footprint megatrackways within approximately 5,280 acres.
The trackways contain footprints of numerous amphibians, reptiles and insects (including previously unknown species), plants and petrified wood dating back 280 million years, which collectively provide new opportunities to understand animal behaviors and environments from a time predating dinosaurs. The site contains the most scientifically significant Early Permian track sites in the world.
There are opportunities for hiking, horseback riding and off-highway vehicle driving in portions of the monument. Viewing trackways is limited, however; as they are discovered, and to preserve them for ongoing and future scientific study, the trackways are removed and transported to the New Mexico Museum of Natural History and Science in Albuquerque. The new Museum of Nature and Science in downtown Las Cruces also has a major new exhibit on the monument (see "Museums on the Move," December 2012).
The BLM is developing plans to facilitate public access to the National Monument. There are currently no facilities or signs for or at the Monument; for updates, see www.blm.gov/nm/st/en/prog/recreation/las_cruces/trackways.html.
Directions: Coming from Las Cruces, traveling on Picacho Ave./Hwy. 70, at the stop light with Shalem Colony Trail, go north on Shalem Colony Trail for approximately 5.5 miles. Prior to reaching the Rio Grande, you will reach a county road, Rocky Acres Trail. Turn west. Go west approximately one-quarter mile to a dirt road entrance on the left-hand side. Cross over a cattleguard and continue to the west. This road, past about a mile, is for high-clearance, 4wd vehicles only.
What did dinosaurs eat? Some ate lizards, turtles, eggs or early mammals. Some hunted other dinosaurs or scavenged on dead animals. Most, however, ate plants (but not grass, which hadn't evolved yet). Rocks that contain dinosaur bones also contain fossil pollen and spores, which indicate many different types of plants existed during the Mesozoic Era.
Many of these plants had edible leaves, including evergreen conifers and, in the latter part of the dinosaur age, fruit. Although the exact time of origin for flowering plants is uncertain, the last of the dinosaurs almost certainly had fruit available to eat. Dinosaurs were typically plant-eaters for the same reasons that modern herbivores eat plants — namely, because plants were what they could obtain and digest.
Dinosaur discoveries are still being made. On March 17, 2004, clear imprints of the heel, pelvis, tail and shuffling feet of a dinosaur were unearthed at the St. George, Utah Dinosaur Discovery Site at Johnson Farm, providing paleontologists with the first evidence of a "squatting dinosaur." James Kirkland, a Utah State paleontologist, observed that the new discovery suggests the creature rested on its hind end and put its hands down, with claws curled inward, giving scientists new insight into how dinosaurs held their hands. Kirkland speculated, "It may have shuffled forward before walking away, while dragging its tail."
In Early Jurassic times, a shallow lake stretching hundreds of miles existed in what is today southwestern Utah. Dinosaurs congregated on the shores of this lake. The creatures might have crouched there on the shores after eating fish or plants. Since the initial track discovery at the St. George Site in 2000, this locale has grown into North America's largest site for Early Jurassic footprints.
Many of the tracks are well-preserved at the bottom of a three-foot-thick layer of sandstone and belong to the track name Eubrontes, meaning three-toed footprints. They include examples of footpads, claw marks and detailed skin impressions.
Few subjects in the Earth sciences are as fascinating as dinosaurs. The study of dinosaurs in New Mexico stretches our imaginations, provides new perspectives on time and space, and invites people to discover worlds that are quite different from modern Earth.
From a scientific perspective, the study of dinosaurs is important both for understanding the causes of past major extinctions of land animals, as well as for understanding changes in biological diversity caused by previous geological and climatic changes on Earth. These changes are, of course, still occurring. A wealth of new information about dinosaurs has been acquired over the past 30 years, and science's old perceptions concerning dinosaurs as being slow, clumsy, dim-witted beasts have been revised.
For a fascinating adventure into another world, explore the back roads of New Mexico; stop, exit your vehicle, and then sniff, listen, look around, and ask questions. Slowly, carefully, methodically. That is how inquisitive people learn, all the while acknowledging Socrates' famous dictum, "If I am considered an intelligent person, it is only because I admit I know nothing."
Mary Syrett is a freelance writer and photographer,
as well as an amateur paleontologist.