I approach the designated place but I am not able to distinguish the fossils from the surrounding stones. My colleagues group the scattered pieces, some half buried or incomplete, and order (now I can see clearly) a vertebral segment.
By accompanying the members of the Paleontology Commission From the SEP in Coahuila, I am overwhelmed by two certainties: the first is that I must be blind because I can't find anything other than worthless boulders between lechuguillas and governors; the second is that, for trained eyes, the territory of Coahuila is exceptionally rich in prehistoric vestiges of the Mesozoic era, the Cretaceous period in particular, which means speaking of 70 million years ago.
At that time, the landscape of arid hills and valleys that surrounds us today in Rincón Colorado, the ejido of General Cepeda, was very different, almost unimaginable. The horizon stretched out over an immense alluvial plain furrowed by the mighty river which, as it delivered its waters to an inland sea, branched out into a labyrinth of canals and coastal lagoons. Giant ferns, magnolias and palms reigned over lush vegetation pampered by a hot and humid climate, with an atmosphere as dense as it was rich in carbon dioxide. Fish species proliferated in the waters, including molluscs and crustaceans, and turtles and crocodiles were present. Insects multiplied everywhere while the first mammals faced a difficult survival problem, posed from the jaws of large reptiles and, mainly, by those who at the time were the kings of creation: the dinosaurs.
Even the children — perhaps they more than anyone — know them. But several clichés persist regarding these "monstrous antediluvian reptiles" quite insane.
WHAT IS A DINOSAUR?
We owe the term to Richard Owen, English zoologist of the last century, who was among the first to study his fossils and decided to baptize them in Greek:deinos means terrible and sauros lizard, although the meaning of reptile is commonly used. The word has taken hold, although it is incorrect. Thus, there were many small dinosaurs, even herbivores, not terrible at all, while other gigantic reptiles that were properly so could not be considered dinosaurs.
Each new piece of information that broadens the knowledge about these makes paleontologists more convinced of the convenience of creating a separate class; the Dinosauria, which would exclude reptiles but include birds, with which they bear a striking resemblance.
Let's look at the case of mammals. They come from a long-extinct group of reptiles called synapsids. As the only living link that unites two such disparate classes, we have been left with the platypus, a strange animal from Oceania with traits of both: it lays eggs, poorly regulates its body temperature and has spurs with poison. But it grows hair and suckles its young. Similarly, dinosaurs are descended from reptiles, but they are not. They share with these certain characteristics such as the inclusion of at least two vertebrae in the sacrum, similarity in the extremities, constitution of the jaw by several bones, gestation of amniotic eggs (with a large amount of yolk to nourish the embryo), body covered with scales and, particularly, the condition of poikilotherms: their inability to regulate body temperature; that is, they are cold-blooded.
However, recent discoveries dispute this traditional approach. We now know that some dinosaurs were covered with feathers, that they were gregarious, more intelligent than was believed and that in front of the saurischians, those with reptilian hips, many appeared with bird hips or ornithischians. And every day more scientists consider it impossible that they could be cold-blooded. This leads us to an interesting theory about its extinction, which occurred after an existence on Earth of 165 million years ago, another 65 (which marks the end of the Mesozoic era and the beginning of the Cenozoic). According to this theory, not all dinosaur species radically disappeared; some survived and turned into birds.
THE RECONSTRUCTION OF SAURIA
Mysteries and controversies aside, these prehistoric animals have enough charisma to capture all the attention and efforts of those who study them. And in Coahuila there are fossilized remains in overwhelming abundance.
Much of the current territory emerged during the Mesozoic era facing the sea of Tethis, when the configuration of the continents did not resemble the current one. Hence the fortunate nickname of "Cretaceous beaches", with which René Hernández, a science teacher at UNAM, popularized them.
The most conspicuous achievement of the works of this paleontologist and his team in the Presa de San Antonio ejido, municipality of Parras, was the assembly of the first Mexican dinosaur: a specimen of the genus Gryposaurus, commonly called "Duck beak" by the bony protrusion of its frontal portion.
The project that pursued this end dates from 1987. The following year and after 40 days of work in the semi-desert of Coahuila, starting from a find by the farmer Ramón López, the results were satisfactory. Three tons with fossilized remains of plants, seeds and fruits were uprooted from the parched land, plus five groups of marine invertebrates. And - they could not be missing - almost 400 dinosaur bones belonging to the group of Hadrosaurs ("duck beaks") and the battleships Ankylosaurs.
In June 1992, a double of our "duckbill" with 3.5 m high and 7 long was exhibited in the Museum of the Geology Institute of the UNAM, located in the Santa María de la Ribera neighborhood, in the Federal District. According to the story, the first group of schoolchildren to visit him gave him Isauria in honor of the cousin of one of them, named Isaura, who, they said, looked like a drop of water to another.
"Isauria is the cheapest dinosaur in the world," says René Hernández, director of the assembly. His rescue cost 15 thousand pesos; and the reply, which with the same characteristics would have cost the equivalent of 100 million pesos in the United States, came out here at 40 thousand pesos. " Obviously, the work of technicians from Launamy, students who collaborated with Hernández, was considerable. Rescued 70% of the skeleton, made up of 218 bones, it was necessary to classify and clean each of the parts. Cleaning involves removing all sediment with strikers and air instruments. This is followed by the hardening of the bones by bathing them in a substance called butvar, diluted in acetone. Incomplete or missing pieces, such as the skull of Isauria, they were rebuilt in plasticine, plaster or polyester with fiberglass. For this, the parts were modeled taking as reference drawings or photographs of examples assembled in other museums. Finally, and since the original is not exposed due to its enormous weight and the risk of accidents, an exact duplication of the entire skeleton was carried out.
A VISIT TO THE CRETACEOUS WORLD
If Isauria, standing upright after a 70 million year dream, may seem like the most outstanding discovery, it is by no means the only one.
In 1926 German scientists found some bones of the first dinosaur on Mexican soil, also in Coahuila territory. It's about a ornysique from the group of ceratops (with horns on the face). In 1980 the Institute of Geology UNAM started a research project to find mammalian remains in the state. There were no positive results, but the large number of dinosaur fossils found by paleontology fans was found. The second UNAM project in 1987 was joined by the support of the National Council of Sciences and Technology and the government of Coahuila through the SEP. The Paleontology Commission created by it and advised by René Hernández formed a team of professionals whose joint work has rescued a remarkable heritage of fossil specimens belonging to the families Hadrosauridae (Gryposaurus, Lambeosaurus), Ceratopidae (Chasmosaurus, Centrosaurus), Tyranosauridae (Albertosaurus) and Dromeosauridae (Dromeosaurus), as well as fish, reptiles, marine invertebrates and plants that offer great information about the Cretaceous environment. So much so that they have the help of the Dinamation International Society, a non-profit organization for the development of paleontology -with a preference for dinosaurs-, very interested in learning about Mexican advances in the field.
Currently the Paleontology Commission It concentrates its tasks in the areas surrounding Rincón Colorado, where they have detected more than 80 sites with fossils, most of them in Cerro de la Virgen, renamed Cerro de los Dinosaurios. Before starting the laboratory and assembly phases there is a lot of work to be done.
As a first step, they carry out a prospecting to determine the deposits. Sometimes they get a notice from ejidatarios or amateur seekers, when not from an institution that conducts a study and accidentally stumbles upon the fossils. But the most common thing is to go to the reading of geological maps and know from the sedimentation what type of remains can be found and how to treat them.
Rescue or quarry work is quite painstaking; the area is cleaned, transplanting flora and moving stones. Before starting the excavation, the place is squared by square meters. Thus, it is possible to photograph and draw the location of each fossil, as burial conditions provide a lot of data. Annotations with its number, geological characteristics of the place and the person who rescued it correspond to every piece collected.
The quarries in Rincón Colorado exemplify the process. Close to the Museum of the place, they also receive the visit of schoolchildren and tourists eager to enter the world of the Cretaceous. And for those who share the hobby, there is good news: at the end of 1999 the Desert Museum was inaugurated in Saltillo with a pavilion dedicated to paleontology. It is very interesting and necessary, since the recently discovered dinosaur footprints are one more sample of the surprises that Coahuila has in store for us.
ARE THERE DINOSAUR FOSSILS IN OTHER STATES?
Although today Coahuila has the greatest potential, and the bones that emerge on the ground are not very fragmented since sedimentation allowed a more solid fossilization, there are interesting remains in other parts of Mexico. Within the Cretaceous period, Baja California has the most important deposits in the entire North American Pacific. In El Rosario, parties belonging to the groups of Hadrosaurs, Ceratopids, Ankylosaurs, Tyranosaurs and Dromaeosaurids. In addition to finding skin impressions and egg fragments, remains of a theropod appeared that gave rise to a new genus and species:Labocania anomaly. Similar findings have been made in Sonora, Chihuahua and Nuevo León. Also from the Cretaceous are the dinosaur tracks in Michoacán, Puebla, Oaxaca and Guerrero.
The richest town of the Jurassic period is located in the Huizachal canyon, Tamaulipas. In 1982 Dr. James M. Clark gave the name of Bocatherium mexicanuma a new genus and species of protomammal.
It was not, therefore, a dinosaur, like the flying and burrowing reptiles, sphenodons and mammals discovered.
The remains of dinosaurs themselves, carnosaurs and ornithopods are very fragmented. The same happens with the Chiapas fossils, dated 100 million years ago. Finally, in San Felipe Ameyaltepec, Puebla, large skeletons have been found so far only attributable to some type of sauropod.
