Bird, pterosaur, and dinosaur footprints discovered in Coahuila

This is the most diverse record; they are very similar to those of geese, herons, and magpies today. Find out more about the discovery.

Bird, pterosaur, and dinosaur footprints discovered in Coahuila
Discovery of bird, pterosaur, and dinosaur footprints in Coahuila. Image: courtesy of Dr. Francisco Vega Vega via UNAM

Francisco Vega Vera, the researcher at the Institute of Geology (IGl), participated in the study of bird tracks from the Late Cretaceous, from two localities recently reported for Coahuila, with an approximate age of 66.1 million years, which allows documenting the coexistence between these, pterosaurs and dinosaurs. One of the localities was found by Coahuila naturalist José Flores Ventura.

It is the record with the greatest diversity of bird footprints -of a semi-palmate type- that has been documented and that dates from an age close to the extinction of dinosaurs (66 million years ago), in an environment close to the ancient coast of Coahuila, said Vega Vera. The record of small invertebrates (nematodes and insect larvae, among others) was also found, "an association that suggests that the vertebrates fed on organic matter that accumulated in estuaries or marshes near the coast," said the university researcher.

We are confirming what other researchers in the past had interpreted for this sediment package, that is to say, that it is a transitional environment between freshwater and marine, affirmed Vega Vera. In another of the localities studied, above the level with footprints, a layer of sediments with spherules was found, a product of the impact of the Chicxulub asteroid, in the Yucatan Peninsula, which generated alterations that led to the extinction of dinosaurs and other animals.

The presence of the spherules a few meters above the footprints supports the age we had estimated for this association between birds, pterosaurs, and dinosaurs, of approximately 66.1 million years, that is, 100 thousand years before the great extinction at the end of the Cretaceous. A relevant aspect of this study is the similarity of the fossil footprints with some present-day birds such as the goose, magpie, herons, and egrets.

The birds are descended from dinosaurs that inhabited the Earth during the Mesozoic Era, it is an important area to try to understand why the flying reptiles and dinosaurs disappeared in the Late Cretaceous and the birds continued. This discovery was recently published in the Journal of South American Earth Sciences, whose first author is Dr. Claudia Serrano Brañas, the research associate at the Smithsonian Institution and the Benemérita Escuela Normal de Coahuila.

The pterosaur tracks belong to the Azhdarchidae group, which includes the largest pterosaurs, such as Quetzalcoatlus. "We estimate that the wingspan could have reached four meters. The dinosaur footprints show similarity to those of tyrannosaurs."

The study of these footprints will continue to identify them more precisely. "The localities studied in Coahuila represent an important finding since there are few known sites in the world with footprints of a similar age: three in the United States, one in Argentina and another in South Korea".

Coahuila is considered a classic site for paleontology, since dinosaurs are found there, among many other groups of diverse geological ages. This discovery somehow confirms its transcendence, with a heritage that must be attended, studied, and preserved.