ZUMPANGO.- A groundbreaking new study based on fossils from the massive Santa Lucía paleontological site is offering fresh insights into how ancient animal communities responded to shifting climates in the Basin of Mexico. Biologist José Omar Moreno Flores recently defended his master's thesis, marking the first in-depth analysis of microvertebrate fossils from the area, a discovery that promises to reshape our understanding of the region's natural history.

Moreno Flores's research, conducted for his Master's in Environmental Sciences at the National Technological Institute of Mexico, Zacapoaxtla campus, focused on the response of microvertebrate communities to climate changes during the Pleistocene epoch. Supervised by Professor Guillermo A. Woolrich Piña and INAH researcher José Alberto Cruz Silva, with external guidance from INAH's Felisa Aguilar Arellano and Joaquín Arroyo Cabrales, the thesis sheds light on a paleontologically underexplored northern section of the Basin of Mexico.

Why Tiny Bones Matter

While massive mammoths often steal the spotlight at fossil sites, this study highlights the critical role of microvertebrates – defined as animals weighing between 2 grams and 5 kilograms as adults, including creatures like squirrels, rabbits, bats, lizards, fish, and birds.

"They are excellent ecological markers," explained Moreno Flores. "Their findings can be directly integrated into conservation programs." These small fossils are highly sensitive indicators of environmental conditions and past climate shifts, providing detailed data that larger fossils often cannot. The study underscores the importance of multidisciplinary research, particularly the careful recovery of microfossils, which are frequently overlooked during larger excavations.

A Treasure Trove at Santa Lucía

The Santa Lucía paleontological site, uncovered during the construction of the Felipe Ángeles International Airport, spans over 3,700 hectares and has yielded over 500 excavation points. Among these, 78 locations revealed a significant number of microvertebrate remains, totaling 5,422 specimens. These include amphibians, reptiles, birds, and mammals, whose presence at various depths allows scientists to trace environmental changes from over 30,000 years ago to the present day.

Moreno Flores's analysis identified 53 distinct groups of organisms, including a rich variety of birds (28 species), mammals (14 species), as well as amphibians and reptiles. Notably, aquatic birds were found to be the most abundant group, indicating periods when Lake Xaltocan, now largely desiccated, supported a thriving wetland ecosystem.

Clues to a Changing Landscape

The study revealed clear shifts in the structure and composition of these ancient communities across different periods, directly linked to climatic factors. For instance, some species, like ground squirrels, are now found in different regions (e.g., Pachuca), while others, such as flamingos, kangaroo rats, and desert tortoises, are no longer present near Santa Lucía. Even the iconic axolotl, once common in the area, has disappeared due to the lake's drying up, painting a vivid picture of ecological transformation.

"In the Basin of Mexico, Santa Lucía boasts the highest diversity of small vertebrates, making it one of Mexico's most diverse microvertebrate sites, second only to Loltún caves in Yucatán and San Josecito in Nuevo León," stated the research. This study marks one of the first in Mexico to use qualitative statistical analysis to precisely pinpoint how environmental conditions changed over time, specifically showing significant shifts in microvertebrate communities during the Pleistocene and Holocene in response to climate.

The findings from Santa Lucía emphasize the dynamic nature of ancient ecosystems and provide crucial context for understanding current environmental challenges and informing future conservation efforts.