MEXICO CITY.- Archaeologists working along the route of the Mexico City–Querétaro passenger railway have uncovered a possible ancient ossuary containing human remains, ceramics and stone artifacts near the Buenavista terminal, in a discovery that could shed new light on burial practices during one of the most transformative periods in Mexican history.

The discovery, announced by Mexico's National Institute of Anthropology and History (INAH), includes nine sets of human skeletal remains, five mandibles and a variety of other bones, some of which show evidence of intentional cranial modification. Associated objects suggest that the deposit may date to the Late Postclassic period (1200–1519 CE) or the early years of contact between Indigenous communities and Spanish conquerors (1519–1535 CE).

The find is particularly significant because it was made within the boundaries of the ancient Nonoalco neighborhood, historically part of the island settlement of Tlatelolco, one of the most important urban centers in the pre-Hispanic Valley of Mexico.

The human remains were first identified on September 17, 2026, during construction work for the railway near Buenavista station. Archaeological investigations were subsequently conducted under the supervision of INAH, as part of a salvage project coordinated by archaeologist Víctor Francisco Heredia Guillén.

Excavations reached approximately 1.40 meters below the surface, revealing skulls, jaws, pelvic fragments, femurs, ribs and teeth. Further exploration uncovered a deposit in which the bones were no longer arranged in their original anatomical positions, suggesting that they had been collected and reburied after their initial interment.

According to field archaeologist Josué Castillo Sánchez, investigators have so far recorded skeletal remains representing nine individuals. Two exhibit evidence of cranial modification, although the precise nature of these alterations has not yet been established.

Specialists at INAH's Physical Anthropology Laboratory will examine the remains to determine the individuals' ages, sexes and the characteristics of the cranial modifications.

A discovery between two historical worlds

One of the most intriguing aspects of the discovery is the combination of human remains with objects associated with everyday life in the final centuries of pre-Hispanic Mexico.

Archaeologists recovered pottery belonging to the Aztec III period, dated approximately 1350–1520 CE, including plates, cooking vessels and specialized containers used in salt production around ancient Lake Texcoco.

Additional discoveries include seven miniature spindle whorls, two figurines, fragments of grinding stones and small stone blades, many made from green obsidian. Researchers believe some of the obsidian may have originated in the Sierra de las Navajas region of Hidalgo, a source of this material in central Mexico.

These objects provide valuable archaeological context, although researchers have not yet established whether the deposit was created before or after the arrival of the Spanish.

José Manuel Cervantes Pérez, head of the Physical Anthropology Laboratory, explained that the combined evidence may point to the transition between the final pre-Hispanic years and the colonial period.

The location itself strengthens this possibility. Nonoalco was one of 19 pre-Hispanic neighborhoods, or calpulli, on the island of Tlatelolco. The discovery also occurred close to the Church of San Miguel Nonoalco, a 16th-century religious structure that served as a chapel visited by Franciscan friars associated with the Convent of Santiago Tlatelolco.

This proximity raises questions about the relationship between Indigenous burial customs and the funerary practices introduced during the Spanish colonial period.

"The remains provide evidence of funerary practices. We have reports that ossuaries found in Mexico City are associated with the viceregal period or even the period of contact, but what is also striking is the presence of material from the pre-Hispanic era," Cervantes Pérez said.

What the bones may reveal

An ossuary is a place where human bones are collected and deposited, often after bodies have undergone an earlier burial elsewhere. Such deposits can provide information about how societies organized burial spaces, treated ancestral remains and responded to changing religious or social circumstances.

Physical anthropologist Abril Machain Castillo, responsible for the exhumation, explained that the composition of the assemblage is one of the strongest indications that the newly discovered deposit may have served this purpose.

Rather than containing complete skeletons in their original positions, the deposit is dominated by relatively durable skeletal elements, including skulls and long bones. Smaller and more irregular bones are notably absent.

This pattern is consistent with the possibility that remains were moved from earlier graves to make room for subsequent burials.

"Originally, these individuals were buried in a place that was later used to bury others. The people who had been interred first were then removed and placed somewhere else, in this case, the ossuary," Machain Castillo explained.

The discovery may eventually help researchers understand whether these practices reflected long-established Indigenous traditions, changing colonial burial customs or some combination of both. For now, these interpretations remain preliminary.

Archaeology beneath a modern metropolis

Mexico City stands upon layers of settlements extending back centuries before the Spanish conquest, making construction projects an important opportunity for archaeological investigation.

The Buenavista discovery demonstrates how modern infrastructure development can reveal physical evidence of communities whose history remains partially hidden beneath the contemporary urban landscape.

Mexico's Secretary of Culture, Claudia Curiel de Icaza, emphasized that the discovery raises questions extending beyond the identification of human remains.

"A possible ossuary tells us not only about death: it raises questions about how the ancient communities of this territory treated and remembered their dead during a time of profound change," she said.

She added that the objects associated with the deposit could help researchers examine the relationship between different historical periods, emphasizing the importance of careful scientific analysis before reaching conclusions.

Following their documentation at the excavation site, the remains and artifacts were transferred to specialized laboratories in Tula de Allende and Tepeji del Río de Ocampo, in the state of Hidalgo.

There, researchers will undertake cleaning, conservation and detailed examination of the skeletal, ceramic and stone materials.

Although the precise chronology and original function of the deposit remain unresolved, the discovery offers an opportunity to investigate the lives, deaths and cultural transformations of communities that occupied the northern part of the ancient Tlatelolco settlement.

As archaeological studies continue, the bones and objects recovered beneath the railway construction site may help reconstruct a chapter of Mexico City's history that survived underground for nearly five centuries.