Big herbivorous dinosaurs ate crustaceans as a side dish

Some big plant-eating dinosaurs roaming present-day Utah some 75 million years ago were slurping up crustaceans on the side, a behavior that may have been tied to reproductive activities, says a new University of Colorado Boulder study.

CU Boulder Associate Professor Karen Chin excavating dinosaur coprolites at Grand Staircase-Escalante National 
Monument in Utah. The new study shows herbivorous dinosaurs also were eating crustaceans, likely seasonally 
[Credit: University of Colorado]

The evidence for the crustacean-chowing dinosaurs comes from fossilized feces samples known as coprolites, said Associate Professor Karen Chin, curator of paleontology at CU Boulder's Museum of Natural History. Dating to the late Cretaceous Period, the coprolites were discovered in Grand Staircase-Escalante National Monument in southern Utah by a team from the Denver Museum of Nature & Science who invited Chin out to their dig.

From what we know about dinosaurs, this was a totally unexpected behavior," said Chin. "It was such a surprising discovery we wondered what the motivation could have been."

Chin said the Utah coprolites were similar to those she has examined from Montana -- which likely were from duck-billed dinosaurs known as hadrosaurs -- in that both were similar in size and held jumbled fragments of rotting wood. A closer look at some of the Utah coprolites also turned up thick bits and pieces of fossilized shell, an indication crustaceans were living in the decaying, coniferous wood, she said.

Because crustacean shells turned up in at least 10 coprolite samples in three different stratigraphic layers of the national monument over a distance of about 13 miles, Chin thinks their ingestion by the dinosaurs was purposeful and would have provided valuable protein and calcium sources.

Examples of modern crustaceans, which have hard exoskeletons, include lobsters, crab, shrimp and crayfish. Some of the coprolites examined were probably around two gallons in volume, Chin said.

The size of the crustacean shell bits in the coprolites indicate the crustaceans were at least two inches in length and perhaps larger, said Chin. Individual crustaceans comprised from 20 to 60 percent of the width of a common hadrosaur beak, suggesting it was unlikely the crustaceans were unwittingly swallowed, she said.

"While it is difficult to prove intent regarding feeding strategies, I suspect these dinosaurs targeted rotting wood because it was a great source of protein in the form of insects, crustaceans and other invertebrates," said Chin. "If we take into account the size of the crustaceans and that they were probably wriggling when they were scooped up, the dinosaurs would have likely been aware of them and made a choice to ingest them."

Even though the team is unable to determine what kind of crustaceans they were, fossil crab claws have been found in the same area in a slightly older geologic formation. Present-day Utah appears to have been next to or near a sea during the Cretaceous Period, said Chin.

Chin also suspects the consumption of crustaceans may have been a seasonal dietary shift, perhaps tied to breeding and egg-laying activities of dinosaurs. She notes contemporary bird species -- which are technically avian dinosaurs -- often consume more protein and calcium during the breeding season to support successful reproduction.

"If we found one coprolite with a crustacean fossil in it, that would be a really interesting scientific discovery," Chin said. "But it wouldn't necessarily indicate a recurring feeding behavior. We now have multiple coprolites with crustacean fossils, showing that at least some types of herbivorous dinosaurs occasionally engaged in this unanticipated feeding strategy."

The researchers sliced the coprolite material into thin sections that were then analyzed with an electron microprobe to determine their chemical composition -- in this case they found a preponderance of calcium, said Chin.

Hadrosaurs were one of the most common dinosaur type of the Cretaceous, growing up to 30 feet long and weighing up to three tons. Some species had characteristic crests on their heads. They also had specialized teeth for grinding plant material, and are thought by some paleontologists to have roamed in herds and nurtured their young.

A paper on the subject was published in the journal Scientific Reports.

Source: University of Colorado at Boulder [September 21, 2017]

Read More

Ancient amphibian had mouthful of teeth

The idea of being bitten by a nearly toothless modern frog or salamander sounds laughable, but their ancient ancestors had a full array of teeth, large fangs and thousands of tiny hook-like structures called denticles on the roofs of their mouths that would snare prey, according to new research by paleontologists at the University of Toronto.

The Early Permian dissorophid Cacops displays its fearsome dentition as it preys
on the hapless reptile Captorhinus [Credit: Brian Engh]

In research published online in PeerJ, an open access journal, Robert Reisz, distinguished professor of paleontology at University of Toronto Mississauga, explains that the presence of such an extensive field of teeth provides clues to how the intriguing feeding mechanism seen in modern amphibians was also likely used by their ancient ancestors.

The researchers believe that the tooth-bearing plates “were ideally suited for holding on to prey, such as insects or smaller tetrapods, may have facilitated a method of swallowing prey items via retraction of the eyeballs into the mouth, as some amphibians do today."

In many vertebrates, ranging from fish to early synapsids (ancestors of mammals), denticles are commonly found in dense concentrations on the bones of the hard palate (roof of the mouth). However, in one group of tetrapods, temnospondyls (which are thought to be the ancestors of modern amphibians), these denticles were also found on small, bony plates that filled the large soft part of the palate. The entire roof of the mouth was covered with literally thousands of these tiny teeth that they used to grab prey. Since these toothy plates were suspended in soft tissue, they are often lost or scattered during fossilization.

The external morphology of the palatal plates in the sampled specimen (ROM 76838) and Pasawioops. 
(A–C) images of the sampled block of palatal plates (ROM 76838) from various views; (D) an image 
of the dorsal surface of the palatal plates; (E) an enlarged view of the denticulate surface of the plate; 
(F) an individual tooth on the plate, showing fluting; (G) an SEM image of the block from which the plates 
were isolated; (H) enlarged SEM image of the denticulate surface of the plate; (I) an SEM image 
of a single tooth; (J) an image of the palatal view of the holotype of Pasawioops (OMNH 73019); 
(K) An enlarged view of the palatal plates; (L) an enlarged view of the dentition on the palatal 
plates showing the orientation of the dentition [Credit: Bryan M. Gee et al., PeerJ]

Denticles are significantly smaller than the teeth around the margin of the mouth – on the order of dozens to a couple hundred microns in length. They are actually true teeth, rather than just protrusions in the mouths of these tetrapods, says Reisz and his colleagues, Bryan Gee and Yara Haridy, both graduate students in paleontology.

“Denticles have all of the features of the large teeth that are found on the margin of the mouth,” says Reisz. “In examining tetrapod specimens dating back (approximately) 289 million years, we discovered that the denticles display essentially all of the main features that are considered to define teeth, including enamel and dentine, pulp cavity and peridontia.”

In reaching these conclusions, the researchers analyzed specimens unearthed from the fossil-rich Dolese Brothers Limestone Quarry near Richards Spur, Okla. They were extraordinarily well preserved, making them ideal candidates for study.

The researchers extracted and isolated the denticle-bearing plates, created thin section slides and examined them under the microscope – no small feat since denticles on this animal were only about 100 microns long.

Reisz and his graduate students suggest that the next big question relates to evolutionary changes to the overall abundance of teeth: If these ancient amphibians had an astonishing number of teeth, why have most modern amphibians reduced or entirely lost their teeth?

Author: Elaine Smith | Source: University of Toronto [September 14, 2017]

Read More

Earth's oldest trees in climate-induced race up the tree line

Bristlecone pine and limber pine trees in the Great Basin region are like two very gnarled, old men in a slow-motion race up the mountaintop, and climate change is the starting gun, according to a study from the University of California, Davis.

Gnarled, dead bristlecone pine trees, which can live more than 5,000 years, stand where young limber pine grow 
around them. Limber pine is beginning to colonize areas of the Great Basin once dominated by bristlecones 
[Credit: Brian Smithers/UC Davis]

The study, published in the journal Global Change Biology, shows that the tree line has been steadily moving upslope over the past 50 years in the Great Basin. The region extends from California's Sierra Nevada, across Nevada to Utah's Uinta Mountains. Its north and south are framed by the Columbia and Colorado rivers' watersheds.

The study also found that limber pine is successfully "leapfrogging" over bristlecone pine. They are growing in soils once almost completely dominated by bristlecone pine, and they are moving upslope at a faster rate than the bristlecone pine.

Charging upslope

"We are seeing very little regeneration anywhere in bristlecone ranges except in the tree line and, there, limber pine is taking all the good spots," said the study's corresponding author Brian Smithers, a Ph.D. candidate in the Department of Plant Sciences at UC Davis. "It's jarring because limber pine is a species you normally see further downslope, not at tree line. So it's very odd to see it charging upslope and not see bristlecone charging upslope ahead of limber pine, or at least with it."

Dead bristlecone pines stand among limber pine trees on the California side of the White Mountains, 
part of the Great Basin region [Credit: Brian Smithers/UC Davis]

The study concludes that if bristlecone pine trees are unable to advance upslope because they are blocked by limber pine, bristlecones could face a reduction of their range and possibly local extinctions.

Earth’s oldest living trees

Bristlecone pine trees are Earth's oldest individual trees and can live for more than 5,000 years. No spring chicken, limber pine trees can live 2,000 years or more.

Both tree species have seen many climate changes during their time on Earth -- from extremely warm periods to ice ages -- and have slowly advanced across the landscape. Over millennia, bristlecone pine trees have moved from the lowlands of the Great Basin up to the current tree line. But, the study notes, neither bristlecone nor limber pine have ever experienced climate change and temperature increases as rapidly as what has been occurring in recent decades.

Bristlecone pine trees grow on soils and in conditions where few other species can live. But limber pines in the 
Great Basin region, such as California’s White Mountains, are beginning to give them some competition 
[Credit: Brian Smithers/UC Davis]

Legacy effects

Smithers said he doesn't expect bristlecone pine adult trees to be impacted much by current climatic shifts, as those trees are well-established. But how, if and where new bristlecone pine trees will regenerate is less certain, particularly as other species like limber pine take up valuable space for them to germinate.

"The things we're doing today have legacy effects for thousands of years in the Great Basin," Smithers said. "When those trees do start to die, they won't likely be replaced because it's just too hot and dry."

The study suggests that land managers identify the specific bottlenecks for a species to live long enough to reproduce, and focus on that stage. For long-lived trees like bristlecone and limber pines, the bottleneck is at the time of their initial establishment, not hundreds and thousands of years into their adulthoods.

Author: Kat Kerlin | Source: University of California - Davis [September 14, 2017]

Read More

New prehistoric crocodile species identified

Around 95 million years ago, a giant relative of modern crocodiles ruled the coastlines and waterways of what would one day become north central Texas.

Dr. Thomas Adams with the skull of Deltasuchus motherali 
[Credit: Arlington Archosaur Site]

A team including UT’s Stephanie Drumheller-Horton has identified this species, Deltasuchus motherali. They found that adults grew up to 20 feet long and, based on the bite marks discovered on the fossilized bones of prey animals, ate whatever they wanted in their environment, from turtles to dinosaurs.

The team found the bones in a place one normally doesn’t think to look for ancient fossils—in the heart of the Dallas-Fort Worth Metroplex.

The findings were recently published in the Journal of Vertebrate Paleontology.

Drumheller-Horton collaborated with Thomas Adams, curator of paleontology and geology at the Witte Museum in San Antonio, Texas, and Chris Noto of the University of Wisconsin–Parkside.

Deltasuchus motherali: A Large Neosuchian Crocodyliform from the Upper Cretaceous (Cenomanian) 
Woodbine Formation of North Texas [Credit: Arlington Archosaur Site]

The site that produced the new species was discovered in Arlington, Texas, in 2003 by amateur fossil hunters Art Sahlstein, Bill Walker, and Phil Kirchoff.

Dubbed the Arlington Archosaur Site, the area is undergoing rapid residential development, and paleontologists have been working with local volunteers and fossil enthusiasts to excavate the site over the past decade.

“We simply don’t have that many North American fossils from the middle of the Cretaceous, the last period of the age of dinosaurs, and the eastern half of the continent is particularly poorly understood,” Drumheller-Horton said. “Fossils from the Arlington Archosaur Site are helping fill in this gap, and Deltasuchus is only the first of several new species to be reported from the locality.”

Deltasuchus motherali is named for one of the site volunteers, Austin Motheral, who first uncovered the fossils of this particular crocodile with a small tractor when he was just 15 years old.

Volunteers working to uncover fossils, including those of Deltasuchus, in 2009 
[Credit: Arlington Archosaur Site]

Work on the site is supported by a grant from the National Geographic Society, which is funding continued excavations and study of this unique fossil area. Fossils from the site, including the Deltasuchus motherali bones, are part of the collections of the Perot Museum of Nature and Science in Dallas.

Deltasuchus is the first of what may prove to be several new species described from this fossil site. The area preserves a complete ancient ecosystem ranging from 95 million to 100 million years old, and its fossils are important in advancing the understanding of ancient North American land and freshwater ecosystems.

While most of Texas was covered by a shallow sea at the time, the Dallas-Fort Worth area was part of a large peninsula that jutted out from the northeast. The peninsula was a lush environment of river deltas and swamps that teemed with wildlife, including dinosaurs, crocodiles, turtles, mammals, amphibians, fish, invertebrates, and plants.

Source: University of Tennessee at Knoxville [September 13, 2017]

Read More

'Teotihuacan: City of Water, City of Fire' at the de Young Museum in San Francisco

The Fine Arts Museums of San Francisco (FAMSF) are pleased to premiere Teotihuacan: City of Water, City of Fire, the first major U.S. exhibition on Teotihuacan in over twenty years. The ancient metropolis of Teotihuacan is one of the largest and most important archaeological sites in the world, and the most-visited archaeological site in Mexico.

Circular relief, 300–450. Stone, 125 x 103 x 25 cm [Credit: Archivo Digital de las Colecciones del 
Museo Nacional de Antropología/INAH-CANON/ Fine Arts Museums of San Francisco]

At its peak in 400 CE, Teotihuacan was the cultural, political, economic, and religious center of Mesoamerica and inhabited by a multiethnic population of more than 100,000 people. This historic exhibition will feature more than 200 artifacts and artworks from the site and is a rare opportunity to view objects drawn from major collections in Mexico, some recently excavated – many on view in the U.S. for the first time – together in one spectacular exhibition.

Mexico, Anahuac, Teotihuacan, Moon Pyramid [Credit: Eye Ubiquitous/UIG via Getty Images/
 Fine Arts Museums of San Francisco]

“We are proud to have been working in collaboration with our cultural partners in Mexico for over 30 years,” says Max Hollein, Director and CEO of FAMSF. “In this groundbreaking exhibition, an abundance of recent archaeological discoveries will offer visitors to the de Young insight into the life of the ancient city and give greater context and significance to the Teotihuacan murals in our own collection.”

Feathered Serpents and Flowering Trees mural (Feathered Serpent 1), 500–550. Earthen aggregate, stucco,
and mineral pigments, 56.5 x 407 cm. Fine Arts Museums of San Francisco, Bequest of Harald J. Wagner, 
1985.104a [Credit: Fine Arts Museums of San Francisco]

Located approximately 30 miles outside of modern-day Mexico City, Teotihuacan was founded in the first century BCE near a set of natural springs in an otherwise arid corner of the Valley of Mexico. At its height  a few centuries later, the city covered nearly eight square miles and featured enormous pyramids, long avenues, and residential compounds. Highlights of the exhibition will include artifacts recently excavated from the site of the Feathered Serpent Pyramid, as well as objects from both recent and historic excavations of the Moon Pyramid, and the Sun Pyramid—the three largest pyramids at Teotihuacan.

Mask, 300–600. Green serpentine, 21.6 x 20.5 x 10.5 cm. Dumbarton Oaks Research Library and 
Collections, Robert Woods Bliss Collection [Credit: © Dumbarton Oaks, Pre-Columbian 
Collection, Washington, DC/Fine Arts Museums of San Francisco]

The exhibition, which will travel to the Los Angeles County Museum of Art (LACMA), will also reunite exquisite mural fragments in FAMSF’s collection with others originating from the same residential compound at Teotihuacan. In 1986, FAMSF repatriated a number of murals as part of an unprecedented joint agreement with Mexico’s National Institute of Anthropology and History (INAH). Together they established a program of collaborative conservation and exhibition. Alongside these murals will be monumental and ritual objects from the three pyramids, as well as ceramics and stone sculptures from the city’s apartment compounds, which were inhabited by diverse peoples from many parts of Mexico.

Tripod vessel with blowgunner, 450–550. Ceramic with post-fire stucco and pigment,13.7 x 14.6 cm. Los Angeles 
County Museum of Art, Gift of Constance McCormick Fearing,[Credit: © Museum Associates/LACMA/ 
Fine Arts Museums of San Francisco]

“The past ten years have seen major revelations in Teotihuacan archaeology. With these discoveries comes a new sense of Teotihuacan that will have an impact for generations to come,” says Diego Prieto Hernández, INAH General Director. “We are grateful for the enthusiastic and abiding partnerships we have developed with the Fine Arts Museums of San Francisco and the Los Angeles County Museum of Art. Such exchanges are crucial to create a shared understanding and vision across countries and cultures, a common basis for our human experience."

Mural fragment (feathered feline), 500–550. Earthen aggregate, stucco, and mineral pigments, 
67.5 x 102 cm. Fine Arts Museums of San Francisco, Bequest of Harald J. Wagner, 1985.104.5 
[Credit: Fine Arts Museums of San Francisco]

The national and international teams working at the main pyramids have made significant discoveries since the last major Teotihuacan exhibition in 1993, when the de Young hosted Teotihuacan: Art from the City of the Gods. By bringing objects from various excavations together and encouraging visitors to understand the context of specific sites within the city, the new exhibition will provide a rare opportunity for Bay Area audiences and visitors to experience a significant place in Mexico's historical and cultural landscape.

Mural fragment (bird with shield and spear), 500–550. Earthen aggregate, lime plaster, and mineral pigments, 
29.5 x 31.5 cm. Fine Arts Museums of San Francisco, Bequest of Harald J. Wagner, 1985.104.9 
[Credit: Fine Arts Museums of San Francisco]

“This exhibition will give visitors the chance to be immersed in the history of Teotihuacan and its urbanism through encounters with 200 objects,” says exhibition curator Matthew H. Robb. “It is an opportunity to anchor these objects on the map of the site to understand how art held communities together in a large, complex, cosmopolitan city— offering valuable lessons for contemporary audiences.”

Standing figure, 200–250. Greenstone, 36 x 16.5 cm. Zona de Monumentos Arqueológicos 
de Teotihuacán / INAH [Proyecto Tlalocan] [Credit: Jorge Pérez de Lara Elías, 
© INAH/Fine Arts Museums of San Francisco]

In the sixth century, a devastating fire in the city center led to Teotihuacan’s rapid decline, but the city was never completely abandoned or forgotten; the Aztecs revered the city and its monuments, giving many of them the names we still use today. Teotihuacan is now a UNESCO World Heritage Site and attracts upwards of four million visitors annually.

Feathered Serpent head, 200–250. Stone, stucco, and pigments, 70 x 70 x 200 cm. Zona de Monumentos Arqueológicos 
de Teotihuacán / INAH [Museo de la Cultura Teotihuacana] [Credit: Jorge Pérez de Lara Elías, © INAH/ 
Fine Arts Museums of San Francisco]

Teotihuacan: City of Water, City of Fire is curated by Matthew H. Robb, chief curator of the Fowler Museum at UCLA and former curator of the arts of the Americas at FAMSF. The exhibition will be on view at the de Young Museum in San Francisco from September 30, 2017, through February 11, 2018. It will travel to the Los Angeles County Museum of Art (LACMA) from March 25 through July 15, 2018.

This exhibition could not have been possible without a major grant from the National Endowment for the Humanities: Exploring the human endeavor.

In Detail

Teotihuacan: City of Water, City of Fire brings together art and artifacts from recent excavations with objects found as long as a century ago. These finely crafted works demonstrate how the city’s dominant ideology permeated everyday spaces, united a diverse population, and provided a guide for citizens as they navigated Teotihuacan’s streets. The Aztecs revered Teotihuacan and gave the city and its major monuments their names. This exhibition is organized geographically around these places.

Eccentric, 200–250. Obsidian, 6.7 x 38.4 x 1.6 cm. Zona de Monumentos Arqueológicos de Teotihuacán/ 
INAH [Acervo] [Credit: Jorge Pérez de Lara Elías, © INAH/Fine Arts Museums of San Francisco]

The exhibition begins with recent discoveries from a tunnel found underneath the Feathered Serpent Pyramid by Mexican archaeologists in 2003. Over a decade of explorations yielded an astonishing array of objects: enigmatic sculptures that may represent Teotihuacan’s founding ancestors and large quantities of vessels depicting one of Teotihuacan’s most important deities, the Storm God. Shells likely originating from the Gulf of Mexico were also found, some incised with designs from other parts of Mesoamerica, indicating that even early in its history Teotihuacan was already a major regional hub.

Detail of two standing anthropomorphic sculptures discovered near the terminus of the tunnel beneath the Ciudadela 
and the Feathered Serpent Pyramid [Credit: Sergio Gómez Chávez/Fine Arts Museums of San Francisco]

Teotihuacan was a highly organized city, built in a grid like plan over roughly eight square miles, situated along the north-south axis formed by the Street of the Dead, and made up largely of architecturally similar single-story residential buildings varying in size and level of luxury. These apartment compounds housed many of Teotihuacan’s residents. The first gallery introduces the art forms for which Teotihuacan is best known and highlights important deities, including the Storm God, with his goggle eyes and distinctive nose plaque; the Old Fire God, an elderly figure who sits cross-legged and bears a brazier atop his head; the Water Goddess, known from large monuments; and the Maize God, who symbolized the life-sustaining power of this crop and may be the subject of Teotihuacan’s famous stone masks.

Mexico. Archaeological Site of Teotihuacan, Sun Pyramid [Credit: Hermes Images/
AGF/UIG via Getty Images/Fine Arts Museums of San Francisco]

The next gallery showcases objects from a range of residential compounds, demonstrating aspects of daily and ceremonial life for Teotihuacan’s citizens. Immigrant groups from across Mesoamerica frequently occupied distinct neighborhoods, or barrios. Here they maintained traditions from their places of origin and simultaneously integrated themselves into the fabric of the city and its dominant ideology. In a compound on the city’s western edge, for example, people from Oaxaca carried out Zapotec lifeways, including the use of Zapotec calendrical signs. An offering on the city’s eastern edge included delicately painted ceramic figurines of women and infants. And on the city’s southern periphery, the working-class residents of Tlajinga specialized in the mass production of utilitarian obsidian blades and played a crucial role in Teotihuacan’s economy.

Mexico, Anahuac, Teotihuacan, Smaller pyramids in the foreground 
of Sun Pyramid [Credit: Eye Ubiquitous/UIG via Getty Images/ 
Fine Arts Museums of San Francisco]

La Ventilla, to the southwest of Teotihuacan’s ceremonial core, is presented as an archetypal Teotihuacan residential area. Artisans from La Ventilla created spectacular artworks to satisfy local and regional markets. These included iconic ceramic tripod vessels and elaborate incense burners—or incensarios. More incensarios have been found at La Ventilla than anywhere else in the city. They were often decorated with mass-produced, mold-made clay decorations that were applied to their surfaces.

View of the facade of the Feathered Serpent Pyramid, assembled as a mosaic of large and small sculptures. The head of the 
Feathered Serpent juts out from the tablero. Its body wraps around the building and carries a headdress thought to 
represent a primordial crocodile, or the so-called War Serpent. The shells surrounding the Feathered Serpent 
emphasize that the building represents a watery location, like a mountain rising from the sea 
[Credit: Jorge Pérez de Lara Elías, © INAH/Fine Arts Museums of San Francisco]

The Feathered Serpent Pyramid and the surrounding Ciudadela are next explored. Though smaller in comparison to the Sun and Moon Pyramids, the Feathered Serpent Pyramid was covered in elaborate, monumental carvings of undulating serpents. At the time of its construction, around 250 CE, a series of large-scale sacrificial offerings were made, including the burial of more than 200 individuals. Many of the victims wore necklaces of shell carved to look like human teeth—a few included actual human jawbones – and were discovered in positions that imply they were tied and bound at the time of death. These sacrifices suggest an era of significant military might at Teotihuacan.

View of an area immediately east of the Feathered Serpent Pyramid, looking south. The fragments seen here tumbled down 
from the eastern facade of the building; some may have been deliberately thrown down in an attempt to desacralize the 
pyramid [Credit: Jorge Pérez de Lara Elías, © INAH/Fine Arts Museums of San Francisco]

The Sun Pyramid is Teotihuacan’s largest structure and one of the largest ever built in the ancient world. It rises about 206 feet high and was built in one single, massive construction effort around 200 CE. Recent excavations have uncovered offerings of greenstone objects and evidence for programs of exterior sculpture depicting motifs related to fire and jaguars. Large pieces have also been discovered at the pyramid’s summit, including a statue of the Old Fire God—a deity with deep roots in central Mexico; early Teotihuacan leaders sought to bind the different ethnic groups inhabiting the city together by creating a single, modified version of the Old Fire God.

View of the Sun Pyramid looking east. At 63 meters tall, the Sun Pyramid was one of the largest and tallest structures
 in the Western Hemisphere until the development of the skyscraper in the nineteenth century 
[Credit: Jorge Pérez de Lara Elías, © INAH/Fine Arts Museums of San Francisco]

After its monumental architecture, Teotihuacan is perhaps best known for its complex fresco murals, which decorated the city’s apartments and administrative centers. Stunning murals from high-status compounds in the Techinantitla section just east of the Moon Pyramid are on view in the next gallery, featuring exceptional mural fragments from FAMSF’s collection reunited with others from the same compound.

Site map of Teotihuacan [Credit: Hilary Olcott/Fine Arts Museums of San Francisco]

The Moon Pyramid, Teotihuacan’s second-largest structure, at a height of approximately 141 feet, is explored next. Excavations there have revealed a seven-phase construction sequence beginning sometime between 50 and 150 CE, with the monument achieving its largest size between 300 and 400 CE. During the fourth phase of construction, the pyramid was greatly enlarged, indicating a period of increasing wealth and political centralization. The completion of the construction was marked by a dedication event that involved the sacrifice of many humans and predatory animals. The sacrificial offering also included objects made of exceptionally precious materials such as greenstone, obsidian, slate, and pyrite. Many of these offerings, which were carefully arranged, seem to have connections to rituals relating to the origin of the cosmos.

The exhibition concludes at the compound of Xalla, located to the east of the Moon Pyramid plaza and just north of the Sun Pyramid. The compound was likely a site for the city’s powerful ruling elite, indicated by its architectural complexity and the large quantity of ornamental sculpture found there. Many objects from Xalla bear evidence of a violently destructive event that marked the beginning of Teotihuacan’s collapse.

At around 550 CE, the ceremonial center of the city was burned; ritual objects, such as the large marble sculpture shown in the final gallery, were intentionally smashed and scattered. After the great fire, the systems of urban and religious maintenance that had been successful for more than 400 years fell apart. Much of the population left the city, and Teotihuacan’s regional dominance ended. But the site itself was never forgotten, and its legacy lives on as a powerful model of ancient Mesoamerican urbanism.

Source: Fine Arts Museums of San Francisco [September 08, 2017]

Read More