Category: Slideshows

NSF funds research to unravel Arizona’s prehistoric puzzle: The Hohokam ceramic industry

Post author By Margaret Allen
Post date July 19, 2010

Can a manufacturing industry purr along without a class system of managers and workers? That’s part of a longtime mystery that may soon be solved: How did a prehistoric, egalitarian people called the Hohokam produce large quantities of decorated ceramic vessels without a “manager” hierarchy?

Archaeologists from Southern Methodist University in Dallas and the Cultural Resource Management Program of the Gila River Indian Community in Arizona have launched a unique research partnership to solve the puzzling mechanics of the large-scale industry.

The vessels were made in about 1000 A.D. by a culture archaeologists call the Hohokam. The ancient people used the pottery for daily serving, storage, and social and religious gatherings. Today’s Gila River residents, the O’odham, are descendants of the Hohokam.

Reidus hilli, John Graf, SMU, coelacanth, Dipluridae,

The National Science Foundation is funding the research with a $134,636 grant.

Unprecedented partnership
Under the landmark research partnership, the tribe and SMU hope to decipher the mechanics of the Hohokam ceramic technology and manufacturing techniques.

The three-year project examines artifacts and ceramic production materials from 12 sites in the Sonoran Desert just south of what is now Phoenix, according to archaeologists and co-investigators Sunday Eiselt and J. Andrew Darling. Eiselt is director of the SMU-in-Taos Archaeological Field School and an SMU assistant professor in the SMU Department of Anthropology. Darling is director of the O’odham tribe’s Cultural Resource Management Program.

The analysis looks at a slice of time from 1000 A.D. to 1070 A.D. when production of the decorated ceramic pots, known as “red-on-buff,” was at its peak, said Eiselt and Darling.

Ritually regulated or a managerial elite?
The researchers will probe how a prehistoric society that was fairly egalitarian, without cities or strict social classes, was able to mass-produce ceramic pottery, Eiselt said.

The pottery was critical to a complex system of water management devised by the Hohokam. They used hand-dug canals to irrigate thousands of miles of desert, making the land suitable for growing a wide variety of farm crops.

As pottery specialists living along the middle Gila River, the Hohokam produced and perhaps traded thousands of vessels to the entire region in return for agricultural commodities from surrounding groups, according to the researchers.

“With production output at the level suggested by the millions of sherds and vessel fragments recovered from archaeological sites of this period, we would expect to find political hierarchies, craft specialists, guilds and mass-production techniques,” Eiselt said. “In this situation that wasn’t the case. The results have the potential to show that highly productive craft industries can occur in the absence of managerial elites.”

Hierarchical forms of management for mass-production are more familiar in the non-Indian world, Darling said.

“It’s been postulated by archaeologists that stratification and ranking can be superceded by alternative approaches to production in quantity,” Darling said. “That’s particularly true for societies whose traditional beliefs are not ruled by the bottom line or production and demand.”

Which theory is right?
Eiselt and Darling said the current study will test two competing hypotheses by probing the organizational principles and capacity of core Hohokam technological systems:

The first proposes that a number of villages were producing ceramics independently and trading them for agricultural products — such as cotton — to outside consumers.
The second proposes that ceramic manufacturing was highly concentrated in one or a few villages that were supplied with raw materials by other villages. That implies a greater level of inter-village coordination to create greater economies of scale at the expense of emerging settlement hierarchies.

“The competing hypotheses will be tested through geochemical and petrographic examination of raw materials and ceramic artifacts in order to determine how the Hohokam achieved such great economic and production success,” Eiselt said.

Petrographic thin-section analysis and chemical assays will target the components of red-on-buff sherds — including clay, temper and paint — to identify and characterize raw material sources and reconstruct patterns of ceramic manufacture, the researchers said.

The mineralogical and chemical composition of raw material from different geographical sources will be compared to ceramics from sites across the region.

“This will enable us to map the circulation of raw materials, not just finished products, and thereby identify, geochemically, not only resource trade, but the segmentation of tasks among producer communities, in so far as that existed,” Eiselt said.

From there the researchers can test whether ceramic manufacture for exchange was concentrated at independent centers, or whether there was a division of labor in the production and distribution of raw materials that was part of a broader system for enhancing production efficiency. It will also show whether or how the productive system connected with regional exchange or nascent market systems.

Building on existing Gila research
The project is part of the community’s efforts to recover information from archaeological sites impacted by centuries of development, said Darling. Work will take place on the Gila River Indian Community Reservation under the oversight of the Cultural Resource Management Program.

Results will aid the Pima-Maricopa Irrigation Project, an ongoing effort to restore water resources that were historically lost to the O’odham — previously called Pima — through diversion and damming, Darling said.

The research project builds on earlier fieldwork conducted by the Gila River’s tribal archaeology program. The tribe, in turn, hopes to benefit from SMU’s archaeological expertise, Darling said.

“This is building the tribe’s capacity to conduct scientific research on its own,” he said. “Through collaborative research projects with SMU the tribe is able to exercise its sovereignty in the areas of intellectual research and academic development — not just to inform the world, but to restore the past to the community for their benefit and for future generations at Gila River.”

Both entities benefit, Eiselt said.

“The Gila River Indian Community is investigating the past within the confines of its community with its own team of cultural resource specialists and highly trained archaeologists,” Eiselt said. “It is a rare privilege for SMU to collaborate.” — Margaret Allen

Tags B. Sunday Eiselt, Dedman College, SMU Department of Anthropology

Fossils & Ruins Plants & Animals Slideshows

Texas discovery: Rare 95 million-year-old flying reptile Aetodactylus halli is new genus, species of pterosaur

Post author By Margaret Allen
Post date April 26, 2010

A 95 million-year-old fossilized jaw discovered in Texas has been identified as a new genus and species of flying reptile, Aetodactylus halli.

Aetodactylus halli is a pterosaur, a group of flying reptiles commonly referred to as pterodactyls.

The rare pterosaur — literally winged lizard — is one of the youngest members in the world of the pterosaur family Ornithocheiridae, says paleontologist Timothy S. Myers, who identified and named Aetodactylus halli.

The newly identified reptile is only the second ornithocheirid ever documented in North America, Myers says. He is a postdoctoral fellow in the Roy M. Huffington Department of Earth Sciences at Southern Methodist University in Dallas.

Aetodactylus halli would have soared over what is now the Dallas-Fort Worth area during the Cretaceous Period when much of the Lone Star state was under water, covered by a vast ancient sea.

Click here to view larger image of Aetodactylus halli

While rare in North America, toothed pterosaurs belonging to the Ornithocheiridae are a major component of Cretaceous pterosaur faunas elsewhere in the world, Myers says. The Texas specimen — a nearly complete mandible with most of its 54 teeth missing — is definitively younger than most other ornithocheirid specimens from Brazil, England and China, he says. It is five million years younger than the only other known North American ornithocheirid.

Myers describes the new species in the latest issue of the Journal of Vertebrate Paleontology.

Myers named the pterosaur Aetodactylus halli after Lance Hall, a member of the Dallas Paleontological Society who hunts fossils for a hobby. Hall found the specimen in 2006 in North Texas. It was embedded in a soft, powdery shale exposed by excavation of a hillside next to a highway. The site was near the city of Mansfield, southwest of Dallas and west of Joe Pool Lake. Hall donated the specimen to SMU.

Pterosaurs ruled the skies from the late Triassic, more than 200 million years ago, to the end of the Cretaceous, about 65 million years ago, when they went extinct. They represent the earliest vertebrates capable of flying.

Fossil hunter saw long row of teeth sockets
The Aetodactylus halli jaw was discovered in the geologic unit known as the Eagle Ford Group, which comprises sediments deposited in a shallow sea, Myers says. Outcrop of the Eagle Ford Group extends northward from southwestern Texas into southern Oklahoma and southwestern Arkansas.

“I was scanning the exposure and noticed what at first I thought was a piece of oyster shell spanning across a small erosion valley,” Hall recalls of the discovery. “Only about an inch or two was exposed. I almost passed it up thinking it was oyster, but realized it was more tan-colored like bone. I started uncovering it and realized it was the jaw to something — but I had no idea what. It was upside down and when I turned over the snout portion it was nothing but a long row of teeth sockets, which was very exciting.”

SMU vertebrate paleontologist Louis L. Jacobs, a dinosaur expert internationally recognized for his fossil discoveries in Texas and Africa, and SMU paleontologist Michael J. Polcyn, recognized for his expertise on the extinct marine reptiles called mosasaurs, both told Hall it was a pterosaur and an important find.

Unique jaw differs from others
The 38.4-centimeter Aetodactylus jaw originally contained 54 slender, pointed teeth, but only two remain in their sockets, Myers says. The lower teeth were evenly spaced and extended far back along the jaw, covering nearly three quarters of the length of the mandible. The upper and lower teeth interlaced when the jaws were closed.

In Aetodactylus, changes in tooth size along the jaw follow a similar pattern to those of other ornithocheirids. However, Aetodactylus differs from all other ornithocheirids in that its jaws were thin and delicate, with a maximum thickness not much greater than 1 centimeter, Myers says. But the specimen does compare favorably with Boreopterus, a related pterosaur from the Early Cretaceous of China, in terms of the number of teeth present in the lower jaw, he says.

Myers has estimated the wingspan around roughly 3 meters, or about 9 feet, indicating Aetodactylus would have been a “medium-sized” pterosaur, he says. While it’s not known how Aetodactylus died, at the time of death the reptile was flying over the sea and fell into the water, perhaps while fishing, Jacobs says.

Find hints at new diversity of pterosaurs
North American pterosaurs that date from the Cretaceous are all toothless, except for Aetodactylus and Coloborhynchus, Myers says. The thinness of the jaws, upward angle of the back half of the mandible and the lack of a pronounced expansion of the jaw tips indicate that Aetodactylus is different from other ornithocheirids and represents a new genus and species of pterosaur.

“Discovery of another ornithocheirid species in Texas hints at a diversity of pterosaurs in the Cretaceous of North America that wasn’t previously realized,” Myers says. “Aetodactylus also represents one of the final occurrences of ornithocheirids prior to the Late Cretaceous transition to pterosaur faunas that were dominated by the edentulous, or toothless, species.”

Texas now claims the only two of their kind
Hall on April 14 was presented with the Dallas Paleontological Society’s highest honor, the Lloyd Hill award. The award is named for the late Lloyd Hill, an amateur fossil hunter and longtime member of the Dallas Paleontological Society. Hill wrote the well-regarded novel The Village of Bom Jesus.

Much of Texas was once submerged under the Western Interior Seaway. The massive sea split North America from the Gulf of Mexico to the Arctic Ocean.

On shore, the terrain was flat and flowering plants were already dominating flora communities in this part of North America, according to paleobotanist Bonnie Jacobs, associate professor of Earth Sciences at SMU.

“There were still conifers and ferns as well, but mostly of the sort that had tiny needle leaves, like junipers,” says Bonnie Jacobs. “Sycamores and their relatives would have been among the flowering plants.”

The first ornithocheirid remains from North America, discovered in Fort Worth, were described by former SMU student Young-Nam Lee and donated by amateur collector Chris Wadleigh, says SMU’s Louis Jacobs.

“The ancient sea that covered Dallas provided the right conditions to preserve marine reptiles and other denizens of the deep, as well as the delicate bones of flying reptiles that fell from their flight to the water below,” says Louis Jacobs, a professor in SMU’s Huffington Department of Earth Sciences.

“The rocks and fossils here record a time not well represented elsewhere in North America,” says Louis Jacobs. “That’s why two species of ornithocheirids have been found here but nowhere else, and that’s why discoveries of other new fossils are sure to be made by Lance Hall and other fossil lovers.”

Myers’ article in the Journal of Vertebrate Paleontology is titled “A new ornithocheirid pterosaur from the Upper Cretaceous (Cenomanian-Turonian) Eagle Ford Group of Texas.”

The research was funded by SMU’s Roy M. Huffington Department of Earth Sciences and SMU’s Institute for the Study of Earth and Man.

Tags Bonnie F. Jacobs, Dedman College, Institute for the Study of Earth and Man, Louis L. Jacobs, Michael J. Polcyn, Timothy S. Myers

Earth & Climate Researcher news Slideshows Technology

USGS-SMU volcano monitoring targets hazard threat to Marianas, U.S. military, commercial jets

Post author By Margaret Allen
Post date February 24, 2010

Technology designed to detect nuclear explosions and enforce the world’s nuclear test-ban treaty now will be pioneered to monitor active volcanoes in the Northern Mariana Islands near Guam. The island of Guam soon will be the primary base for forward deployment of U.S. military forces in the Western Pacific.

The two-year, $250,000 project of the U.S. Geological Survey and Southern Methodist University will use infrasound — in addition to more conventional seismic monitoring — to “listen” for signs a volcano is about to blow. The plan is to beef up monitoring of lava and ash hazards in the Northern Mariana Islands, a U.S. commonwealth.

The archipelago’s active volcanoes threaten not only residents of the island chain and the U.S. military, but also passenger airlines and cargo ships.

The USGS project calls for installing infrasound devices alongside more traditional volcano monitoring equipment — seismometers and global positioning systems.

SMU Researcher to study human-fire-climate interactions

Scientists at SMU, which the USGS named the prime cooperator on the project, will install the equipment and then monitor the output via remote sensing. The project is a scientific partnership of the USGS, SMU and the Marianas government.

An infrasound experiment
Infrasound hasn’t been widely used to monitor volcanoes, according to noted volcano expert and SMU geology professor James E. Quick, who is project chief. Infrasound can’t replace seismometers but may help scientists interpret volcanic signals, Quick said.

“This is an experiment to see how much information we can coax out of the infrasound signal,” he said. “My hope is that we’ll see some distinctive signals in the infrasound that will allow us to discriminate the different kinds of eruptive styles — from effusive events that produce lava flows, or small explosive events we call vulcanian eruptions, to the large ‘Plinian’ events of particular concern to aviation. They are certain to have some characteristic sonic signature.”

SMU geologists in recent decades pioneered the use of infrasound to monitor nuclear test-ban compliance, and they continue to advance the technology. For the USGS project, they’ll install equipment on three of the Marianas’ 15 islands. In the event magma begins forcing its way upward, breaking rocks underground and ultimately erupting, seismometers will measure ground vibrations throughout the process, GPS will capture any subtle changes or deformities in the surface of the Earth, and infrasound devices will record sound waves at frequencies too low to be heard by humans. Infrasound waves move slower than the speed of light but can travel for hundreds of miles and easily penetrate the earth as well as other material objects.

Volcanoes active on nine islands
Nine Mariana islands have active volcanoes. On average, the archipelago experiences about one eruption every five years, said Quick, who was previously program coordinator of the USGS Volcano Hazards Program.

Most recently a volcano erupted in 2005 on the island of Anatahan, the largest historical eruption of that volcano, according to the USGS. It expelled some 50 million cubic meters of ash, the USGS reported, noting at the time that the volcanic plume was “widespread over the western Philippine Sea, more than 1300 nautical miles west of Anatahan.” A volcano that erupted on the island of Pagan in 1981 has been showing many signs of unrest, Quick said.

Besides the USGS volcano project, SMU has been active in the Marianas through a memorandum of agreement to help the local government search for alternative energy sources, in particular geothermal.

The Marianas volcano project is part of a larger USGS program that is investing $15.2 million of American Recovery and Reinvestment Act funds to boost existing monitoring of high-risk volcanic areas in partnership with universities and state agencies nationwide.

US military deploying to nearby Guam
In targeting the Marianas, the USGS cited the evacuation of residents from the northern islands after the 1981 eruption on Pagan, as well as the threat to the main island of Saipan and to nearby Guam. A U.S. territory, Guam is expected to be home to about 40,000 U.S. military and support personnel by 2014, including 20,000 Marines and dependents redeployed from Okinawa. The Marines will use the island as a rapid-response platform for both military and humanitarian operations. The military also has proposed using the Northern Marianas for military exercises.

The USGS cited also the threat of volcanic ash plumes to commercial and military planes. Air routes connect Saipan and Guam to Asia and the rest of the Pacific Rim, as well as Northeast Asia to Australia, Indonesia, the Philippines and New Zealand.

Worldwide from 1970 to 2000 more than 90 commercial jets have flown into clouds of volcanic ash, causing damage to those aircraft, most notably engine failure, according to airplane maker Boeing.

Volcanic ash hazard to aircraft
Volcanic ash plumes can rise to cruise altitudes in a matter of minutes after an eruption, Quick said. Winds carry plumes thousands of miles from the volcanoes, he explained, and then the plumes are difficult or impossible to distinguish from normal atmospheric clouds.

Monitoring by remote sensing allows USGS scientists to alert the International Civil Aviation Organization’s nine Volcanic Ash Advisory Centers as part of ICAO’s International Airways Volcano Watch program. The centers then can issue early warnings of volcanic ash clouds to pilots.

“Monitoring on the ground gives early warning when an eruption begins, as well as an indication that an eruption might be imminent,” Quick said. “The contribution by the USGS and its university partners for volcano monitoring is to provide that earliest warning — or even a pre-eruption indication — that a volcano is approaching eruption so that the volcanic ash advisory centers can get the word out and alerts can be issued.”

The USGS objective is for infrasound on Saipan, four seismometers on Anatahan, which currently has only one functioning seismometer, two seismometers on Sarigan, and GPS on Anatahan, Sarigan and Saipan.

Safer for residents
Improved monitoring, Quick said, even might allow evacuated islanders to return to their homes — especially understandable for the island of Pagan, given its freshwater lakes, lush forests, black and white sand beaches and abundant fishing.

“A lot of people would like to move back, but it’s considered unsafe absent monitoring,” he said. “If we can establish monitoring networks on these islands, then I think it becomes more practical for people to think about returning. Properly monitored, one should be able to give adequate warning so that people could evacuate.”

Quick is a professor in the SMU Roy M. Huffington Department of Earth Sciences as well as associate vice president for research and dean of graduate studies at SMU. — Margaret Allen

SMU is a nationally ranked private university in Dallas founded 100 years ago. Today, SMU enrolls nearly 11,000 students who benefit from the academic opportunities and international reach of seven degree-granting schools. For more information see www.smuresearch.com. Follow SMU Research on Twitter, @smuresearch.

SMU has an uplink facility located on campus for live TV, radio, or online interviews. To speak with an SMU expert or book an SMU guest in the studio, call SMU News & Communications at 214-768-7650.

Tags Dedman College, Huffington Department of Earth Sciences, James E. Quick

Fossils & Ruins Plants & Animals Researcher news Slideshows

World’s first full skeletal mount of Paluxysaurus jonesi dinosaur reveals new biology

Post author By Margaret Allen
Post date December 10, 2009

The Early Cretaceous sauropod Paluxysaurus jonesi weighed 20 tons, was 60 feet long and had a neck 26 feet long, according to the scientists who have prepared the world’s first full skeletal mount of the dinosaur.

The massive Paluxysaurus jonesi, prepared for the Fort Worth Museum of Science and History in Fort Worth, was unveiled Nov. 20 when the museum opened in a new $80 million facility. The Paluxysaurus mount enables Texans to see their state dinosaur in three dimensions for the first time.

The reconstructed skeleton is yielding clues to the biology of the animal and its relationship to other similar dinosaurs, says Dale Winkler, lead consultant for anatomy and posture on the skeletal mount.

Winkler is director of the Shuler Museum of Paleontology at SMU and a research professor in the Roy M. Huffington Department of Earth Sciences. Winkler has worked with Paluxysaurus bones since crews from SMU and the Fort Worth museum began to unearth them in the early 1990s.

In preparing the mount, Winkler said he was surprised at how extremely long the neck was — at 26 feet — compared to the tail, and he found the head especially striking.

“It was really exciting to see what the head looked like,” Winkler says. “Paluxysaurus had very high cheeks compared to its relatives. Once the bones defining the opening of the nose were connected, it showed that the nostrils were turned up on top of the snout, instead of out like Brachiosaurus.”

Skeletal mount reveals animal’s anatomy, size and stature
A relative of Brachiosaurus and Camarasaurus, Paluxysaurus lived about 110 million to 115 million years ago. The dinosaur was identified and named in 2007 by Peter J. Rose. The Fort Worth skeleton was assembled from a combination of actual fossil bones from at least four different dinosaurs found on private ranch land in North Central Texas and from cast lightweight foam pieces modeled on original bones. The mount enables scientists to better understand the animal’s anatomy, size and stature on questions like “How were the legs situated, and how did the shoulders relate to the hips?”

From the skeletal mount, the scientists learned that Paluxysaurus was more than 6 feet wide and nearly 12 feet tall at the shoulder, although built fairly light, Winkler says. Its teeth are a lot slimmer than those of its closest relatives, indicating Paluxysaurus gathered and processed food differently, using its teeth not for chewing, but to grab food, he says.

Paluxysaurus had a long neck like Brachiosaurus, and a tail almost as long, but wasn’t quite so gigantic. Scientists also learned Paluxysaurus had relatively long front arms, unlike Diplodocus, making its back more level. The dinosaur’s shoulder turned out fairly high, and the hips were wide, Winkler says, and it had reached a more advanced stage of evolution than Late Jurassic sauropods.

Paluxysaurus’ massive pelvis and its sacrum have never before been viewed by the public, he says. Its ilium, the largest bone in the pelvis, is similar to that of titanosaurids of the Late Cretaceous, mainly found in South America. However, one titanosaurid, called Alamosaurus, entered North America and is known from Big Bend National Park in southwest Texas.

The bones assembled for Fort Worth’s Paluxysaurus mount were recovered by students, faculty, staff and hundreds of volunteers over the past 16 years.

DFW’s ancient Cretaceous past included dinosaurs along a shallow sea
Most bones were found in masses of hardened sandstone dug from a Hood County quarry on the private ranch of Bill and Decie Jones.

It took more than a decade to remove the specimens because they were embedded in a hard sandstone matrix, said Louis L. Jacobs, a world-renowned paleontologist, dinosaur fossil hunter and a professor in the Earth Sciences department at SMU. Jacobs helped unearth and prepare the bones.

The end result is a skeleton that is “absolutely awe-inspiring,” Jacobs says. “Paluxysaurus and the plants and animals it lived among show us the truly unique position Texas held in the Cretaceous world. The exhibits at the Fort Worth museum tell that story to the people who now live where the giants used to walk.”

Sauropods weren’t common during the Early Cretaceous. The Fort Worth specimen is morphologically distinct from all other sauropods described and named in North America at that time, according to the research of Rose, who is now a doctoral student at the University of Minnesota. Rose identified the type specimen and named the animal while a graduate student in geology at SMU.

The Paluxysaurus dinosaurs lived near the shore of the rising Cretaceous seas that eventually covered Texas, amid large-trunked conifer trees that are now extinct. The semi-arid environment nurtured relatives of sago palms but few flowering plants, which were just beginning to spread out across the Earth, Winkler says.

The scientists say the Jones Ranch bone bed is one of the richest accumulations of sauropod bones in North America.

A group apparently died together there in a common death, perhaps a forest fire, according to earlier research of Winkler and Rose.

The quarry has produced hundreds of bones, all within an area of 400 square meters. Fossil hunters found 60 to 70 percent of the bones needed to reconstruct a single Paluxysaurus skeleton, says Aaron Pan, curator of the Fort Worth museum. Most of the bones, however, are too fragile or deformed to be mounted 15 feet in the air, Pan says.

“We were happy to have as much of it as we do,” Pan says, noting that the museum welcomes fossil researchers. “Most of our material is available. So if a researcher did want to see any of it, we’d be happy to have them come.”

Huge, multi-year project recreated skeleton with bones and casts
Paleontologists from both the museum and SMU helped exhibit fabricator and model-maker Robert Reid Studios, located near Fort Worth, mount the bones. About 15 percent to 20 percent of the skeleton is actual fossil bone, while the remaining bones are casts, says Pan.

Preparing the fossils for mounting and modeling was a huge, multi-year project. The cast bones were computer modeled using laser scanning, says Michael J. Polcyn, director of the Earth Sciences department’s image analysis lab at SMU.

“I was able to scan available bones in 3D and manipulate them in the computer to remove distortion, create mirrored pieces — for example right or left — and model missing portions,” Polcyn says. “I was then able to use the computer models to produce life-sized physical models of the bones using computer-controlled machining techniques.”

Many of the very large bones remain all or partially embedded in blocks of quarry rock, due primarily to the logistical challenge of removing them. For example, the 11-ton block containing the pelvis and sacrum required hoisting with an industrial crane. For some large blocks, tons of rock were painstakingly cut with diamond-blade saws from around the various bones to make them manageable in the SMU labs, Winkler says.

Rock was partially removed from the pelvis and sacrum so that Polcyn could scan them. The scientists then constructed a model using dense foam that was cut to form the basic shape. Crews from Robert Reid Studios coated them with epoxy resin to give them hardness, then added a layer of bone texture and painted them to match.

In the case of the long neck, much was preserved, but many of the bones were distorted by sediment load, which essentially crushed the bone, Polcyn says. He studied the neck vertebrae and made a model. Only two of the skull bones were recovered: the left maxilla and a nasal bone, which defined the top front of the face. Polcyn worked closely with a sculptor to reconstruct the skull by studying related groups of dinosaurs.

Preparation of the skeletal mount was funded by the Fort Worth Museum of Science and History. — Margaret Allen

Follow SMUResearch.com on Twitter.

For more information, www.smuresearch.com.

SMU is a nationally ranked private university in Dallas founded 100 years ago. Today, SMU enrolls nearly 11,000 students who benefit from the academic opportunities and international reach of seven degree-granting schools. For more information see www.smu.edu.

Tags Aaron Pan, Dale Winkler, Dedman College, Huffington Department of Earth Sciences, Louis L. Jacobs, Michael J. Polcyn, Paluxysaurus jonesi, Peter J. Rose

Earth & Climate Fossils & Ruins Researcher news Slideshows

Tropical Central Africa — now The Congo Basin — was arid, treeless during Late Jurassic

Post author By Margaret Allen
Post date November 10, 2009

The Congo Basin — with its massive, lush tropical rain forest — was far different 150 million to 200 million years ago.

At that time Africa and South America were part of the single continent Gondwana. The Congo Basin was arid, with a small amount of seasonal rainfall, and few bushes or trees populated the landscape, according to a new geochemical analysis of rare ancient soils.

The geochemical analysis provides new data for the Jurassic period, when very little is known about Central Africa’s paleoclimate, says Timothy S. Myers, a paleontology doctoral student in the Roy M. Huffington Department of Earth Sciences at SMU.

“There aren’t a whole lot of terrestrial deposits from that time period preserved in Central Africa,” Myers says. “Scientists have been looking at Africa’s paleoclimate for some time, but data from this time period is unique.”

There are several reasons for the scarcity of deposits: Ongoing armed conflict makes it difficult and challenging to retrieve them; and the thick vegetation, a humid climate and continual erosion prevent the preservation of ancient deposits, which would safeguard clues to Africa’s paleoclimate.

Myers’ research is based on a core sample drilled by a syndicate interested in the oil and mineral deposits in the Congo Basin. Myers accessed the sample — drilled from a depth of more than 2 kilometers — from the Royal Museum for Central Africa in Tervuren, Belgium, where it is housed. With the permission of the museum, he analyzed pieces of the core at the SMU Huffington Department of Earth Science’s Isotope Laboratory.

“I would love to look at an outcrop in the Congo,” Myers says, “but I was happy to be able to do this.”

The Samba borehole, as it’s known, was drilled near the center of the Congo Basin. The Congo Basin today is a closed canopy tropical forest — the world’s second largest after the Amazon. It’s home to elephants, great apes, many species of birds and mammals, as well as the Congo River.

Myers’ results are consistent with data from other low paleolatitude, continental, Upper Jurassic deposits in Africa, and with regional projections of paleoclimate generated by general circulation models, he says.

“It provides a good context for the vertebrate fossils found in Central Africa,” Myers says. “At times, any indications of the paleoclimate are listed as an afterthought, because climate is more abstract. But it’s important because it yields data about the ecological conditions. Climate determines the plant communities, and not just how many, but also the diversity of plants.”

While there was no evidence of terrestrial vertebrates in the deposits Myers studied, dinosaurs were present in Africa at the same time. Their fossils appear in places that were once closer to the coast and probably wetter and more hospitable, he says.

The Belgium samples yielded good evidence of the paleoclimate. Myers found minerals indicative of an extremely arid climate typical of a marshy, saline environment. With the Congo Basin at the center of Gondwana, humid marine air from the coasts would have lost much of its moisture content by the time it reached the interior of the massive continent.

“There probably wouldn’t have been a whole lot of trees; more scrubby kinds of plants,” Myers says.

The clay minerals that form in soils have an isotopic composition related to that of the local rainfall and shallow groundwater. The difference in isotopic composition between these waters and the clay minerals is a function of surface temperature, he says. By measuring the oxygen and hydrogen isotopic values of the clays in the soils, researchers can estimate the temperature at which the clays formed.

Myers presented his research, “Late Jurassic Paleoclimate of Central Africa,” at a scientific session of the 2009 annual meeting of The Geological Society of America in Portland, Ore., Oct. 18-21. The research was funded by the Roy M. Huffington Department of Earth Sciences at SMU and SMU’s Institute for the Study of Earth and Man. — Margaret Allen

Tags Dedman College, Huffington Department of Earth Sciences, Timothy S. Myers

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