Smithsonian Science » paleontology

Newly discovered prehistoric turtle co-existed with world’s biggest snake

John Barrat — Wed, 07 Apr 2010 13:51:43 +0000

The discovery of a new fossil turtle species in Colombia’s Cerrejón coal mine by researchers from the Smithsonian Tropical Research Institute in Panama and the Florida Museum of Natural History helps to explain the origin of one of the most biodiverse groups of turtles in South America.

Image right: The thick fossil carapace of a newly discovered prehistoric turtle.

Cerrejonemys wayuunaiki takes its genus name from Cerrejón, and emys—Greek for turtle. Its species name is the language spoken by the Wayuu people who live on the Guajira Peninsula in northeastern Colombia near the mine. About as thick as a standard dictionary, this turtle’s shell may have warded off attacks by the Titanoboa, thought to have been the world’s biggest snake, and by crocodile-like creatures living in its neighborhood 60 million years ago.

Image left: Carlos Jarmillo with turtle specimens in the Cerrejón coal mine.

“The fossils from Cerrejón provide a snapshot of the first modern rainforest in South America—after the big Cretaceous extinctions and before the Andes rose, modern river basins formed and the Panama land bridge connected North and South America,” explains Carlos Jarmillo, staff scientist at the Smithsonian who studies the plants from Cerrejón.

“We are still trying to understand why six of this turtle’s modern relatives live in the Amazon, Orinoco and Magdalena river basins of South America and one lives in Madagascar,” explains Edwin Cadena, first author of the study and a doctoral candidate at North Carolina State University. This discovery “closes an important gap in the fossil record and supports the idea that the group originated near the tip of South America before the continent separated from India and Madagascar more than 90 million years ago.”

Image right: An artist’s conception of the giant prehistoric snake Titanoboa. (Illustration by Jason Bourque)

Cadena will characterize two more new turtle species and analyze the histology of fossil turtle bones from the Cerrejón site. “I hope this will give us an even better understanding of turtle diversity in the region and some important clues about the environment where they lived.”

Prehistoric pollination: Sawfly mouthparts fit tubular channels of gymnosperm cones

John Barrat — Fri, 06 Nov 2009 17:40:15 +0000

Scientific evidence shows that almost all of the earliest angiosperms (flowering plants) were pollinated by insects. Whether such a relationship existed between insects and early gymnosperm species (non-flowering plants with exposed seeds, such as conifers) has been widely disputed. Smithsonian scientists and colleagues, however, have recently found evidence that gymnosperm plants shared an intricate pollination relationship with scorpionfly insects 62 million years before flowering plants appear in fossil records. The team’s findings are published in the scientific journal Science, Friday, Nov. 6.

Illustration: Eurasian mid Mesozoic scorpionflies feeding on gymnosperm ovulate organs, each with tubular access to deeper-seated rewards such as nectar or pollination drops. (Illustration by Mary Parrish)

Conrad Labandeira, paleoentomologist at Smithsonian’s National Museum of Natural History, and team members examined both the specialized features of scorpionfly mouthparts and the unique reproductive features of coexisting gymnosperm plants. The proboscis (elongated tubular mouthparts) of these insects, which was up to 1.3 centimeters long, was either hairy or had ridges, and frequently had pads at the tip to suck up fluids, similar to the structure of modern hoverflies, moths and butterflies. The presumed gymnosperm hosts bore deep funnel-like or tubular channels, also up to 1.3 centimeters long, containing nectar-like pollen drops.

The reproductive anatomy of the plants was typically gymnospermous, but show important modifications for insect attraction, similar to modern flowering plants. However the lineages of these plants and their scorpionfly pollinators became extinct during the mid-Cretaceous period (approximately 105 million years ago) just as flowering plants and their newly evolved pollinators, such as moths and butterflies, came on the scene.

Photos: Lichnomesopsyche gloriae (Mecoptera: Mesopsychidae), from the late Middle Jurassic of northeastern China, showing head and long, hairy proboscis. (Photos by Wenying Wu)

“This exciting discovery now answers the conclusions that paleobotanists were making recently regarding ‘strange’ structures occurring in the ovulate organs of some Mesozoic gymnospermous plants,” said Labandeira. “One such fructification of an extinct Early Cretaceous cheirolepidiaceous conifer family, Alvinia bohemica, is the best example of an anatomically complicated, jerry-rigged device to achieve insect pollination. There were contemporaneous, matching, elongate insect mouthparts, and other evidence, that indicate presence of a gymnosperm-based pollination mode from the deep past.”

The evolution of this type of elongated mouthpart among insects occurred at least five separate times during a 13-million-year span during the Middle Jurassic period. The pollinating relationship between modern pollinators and flowering plants was an independent evolutionary occurrence, separate from the scorpionfly and gymnosperm plants.

Smithsonian to host online Climate Change conference Sept. 29-Oct. 1

John Barrat — Wed, 23 Sep 2009 12:17:34 +0000

The Smithsonian Center for Education and Museum Studies is hosting “Climate Change,” a three-day, free, education online conference Tuesday, Sept. 29 through Thursday, Oct. 1. This is the second in a series of Center for Educatin and Museum Studies conferences where researchers and curators from around the Smithsonian Institution come together to address a single subject.

“Climate Change” will feature sessions everyone will find thought provoking and relevant. Some sessions will be of special interest to educators while others will engage entire classrooms and the general public. Throughout the conference, participants will explore Smithsonian research and collections related to the evidence, impact and response to climate change. Alongside Smithsonian scientists and curators, the public will examine the issues surrounding climate change from the perspectives of science, history and art.

Photo: Scott Wing has used ginko fossils like this to estimate the amount of carbon dioxide in the atmosphere during the Eocene. (James DiLoreto)

“We’re excited to offer this online seminar on such an important and timely topic as climate change. The Smithsonian, with its experts, collections and partners is uniquely qualified to do so,” Wayne Clough, Secretary of the Smithsonian, says. “Our first seminar, on Abraham Lincoln, was a resounding success that started an online dialogue that continues today—here and abroad.” Presenters include:

*Bert Drake, senior scientist at the Smithsonian Environmental Research Center, who leads two major studies of the impact of atmospheric carbon dioxide on ecosystems;

*Don Moore, associate director for animal care at the Smithsonian’s National Zoological Park, who helps create conservation-management plans for wildlife; and

*Scott Wing, paleontologist at the Smithsonian’s National Museum of Natural History, who specializes in prehistoric plant life and its reactions to climate change.

The conference will show the depth of research that the Smithsonian is conducting on climate change. Smithsonian scientists and other experts will lead participants in explorations of Smithsonian research on this important issue via live presentations, moderated forums and demonstrations. Through live streaming, speakers will respond to questions and comments from the audience. All of the conference sessions will be recorded and archived and can be replayed at any time via the Web at www.SmithsonianEducation.org.

Registration is open to everyone at www.SmithsonianEducation.org/Climate.

This site also features a blog about climate change and an archive of the first online conference, “Abraham Lincoln,” which attracted more than 3,000 participants on six continents.

Fossils of tiny cupuladriid colonies reveal extinction can lag more than one million years after its cause

John Barrat — Wed, 05 Aug 2009 19:14:30 +0000

A new Smithsonian study that examines 10 million years of the evolution of tiny coral-like organisms called cupuladriid bryzoans has revealed that some species of this organism lingered on earth for more than one million years after the event that ultimately caused their extinction: the rising of the Isthmus of Panama. The extremely long period that elapsed between the rising of the isthmus and the actual disappearance of these animals is causing scientists to reassess the eventual impact modern habitat loss and environmental degradation may have on organisms whose populations have been reduced and are currently under stress.

Following the rise of the Isthmus of Panama four million years ago—a volcanic event which shut off the flow of nutrient-rich water from the Pacific into the southwestern Caribbean—certain species of cupuladriid bryzoans living in the Caribbean showed a swift drop in population, yet they lingered for another 1 to 2 million years before they eventually became extinct.

Photo: This fossil shell once hosted a cupuladriid colony that reproduced sexually.

Aaron O’Dea and Jeremy Jackson, paleocologists at the Smithsonian Tropical Research Institute in Panama, made their discovery through long-term study of the cupuladriid shells found in geologic deposits on both sides of the Isthmus of Panama. Cupuladriids grow in small, free-living colonies attached to domed, dime-size shells. New colonies are created both sexually, with larvae, and by cloning, through the regeneration of fragments broken from shells. Although similar in appearance to the untrained eye, different cupuladriid species have distinct shell characteristics that allow scientists to identify specific species in the fossil record, track populations over time, and observe how species respond to environmental change and how they reproduce.

Photo: This image shows the front and back of two fossil cupuladriids. The one on top reproduced sexually, and the one on the bottom reproduced by cloning. An outline of the triangular fragment from which the bottom colony regenerated can be seen in the lower right image.

A second discovery made by O’Dea and Jackson was that after the closing of the Isthmus of Panama and the halting of nutrient-rich waters into the Caribbean, the dominant mode of reproduction in Caribbean cupuladriids shifted from asexual cloning to sexual reproduction. Species that were able to change their primary means of reproduction from cloning to sexual survived in the new nutrient-deficient environment of the Caribbean. Those that did not change went extinct. New species of cupuladriid that appeared in the Caribbean during this period reproduced sexually. On the Pacific side of the Isthmus, where the waters remained nutrient rich, cloning remained the dominant mode of reproduction.

The question remains as to why extinction lagged for as long as 1 to 2 million years after the Pacific currents were cut off from the Caribbean and the reproductive productivity of certain cupuladriid species declined, O’Dea and Jackson write in their report, published recently in the Proceedings of the Royal Society B.

Photo: A living colony of cupuladriid bryzoans. (Photos by Aaron O’Dea)

“Significant differences in the patterns of abundance between species that went extinct and those that survived provide an important clue.” Species that survived maintained or increased their numbers immediately following the rise of the Isthmus of Panama, the scientists point out. “Most extinct species declined dramatically during this same time.”—John Barrat

Fossil teeth of 15-million-year-old browsing horse found in Panama Canal excavations.

John Barrat — Wed, 22 Jul 2009 08:10:19 +0000

The fossil teeth of a 15- to 18-million-year-old three-toed browsing horse, Anchitherium clarencei, were recently discovered by scientists from the Smithsonian Tropical Research Institute and the University of Florida. They found the teeth during excavations of newly exposed rock in the earthworks of the Panama Canal. Bruce MacFadden, curator of vertebrate paleontology at the Florida Museum of Natural History, University of Florida in Gainesville, described the fossil in a recent issue of the Journal of Paleontology.

Photo: This fossil of Anchitherium clarencei, found in the Panama Canal earthworks, is now in the collection of the University of Florida. (Photo courtesy Aldo Rincon)

The discovery significantly extends the southern tip of the known range of this prehistoric animal, and adds to previous fossil evidence discovered in strata from roughly the same period in Florida, Nebraska and South Dakota. It is by far the most complete fossil of a horse collected at the canal site in excavations spanning the last century; characteristics such as the shape of the horse’s teeth indicate it was primarily a forest-dwelling browser. This evidence supports MacFadden’s belief that the habitat of Panama was once a mosaic of relatively dense forest and open woodlands.

The ongoing excavation of the Panama Canal waterway to make the canal wide enough for supersized cargo ships has been a dream come true for Carlos Jaramillo, senior scientist at the Smithsonian Tropical Research Institute in Panama, and his colleagues. Jaramillo, working with the University of Florida and the Panama Canal Authority, organized a team of researchers and students who rush in to map and collect newly exposed fossils in the canal earthworks following large dynamite blasts set off by canal excavators. It was during one of these collecting excursions that Aldo Rincon, a paleontology intern at the Tropical Research Institute, unearthed the fossil teeth of Anchitherium clarencei.

Photo: Following blasting to expand the Panama Canal, geologists and paleontologists organized by the Smithsonian Tropical Research Institute rush in to map, describe and recover any fossils they can find that might reveal more about the prehistoric ecology of Panama.

The Panama Canal excavation site “is one of very few places in the tropics where we have access to fresh outcrops before they are washed away by torrential rains or overgrown by vegetation,” Jaramillo says.

“We expect the fossils that we have been salvaging to resolve some major scientific mysteries, such as: What geological forces combined to create the Panama land bridge? Was the flora and fauna in Panama before the land bridge closed similar to that in North America, or did it include other elements?”

So far, 10 million cubic meters of earth have been removed from the Canal. The pace of operations is about to accelerate as the Canal Authority awards the final bids for the construction of a third set of locks. More information on the Panama Canal Geology Project is available at striweb.si.edu/jaramillo/current_research/index.html.

NEW ACQUISITION:Research collection of pollen grains given to Smithsonian Tropical Research Institute

John Barrat — Mon, 06 Jul 2009 15:42:58 +0000

Any child can recognize the difference between a rosebush and an oak tree, but given a sample of the tiny pollen grains produced by each of these two plants, few people could match the pollen with its owner. At a microscopic level, however, pollen grains are quite distinct in size, shape and surface structure.

Photo: This electron microscope image shows a pollen grain from the Asteraceae family of flowering plants.

The Smithsonian Tropical Research Institute in Panama was recently given a collection of more than 25,000 different pollen grains and spores, each mounted on a microscope slide and labeled according to the plant that produced it. “The collection is worldwide in coverage with an emphasis on plants of the Americas,” explains collection donor Alan Graham, professor emeritus at Kent State University and curator at the Missouri Botanical Garden.

Graham began the collection in 1954, gathering pollen from plants in the field and from dried specimens in large herbarium collections. A card catalog accompanying the collection is cross-referenced to the slides and contains information on each plant species represented.

Photo: Carlos Jaramillo uses a microscope to study pollen from the Graham collection. (Photo by Marcos Guerra)

Covered by a tough wall, or ‘exine,’ many pollen grains are incredibly resilient, so much so that they show up as fossils in sedimentary rock tens of millions of years old. “It is not unusual to find rich assemblages of fossil pollen and spores in sediments where no other plant fossils—leaves, stems, seeds—exist,” Graham says. Graham, a paleobotanist, uses fossil pollen to reconstruct the vegetative and ecological history of the Americas, with an emphasis on the last 100 million years. “To quickly identify the prehistoric pollen I retrieve from rocks, it was necessary to create this reference collection of known pollen types,” he explains. Some fossil pollen in the collection is 40 to 45 million years old.

A critical bit of information included in the plant descriptions in Graham’s card catalog are the ecological conditions under which each plant grows and its geologic range. This data is essential to understanding the history of the vegetation and environments of the New World, “giving us a picture of how the earth got to this one brief instant of time we are living in right now, and where it may be headed,” Graham says.

Carlos Jaramillo with labeled boxes that hold some 25,000 samples of pollen grains that were mounted on microscope slides by Alan Graham. (Photo by Marcos Guerra)

“This is one of the largest pollen collections in the world, unique in its coverage of North America and Latin America,” says Carlos Jaramillo, a stratigrapher at the Smithsonian Tropical Research Institute. “Soon, we plan to have all of the components of this collection in digital format, to share on the Web with everyone around the world.”

SCIENCE BRIEF:Dog bones reveal ecological history of California’s Channel Islands

John Barrat — Mon, 06 Jul 2009 14:04:47 +0000

A recent study of dog bones excavated from archaeological sites on the Channel Islands of California has cast new light on the past ecology of the islands and the impact that domestic dogs—brought to the islands by Native Americans more than 6,000 years ago—may have once had on the islands’ animals and ecosystems.

Photo: An archaeological site on California’s San Nicolas Island contains the remains of two dogs buried side-by-side some 600 years ago. (Photo by Rene Vellanoweth)

Today, dogs have been removed from all but one of the islands, yet during the early Holocene Native Americans came to the islands bringing with them small, short-faced dogs for hunting, companionship and protection, says Smithsonian National Museum of Natural History Anthropologist Torben Rick.

Over time, the dogs increased in numbers and inevitably had a strong impact on the bird and sea mammal populations living on the islands, killing some and driving great numbers to offshore islets and other isolated areas.

Data for the study by Rick, lead researcher on the project, and his colleagues was collected through a careful review of published and unpublished scientific papers containing accounts of dog bones found at archaeological sites on the islands. Accounts of some 96 dogs from 42 archaeological digs on six of the eight islands were identified by the researchers. Evidence ranged from burned bones of dogs that had been eaten and complete skeletons of dogs that had been ritualistically buried, to pins made from a dog’s tibia and ulna.

“Overall, the data suggest that dogs generally were not consumed, except perhaps during times of scarcity,” Rick notes. “Native villages and their dogs were present across much of the islands, especially around the coastlines and near good water sources. Dogs, along with island foxes and humans, influenced the biogeography and breeding behavior of birds, marine mammals and other animals.”

Documenting the activities of ancient people, and the animals they introduced, can improve models of ancient island ecosystems and enhance managing and restoring these habitats by providing baseline data on how island ecosystems may have been structured in the past.

“Given the lengthy presence of people and dogs on the islands,” modern ecological conditions on the islands appear to be radically different than what existed for much of the Holocene,” Rick says. —John Barrat

Fossils Show Prehistoric Global Warming

John Barrat — Fri, 22 May 2009 12:52:32 +0000

The Past as Prologue
For those who think that global warming is a 21st-century phenomenon, Scott Wing, a scientist at the Smithsonian’s National Museum of Natural History, has news about the past.

Wing headed an international team of scientists whose discovery of plant fossils in the Bighorn Basin of northwestern Wyoming helps document the consequences of a sudden global warming, called the Paleocene-Eocene Thermal Maximum (PETM), 55 million years ago.

Experts believe the PETM, which was caused by a massive release of carbon into the atmosphere, may be an analogue for what is happening today as humans burn increasing amounts of fossil fuel and release large amounts of carbon dioxide.

Plant Movement Signals Global Warming
For nearly 15 years, Wing and his team dug through sediments deposited during uplift of the Rocky Mountains, looking for fossils of the right age and condition. Their discoveries proved that warming caused major shifts in the distribution of plants, allowing southern-dwelling trees and shrubs, related to poinsettia, sumac, and paw-paw, to move some 1,000 miles north in less than 10,000 years. These subtropical invaders flourished for about 100,000 years in what we now know as Wyoming. As carbon dioxide levels dropped and temperatures cooled again, plants related to birches and bald cypress came to dominate the vegetation.

The study and interpretation of this fossil record helps other scientists project future changes in plant life that may result from global warming induced by human activity.