In December
2003, we traveled on a remarkable and arduous expedition to the southernmost
continent of the planet in search of marsupials. With the support of the U.S.
National Science Foundation, and Argentina’s Museo de La Plata and Instituto
Antártico Argentino, we hoped to find evidence of the pouched mammals
to help piece together their journey through the Antarctic millions of years
ago.
Paleontologists screen rocks for the remaining
bones of a meat-eating dinosaur found in the Naze, a peninsula on northern James
Ross Island in Antarctica. Photo courtesy of James Martin.
Marsupials appear to have originated in North America, yet somehow are now mostly
isolated on the continent of Australia. One hypothesis is that during the Late
Cretaceous, sometime between 65 to 75 million years ago, a dispersal route extended
from North America through South America, across Antarctica and into Australia.
Marsupials followed the corridor, possibly in response to competition from nonpouched
mammals.
In 1998, on an expedition to Vega Island, east of the Antarctic Peninsula, Dan
Chaney of the Smithsonian Institution discovered a hadrosaurine dinosaur tooth.
As the earliest appearance of these duckbilled dinosaurs is in North America,
the hadrosaur tooth suggested that a dispersal route existed during the Late
Cretaceous that would have allowed other creatures to migrate as well. However,
one tooth, although extremely suggestive, was not enough evidence to confirm
our migration hypothesis. Therefore, our 2003 expedition was launched to return
to Vega Island in hopes of finding evidence of elusive marsupial mammals.
Just before Thanksgiving in 2003, members of the expedition crowded onto a research
vessel, the Lawrence M. Gould, in Punta Arenas, Chile, for the voyage
across the Drake Passage to Antarctica. The Drake Passage has the reputation
of being one of the roughest crossings in the world; we were not disappointed.
Four days and many queasy stomachs later, we arrived on the east side of the
Antarctic Peninsula, but icebergs had blown into the Antarctic Sound, preventing
us from getting all the way to Vega Island. We revised our schedule and headed
for Palmer Station on the western side of the Antarctic Peninsula.
On the voyage along the western side of the peninsula, the scene was awe-inspiring,
with iceberg-filled seas and islands possessing magnificent glaciers extending
down to the sea. We saw seals, whales, penguins and many seabirds. The weather
was fantastic on this side of the peninsula, but we knew we had to return to
the stormy eastern side.
Once again, the Antarctic Sound was choked with icebergs, but our captain, Mike
Terminal, maneuvered carefully through the iceberg fields by taking a different
route through the islands and arriving in Herbert Sound in the Weddell Sea.
We steamed toward Vega Island, but soon found the sea was still frozen.
Our ship was not an “icebreaker,” per se, but was rated to break foot-thick
ice. So, we began the process of breaking our way toward Vega. We often would
get stopped by the ice, go into reverse and plow ahead until we were stopped
again. The ice became 3 to 4 feet thick, and finally we realized we could not
make it to Vega Island. Our spirits dropped because we could see the island
only a few miles ahead. Then, the ship got completely stuck.
The crew tried many different ways to free the ship, everything from attempting
to tilt the ship to utilizing fire hoses filled with seawater to melt the ship
out. All during this time, we thought of the stories of Ernest Shackleton and
the Endurance crew’s miraculous survival in the early 1900s. Four
hours later, the ship was freed thanks to the expertise of our captain and crew,
and we returned to open water.
We now had to decide our next course of action, as it was clearly impossible
to return to Vega Island. Our only recourse was to offload nearby onto James
Ross Island. A northern peninsula of the island, the Naze, possessed Late Cretaceous
rocks, but they were deposited in much deeper marine environments compared to
those at Vega Island. Thus, we figured we probably would not find any terrestrial
creatures, and that we would have to be content with marine reptiles and invertebrates.
The closest site where we could offload from the Zodiac boats was 4 miles from
the Naze, and, due to the shallow sea, that site was 2 miles from the ship.
We established camp — putting up cook tents, wash tents, storage tents,
bathroom tents and sleeping tents. Following the daunting task of erecting a
camp that would sustain us against the Antarctic weather for the next month,
the ship disappeared, leaving us with a feeling of abandonment, which was quickly
replaced by awe for the striking beauty around us.
Our new home was comfortable, and we found our Scott tents (named
for the Antarctic explorer, Robert Scott, who froze to death in one) sturdy
enough to withstand the harsh wind and snow. Very often, we would awake to 3
to 6 inches of snow covering the camp (which was christened Camp Slap Ya Mama
for a Cajun seasoning that became very popular at mealtime). The dryness of
Antarctica caused the snow to sublimate, and normally only a single field day
was lost following snowstorms.
The food was very good and was not freeze-dried. We kept fresh meat in snowfields
and got our drinking water from snowmelt. Camp life was usually fun and often
when we were snowbound, we read, played games and, in particular, fulfilled
our obligation to scientifically document and conserve the fossils we had found.
The areas we wished to survey for fossils were 4 miles away from our camp. Every
day, we would hike at least 8 miles roundtrip to the Naze and back. Sometimes
we would return to find our morning pathway had floated out to sea! We had hoped
to find fossils from Cretaceous marginal marine sediments, but we encountered
relatively few specimens. Day after day, we found little, we tired and ached,
and began feeling our expedition would result in failure. But one afternoon,
our luck changed — we found several bones of what appeared to be a medium-sized
fossil reptile.
We were working in marine rocks, but the bones looked nothing like the extinct
reptiles (mosasaurs and plesiosaurs) we had found previously. We all wanted
to exclaim “dinosaur!” But finding a dinosaur in relatively deep marine
environments was definitely unexpected. Finally, we recovered a diagnostic toe
bone, and we all had to admit, as one graduate student proposed, that we had
found a dinosaur!
We collected all we could before the day’s end and headed back to camp
elated. The entire camp took on a new attitude; no longer was fatigue and pain
a factor — now we looked forward to recovering more of the creature.
For
the next several days, we returned to the dinosaur site and scoured the surface.
We also screened the loose material within a 100-foot radius of the find. As
a result, we found much of the lower legs, parts of vertebrae, cranial material
and some fragmentary teeth. In the field, the elements appeared like those of
a theropod dinosaur, but the foot structure seems very primitive for a carnivorous
dinosaur existing at the end of the Mesozoic. Removal of the fossils from the
rock is currently under way in our museum laboratory for comparisons with known
meat-eating dinosaurs.
An artist’s rendering shows what a newly found theropod (meat-eating) dinosaur
might have looked like when it died, around 70 million years ago. Paleontologists
found the bones of the dinosaur on a trip to the Antarctic. They were there
in hopes of discovering marsupial fossils that would provide evidence of a dispersal
route from North America down to the Antarctic and then to Australia between
65 and 75 million years ago. Image courtesy of the National Science Foundation.
Overall, we are happy with our results. The dinosaur does not appear to be related
to North American dinosaurs, as is the hadrosaur we had found previously. The
new dinosaur appears to be a primitive holdover of the original Gondwanan dinosaur
assemblage that existed before the dispersal route was established. Therefore,
based upon the occurrence of the duckbilled dinosaur and the new dinosaur, we
believe that the Antarctic fossil assemblage at the end of the Cretaceous is
a melting pot of local species as well as those that dispersed from North America,
through South America and on to Antarctica. If dinosaurs could made the sojourn,
we think that marsupials were walking in their footsteps. And modern birds,
which occurred in abundance in Antarctica before anywhere else in the world,
may very well have been going the other way, migrating northerly along the coast
to areas such as New Jersey, where their bones are rarely found in the fossil
record.
Our expeditions to the continent of Antarctica, where penguins and seals now
live, has brought us great information about animals in the distant past and
showed that the world, and particularly Antarctica, was much warmer around 70
million years ago compared to the present. In the Late Cretaceous, Antarctica
may have provided a transit route for life between the Americas and Australia
just before the end of the Age of Reptiles. As a result, endemic species and
immigrants were interacting, but they had only a short time before the terminal
Cretaceous extinction 65 million years ago, when the dinosaurs disappeared.
The modern birds and probably marsupials survived to colonize the post-Cretaceous
landscape. To continue developing this idea, we return to Vega Island this month,
once again in search of marsupials.
| Investigating
the Antarctic Weather rules in the Antarctic. But despite the constant threat of being snowed in and stuck inside a tent for two weeks of a six-week field season, the geologists and paleontologists who work on the southernmost continent have succeeded in finding a plethora of information. “You can’t have that large a landmass with animals living on it and have nothing to say,” says Philip Currie, a vertebrate paleontologist at the Royal Tyrrell Museum in Alberta, “but very few paleontologists have been able to go there and explore.” The first bone collected in Antarctica was an amphibian jaw, during a geology survey in 1968, says William Hammer, a paleontologist at Augustana College, in Rock Island, Ill. A year later, the first paleontology expeditions sponsored by the National Science Foundation (NSF) departed for the Antarctic and found an Early Triassic mammal-like reptile, Listrosaurus, which gave a big fossil boost to the theory of plate tectonics. “That’s really what got things started,” Hammer says, and after a several-year lull, more field trips in the 1980s and early 1990s discovered more reptiles and amphibians, as well as the first dinosaurs. That trend has continued, with researchers announcing a new sauropod species after last year’s NSF expeditions. Getting to the continent now is easier than ever before: Geologic mapping “clearly shows where rocks are of the right age” for further prospecting, Currie says, and scientists can now download locations on GPS receivers and direct helicopters to those sites that might produce bones. Helicopters were necessary in the recent discovery of dinosaurs, which occurred in the higher-up sediments in the Transantarctic mountain chain, with some located at 13,000-foot elevations, Hammer says. Cooperation among researchers has also been key to recent progress. Currie and Hammer have worked with others focusing on the late Paleozoic and Mesozoic in the Antarctic, including Molly Miller, a paleoecologist from Vanderbilt University, in Nashville, Tenn. The collaboration is in the field, in the lab and then in publishing and presenting results later. Miller says that she and her colleagues communicate in very interdisciplinary ways. And technology has furthered that communication. Hammer tells of how he came back to camp one day “and the camp manager says, ‘hey, you have a phone message.’ In the 1970s, you couldn’t even get a message to someone that you’re alive.” But now iridium phones can keep researchers in the field connected, which enabled Hammer to discuss bone discoveries with James Martin and Judd Case in the field last season, despite the distance between their field sites (see main story). Getting into the field still remains difficult, however, especially with limited helicopter time. For almost a decade, the majority of U.S. efforts in the Antarctic have been devoted to building the new South Pole station, which has left fewer resources for geologists who need to conduct their fieldwork. The station construction “receives the most logistics and aircraft hours,” says John Isbell, a sedimentologist from the University of Wisconsin at Milwaukee, “so there are only a limited number of hours to go elsewhere.” The construction should be completed by sometime next year. Planning for helicopter time, Hammer says, comes in addition to the usual needs of food, clothing, field plans and compatible co-workers stuck in the field together for weeks on end. Nevertheless, he says, “I’m trying to take bigger field parties so we can get more done,” with a variety of specialists among them. Hammer, Isbell, Miller and others all have grants in the works to NSF for future expeditions, but the expectation is that it will take years to get through the process, plan the trips, and then finally go. “We know what we need to do next season, but we can’t go back next season,” Hammer says, which may be one of the more frustrating things about working in the Antarctic, versus in more easily accessible sites such as Wyoming, or even the deserts of China. Still, the Antarctic has its geologic perks. “Why do I love to go to Antarctica rather than go to Tennessee? The real answer is the exposure of rock,” Miller says. “There’s basically no soil — where there’s rock, you can see it.” She says that the vast Transantarctic mountain chain holds a wealth of data in its very thick sediment layers, and “the layers record events, life, and [the] environment of the time when they were deposited better than anywhere else on Earth.” Miller’s work has used trace fossils to find out about previous environmental conditions on the continent, showing how the presence of water may have changed over time. “Antarctica is kind of this strange place because it’s probably undergone, since the Tertiary, the biggest ecological shift on the planet,” Hammer says. Understanding the Antarctic during past climate regimes, when it was at similarly high latitudes, and understanding why the ecosystem requirements were so different than they are today, he says, may give some predictive indications for future climate changes. “We’re still trying to solve the pieces of the puzzle,” he says, including how the animals there “were adapted to live in this ecosystem.” Clearly, Currie says, “the more people are put down there, the more will be found.” Naomi Lubick Back to top |
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