ANTARCTICA

“G-495, G-495, Gordon Valley. This is 3-6-Juliet inbound. You guys ready for us?”

We were not. And we knew they were inbound well before they called because we could hear the rotors echoing to us from down-glacier. It had been about 50 minutes since one of the National Science Foundation helicopters, call sign 3-6-Juliet, had dropped off Adam, Roger, and myself at our soon-to-be campsite for the next week. We were in Gordon Valley in the Transantarctic Mountains, a Middle Triassic (245 Ma) fossil site that had been fruitful in the past for both vertebrates and paleobotanical work (in the form of a standing petrified forest). In those 50 minutes we had to find an appropriate campsite, one that was on relatively level ground and offered us some sort of protection from the ferocious winds that could gust off the polar ice cap toward the frozen Ross Sea. The site we found was a few hundred yards from the helo site across mostly flat, but very boulder-ful, terrain. The goal was to get the supplies that had been dropped off at the helo site with us on the first run (cots, luggage, equipment, one of our diamond-blade rock saws (HEAVY), and a lot of food) to the campsite before the helo returned with the tent itself. Helicopter time is a precious commodity among research teams in Antarctica and we didn’t want to have to waste ours by making 3-6-Juliet hover while we finished. We did end up clearing the helo area after some quick and heroic heaving. As 3-6-Juliet descended I pulled the hood of my ‘big red’ Antarctic Program coat over my face and hid behind the helo landing area marker, a long strip of fluorescent orange plastic on the end of a piece of bamboo wedged between two rocks.

Sidor graduate students Brandon Peecook and Adam Huttenlocker pose in front of some wind sculpted sandstones from the Middle Triassic in Gordon Valley, Transantarctic Mountains. Mt. Falla is in the background.

The three of us had a very successful week camped out at Gordon Valley. The flat expanse we were camped on was littered with fossils, white chunks and specks sticking out against the brownish-red sandstone. In our first afternoon of exploration we found a number of specimens and marked them with cairns, little piles of rocks. The team had done reconnaissance here before my arrival and so a few cairns already existed. With all of these piles it was easy to get disoriented.

The tent. Our home away from home for about a week. We were the only living vertebrates in any direction for 30+ miles.

The most exciting specimen we checked out was a strip of bone sticking out of the hillside a few meters below the plane of our tent. Roger had concluded it was part of a temnospondyl skull. Temnospondyls were mostly large, aquatic predators during the late Paleozoic and early Mesozoic and may in fact be the group that modern batrachians (frogs + salamanders) came from. Only very little bone was exposed, about six inches of what was inferred to be the right cheek. After more careful prodding we found the same region on the left side of the skull. This told us that the skull was potentially complete (!) and that it was almost certainly upside down.

“Is it weird to only have the skull, with, like, no lower jaw or other body parts?” No, and especially not in this case. The rock layer it was found in was a conglomerate, an amalgamation of differently sized bits of rock (clasts) cemented together with finer sediments. This was also a river setting. As this animal decomposed and fell apart, the river likely transported some of its body. Given all this abuse it is no wonder that only the most robust, heavily ossified regions (like the skull) stand a chance of preservation.

Adam and I spent the week on that hillside using chisels and rock saws to dig a roughly triangular trench around where we believed the skull to be. We never hit bone while digging the trenches and we began to worry that perhaps the snout of the animal wasn’t even there. On the fourth day we decided to chip off the area where we thought we’d find the end of the snout… and there was nothing. This was disappointing, as we’d spent many hours preparing for a snout! As we moved in closer to where we knew there was bone, a big (non-fixable) crack ran through the now most snout-ward region of the block. When we pried the rock apart via this crack we were elated.

We could see many little teeth pointing up to the sky in praise! What’s more the crack had run right in front of the end of the snout, meaning next to no bone was lost. Huzzah! The skull ended up being about 32 inches long from braincase to snout-tip and is much narrower than more familiar temnospondyl skulls.


Adam and Brandon pose as the missing body of the 32-inch-long temnospondyl skull. The total body length would have been approximately 10 feet.

After three solid days of excavating, the rock-encrusted skull was wrapped with several rolls of duct tape, and on day 4 was lifted to the helicopter landing site to be transported back to camp (along with the rest of the fossils). The final weight of the block was about 200 pounds. The fossil is being prepped at the Burke Museum where it (and other Antarctic fossils) will ultimately go on display.

There are already two distinct genera of temnospondyl known from Gordon Valley, Kryostega collinsoni and Parotosuchus sp., and it looks like we may add a third. At this point anywhere else in the world paleontologists would use plaster to protect the fossil before removing it from the ground. In Antarctica, plaster = frozen powder, so we instead covered the skull with rags and wrapped it in duct tape. A lot of it. We used two 345-foot rolls going around and around the skull. Once the skull was free and fully wrapped Adam and I put it in the tent bag and, with the help of a shovel, carried all 200+ lbs. of it uphill to the helo area.


Parotosuchus sp., a temnospondyl discovered at Gordon Valley during a previous expedition.

Kannemeyeria, a large dicynodont therapsid. These large herbivores were incredibly common parts of terrestrial faunas throughout the Permo-Triassic. In South Africa they are the base of the Karoo's biostratigraphic system of correlating rock formations.

Cynognathus crateronotus. A large carnivorous cynodont therapsid that is a relatively close relative of the mammals. Antarctica was not a desert at the time.
Also recovered from Gordon Valley were limb elements and skull elements belonging to different therapsid (mammal-like reptiles, but never use this term) lineages, such as kannemeyeriid dicynodonts and the famous cynodont Cynognathus.

Many of these taxa are shared with the very well sampled Karoo Basin in South Africa. During the Permian and Triassic a number of basins formed along the southwest border of Pangaea in what are now Argentina, South Africa, Antarctica, and Australia. This is what got Christian Sidor, Adam's and my advisor, interested in Antarctic research in the first place. We know so much about South Africa and very little about other regions of southern Pangaea. Is South Africa truly representative? The largest extinction in the fossil record is at the boundary of the Permian and Triassic. We know a great deal about South Africa’s recovery. Is that how the world recovered, too?

Important lineages, such as basal dinosauromorphs, basal pseudosuchians (stem crocodilians), and many lines of aquatic reptile are known from similarly aged sediments from other parts of the world, but not South Africa. After our expedition we know that the basal pseudosuchians were in Antarctica at this time. By sampling more of the world we will get a better understanding of heterogeneity in global recovery. Also the Antarctic fossil faunas and floras are interesting in their own right for being at such high latitude. Though we know the poles of the planet were warm during the Triassic, plants and animals there would still have to deal with many weeks a year of constant darkness. How did they do it?

Adam and I are attending a NSF workshop next summer to discuss interests from different disciplines in another field camp in the Transantarctic Mountains. We’d like to go farther down range and sample some localities that are even lower in the Triassic, closer to the extinction boundary than Gordon Valley. Wish us luck!

Text by Brandon
Skull and "body" photos and captions by Adam

Comments

Popular posts from this blog

Grad Publication: Adam Huttenlocker -- Bigger not always better in a post-extinction world?

Grad Publication: Carolyn Shores takes a very close look at what wolves eat

Congrats Autumn 2018 Graduates!