Wednesday, June 17, 2009

Solnhofen: Archaeopteryx and coprolites

Last November I made a pilgrimage to see one of the most important relics in Germany. At the Berlin Natural History Museum I genuflected to get a better look at the Berlin Archaeopteryx. The animal is neither dinosaur nor bird, caught somewhere in-between. I can’t remember a time when I wasn’t aware of this animal and its significance in our understanding of evolutionary processes. Wrapped up with the image of a feathered dinosaur is the world “Solnhofen.” Since I was six I’ve known it was the name of a place in Germany, and was home to all the Archaeopteryx fossils that have ever been chipped out and described.

As the rain started to fleck the university van’s windshield, we parked in a small gravel parking lot. Behind the lot was a small quarry filled with slabs of tan rock and piles of limestone. This was the fine-grained, lithographic, Solnhofen limestone. The rock was used for decades as the source of lithographic stone. It’s grain is so fine that it perfectly took ink from minutely detailed images and faithfully trasfered them to paper. As I’ve said before, printing is in my blood, but fossils are close to my heart. It was time to find an early bird (or more importantly a mammal. No fuzzy critters have ever been found in the Solnhofen quarries, despite several fossils of small, terrestrial dinosaurs).

The finely bedded rock breaks along irregular bedding plane after a few hammer strikes. Ideally a chisel is used to pry the planes apart, but I only had my hammer and a cheap aluminum knife I swiped from the youth hostel (I’m an Outlaw in Wiesbaden as a result). But that was enough to discover a few ancient creatures.

Solnhofen isn’t packed with fossils, but I was able to collect more ammonite fossils (spiraled squid shells), a belemite, and I helped excavate a fish vertebral column:

It had been drizzling the whole time we were in the quarry, and the heavens finally opened wide and we all retreated to a shelter that was held up by towers of piled limestone. After eating our soggy lunch, we piled into the bus to see some of the treasures of the quarry in the Jura Museum in Eichstätt.

Paleontology requires an active imagination. The material paleontologists study is the empty hull of a once active organism. It’s hard to stay interested in a lifeless fossil. If the paleontologist’s imagination can conjure the animal from the few clues left behind, it becomes instantly more interesting. Then the paleontologist must use a few key clues to imagine the habitat that lead to this creature. I’m not suggesting paleontologists imagine or fabricate their research. Just that in order to pursue interesting questions, paleontologists have to maintain a picture of a long-vanished world, testing that picture empirically, ultimately revealing the story of life’s struggle to survive. It’s hard to conjure much of anything in the imaginaiton when you’re squatting in a wet quarry looking at squid shells. This is the beauty of a museum.

The Jura Mueusm is actually housed in a castle that was besieged by the Swedes during the Thirty Years War. Someday I'll lay siege to Union Terminal to give it that kind of historical distinction.

This is the fossil of a small fish who sunk to the bottom of the lagoon. His head was lodged in the sediment, but his tail was free to flop around, creating the gashes in the sediment you see surrounding the body. These are the stories that come from the Solnhofen.

The museum holds all the evidence of the extinct ecosystem with rare and unusual speciments that add a new level of complexity to the world of the Late Jurassic. The fossils of dragonflies, perfectly preserved with their multi-faceted eyes and delicate wings were on display:

Small lizards and early sea turtles demonstrate the coast wasn’t far away, a fact also revealed by the Stars of the Solnhofen: The Fliers.

Small pterosaurs recovered from the limestone were prize collectors items in the 19th century. The first Archaeopteryx was thought to be a pterosaur by the quarryman who smuggled it our of the pits and sold it to a local collector who recognized its real significance. The flying reptiles are often preserved with impressions of their leathery wings rippling the stone around the delicate finger bones that supported the wing. Most of the reptiles are small - about the size of a pigeon or seagull - showing they probably didn’t venture very far out to sea, and the coast offered a nearby roost.

The Jura Museum also houses its own Archaeopteryx fossil. This bird is smaller than the pterosaurs and its friend in Berlin. The animal is maybe the size of a robin, but is preserved in all it’s missing-link glory with a toothy bill and delicate feather impressions. I stopped and studied the fossil for several minutes, trying to remember every physical detail of this beautiful little bird.

Eventually I had to wrench myself away to hop back on the bus, but first I tried to take myself back 140 million years to a shallow lagoon rimmed with massive reefs that was a little too salty for most life to function happily. On the surface the waves crashed against the German coast, but below, the quiet, calcitic sediments were an undisturbed tomb for all animals washed into the protected lagoon. Tracks in the sediment reveal the activities of busy horseshoe crabs who took a wrong turn on the way out of the hypersalinated water. Their lazy path terminates with their carapace, preserved for posterity at the end of the trail. Coral and sponges formed the barrier reefs, while jellyfish and squids (some preserved with their ink-sacs intact) drifted through the water, evading marlin-like, ray-finned fish. Overhead pterosaurs rise on the coastal thermals and dive after dragonflies the size of my hand. A small dinosaur, Juravenator, darts through the tropical foliage after a small shrew-like animal who’s too quick to ever become a fossil…who needs a time machine when you have fossils like this?

A view from the battlements of the Jura Museum. Yeah, battlements. Now the castle and museum are owned by the Catholic Church. That's cool right?


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