The Formation and Preservation of the Solnhofen Fossils

Our new Archaeopteryx exhibition has stunning complete fossils of fish, turtles, crocodiles, shrimp, sharks and much more, all from Solnhofen, Germany. In this blog, Dr. Bakker explains why Solnhofen produced and preserved so many spectacular, intact specimens.

The Mystery of Tropical Germany

From the first diggings in the late 1700’s,  Solnhofen presented a profound puzzle: Why was  Germany tropical in the Jurassic?

The fossil evidence was perplexing:

Fish
Amiopsis Lepidota

Big, long-lived reefs grow only in the tropics – how could northern Europe have supported the Solnhofen reef?

Large crocodiles thrive only in the warmest climate – how could giant sea-crocodiles flourish at Solnhofen?

Huge tree ferns today are emphatically warmth-loving plants – how could tropical ferns grow luxuriously at Solnhofen?

The mystery was world-wide. In the Jurassic, big crocodilians, tree ferns and reefs had spread all over Europe, Asia and North America. The tropical belt must have extended into Alaska and far south into Argentina.

Solnhofen was part of the proof that the Jurassic was one of the warmest periods in the history of life. Since the end of the Jurassic, on average Europe and North America suffered a gradual decrease in winter warmth.

Solnhofen – A Real Jurassic Park

Big-Budget movies have made the Jurassic Period  the most famous sector of geological time in our modern world. But in fact, the Jurassic was already world-renowned by the 1830’s. The first carnivorous dinosaurs known from good skeletons came from the Jurassic of Oxford. The first dinosaur tracks discovered in abundance were from the Jurassic of Massachusetts. The first complete skeletons of giant sea-reptiles were excavated from the Jurassic of southern England.

But no locale has gave finer fossils from the Jurassic than Solnhofen, Germany. Beginning in the mid 1700’s, Solnhofen has provided a never-ending stream of petrified animals and plants.

Fish
Liodesmus Sprattiformis

The exquisite skeletons lie in lithographic limestone, a rock that records not only bones but  impressions of skin and other soft tissue. Vertebrate bodies are preserved in exceptional detail. The pterodactyls at Solnhofen often have fossilized wing membranes. Crustaceans and mollusks are often fossilized as complete bodies. Even the most delicate  parts of squid – tentacles, eyes, and ink sacs – are recorded as high-resolution impressions.

Solnhofen lithographic stone has captured a more complete picture of Jurassic life than any other kind of sediment. Fossils are not common – hundreds of rocks slabs must be split to expose a single animal. Fortunately, the discovery of fossils is encouraged by commercial interests. Beginning in 1798, the lithographic stone has been quarried to make stone plates used to print high-resolution images of paintings, etchings and, later, photographs.

Many scientific publications about Solnhofen fossils have been illustrated by drawings of specimens reproduced via lithographic limestone plates.

Why are Solnhofen fossils so magnificent? The environment  around a tropical reef  was perfect for preservation. Reef-building organisms – sponges, microbes, corals – built up an arc of hard calcium carbonate that shielded a quiet lagoon. All manner of salt-water fish and invertebrates hunted for food in the upper warm waters. Land-living animals came to the beach to search for washed-up carcasses. In the air flew ‘dactyls and, on occasion, a  bird.

When an animal died and sank to the bottom of the lagoon, the water chemistry offered protection from  the forces of decay and dismemberment. The hot tropical climate concentrated the salts in the quietest part of the lagoon, so that most decomposers – organisms that would destroy the carcass – were kept away. Salt-loving microbes spread a thin film over the bottom, and this film functioned like a death-shroud, further protecting the body of dead animals. Perfect fossils were formed when the microbial mat excluded every crab, snail and  bottom-living shark that would otherwise destroy the body.

Extinct Sea Turtle
Eurysternum Wagleri

Solnhofen brings to us a picture of half-way evolution. The rich fish fauna was being modernized by natural selection. Old-fashioned armored fish were going extinct. New styles of jaws and fins were being developed among what would become the dominant fish families in the modern world. Many Solnhofen fish were living-fossils in their own day, representing evolutionary designs that had first appeared two hundred million years earlier. Other Solnhofen fish were the first successful members of clans that dominate today.

Pterodactyls and sea-reptiles too were about half-way in their Darwinian trajectory. Sea-turtles had not yet evolved their specialized flipper. Sea-crocodiles were about to suffer extinction and replacement by the new ocean-going species of the Cretaceous Period. Crustaceans were starting the wave of evolution that would continue as modern crabs and shrimp and lobsters.

There collection displayed here in our exhibit is one of the finest samplings of the entire Solnhofen biota. The Archaeopteryx at the center of the exhibit is the only Archaeopteryx in the New World.

The study of dinosaurs and the modern world

Our guest blogger today is Dorothy, who runs the blog site Dinosaur Home. Though she originally majored in philosophy working with computers, her true loves are natural history and paleontology. Here, she’s combined all of her talents to share a post on the importance of dinosaur research for the modern world.

Being fascinated by dinosaurs, I’ve often heard the question “why are creatures that disappeared from the earth so long ago are the center of so much research.”
I believe that the answer (at least as I see it) might be surprisingly simple and I’ve decided to focus on two aspects.

1. Researching prehistoric creatures such as the dinosaurs is a really excellent way to learn how evolution works. One of the best ways to study evolution is to have as long a timeline as possible. A researcher today would need to examine and study a species over many years to see how they change and adapt to changing circumstances. When we examine fossils from millions of years ago we are given a rare glimpse into the dinosaur’s existence and even the rare opportunity to see what they have evolved into – birds. Without the study of prehistoric creatures it wouldn’t be possible to get the whole picture of the changes of biology over a really long time.

2. Research into the story of the disappearance of the dinosaurs is actually a very relevant one. The changing climate that we experience today might be something that reminds researchers of other cycles of climate changes years ago. Whether it was an asteroid, climate changes, changes in the earth’s gravity or any of the other explanations that have been offered, there is a direct relevance to our lives today.

 Sometimes if we want to know what is possible, or what might happen, we have to learn about what has already happened. It is an important scientific goal to investigate various possibilities. If Antarctica was once a snow free continent it might be snow free again. If there are dinosaur fossils found on different continents with similar heritages it certainly helps us imagine the globe very differently than its modern structure.

People all over the world have the tendency to imagine the reality they know as the only possibility; it is thanks to the study of dinosaurs and natural history that we can open our minds to very different realities.  The less knowledge we have, the more reluctant we are to admit changes that are happening and that will continue to happen. The Buddhist call it the “recognition of impermanence” and attribute a lot of importance to it. They believe it is vital to the process of becoming more aware of the impermanence of ourselves, and helps us become less ego centered. In fact the whole theory of there being no self says just that “we are all just a flow of events and changes that never starts and never ends.” It works for the whole picture as well.

Few subjects in the Earth sciences are as fascinating to the public as dinosaurs. The study of dinosaurs stretches our imaginations, gives us new perspectives on time and space, and invites us to discover worlds very different from our modern Earth.
From a scientific viewpoint, however, the study of dinosaurs is important both for understanding the causes of past major extinctions of land animals and for understanding the changes in biological diversity caused by previous geological and climatic changes of the Earth. These changes are still occurring today. A wealth of new information about dinosaurs has been learned over the past 30 years, and science’s old ideas of dinosaurs as slow, clumsy beasts have been totally turned around. Although much has been discovered recently about dinosaurs, there is still a great deal more to learn about our planet and its ancient inhabitants.

For more from Dorothy, visit her blog, Dinosaur Home. For more on paleontology, check out:Dimetrodon sighting!
Roberta, the other brachylophosaur
What’s it like to discover a dinosaur?