The Man Who Made Fossil Fish Famous

Our Archaeopteryx show has bedazzling fossils – the only Archaeopteryx skeleton in the New World, complete with clear impressions of feathers. Plus frog-mouthed pterodactyls, fast-swimming Sea Crocs, and slinky land lizards. Today we learn about the Louis Agassiz and his theories.

Louis Agassiz (1807-1873)

Paris and the Lure of Fish, 1836
Agassiz grew up in Switzerland where he excelled as a student in  chemistry and natural history. He went to Paris to study fish fossils under the Father of Paleontology, Baron Georges Cuvier. The geological history of fish seemed muddled at the time. Agassiz brought order to the fins and scales.

“There’s order in the way fish changed through the ages…” Agassiz concluded. He was the first to map out the long history of fish armor, fish jaws and fish tails.

1) The earliest time periods, the Paleozoic Era, most bony fish carried heavy armor in the form of thick scales covered with dense, shiny bone.

2) In the middle Periods, the Mesozoic, the armored fish became rarer and were replaced by fish with thin, flexible scales.

3) In the later Periods, the Cenozoic, thin-scaled fish took over in nearly all habitats.

4) Today, the old-fashioned thick scales persist only in a few fresh-water fish like the gar.

5) Tails changed too. The oldest bony fish had shark-like tails, with the vertebral column bending upwards to support the top of the fin. Later fish had more complicated tail bones, braced by special flanges, and the base of the tail was more symmetrical.

6) Jaws in the earliest bony fish were stiff, like the jaws of crocodiles. Later fish developed jaw bones that could swing outwards and forwards.

Discovery of the Ice Age
As he traveled across Europe, Agassiz saw evidence of giant ice sheets that had covered the mountains and plains. According to Agassiz’s theory, New England too had been invaded by mile-high ice layers. Giant hairy elephants – woolly mammoths – had frolicked in the frigid habitats. At first,  scholars harrumphed at Agassiz’s idea of a Glacial Period.  But by the mid 1840’s the theory was proven beyond a reasonable doubt.

Boston 1846: Toast of the Town & the New Museum
Fish and glaciers made Agassiz the most famous scientist of his time. When he came to Boston in the 1846, his lectures were so successful that the New England intellectuals wouldn’t let him leave. Poets and politicians, rich merchants and artists all helped raise funds to get Agassiz a professorship at Harvard. He repaid the support by working tirelessly to build a grand laboratory of science and education at Harvard – the Museum of Comparative Zoology. Opened in the 1859,  the MCZ has been a leader in fossil studies ever since.

Design in Nature
Agassiz’s interests spread beyond fish and glaciers. He sought the Plan of Creation, the key to understanding all of Nature. Was it  Evolution? No. Agassiz rejected any notion that natural processes somehow had transformed one species into another. He was a fierce exponent of the theory of Serial Creation: every species of fossil creature was created to fill its ecological role in its special geological time zone.

Darwin and Agassiz
Though he fought Darwin’s theories for his whole life, Agassiz’s work in fact provided support for the new views of evolution. The long trends in fish fins and scales were best explained by Natural Selection. Agassiz’s best students at Harvard went on to become strong supporters of Darwinism.  Endowed faculty positions were established in Agassiz’s name.  Agassiz Professorships were given to Alfred Sherwood Romer, the greatest Darwinian  paleontologist of the 20 century, and to Stephen Jay Gould, the most eloquent defender of Darwin in the last thirty years.

Don’t miss Archaeopteryx: Icon of Evolution, currently on display at HMNS. To read more about Agassiz and Darwin, check out my earlier blog.

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.

Can you spell g-a-u-t-e-n-g-e-n-s-i-s?

It seems like barely a few weeks have gone by since the last public announcement about the discovery and identification of a new fossil human ancestor and here we are again, looking at a new face in the family line up.

Meet Homo gautengensis.

Recently we were “warned” that the discovery of several proto humans were about to hit the headlines. The first of these is now getting the limelight; a new member to the genus Homo no less.

Homo gautengensis lived in what is now South Africa. Gauteng refers to a province in that country, and a term in the local Sesotho language meaning ‘place of gold.’

 Photo courtesy of Darren Curnoe

The preliminary information available through public channels at the time of writing indicate that this new species of hominid, which  measured about three feet tall and weighed around 110 pounds, was capable of walking upright as well as moving around in the trees. They lived from about 2 million years ago to 600,000 years ago. According to the researchers involved in this discovery, Homo gautengensis predated Homo habilis, officially still listed as the oldest known tool making and using human. As you will see below, there are other researchers who claim that Homo habilis had a much greater time depth. This headline grabbing statement will, no doubt, generate an interesting discussion.

This may now change as more context information becomes available. According to Dr. Darren Curnoe thinks it is highly likely that these hominids ‘produced and used stone tools and may even have made fire.” The presence of burnt bones found in association with the human remains points to this alleged use and mastery of fire.

More information will be published in an upcoming issue of the journal HOMO – Journal of Comparative Human Biology. Until then, this seems to be the extent of what the general public knows. What is certainly interesting to note here is that, while the announcement is to be made soon, the skull fragments were found in 1976 in the famous Sterkfontein caves. According to a University of New South Wales publication,

“The surprise finding was based on a partial skull – known by its museum catalogue number Stw 53 – along with two other partial skulls, several jaws, teeth and other bones found at various times at Sterkfontein and other nearby caves.”

This is not the end of the story. As they say in late night commercials: “but wait there is more…”  What is the broader picture here? We all know that when it comes to the study of early human ancestors, hyperbole often abounds in press releases and subsequent newspaper articles. With that in mind, be prepared to read headlines in which the totally incorrect terminology of “missing link” will re-appear. There will also be claims that our understanding of human has been “severely shaken,”  as it was claimed in other cases, again and again. You get the picture.

Homo erectus
Creative Commons License Photo credit Thomas Roche

Aside from all this predictable hoopla, we do have a chronological range (2 million to 600,000 years ago) and a place (Gauteng province, South Africa). Who else was around during that timeframe? As it turns out, quite a few hominids were around during that time span, all members of the genus Homo. Homo rudolfensis lived in East Africa from 1.9 to 1.8 million years ago; Homo habilis lived in Eastern and Southern Africa from 2.4 to 1.4 million years ago; Homo erectus lived in Northern, Eastern and Southern Africa as well as parts of Asia; Homo heidelbergensis lived in Europe, and possibly Asia and Africa from 700,000 to 200,000 years ago.

It looks like the place was crowded. In a way it was, with many more species of hominids present on our planet, mainly Africa, than there are today. In another way, it was not; we should not conjure up images of all these ancient hominids bumping into each other and stepping aside to let the others pass as if it were a busy pedestrian crossing in downtown Tokyo. Chances are that most may not have seen other species, and, if they did, were they aware that these others were different?

The earliest accepted evidence of using and controlling fire dates back to 790,000 years ago, at a site in Israel. If this find is pegged closer to the 2 million years ago mark, this would move the marker of fire use back in time considerably. We are not yet at stage of the game yet to make that call.
I wonder what the next announcement will bring.

Stay tuned.

Digging Sideways For Science

Recently we received the question on our blog, “How far down do you have to dig to get to the Cretaceous-Tertiary boundary?” A similar question that I get in anthropology and paleontology is “How far down do you dig to find a T. rex…..or a Dimetrodon….or an Australopithecus?”

We usually don’t dig down. We dig SIDEWAYS!

Fossils are not that common. You could rent a back-hoe and dig at random in North Texas for a month and not find anything. You need to find those few, special layers that have bones or shells.

So….the best way is to use Nature’s Bulldozer.

Here’s how it works. Nature cuts into rock layers using rivers and streams. River banks and the sides of arroyos show us cross-sections of the rock. We use these natural cuts to search for the layers rich in fossils.

Edaphosaurus pogonias

My HMNS crew has walked, hunched over, for days at a time, scrutinizing the banks of gullies in North Texas, without seeing a thing worth digging. But we must have patience. In the Permian Red Beds, for instance, we do find new sites on average every two days. Last month, we found four spots that had bones of the fin-back Edaphosaurus, one of the earliest plant-eaters that ever evolved.

We didn’t dig those four spots because the bones were few and fragmentary.

But we found a fifth spot in the bank of a gully that had a whole vertebral column of the fin-back Dimetrodon, the top predator of the time. Here we dug in, sideways, and recovered a large part of the skeleton, including hips and shoulder.

To get the Cretaceous-Tertiary transition fossils, we go to Raton, New Mexico. Here steep river banks expose the sediments from 65 million years ago, when the dinosaurs went extinct. We can dig in sideways and excavate thin zones of black clay that preserve pollen and spores from the plants that lived just before and just after the great dino extinction.

To find fossil hominids in Africa, first we’d search aerial photos, looking for cuts made by rivers and streams into sediments laid down about 2 million years ago.

Think “Sideways.”