Interpreting Archaeopteryx by Paul Corts
In 1861, within a limestone quarry in the Solnhofen region of Germany, quarry workers discovered a fossilized skeleton within a large slab of rock. The skeleton was an assemblage of bones set atop an imprint of a radiating feathers (Fig. 1). The bones were slightly disheveled and out of place, and it appeared at first glance that the skull of the animal was completely missing from the fossil. Nevertheless, the fossil, set within a smooth and stunning piece of limestone, was striking in beauty and allowed for detailed examination of the bone and feather structures. Knowing full well that a local physician named Carl Häberlein accepted these precious artifacts of time as payment for medical treatment services, a quarryman made certain to have the fossil brought to Dr. Häberlein.
In 1860, less than a year before the discovery of the skeleton, a fossilized feather was discovered in the very same quarry. The fossil was also well preserved and maintained very distinct, asymmetric features similar to the flight feathers in modern birds. Both fossils date back to the late Jurassic Period. (approximately 150 million years old).
In 1861, after the fossil had found a place for itself in Häberlein’s collection German naturalist Hermann von Meyer studied the fossil. “What was this fossil? What did it represent?” This was the problem that naturalists immediately contended with following the discovery of a new fossil. Von Meyer identified the fossil as a bird, but noted that the fossil contained oddly existing features akin to that of a reptile. Von Meyer named the fossil skeleton Archaeopteryx lithographica. Archaeopteryx means “ancient bird-wing”, while lithographica refers to the lithographic stone the fossil was discovered in.
Look at the image of Archaeopteryx. What is this fossil? What features does it exhibit? What kind of animal does it look like? Complete the following exercise in describing what you see and comparing it to modern day animals. TEACHER’S “TO-DO”: In order for students to complete a thorough examination of Häberlein’sArchaeopteryx, use a life-sized image of the original sketch or earliest authentic photograph of the fossil will allow for the most complete examination and will allow students to compare modern day animal skeletons to the specimen. In addition (ideally), have some modern day skeleton or bone specimens. Students can work in groups.
Imagine you’re the quarry worker who has discovered the fossil skeleton. Assuming that you have a limited knowledge of anatomy or paleontology, you recognize that it looks like a bird of some sort. Describe in detail features you observe in the fossil. Why do you think the fossil is inarticulate (slightly broken up, bones out of place) rather than articulate (specimen in good, intact condition – see example of an articulate dinosaur fossil)?
Now imagine you’re an expert naturalist (like von Meyer) and Dr. Häberlein has come to you with the fossil, asking you to analyze it. You are the first scientist to examine the fossil skeleton thoroughly! Compare the fossil image to the images or models of the following: an ostrich skeleton, a falcon skeleton, a lizard skeleton, and a mammal (beaver) skeleton. Following the examples in lecture, you should be able to describe in detail the differences between Archaeopteryx and the modern-day animals. Catalog the features of the fossil specimen:
“bird-like” features? (falcon-like or ostrich-like?): “reptile-like” features: “mammal-like” features:
You’ve been asked to write a paper for the Natural History Museum in Paris, with a thorough description of your findings from above. What do you think this fossil represents?
For Haberlein and others at the time, fossil collecting was exciting personal hobby. Häberlein had accrued over 1,700 specimens of fossils, ranging from reptiles to plants to fish, all from the lagoon deposits in Solnhofen. In 1862, he decided to sell off his entire personal collection of fossils, including Archaeopteryx.
The opportunity to own Archaeopteryx sparked an intense bidding war between the major natural history museums across Europe at the time. In the end, the British Museum of Natural History became successful in securing Archaeopteryx and the rest of Häberlein’s collection for the hefty price of £700 (British pounds - quite a costly expenditure for that time), with the Archaeopteryx specimen alone costing £450.
Following the fossil’s arrival at the British Museum, Richard Owen, Superintendent of the Museum’s Natural History Department, had the responsibility of describing, classifying and officially publishing his findings concerning the specimen. Owen was a paleontologist and an accomplished anatomist and prominent authority on natural history. Owen believed that organisms followed certain standard, or ideal, forms. Each specimen belonged to a certain category, which could be characterized by certain essential traits. There were no hybrids or transitional forms. Owen, perhaps due to his family affluence and ties to the royal family of England, was also deemed as arrogant, malicious, and self-serving in his career as a scientist. In scientific circles, Owen was know to have been ferociously combative towards those who did not agree with him, and several critics of Owen felt that he at times seemed self-contradictory in the arguments he put forth.
Owen completed his analysis of the in 1863, and published his interpretation in the Philosophical Transactions of the Royal Society of London, a highly regarded journal. In his analysis, Owen argued that the Häberlein’s Archaeopteryx was definitely akin to birds, and contended that von Meyer and other naturalists were mistaken in believing that some features of the specimen were reptilian in nature. Owen even suggested revising the name of the specimen, from Archaeopteryx lithographica to Archaeopteryx macrura, macrura meaning “long-legged”.
DISCUSS: What’s in a name? Why do you think Owen changed the name of the species from “lithographica” (meaning type of bedrock fossil was found in) to “macrura” (meaning fossil exhibited long legs)? Do you feel Owen was justified in making a name change? Many naturalists at the time agreed that Häberlein’s Archaeopteryx exhibited features similar to birds, therefore the classification of the specimen as a bird was justified. Other naturalists at the time, however, were curious to see how the specimen played part in evolution, a controversial theory proposed by Charles Darwin just a few years prior in 1859. Darwin’s book On the Origin of Species, argued that evolution through natural selection caused species to change or diverge into new species. This theory conflicted with the established belief in science that each species descended from an original, separate organism. Darwin argued that the changes brought forth on a species are slow and gradual, and the links connecting the division between major groups were transitional forms. Owen, you may guess, did not regard Darwin’s theory as plausible. Some Naturalists wondered if Archaeopteryx could be the transitional fossil that would link the formidable gap separating birds from reptiles.
One of Darwin’s supporters, Thomas Henry Huxley (Fig. 2), was also eager to see if Archaeopteryx was the link between bird and reptile. Born 1825 into a working-class family, Huxley had very little formal education but was self-taught in the disciplines of science and history. In 1840, Huxley won a scholarship to study medicine, and in his early twenties became an assistant surgeon for the Royal Navy. During his time in the navy, Huxley acquainted himself with notable scientists such as the geologist Charles Lyell and Darwin, and on his tour of duty overseas he became an avid collector and expert of marine invertebrates. After the navy Huxley arrived back in London and worked in the School of Mines. Huxley came from a considerably more modest background than either the affluent backgrounds of fellow Englishmen Darwin and Owen; in fact, the costly acquisition price of the Häberlein fossil collection would have made up one-half of Huxley’s middle-class living expenses; whereas Darwin’s annual income was seven times greater than that of Huxley’s.
Initially dismissive of evolution as a plausible theory, Huxley eventually came to accept evolution after the publication of Origin, and began defending Darwin. Wanting to see if the Häberlein’s Archaeopteryx fit the puzzle of evolution and transitional forms, Huxley conducted his own analysis of the specimen, and in 1868, five years after Owen’s analysis, Huxley published his description of the fossil, entitled Remarks upon Archaeopteryx Lithographica, in the Philosophical Transactions of the Royal Society of London.
This would not be the first time that Huxley would respond to a work of Owen’s. In fact, Huxley and Owen clashed several times before on issues of anatomy. Owen, a staunch opponent of evolution, became quite the public ire of Huxley, and many debates arose between both scholars based on their dislike for one another’s ideologies, as well as their personalities. As much as Owen’s personality was known to be abrasive, Huxley’s attitude towards his opponents was blatantly vindictive. Huxley possessed great expertise in his field of work, and had a knack for maliciously dissecting opponents in debate. Huxley would look for any reason to unabashedly spar with anyone who he felt had opposed or wronged him, and with the opportunity to skirmish with Owen over Archaeopteryx, Huxley jumped at the opportunity to draw blood.
TEACHER’S “TO-DO”: It is important to avoid the myth-conception of “hero/villain” when comparing the backgrounds and personalities of Huxley and Owen: It is easy to see where because of Huxley’s accepted assertion of Archaeopteryx and transitional forms, that we can make Huxley out to be the hero and Owen to be the nasty villain who failed in his assertion. The key here is to present the backgrounds and findings of Huxley and Owen and lead the student through the analysis of comparing both interpretations. It may be helpful to go further into the backgrounds of each scientist, and possibly into Owen’s a little bit further, as to provide a balanced portrayal for both. Huxley’s intelligence and witty demeanor were evident in his alternative interpretation of the fossil, as it could be read as a thinly-veiled romp on what has become widely accepted as analytical errors on Owen’s part. The title of Huxley’s paper disregards Owen’s revised naming of Häberlein’s Archaeopteryx. Huxley begins by pointing out that Owen had incorrectly oriented both the vertebrae column and the wishbone, misidentified features such as the humerus bone and the scapula, and had mistaken the left side of the pelvis, leg, and foot of the animal for the right. Huxley takes Owen to task for Owen’s assertion that only birds have toothless beaks and feathers. Huxley points out that turtles have toothless, beak-like mouths and that the reptilian order of pterodactyls displayed both a beak and teeth structure, and predicts that a more complete specimen of Archaeopteryx would most likely exhibit teeth.
In 1877 a fully articulate specimen of Archaeopteryx was found (Fig. 3). (The specimen was eventually bought by the Germans and brought to the museum in Berlin, thus earning a designation as the “Berlin specimen” of Archaeopteryx. Häberlein’s Archaeopteryx was reassigned as the “London specimen” shortly after.) Most notably, it included a skull. That allowed naturalists to see if Huxley’s bold prediction about teeth would be fulfilled. Huxley could also address the similarity of the pelvis and foot structures in the specimen to that of the dinosaur Compsognathus, also found in Solnhofen.
Now have students compare images of the London and Berlin specimens. Lead students through analysis, comparing bone structures and place particular emphasis on the skull features of the Berlin specimen. Bring the discussion back to the original problem: What does this fossil mean?
Exercise 2: Comparing Specimens of Archaeopteryx
Objective: You are an expert naturalist at a major museum in Europe in the late 1870s. Examine the images of the 1861 (London) and new 1877 (Berlin) Archaeopteryx specimens. Compare bone structures between both specimens.
Bone structure comparison discussion: each image will compare the bone structures between both fossils. Write down any bones you see in the Berlin specimen that are missing from the London specimen.
This image of the Berlin specimen shows the skull that was missing from the London specimen. Look closely at the skull. Knowing what you know about the bird skulls and lizard skulls you observed in the last exercise, how does the skull of the Berlin specimen compare to the other skulls you looked at?
The following slides show particular bone structures of the Berlin specimen, a modern day ratite (ostrich), a modern day falcon, and a modern day reptile. Write down the function of each bone structure in Archaeopteryx and how it compares to the other modern day animals.
Looking back at your initial interpretation of the London specimen: has your interpretation changed at all? If so, how? What do you now think this fossil represents?
TEACHERS - FOR CLASSROOM DISCUSSION: Following the completion of Node 2, present the images of the Berlin specimen and an image of a fossil of compsognathus. Ask students if the see any similarities or differences in each specimen. Animals like Archaeopteryx and compsognathus (Fig. 4), Huxley contends, are part of the much bigger picture concerning transitional forms between organisms. Later, Huxley published On the Animals which are Most nearly Intermediate Between the Dinosaurian Reptiles and Birds. The paper highlights not only the difference between reptiles and birds, but also the differences between ratites (non-flying birds like ostriches, which are closer in relation to reptiles) and carinates (flying birds). No living animal, Huxley continues, can bridge the gap between both reptiles and birds. Huxley asks if there are any fossil birds that are reptilian-like that are still existent today, and if there are any fossil reptiles more bird-like than reptiles of today? Huxley answers that with the evidence of Archaeopteryx, what he considers as the most reptile-like of birds, and the link between ratites and dinosaurs. Huxley in 1870 produces another paper entitled Further Evidence of the AffinityBetween the Dinosaurian Reptiles and Birds. In this paper Huxley describes his work with Professor John Phillips concerning the dinosaur Megalosaurus. The specimen that both men studied, like Archaeopteryx lithographica, had misidentifications, that, once corrected, displayed anatomical features more similar to a ratite than other reptiles. It is here where fossils such as Archaeopteryx, compsognathus, and megalosaurus, Huxley contends, can be seen as transition fossils.
TEACHERS - FOR CLASSROOM DISCUSSION:
In agreeing that Archaeopteryx is a transitional fossil – does that require you to believe/accept the theory of evolution? What about if in accepting the theory of evolution - does that require you to accept that this is a transitional fossil?
Did the differing backgrounds of Huxley and Owen could have lead them to different interpretations? Was Huxley’s middle class background important for him to come up with an alternative interpretation? Could Huxley’s ongoing feud with Owen have motivated him to find an alternative to Owen’s interpretation?
3) Did the knowledge of Compsognathus and Megalosaurus affect the interpretation of Archaeopteryx? Do all these fossils mean something differently as an ensemble than they do separately? If so, what does that indicate to us about interpreting particular bits of scientific evidence?
OPTIONAL BACKGROUND The discovery of fossils is recorded throughout history, since the beginning of civilization. Fossil collecting and categorization by naturalists for the means of documenting natural history was considered a relatively new field of science prior to the mid-1800s. Discuss how fossils impacted the way naturalists viewed similarities in anatomies between modern and prehistoric animals that eventually allowed scientists to construct relationships and timelines in natural history. A helpful guide would be The Meaning of Fossils by Martin Rudwick.