Archaeopteryx (1861): The Fossil Linking Birds and Dinosaurs

Archaeopteryx is a small feathered animal from the Late Jurassic of southern Germany, first known from a fossil feather and a partial skeleton found in the Solnhofen limestone in 1861. Discovered just two years after Charles Darwin published On the Origin of Species, it combined the wings and feathers of a bird with the teeth, claws and long bony tail of a reptile. For more than a century and a half it has stood at the centre of debates about evolution and, in particular, about the origin of birds from dinosaurs.

Background: the Solnhofen limestone

The fine-grained limestones around Solnhofen and Eichstätt in Bavaria formed in warm, shallow lagoons around 150 million years ago, during the Late Jurassic. The lagoon bottoms were often low in oxygen and salty, so few scavengers disturbed the animals that sank into the soft lime mud. The result is one of the world’s great fossil deposits, with delicate impressions of jellyfish, insects, pterosaurs and fish.

The stone was quarried for building and, from around the end of the 18th century, for lithography, the printing technique invented by Alois Senefelder in the 1790s. Quarrymen split thousands of slabs by hand, which meant that fossils were regularly exposed. Local collectors, doctors and officials bought the best pieces, and a trade in Solnhofen fossils already existed by the mid-19th century.

The scientific mood of the time also mattered. Darwin’s On the Origin of Species appeared in November 1859, arguing that species change over time through natural selection. Critics pointed to the lack of “intermediate” fossils between major groups of animals. Any creature that seemed to bridge two such groups was bound to attract enormous attention.

What happened in 1861

The first find was a single fossil feather, preserved as a dark impression on a slab and its counter-slab. In 1861 the German palaeontologist Hermann von Meyer described it and gave it the name Archaeopteryx lithographica, meaning roughly “ancient wing from the lithographic stone”. The feather looked fully modern, which surprised scientists who had not expected feathers so far back in time.

Later in 1861 a far more important specimen surfaced: a partial skeleton found in a quarry near Langenaltheim, close to Solnhofen. It showed the outlines of feathered wings and a long, feathered tail, but the head was largely missing. The fossil came into the hands of Karl Häberlein, a district physician in Pappenheim who collected fossils and sometimes accepted them as payment for medical services.

Häberlein knew the value of what he held. He allowed visitors to view the specimen but restricted drawing and detailed study, and he offered it for sale. Von Meyer soon heard of it and connected it with the feather, and the name Archaeopteryx came to cover the skeleton as well.

The sale to London

Richard Owen, superintendent of the natural history departments of the British Museum, moved quickly to acquire the skeleton. In 1862 the museum bought it as part of a larger collection of Häberlein’s fossils for a price usually given as about £700, a very large sum at the time. German scientists regretted the loss, but no institution in Germany had matched the offer.

Owen published the first full scientific description in 1863 in the Philosophical Transactions of the Royal Society. He interpreted Archaeopteryx firmly as a bird, albeit a strange one with a long tail. Owen was an opponent of Darwin’s explanation of evolution, and he stressed its bird characteristics rather than presenting it as a transitional form.

The specimen is still held by the Natural History Museum in London, which grew out of the British Museum’s natural history collections. It is often called the London specimen and remains one of the museum’s most valuable objects.

Darwin, Huxley and the evolution debate

Darwin took note of Archaeopteryx in later editions of On the Origin of Species, using it as an example of how incomplete the fossil record was and how unexpected discoveries could fill gaps. He did not, however, build his argument around it.

The strongest case was made by Thomas Henry Huxley, the biologist known as “Darwin’s bulldog”. In lectures and papers in the late 1860s, Huxley compared Archaeopteryx and living birds with small meat-eating dinosaurs such as Compsognathus, also from the Solnhofen limestone. He argued that birds and dinosaurs shared many features of the hips and hind limbs and were therefore closely related. In effect, he proposed a version of the theory that is accepted today.

Huxley also re-examined the London specimen and pointed out details Owen had misread. The episode became part of the wider public contest between supporters and opponents of Darwin. Archaeopteryx turned into a symbol: for one side, proof that evolution produced intermediate forms; for the other, simply an odd bird.

Later specimens

A second, much more complete skeleton was found near Eichstätt in the 1870s. Usually called the Berlin specimen, it preserves a complete skull with teeth and wings spread in a striking pose. It was sold through Häberlein’s son Ernst and bought for the Berlin museum in 1880 or 1881, with the industrialist Werner von Siemens providing funds to keep it in Germany. It is now in the Museum für Naturkunde in Berlin, where the 1861 feather is also kept.

Further specimens followed slowly over the next century and a half. Some were long misidentified. One, found in 1855 and therefore actually older than the 1861 finds, had been described as a pterosaur; the American palaeontologist John Ostrom recognised it as Archaeopteryx in 1970. Another, in the Eichstätt museum, was at first taken for a small dinosaur because its feathers are faint.

Today around a dozen skeletal specimens are generally recognised, though experts disagree on whether all belong to one species or to several closely related ones. Together they show animals roughly the size of a magpie or a raven, up to about half a metre long including the tail.

What kind of animal was Archaeopteryx?

Archaeopteryx had broad wings with asymmetric flight feathers, like those of flying birds today, and a wishbone (furcula). These features suggest it could fly or at least glide, although how well it flew is still debated. It lacked the large keeled breastbone that anchors the flight muscles of most modern birds.

At the same time it had many features of small theropod dinosaurs. Its jaws held small, sharp teeth. Each hand had three separate fingers ending in claws. Its tail was a long series of vertebrae with feathers along both sides, unlike the short, fused tail stump of modern birds. Its feet included a “second toe” that could be held somewhat raised, a trait also seen in its dinosaur relatives.

Studies of preserved pigment structures in the 1861 feather, published in 2012 and later, suggested it was dark, probably black. There has also been debate over whether the isolated feather belongs to Archaeopteryx at all, because it was found on its own; recent analyses have mostly supported the traditional attribution.

Myths and facts

Myth: Archaeopteryx is “the first bird”. It is often called that, and its German nickname Urvogel means “original bird”. But palaeontologists no longer see it as a single starting point. It is better understood as one early member of a broad radiation of feathered dinosaurs, some of which were close to the bird line.

Myth: Archaeopteryx is a forgery. In 1985 the astronomer Fred Hoyle and several colleagues claimed the feather impressions on the London specimen had been added in the 19th century. Museum scientists answered in detail in 1986, showing that natural cracks and features matched across slab and counter-slab and ran through the feathered areas. The claim has no support among specialists.

Fact: it really was found two years after Darwin’s book. The timing is one reason Archaeopteryx became famous so quickly. It appeared just as the debate over evolution was at its height.

The modern view of bird origins

For much of the 20th century, many scientists doubted that birds came from dinosaurs, partly because dinosaurs seemed to lack collarbones. The question was transformed after Ostrom described the agile predator Deinonychus in 1969, setting off the so-called dinosaur renaissance. Ostrom showed in detail how closely Archaeopteryx resembled such small theropods.

From 1996 onwards, discoveries in Liaoning, China, including Sinosauropteryx, revealed many dinosaurs with feathers or simpler filaments. These showed that feathers evolved within dinosaurs long before flight. Today most palaeontologists agree that birds are living theropod dinosaurs, the only branch to survive the Chicxulub asteroid impact at the end of the Cretaceous.

Within that framework the exact position of Archaeopteryx is still discussed. A few analyses, notably one in 2011, placed it among deinonychosaurs rather than on the bird line. Most later studies return it to the base of Avialae, the group that includes modern birds, but the details depend on which other fossils are included.

By the numbers

Timeline

• 1790s: Alois Senefelder develops lithography, increasing demand for Solnhofen limestone.
• 1859, November: Charles Darwin publishes On the Origin of Species.
• 1861: Hermann von Meyer describes a fossil feather and names Archaeopteryx lithographica; a partial skeleton is found near Langenaltheim.
• 1862: The British Museum buys the skeleton from Karl Häberlein.
• 1863: Richard Owen publishes the first full description of the London specimen.
• 1868–1870: Thomas Henry Huxley argues that birds and dinosaurs are closely related.
• 1870s: The more complete Berlin specimen, with a skull, is found near Eichstätt; it reaches Berlin around 1880–1881.
• 1970: John Ostrom identifies a specimen found in 1855 as Archaeopteryx.
• 1985–1986: Forgery claims against the London specimen are made and refuted.

Why it matters

Archaeopteryx was one of the first fossils to give the public a concrete picture of evolution in action, appearing at exactly the moment Darwin’s ideas were being fought over. Its mix of reptilian and bird features made the abstract idea of common descent visible on a single slab of stone. Today, surrounded by many other feathered dinosaurs, it remains a cornerstone of the evidence that birds are the living descendants of dinosaurs.