Archaeopteryx (; ), sometimes referred to by its German name, "" () is an extinct genus of bird-like dinosaurs. The genus name derives from the Ancient Greek (), meaning 'ancient', and (), meaning 'feather, wing'. Between the late 19th century and the early 21st century, Archaeopteryx was generally accepted by palaeontologists and popular reference books as the oldest known bird (member of the group Avialae). Older potential avialans have since been identified, including Anchiornis, Xiaotingia, Aurornis, and Baminornis.
Archaeopteryx lived in the Late Jurassic around 150 million years ago, in what is now southern Germany, during a time when Europe was an archipelago of islands in a shallow warm tropical sea, much closer to the equator than it is now. Similar in size to a Eurasian magpie, with the largest individuals possibly attaining the size of a raven, the largest species of Archaeopteryx could grow to about in length. Despite their small size, broad wings, and inferred ability to fly or glide, Archaeopteryx had more in common with other small Mesozoic dinosaurs than with modern birds. In particular, they shared the following features with the dromaeosaurids and troodontids: jaws with sharp teeth, three fingers with claws, a long bony tail, hyperextensible second toes ("killing claw"), feathers (which also suggest warm-bloodedness), and various features of the skeleton.
These features make Archaeopteryx a clear candidate for a transitional fossil between non-avian dinosaurs and avian dinosaurs (birds). Thus, Archaeopteryx plays an important role, not only in the study of the origin of birds, but in the study of dinosaurs. It was named from a single feather in 1861, the identity of which has been controversial. That same year, the first complete specimen of Archaeopteryx was announced. Over the years, twelve more fossils of Archaeopteryx have surfaced. Despite variation among these fossils, most experts regard all the remains that have been discovered as belonging to a single species or at least genus, although this is still debated.
Most of these 14 fossils include impressions of feathers. Because these feathers are of an advanced form (flight feathers), these fossils are evidence that the evolution of feathers began before the Late Jurassic. The type specimen of Archaeopteryx was discovered just two years after Charles Darwin published On the Origin of Species. Archaeopteryx seemed to confirm Darwin's theories and has since become a key piece of evidence for the origin of birds, the transitional fossils debate, and confirmation of evolution. Archaeopteryx was long considered to be the beginning of the evolutionary tree of birds. However, in recent years, the discovery of several small, feathered dinosaurs has created a mystery for palaeontologists, raising questions about which animals are the ancestors of modern birds and which are their relatives.
History of discovery
Over the years, fourteen body fossil specimens of Archaeopteryx have been found. All of the fossils come from the limestone deposits, quarried for centuries, near , Germany. These quarries excavate sediments from the Solnhofen Limestone formation and related units. The initial specimen was the first dinosaur to be discovered with feathers.
The initial discovery, a single feather, was unearthed in 1860 or 1861 and described in 1861 by . "Aus dem lithographischen Schiefer der Brüche von Solenhofen in Bayern ist mir in den beiden Gegenplatten eine auf der Ablösungs- oder Spaltungs-Fläche des Gesteins liegende Versteinerung mitgetheilt worden, die mit grosser Deutlichkeit eine Feder erkennen lässt, welche von den Vogel-Federn nicht zu unterscheiden ist." (From the lithographic slates of the faults of Solenhofen in Bavaria, there has been reported to me a fossil lying on the stone's surface of detachment or cleavage, in both opposing slabs, which can be recognized with great clarity [to be] a feather, which is indistinguishable from a bird's feather.) It is now in the Natural History Museum of Berlin. Though it was the initial holotype, there were indications that it might not have been from the same animal as the body fossils. In 2019 it was reported that laser imaging had revealed the structure of the quill (which had not been visible since some time after the feather was described), and that the feather was inconsistent with the morphology of all other Archaeopteryx feathers known, leading to the conclusion that it originated from another dinosaur. This conclusion was challenged in 2020 as being unlikely; the feather was identified on the basis of morphology as most likely having been an upper major primary covert feather.
The first skeleton, known as the London Specimen (BMNH 37001), was unearthed in 1861 near , Germany, and perhaps given to local physician in return for medical services. He then sold it for £700 (roughly £83,000 in 2020) to the Natural History Museum in London, where it remains. Missing most of its head and neck, it was described in 1863 by Richard Owen as Archaeopteryx macrura, allowing for the possibility it did not belong to the same species as the feather. In the subsequent fourth edition of his On the Origin of Species, Charles Darwin said the following about the discovery.
The genus name derives from the Ancient Greek (), meaning 'ancient', and (), meaning 'feather, wing'. Meyer suggested this in his description. At first he referred to a single feather which appeared to resemble a modern bird's remex (wing feather), but he had heard of and been shown a rough sketch of the London specimen, to which he referred as a "" ('skeleton of an animal covered in similar feathers').
Since then, twelve specimens have been recovered:
The Berlin Specimen (HMN 1880/81) was discovered in 1874 or 1875 on the Blumenberg near , Germany, by farmer Jakob Niemeyer. He sold this precious fossil for the money to buy a cow in 1876, to innkeeper Johann Dörr, who again sold it to Ernst Otto Häberlein, the son of K. Häberlein. Placed on sale between 1877 and 1881, with potential buyers including O. C. Marsh of Yale University's Peabody Museum, it eventually was bought for 20,000 Goldmark by the Berlin's Natural History Museum, where it now is displayed. The transaction was financed by Ernst Werner von Siemens, founder of the company that bears his name. Described in 1884 by Wilhelm Dames, it is the most complete specimen, and the first with a complete head. In 1897 it was named by Dames as a new species, A. siemensii; though often considered a synonym of A. lithographica, several 21st century studies have concluded that it is a distinct species which includes the Berlin, Munich, and Thermopolis specimens.
Consisting of a torso, the Maxberg Specimen (S5) was discovered in 1956 near Langenaltheim; it was brought to the attention of the German paleontologist Florian Heller in 1958 and described by him in 1959. The specimen is missing its head and tail, although the rest of the skeleton is mostly intact. Although it was once exhibited at the Maxberg Museum in Solnhofen, it is currently missing. It belonged to Eduard Opitsch, who loaned it to the museum until 1974. After his death in 1991, it was discovered that the specimen was missing and may have been stolen or sold.
The Haarlem Specimen (TM 6428/29, also known as the Teylers Specimen) was discovered in 1855 near , Germany, and described as a Pterodactylus crassipes in 1857 by Meyer. It was reclassified in 1970 by John Ostrom and is currently located at the Teylers Museum in Haarlem, the Netherlands. It was the very first specimen found, but was incorrectly classified at the time. It is also one of the least complete specimens, consisting mostly of limb bones, isolated cervical vertebrae, and ribs. In 2017 it was named as a separate genus Ostromia, considered more closely related to Anchiornis from China.
The Eichstätt Specimen (JM 2257) was discovered in 1951 near Workerszell, Germany, and described by Peter Wellnhofer in 1974. Currently located at the Jura Museum in Eichstätt, Germany, it is the smallest known specimen and has the second-best head. In 2007, Phil Senter classified Jurapteryx, A. siemensii and A. bavarica as junior synonyms of A. lithographica, suggesting that proposed diagnostic features of these taxa based on proportional and dental differences can be explained by ontogeny.
The ('Unnumbered Specimen') was discovered in the 1970s near Eichstätt, Germany, and described in 1988 by Wellnhofer. Currently located at the Bürgermeister-Müller-Museum in Solnhofen, it originally was classified as Compsognathus by an amateur collector, the same mayor Friedrich Müller after which the museum is named. It is the largest specimen known and may belong to a separate genus and species, Wellnhoferia grandis. It is missing only portions of the neck, tail, backbone, and head.Elżanowski A 2001b. "A new genus and species for the largest specimen of Archaeopteryx ". Acta Palaeontologica Polonica 46: 519–532.
The Munich Specimen (BSP 1999 I 50, formerly known as the ) was discovered on 3 August 1992 near Langenaltheim and described in 1993 by Wellnhofer. It is currently located at the Paläontologisches Museum München in Munich, to which it was sold in 1999 for 1.9 million . What was initially believed to be a bony sternum turned out to be part of the coracoid, but a cartilaginous sternum may have been present. Only the front of its face is missing. It has been used as the basis for a distinct species, A. bavarica,Wellnhofer, Peter. Archaeopteryx. Der Urvogel Von Solnhofen. München: Friedrich Pfeil, 2008, p. 54. but more recent studies suggest it belongs to A. siemensii.
An eighth, fragmentary specimen was discovered in 1990 in the younger Mörnsheim Formation at Daiting, Suevia. Therefore, it is known as the Daiting Specimen, and had been known since 1996 only from a cast, briefly shown at the Naturkundemuseum in Bamberg. The original was purchased by palaeontologist Raimund Albertsdörfer in 2009. It was on display for the first time with six other original fossils of Archaeopteryx at the Munich Mineral Show in October 2009. The Daiting Specimen was subsequently named Archaeopteryx albersdoerferi by Kundrat et al. (2018). After a lengthy period in a closed private collection, it was moved to the Museum of Evolution at Knuthenborg Safaripark (Denmark) in 2022, where it has since been on display and also been made available for researchers.
Another fragmentary fossil was found in 2000. It is in private possession and, since 2004, on loan to the Bürgermeister-Müller Museum in Solnhofen, so it is called the Bürgermeister-Müller Specimen; the institute itself officially refers to it as the "Exemplar of the families Ottman & Steil, Solnhofen". As the fragment represents the remains of a single wing of Archaeopteryx, it is colloquially known as "chicken wing".