Why might dinosaurs have been warm-blooded animals with wings?

In 1860, nearly a century had passed since the start of the Industrial Revolution. Wars raged across the entire Eurasian continent; machinery, steel, and coal seemed to be dragging the whole world forward, and half of human society was being uprooted.

Yet all of this seemed not to have disturbed a place in southern Germany called Solnhofen, which at the time still belonged to the Kingdom of Bavaria. Because it was rich in sedimentary limestone, quarrying was a traditional industry in Solnhofen. The workers of Solnhofen carefully chiselled open the limestone along the bedding planes, and often found unexpected gifts: animal fossils sandwiched in the middle of the limestone, as exquisitely detailed as prints. One day that year, a quarry worker chiselled open a "print" and found sandwiched inside afossil formed from a feather。

The fossil feather impression discovered in 1860. The limestone of Solnhofen is flat and fine, and was often used as printing lithographic stone. The limestone strata of this region formed in the Late Jurassic, about 150 million years ago, when Europe was much closer to the equator than it is today; the low-oxygen environment at the bottom of the dense shallow seas and lagoons [xì], along with carbonate sand layers, readily preserved ancient organisms intact and formed fossils. Image: H. Raab / wikimedia

We can no longer know what the German palaeontologist Hermann von Meyer felt when he saw this feather from 150 million years ago - previously the earliest known bird fossils existed only in the much later Cenozoic Eocene. In 1861 Meyer published a scientific name for this feather: Archaeopteryx lithographica - Archaeopteryx means "ancient wing or feather," and the specific epithet lithographica means "lithographic stone print," rendered in Chinese as "Archaeopteryx”。

Restoration of an Archaeopteryx chasing a Compsognathus. Image: Durbed / wikimedia

What the Germans missed

No one expected that, only a few months after the name was published, a skeletal fossil of Archaeopteryx would be found nearby at Langenaltheim. This skeletal fossil was missing the head and cervical vertebrae, whileclearly preserving feather-like structures。

The quarry owner who possessed this specimen paid it to the local doctor and fossil collector Karl Häberlein as medical fees. Häberlein intended to sell the specimen to raise a dowry for his daughter, and this move drew attention from all sides.

The Archaeopteryx skeleton fossil found in Germany in 1861, later known as the "London specimen." The origin of this name will be explained below. Image: H. Zell / wikimedia

In the mid-nineteenth century, the nations of continental Europe and Britain had long been engaged incovert rivalryover national power, science and technology, and scholarship. The many natural discoveries the British made in their colonies put great pressure on the European scientific community, and Germany was naturally unwilling to let its own major discoveries fall into others' hands. On the other side, another undercurrent was stirring, originating from the British naturalistDarwinand his monumental work On the Origin of Species, published in 1859.

Darwin and the first evolutionary tree he drew. Image: Charles Darwin & Julia Margaret Cameron / wikimedia

The evolutionary ideas and theory of natural selection put forward in On the Origin of Species were epoch-making, but in the mid-nineteenth century,religion still held sway in the realm of thought, and as soon as the book was published it was bound to come under attack from many quarters. One line of fire came from another Englishman, the palaeontologist and founder of the Natural History Department of the British Museum,Richard Owen（Richard Owen）。

Owen was very clear about what this skeleton meant for Darwin - if birds had evolved from reptiles, then this specimen, possessing features of both birds and reptiles, was exactly thetransitional fossilDarwin had been searching for, solid evidence of evolution. Although Owen was the namer of the dinosaurs and an outstanding naturalist, he himself upheld creationism and saltationism; as a devout Catholic, he detested and constantly attacked Darwin and On the Origin of Species, and was determined to secure the Archaeopteryx specimen for his own research.

Owen with a moa skeleton. Owen's main contribution to academia was promoting the establishment of the Natural History branch of the British Museum, yet he was narrow-minded, spared no effort in excluding those who differed from him, and combined with other misdeeds in his later years that damaged others' research, he was expelled from the Royal Society. Image: John van Voorst / wikimedia

After lengthy negotiations, Owen finally transported this Archaeopteryx fossil, along with more than 1,000 other specimens of organisms, back to the British Museum at the high price of 700 pounds. Quite ironically, the Germans lost this priceless treasure partly because another opponent of Darwin, the German palaeontologist J. Andreas Wagner, went around Germany claiming that this specimen was not a transitional bird fossil and had no significant value, soGerman circles did not make a full effort to recover it。

Owen had already lost

Owen obtained this Archaeopteryx fossil, later calledthe "London specimen,"and immediately began research, publishing a detailed study report in 1863 and naming it A. macrura, concluding it was merely a peculiar bird. Although Owen deliberately concealed things - for example, he ignored the presence of teeth on the jaw fragments of the London specimen and insisted that an Archaeopteryx beak would be found in the future - he still could not avoid the fact that the specimen had an abundance of dinosaur features.

Comparison of the forelimb of Deinonychus (left) and the forelimb of Archaeopteryx (right). Image: John Conway / wikimedia

In 1866, in the fourth edition of On the Origin of Species, Darwin could not hide his excitement and wrote these words -

All birds were once thought to have appeared suddenly after the Eocene; but we now know that Professor Owen, with his authority, confirmed that birds were already active during the "Upper Greensand" deposition period (about 75 million years ago); yet recently, in the limestone of Solnhofen, a strange Archaeopteryx was discovered, dragging a tail like a lizard's but with every joint covered in feathers, and with wings bearing freely movable claws; nothing could more strongly convince one that our knowledge of the former inhabitants of this world remains pitifully poor.

No matter how much they crossed swords, Owen, clinging to erroneous views, lost this round.

The story told by Archaeopteryx

Yet the Germans still possessed the limestone quarries of Solnhofen. In 1874,a secondArchaeopteryx skeletal fossil was discovered at Blumenberg by the farmer Jakob Niemeyer. This specimen was extremely complete,preserving a skull with teeth. To get money to buy a dairy cow, Jakob sold the specimen in 1876, passing through two hands, to Ernst Otto Häberlein, son of Karl Häberlein.

The American Yale University researcher O. C. Marsh had also long coveted it, but in the end the German industrialist Ernst Werner von Siemens stepped in, bought the specimen for 20,000 marks, and donated it to the Berlin Natural History Museum. This specimen finally did not leave Germany, and so was later known asthe "Berlin specimen"。

The "Berlin specimen" was the first Archaeopteryx specimen with a complete skull. Image: H. Raab / wikimedia

In 1884, through the research of Wilhelm Dames, it was found that this more complete specimen differed from the London specimen, and to commemorate Siemens's contribution, it was named A. siemensii.

In the more than one hundred years since then, as time passed and the world changed greatly, new Archaeopteryx fossils were discovered one after another in the Solnhofen limestone region, but they remained extremely rare. As of 2018,a total of 12 had been announced, and the process of discovering each specimen since then has been filled withinteresting stories. For example, in 1970, the famous American palaeontologist J. Ostrom, who studied ancient birds, discovered that a specimen once identified by Meyer in 1857 as a pterosaur actually had faint feather impressions, and he determined that it was in fact the earliest-discovered Archaeopteryx fossil; the third skeletal specimen, the Maxberg specimen, discovered in 1958, was found to have been lost after its owner Eduard Opitsch died in 1991, possibly stolen, and its whereabouts remain unknown to this day.

Some "Archaeopteryx" specimens and restorations compared in size with a human. Image: Jaime Headden & F. Spindler / wikimedia; Chinese localization: Species Calendar

Do you still remember that feather from the beginning? It was once theholotypeof the scientific name Archaeopteryx A. lithographica - in taxonomic research, the publisher of a name must designate a specimen as the "representative" corresponding to that name, and this is the holotype.

However, in 1996, researchers concluded that thisspecimen of the first feather was very likely not ArchaeopteryxA. lithographica, but came from another undiscovered theropod dinosaur or bird. After prolonged debate, on October 3, 2011, the London specimen was redesignated as the neotype for the name Archaeopteryx A. lithographica, and Owen's A. macrura thus became a synonym and was no longer recognized.

Amid all this, the loves and hatreds of taxonomists are hard to sum up in a single word.

From dinosaurs to birds

Back then, while Owen was holding up a lantern to find fault with Darwin, the man known as "Darwin's Bulldog,"Huxley(Thomas Henry Huxley), was not idle. After carefully studying the London specimen, he not only refuted Owen's concealments and omissions, but also put forward a view that was astonishing at the time:birds very likely originated from dinosaurs. This meant that dinosaurs had not gone completely extinct; at least one branch had lived on alongside humans all along.

Huxley was called "Darwin's Bulldog"; to counter Owen's theories, he pointed out that the brain anatomy of humans and gorillas is similar. Image: Lock & Whitfield / wikimedia

Huxley of course did not speak without evidence. Although the Archaeopteryx skeleton shares identical or similar features with birds - it has feathers and a furcula, partially fused carpal bones, a first toe of the hind limb opposed to the other toes (good for grasping but not long enough), and so on - the vast majority of its features, such as the extremely long caudal vertebrae, the tongue-shaped scapula, the absence of a bird beak, the presence of teeth, and the separate metatarsals, are allcloser to theropod dinosaurs. In fact, the Archaeopteryx "Solnhofen specimen," described in 1988, was initially thought by amateur collectors to belong to the genus Compsognathus.

Compared with modern birds (right), Archaeopteryx (left) had much longer caudal vertebrae. Image: wikimedia

Even so, living birds still look far too different from dinosaurs and other reptiles. In 1926, the Danish biologist Gerhard Heilmann publishedThe Origin of Birds, arguing on the basis that dinosaurs lacked a furcula that birds were unrelated to dinosaurs, holding that the similarities between Archaeopteryx and dinosaurs came from convergent evolution, and that birds originated from the Thecodontia.

This bookinfluenced views on the origin of birds throughout the first half of the 20th century, and Huxley's view fell silent. It was not until 1964 that the aforementioned palaeontologist Ostrom once again took up the bird-dinosaur origin view based on the newly discovered Deinonychus antirrhopus, and by using morphological phylogenetic trees, closely linked birds and dinosaurs once more.

The revolutionary discoveries came from the East. From 1994 onward,a large number of fossils of ancient birds and feathered dinosaurs were discovered in western Liaoning, China- Sinosauropteryx, Confuciusornis, Jeholornis, Anchiornis, Microraptor, and Xiaotingia zhengi.

Fossil and restoration of Sinosauropteryx. Image: Laikayiu / Inner Mongolia Museum; Robert Nicholls / wikimedia

These discoveries not only completely changed the academic understanding of the origin of birds, but alsoupdated people's conception of dinosaurs- dinosaurs could have feathers, could be warm-blooded, could build nests, could raise young; agile, running dinosaurs replaced the monster image we saw in old science fiction films of creatures lying on the ground with stiff tails. This was in some sense a continuation of the "Dinosaur Renaissance" led by the American palaeontologist Robert Thomas Bakker in the 1960s.

Today, we can finally regard birds with considerable certainty as one branch of dinosaurs; the traditionally extinct "dinosaurs" have become a paraphyletic group, and the more appropriate term is"non-avian dinosaurs,"while the definition of birds has also been updated to "the most recent common ancestor of Archaeopteryx and the sparrow, and all its descendants."

From dinosaur, to bird. Image: uga.edu

In the more than 150 years from the discovery of the Archaeopteryx feather fossil to today, human society has undergone several upheavals. In 1867, a boy named Wilbur Wright was born in Indiana, USA; in 1903, the Wright brothers invented the airplane, and humanity achieved powered flight for the first time -

150 million years after Archaeopteryx grew asymmetrical feathers and skimmed over the surface of a lagoon, another terrestrial vertebrate took its first step toward the blue sky and the starry heavens.

This article is the 242nd article of the 4th year of Species Calendar, from Species Calendar author @Zhong Shushu.