After going unnoticed for over 140 years, a total of eight 2 cm long hatchlings were found in the fossils of the Berlin and Teylers specimens of Archaeopteryx.
The upper body of a winged and beaked animal with fossilized bones extends from the ventral side of the Berlin specimen’s thorax. Among its very small bones are elongated scapulae and hatchet-like coracoids, as seen in Archaeopteryx.
Three other beaked animals in its vicinity show surface morphology preservation, one of which is visible from head to tail, all fossilized in a clinging pose, demonstrating that Archaeopteryx hatchlings displayed clinging behavior.
Two similar animals were identified next to each other in the Teylers specimen’s fossil. One of these fossilized after dying while it was hatching from its egg. Its third wing finger crosses underneath the second as in Archaeopteryx. The other shows surface morphology preservation of the torso, head and part of one forelimb (including a finger claw), trachea, tail feathers, and structures that almost certainly correspond to both erupted and non-erupted teeth.
A disarticulated wing that is similar to that observed in one of the Teylers hatchlings was discovered in the fossil of the isolated Archaeopteryx feather, representing the first association between this isolated feather and Archaeopteryx animals.
Together with the descriptions of non-rigid eggs in Volume I and egg littering in Volume III, the still-lives of the Berlin and Teylers ground nests brought forward here enrich Archaeopteryx’s rediscovery as a nesting animal and help propel a new era of more detailed fossil analysis that may bring great contributions to evolutionary biology.
All Archaeopteryx specimens were believed to represent the remains of floating carcasses that sunk to the bottom of Jurassic lagoons in an area called Solnhofen, in Germany.
However, two specimens of this extinct animal, known as the Berlin and Teylers specimens, are shown here to lie atop of radiodense and non-rigid fossilized eggs averaging 1,3 cm in their longer axis, some containing directly visible fetuses with surface morphology preservation.
One of such egg-enclosed fetuses shows a toothed beak.
X-ray evidence of a similar egg in a third specimen – the mysteriously disappeared Maxberg specimen for which X-rays are available – is also presented.
These eggs are in the size range of Archaeopteryx’s pelvic opening and also of hatchlings described in Volume II of this book.
This first volume exposes the existence of non-rigid eggs in the bird lineage, raising important questions about the origin of birds and opening new possibilities for research in reproduction (the process by which living organisms give rise to others), development (the process by which new adult organisms are formed from single cells) and evolution (the process by which heritable features progress from generation to generation).
Introductory note on the most famous fossil in the world and its rediscovery
The Berlin Archaeopteryx is the most famous fossil in the world and the icon of evolution.
It is on display at the Naturkundemuseum Berlin (Berlin’s Museum of Natural History).
The fossil is in reality composed of two stone plates (slabs) that separated from each other when the fossilized animal was first exposed. The main slab is the one that is universally known and exhibited to the public whereas its counterslab is well guarded in the Collection Room of the same museum.
The main slab is the one that contains the fossilized skeleton of the animal. In turn, the counterslab contains the fossilized structures of the wing feathers in inverted position relative to the main slab.
According to the theory of evolution, species evolved on our planet from variants of previous ones by combining characteristics inherited from preexisting animals with newly developed ones that were retained and transmitted to offspring.
Archaeopteryx combines feathered wings and feet that resemble those of a bird with two characteristics we do not see in today’s birds: a toothed bony beak and a bony feathered tail.
The Berlin specimen of Archaeopteryx is the best preserved specimen of this species and the announcement of its discovery in 1877, shortly after the initial works on the theory of evolution were published, made it uniquely popular ever since.
The Rediscovery of Archaeopteryx is intimately related with the theory of evolution and one of its main achievements: the tree of life – phylogeny of life –, which is the path followed by life forms until they reached their current characteristics.
The Teylers specimen will also be rediscovered in this book.
This book is based mostly on discoveries made in the Berlin specimen of Archaeopteryx but other specimens were studied too, which will also be briefly introduced here, in addition to the isolated Archaeopteryx feather fossil from which the Archaeopteryx name (meaning “old wing”) is derived. All these fossils were found in the same German geological unit – the approximately 155 million year old Solnhofen formation – from the Jurassic period (200 to 145 million years ago).
Beyond its asymmetry, there are aspects of this feather’s morphology that would be relevant to its potential to allow the animal it derived from to fly. Namely, the ramifications of its shaft into barbs, of these into barbules and the existence of hooks between barbules. Documenting these successive ramifications would be relevant because they would give stability to the feather’s structure during movement through the air. In volume III evidence of these structural features in the isolated feather will be shown to an extent that, to my knowledge, is unprecedented.
Before this book no association had ever been established between the isolated feather fossil and the Archaeopteryx animal except for some characteristics in the structure of the isolated feather that are shared with the feathers of the fossilized Archaeopteryx animals.
In volume II of this book, which is dedicated to the description of the discovery of hatching animals and hatchlings in Archaeopteryx fossils, I will, for the first time, establish a direct relationship between the isolated feather and fossilized animals.
The Berlin specimen, announced in 1877, was the second of these animals to be announced, after the London specimen. But, in fact, another fossil – the Teylers specimen –, which resides in the Teylers museum in the Netherlands, was actually found first, in 1855.
The Teylers specimen will also be rediscovered in this book.
Interestingly, it will be the second time it is rediscovered because John Ostrom, the author at the root of the theory that birds derived from dinosaurs, realized that it corresponded to the fossilized remains of an Archaeopteryx at a time when it was believed to represent the remains of a pterosaur.
Archaeopteryx lived in the Jurassic period, about 155 million years ago1, in an archipelago that would have existed at the edge of the Tethys Sea, which is believed to have been situated between a northern and a southern supercontinent, at a time when the Atlantic Ocean had not yet separated the land masses that would become North America and Europe.
All the twelve known specimens of this animal were believed to have sunk into the bottom of marine lagoons in Jurassic Solnhofen because of the general characteristics of the stone sediment in the geological unit where they were found.
This implies that these animals would have drifted dead for a period of time before sinking, possibly following dragging from nearby land by rain water.
I revisited the Berlin specimen thinking that it might have died where it was found instead of having been dragged by rain waters into a lagoon where it floated and sank because of two reasons: (1) its skeleton is fully articulated and (2) its fossilized pose is reminiscent of that of a nesting bird if we look at the fossil from a different perspective than the one used for its display, by simply rotating it ninety degrees clockwise – as can be seen in A Paradigm Shift.
The research presented here on the main slab of the most famous fossil in the world was done on Mondays, when the Naturkundemuseum Berlin is closed to the general public.
The main slab of the fossil is so fragile that it is currently only accessible for research in its exhibition room.
What is more, all photography and microscopy sessions on the main slab of the fossil were performed while it was kept in its exhibition mount, inside the exhibition room dedicated to Archaeopteryx.
The need to keep the fossil in its exhibition mount required considerable attention during the stereomicroscopy sessions.
The research that will be presented here included an inspection of the fossil’s back surface, which involved opening the case that protects it, to see if eggs resided underneath the nesting animal.
The results of exploring the two slabs of the Berlin specimen’s fossil in search for eggs, embryos and fetuses will be presented in this book volume. Important findings in two other fossils of Archaeopteryx specimens will also be presented here: in the Teylers and in that of the mysteriously disappeared Maxberg specimen.
Hatchlings, some clinging to neighboring structures, will be described in Volume II and evidence of colonial nesting, very much like we can observe in bird colonies today, will be presented in Volume III. When I reach Volume V I will start elaborating on a new theory for the origin of birds.
This animal was believed to have lived and nested on trees but its eggs and nest had never been found.
The fact that it will be shown to be nesting on the ground will impact in our understanding of how feathers evolved from other structures, how wings evolved from the forelimbs of terrestrial animals and how flight came to exist.
To conduct this research, I had to travel and often bring along photographic equipment and my own stereomicroscope.
Those journeys were interspersed with data exploration anywhere I could sit to look at my computer for more than ten minutes.
I did this for over four years in addition to overseeing my company and now it is time to bring the resulting discoveries to you.
I strongly encourage the reader to visit the Berlin specimen some day and hope you will feel as if watching a living animal caught in a still-life.
Hopefully, its display position will be corrected by then so you can see it as it was before its death while nesting in Solnhofen.
Until then, I encourage you to delve into the details of its rediscovery.
Let’s find out more about this animal that lived on this planet, among others of its kind, over 150 million years ago, like we also do today.
It died protecting its eggs and children and they are hereby revealed in fossilized still lives as if for us to witness their tragic story.
“What you are claiming only happens once every fifty years. No, it happens once every hundred and fifty years, I responded.”
In Preface, The Rediscovery of Archaeopteryx (Volume I)
Ground breaking findings went unnoticed for over 140 years on the Mona Lisa of fossils despite its display before millions of visitors and scrutiny by generations of researchers.