Have you heard? There is a new Archaeopteryx in town. Number 12, to be exact. Technically, this specimen has been around since 2010, but was only formally described three weeks ago, thereby making up for the tragic loss of the Haarlem specimen (now renamed as Ostromia crassipes) last year.

Archaeopteryx has since long formed a central piece in evolutionary debates. At the time of its discovery, it was the first Really Old Bird ever found. Moreover, its discovery in 1861 came just a few years after Darwin’s magnum opus On the Origin of Species, in which Darwin argued that one species could evolve into another. Archaeopteryx with its dapper mix of both reptilian and avian features was seen as a true transitional fossil, proving Darwin’s theory. Upon hearing of its discovery, in a letter from the Scottish palaeontologist Hugh Falconer dated 3 January 1863, Darwin replied to express his interest and excitement:

I particularly wish to hear about the wondrous Bird; the case has delighted me, because no group is so isolated as Birds”

Archaeopteryx specimens are extremely rare. Until recently, only 11 specimens were known to science, all found in a small area north of Munich in Germany. At the time of deposit, around 150m years ago, this area constituted a tropical lagoon, and its soft sandy sea floor proved to be a perfect environment for the exceptional preservation of delicate features, such as small bone details and feathers (the technical term for such an area is a Konservat Lagerstätte).

The new specimen represents a largely intact skeleton lying on its left side. The stone slab it is preserved in was found in a number of pieces, resulting in some bone loss along the vertebral column. No feathers are preserved. The skull has been dislocated from the body and rotated downwards and back, giving the specimen a characteristic look that is very different from the classical death pose with the head and neck arching backwards towards the tail. The stone slab also contains a beautiful ammonite, for those who prefer their fossils spineless.

Facebook Twitter Pinterest The specimen under UV light, which enhances visibility of detail, showing its distinct headpose (downwards and backwards). Photograph: Rauhut, O.W.M., Foth, C. & Tischlinger, H./https://doi.org/10.7717/peerj.4191/fig-5

It was found by a private collector in a quarry that is open to the public near the village of Schamhaupten, in the summer of 2010. Its existence was known to the Old Bird In-crowd, but it had yet to be formally described. The collection of fossils by private individuals and commercial collectors has been the topic of much debate in the palaeontology community, with some arguing that private and commercial collection ruins delicate fossil localities, removes fossil specimens from their context and prevents proper study. Recently, Germany even installed a Cultural Property Protection Act that limits the collecting of and trade in fossils with the purpose to prevent often vulnerable natural history resources being overexploited or vandalised.

To collect or not to collect: are fossil-hunting laws hurting science? Read more

The description of this privately collected Archaeopteryx specimen was published last week, and not only provides it new information about this iconic fossil, it is also a great example of how professional palaeontologists and private collectors can work together and do great science. After the private collector realised that he had a potentially very rare specimen in his hands, he alerted the authors of the study, who then took great care to establish the geological context of the specimen. In addition, the finder loaned the specimen to the authors of the study for further scientific study and it is now on public display at the Dinosaurier Freiluftmuseum Altmühltal in Denkendorf, Bayern. There, it is now available for everyone to see. This is what a successful collaboration between professional palaeontologists and private collectors can look like.

Although Archaeopteryx specimens have been thoroughly studied since the initial discovery of the genus, the new specimen shows valuable new anatomical details, such as the close association of the jugal and postorbital bones (two bones that form part of the orbit) and the convexity of the posterior articular surface of the cervical vertebrae. However, more Archaeopteryx specimens, with various states of preservation and fragmentation became known over the years, scientists started to observe variation in skeletal characters within the group of specimens collectively referred to as Archaeopteryx. In parallel, our knowledge of the anatomy of small avian and non-avian theropods has increased tremendously over the last decades. It is time to ask the million dollar question: what, if anything, is an Archaeopteryx?

For instance, it had been suggested that Archaeopteryx can be defined based on the absence of an opening in the mandible (Elzanowski, 2002), but such a mandibular opening is also lacking in some theropod dinosaurs. In addition, Archaeopteryx appears to have had only eight to nine teeth in its upper jaw (maxillary) bone, which is rather low for theropod dinosaurs, but similar numbers of maxillary teeth are present in species of Dromaeosaurus. Possible characteristic features of Archaeopteryx include the shape of the opening for the trigeminal nerve in the skull, the shape of the jugal bone and the number of cervical and dorsal vertebrae, but the presence and extent of these features in other theropod dinosaurs is not always known and deserves further study.

Facebook Twitter Pinterest View of the new specimen’s upper jaw under UV light (A) and interpretative drawing (B). The maxilla (m in drawing) bears 9 teeth, considered a defining character for Archaeopteryx by the authors . Scale bar 1 cm. Photograph: Rauhut, O.W.M., Foth, C., & Tischlinger, H./https://doi.org/10.7717/peerj.4191/fig-8

With this new specimen, the authors conclude that an Archaeopteryx cannot be characterized by a single, unique feature, but rather by a set of features that together form a unique combination. This “emended differential diagnosis” is an updated description that separates Archaeopteryx from all other theropod taxa. Many of the specimens show several of the features named in this new diagnosis, such as the Berlin, Solnhofen, Munich and Eichstätt specimens, and these can confidently be referred to as Archaeopteryx. More problematic are those specimens that do not preserve any of the skeletal features described in the emended differential diagnosis. These specimens include the “chicken wing” specimen, constituting only a right wing, and the Maxberg specimen, for which only casts and a description are available as the original is lost. These specimens are now only tentatively referred to as Archaeopteryx.

Of the Twelve Specimens Once Known as Archaeopteryx (SPOKA), only nine continue to carry that name. At the end of the day, we can’t all be winners. But even within that group of nine specimens, no two Archaeopteryx look the same. Rauhut and colleagues report that there is significant variation in the size, shape, spacing and orientation of the teeth, as well as differences in body size between the different specimens. This could be an ontogenetic pattern, with larger individuals representing adults with more developed dentition. Alternatively, as the Solnhofen Basin constituted a tropical island archipelago during the Late Jurassic, these differences in body size and dentition could be interpreted as island adaptations. Similarly to today’s Galápagos finches, different populations of Archaeopteryx may have adapted to different insular environments. And back to Darwin we are.

Have we lost an Archaeopteryx but gained a new species of theropod dinosaur? Read more

References

Elzanowski, A., 2002. Archaeopterygidae (Upper Jurassic of Germany) In: Chiappe LM, Witmer LM, eds. Mesozoic Birds. Above the Heads of Dinosaurs. Berkeley: University of California Press. 129-159



Foth C, Rauhut OWM. 2017. Re-evaluation of the Haarlem Archaeopteryx and the radiation of maniraptoran theropod dinosaurs. BMC Evolutionary Biology 17:236

Rauhut, O.W.M., et al., 2018. The oldest Archaeopteryx (Theropoda: Avialiae): a new specimen from the Kimmeridgian/Tithonian boundary of Schamhaupten, Bavaria. PeerJ 6:e4191.