Tuesday 6 November 2018

Archaeopteryx albersdoerferi: The Phantom Urvögel described.

The first Archaeopterygid Bird, or Urvögel, Archaeopteryx lithographica, was described from the Solnhofen Limestone of Bavaria in 1861, and immediately recognised as an ancestral Bird, which presumably lived shortly after the split between Birds and non-Avian Dinosaurs. Since this time a series of further specimens have been described from the Solnhofen Limestone, which are variously regarded as four separate species of Archaeopterygid (Archaeopteryx lithographica, Archaeopteryx siemensii, Archaeopteryx bavarica, and Wellnhoferia grandis), different growth stages of the same species (this is not unreasonable, modern Birds reach their full size before attempting to fly, so there is a clear distinction between chicks and adults, but Mesozoic Birds are known to have taken to the wing long before reaching full size), or some combination of the two. In the early 1990s a private collector found a specimen in a limestone bed belonging to the Mörnsheim Formation at a quarry near Daiting in Bavaria which was initially thought to be a Pterosaur, and which changed hands several times before being recognised as an Archaeopterygid Bird. Unfortunately, the collector who owned the specimen at this time was reluctant to part with it, nor make it available for examination by the scientific community, gaining the specimen the nickname ‘The Phantom’, due to its status as an unknown Archaeopterygid.

In a paper published in the journal Historical Biology on 24 October 2018, Martin Kundrát of the Center for Interdisciplinary Biosciences at the University of Pavol Jozef Šafárik, and the Department of Organismal Biology at Uppsala University, John Nudds of the School of Earth and Environmental Sciences at the University of Manchester, Benjamin Kear of the Museum of Evolution at Uppsala University, Junchang Lü of the Key Laboratory of Stratigraphy and Paleontology of the Chinese Academy of Geological Sciences, and Per Ahlberg, also of the Department of Organismal Biology at Uppsala University, formally describe the Daiting Archaeopterygid as a new species.

The Mörnsheim Formation overlies the Solnhofen Limestone and is slightly younger, though still Late Jurassic; the layer that produced the Daiting Archaeopterygid is about 400 000 years younger that the Solnhofen specimens. Like the Solnhofen Limestone, the Mörnsheim Formation was laid down in a lagoon between a reef and the shore, but beyond this the conditions appear to have somewhat different, with the Solnhofen Limestone forming in a hypersaline environment similar to the Dead Sea, where nothing lived but anything that fell in was likely to be excellently preserved, whereas the Mörnsheim deposits were formed in a more open system with connections to the sea, as shown by numerous Fish and Cephalopod fossils, and therefore rather less perfect preservation.

The Daiting Archaeopterygid is formally described under the name Archaeopteryx albersdoerferi, in honour of Raimund Albersdörfer, the German palaeontologist who obtained the specimen in 2009, and made the specimen available to scientists, offering it on long-term loan to the Bavarian State Collection of Paleontology and Geology in Munich, and voluntarily entering into a contract not to sell the specimen to any non-public buyer. The specimen comprises a strongly compressed partial skeleton, including the skull and mandible. This varies from other previously described Archaeopterygids in a number of ways, but importantly it is smaller than any previously described specimen, and at least as mature as the largest, ruling out the possibility that it could be a more juvenile form of the same species.

Archaeopteryx albersdoerferi from the Upper Jurassic Mörnsheim Formation (Lower Tithonian) of Germany (Bavaria). The type specimen in natural light (a) and UV light (b); note asterisk showing position of putative integumentary imprints preserved inside the limestone. Abbreviations: crf, craniofacial region of skull; ?fi, putative proximal part of fibula; fu, furcula; lco, left coracoid; lh, left humerus; llj, left lower jaw; lm, left manus; lr, left radius; lsc, left scapula; lrl, putative left radiale; lu, left ulna; nc, neurocranial region of skull; rco, right coracoid; rfe, proximal part of right femur; rh, right humerus; rsc, right scapula; ?, unknown element/s. Kundrát et al (2018). 

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