Wednesday, January 23, 2019

Messel Bird Fossil offers unique feather preservation, and more

Messel Pit fossils—plant and animal life from roughly 50 million years ago, formed during the early Eocene Epoch of the Paleogene Period.

In that time, the fossil record of modern birds greatly improves, both in number of specimens and their completeness, providing a crucial window into the evolution of today’s birds.

The Messel Pit in Germany was rightfully declared a UNESCO World Heritage Site in 1995, due to its significance in geological and scientific importance.

Before becoming a UNESCO World Heritage Site, brown coal and later oil shale was actively mined at the pit from 1859. Commercial oil shale mining ceased in 1971, with plans for a landfill shortly thereafter.

Those plans thankfully never came to fruition, allowing local interests to purchase and secure the site.

In the few years between the end of mining and 1974, when the state began preparing the site for garbage disposal, amateur collectors were allowed to collect fossils. The amateurs developed the "transfer technique" that enabled them to preserve the fine details of small fossils, the method still employed in preserving the fossils today (source: Wikipedia).

Messel Fossil Transfer Method
Image Property of; http://www.senckenberg.de/root/index.
https://avianmusing.blogspot.com/
As a former collector myself, I am fortunate enough to still own a couple of these beautifully preserved Messel birds.

Here I report on one those birds, a bird as of now, not previously described.

The specimen features an assortment of feather types, as well as a complete skull, wing bones and a possible partial sternum. 

Unidentified Messel Bird Fossil
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/
To photograph the fossil, I employed both natural light and an LED Tracing Light Box. Photography equipment used included a Nikon Coolpix P900 camera and a Dino-Lite AM3111 0.3MP Digital Microscope.

In order to see finer details surrounding the skeleton, an LED Tracing Light Box was positioned under the fossil, illuminating the plumage before images were taken. 

Unidentified Messel Bird Fossil
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/
Plumage details.

Approximately six primaries are preserved near the skull, one with a certain asymmetric shape (narrower leading edge), indicating an aerodynamic function. The rachis on the flight feathers appear wide and stiff. 

Unidentified Messel Bird Fossil Wing
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/
At the base of these primary feathers lies what looks to be loosely arranged covert feathers. Did these coverts help smooth airflow over the wings? 

Unidentified Messel Bird Fossil Wing Coverts
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/
Feathers surrounding the top of the skull and neck collar (ruff) give the impression of being covered by hair-like filoplumes. Directly behind the skull feathers (top of skull) is a single body contour feather with symmetrical vanes. Its rachis is very thin and pliable. 

Unidentified Messel Bird Fossil Crown Feathers and Contour Feather.
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/
The Messel bird fossil also reveals a couple of uncommon body feathers that might be described as a semiplume, while others have the appearance of longer hair-like filoplumes. 

Unidentified Messel Bird Fossil Semiplume Feather.
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/ 
Unidentified Messel Bird Fossil Possible Filoplume Feather.
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/
One of the most intriguing, and oddly placed feathers on this fossil lies directly on top the wings flight feathers. The identification and original placement of this feather(s) still escapes me, however, what is truly curious is that it appears to preserve some sort of color pattern to it (black dots). 

Unidentified Messel Bird Fossil Feather with possible color pattern.
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/
Strangest of all feather preservation on this unidentified bird are the solid tips to the ends of some of the primaries and secondaries. Are these wide tips extensions of the feather’s rachis (rachis dominated)? Or are they highly fused barbs like we see at the ends of Cedar Waxwings (Bombycilla cedrorum) feathers? What purpose would this type of feather have to this ancient bird? 

Unidentified Messel Bird Fossil feather tip
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/
Unidentified Messel Bird Fossil feather tip
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/
Unidentified Messel Bird Fossil feather tip
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/
Unidentified Messel Bird Fossil feather tip
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/
Unidentified Messel Bird Fossil feather tip
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/

Aside from the waxwing feather, I have not found any other modern analog to compare this feature to, nor has the fossil record provided a clue.  

Cedar Waxwing (Bombycilla cedorum) feather tips.
Image Property of: Nature.org
https://avianmusing.blogspot.com/
What about the incomplete skeleton?

A partial sternum is tentatively identified based on its general shape, and proximity to the articulated wing bones. 

Unidentified Messel Bird Fossil possible sternum.
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/
The wing bones measure as follows; humerus 30mm, ulna 35mm, radius 32mm, carpometacarpus 20mm, phalanges of digit II 10mm.

The carpometacarpus also features an alular phalanx, with a splint-like alular claw perhaps flipped on its side (see cropped photo below).

Unidentified Messel Bird Fossil alular phalanx with possible claw.
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/
The skull is complete and articulated with the mandible. The head appears slightly smaller relative to the accompanying bone sizes. Skull of this bird measures 40mm. The beak alone measures 17mm. 

Unidentified Messel Bird Fossil Skull
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/
Closer inspection of the beak with a Dino-lite microscope brought to light a distinctively hooked tip, classically seen in extant raptors. In addition to the hooked tip, the fossil beak also appears to possess a few possible sensory pits (Herbst corpuscles). 

Unidentified Messel Bird Fossil hooked beak.
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/

Potential recognized species.

My initial choice of reference was Gerald Mayr’s book, Avian Evolution; The Fossil Record of Birds and its Paleobiological Significance (2017). Mayr provides a comprehensive look at the interrelationships and origin of crown group birds.

After numerous side-by-side comparisons of skulls both online and in text, I felt pretty certain that my Messel bird placed somewhere within the Early Paleogene parrot-like birds, more specifically, close to the halcyornithid Cyrilavis colburnorum. 

Cyrilavis colburnorum.
Image from Ksepka, Clark and Grande (2011)
https://avianmusing.blogspot.com/
Cyrilavis, from the North American Green River Formation, boast a very similar looking skull to my fossil bird. Its measurements however were slightly larger, not only in skull and beak length, but in every other skeletal component available for comparison. These figures were obtained through the research paper; Stem Parrots (Aves, Halcyornithidae) from the Green River Formation and a Combined Phylogeny of Pan-Psittaciformes, (Ksepka, Clark and Grande 2011).

I returned back to Avian Evolution; The Fossil Record of Birds and its Paleobiological Significance, discovering further examples (fossil images) of early Psittacopasseres, including the messelasturids Tynskya, also from the Green River Formation, and Messelastur from the same Messel fossil site. 

Skeletons of early Eocene representatives of Psittacopasseres.
Image from Avian Evolution; Gerald Mayr; 2017
https://avianmusing.blogspot.com/
Messelastur (according to Mayr) retained some key features, as opposed to other Psittacopasseres, which involved a very deep lower jaw and raptor-like pedal claws. The lower jaw of my Messel fossil appears deeper than Cyrilavis, but in no way would I have the expertise to claim “very much deeper”.

Mayr goes on to state that these similarities to raptorial birds are of particular interest because analyses of molecular data either identified falcons as the closest extant relatives of Psittacopasseres or supported a sister group relationship between parrots and owls.

Does the shorter, hook-tipped, raptor-like bill of my fossil indicate another trait of a messelaturid?

To be clear, my personal analysis of this Messel bird fossil has in no way scientific credibility behind it. This was conducted out of pure joy and respect for the fossil. My identification of feather types, bones, sensory pits, bill morphology and actual species may be completely wrong. Your thoughts and opinions are just as important, and may differ from my own.

Let’s continue to enjoy this remarkable bird by visualizing a setting which places this hypothetical carnivorous parrot on the ground, searching for invertebrates or small rodents. Its cursorial habits naturally select stiff feather tips to help protect the flight feathers during ground foraging, but are also co-opted for use in startling prey.

A prey item scampers to the underbrush, but is closely pursued by this low-flying predatory bird. Frustrated, the bird pokes its protected feathered head into the leaf litter hoping to sense movement.

The prey item bolts, but is grabbed by this bird’s raptor-like pedal claws, and quickly dispatched with its hook-tipped bill.      

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