Tuesday, October 24, 2017

Ancient preen oil: Researchers discover 48-million-year-old lipids in a fossil bird

Another ancient bird discovery brought to you by; www.sciencedaily.com

Date: October 18, 2017

Source: Senckenberg Research Institute and Natural History Museum

As a rule, soft parts do not withstand the ravages of time; hence, the majority of vertebrate fossils consist only of bones. Under these circumstances, a new discovery from the UNESCO World Heritage Site "Messel Pit" near Darmstadt in Germany comes as an even bigger surprise: a 48-million-year old skin gland from a bird, containing lipids of the same age. The oldest lipids ever recorded in a fossil vertebrate were used by the bird to preen its plumage. The study is now published in the scientific journal Royal Society Proceedings B.

Credit: Copyright: Sven Traenkner/ Senckenberg

Birds spend a large amount of time preening their plumage. This makes sense, since the set of feathers adds to each bird's particular appearance, isolates and enables them to fly. In this preening ritual, the uropygial gland, located at the lower end of the bird's back, plays an important role. It produces an oily secretion used by the birds to grease their plumage in order to render it smoother and water-repellent.

Together with a group of international colleagues, Dr. Gerald Mayr, head of the Ornithology Section at the Senckenberg Research Institute, now discovered the oldest occurrence of such preen oils in birds known to date. With an age of 48 million years, this ancient preen oil constitutes a small scientific sensation. "The discovery is one of the most astonishing examples of soft part preservation in animals. It is extremely rare for something like this to be preserved for such a long time," says Mayr.

The organic materials that the soft parts consist of usually decompose within decades, or even just a few years. Several-million-year-old feathers and fur remnants are only known from a small number of fossil sites to date, including the oxygen-poor oil shale deposits of the Messel fossil site. This site also yielded the uropygial gland and the contained lipids examined in the course of this study. 

"As shown by our detailed chemical analysis, the lipids have kept their original chemical composition, at least in part, over a span of 48 million years. The long-chain hydrocarbon compounds from the fossil remains of the uropygial gland can clearly be differentiated from the oil shale surrounding the fossil," explains Mayr. The analysis offers proof that the fossil artifact constitutes one of the oldest preserved uropygial glands -- a suspicion which had already been suggested by the arrangement at the fossil bird skeleton, albeit not finally confirmed.

To date, it is not clear why the lipids from the uropygial gland were able to survive for so long. It is possible that hey hardened into nore decomposition-resistant waxes under exclusion of oxygen. In addition, the researchers assume that one of the properties of the preen oil played a role that is still shown by modern birds today -- its antibacterial components. They may have been the reason that after the bird's death only few bacteria were able to settle in, preventing the full-on decomposition.

For Mayr and his colleagues, the discovery constitutes a milestone for paleontologists. "The 40-million-year-old lipids demonstrate the potential extent of preservation possible under favorable conditions -- not just bones and hairs and feathers, as previously assumed. If we find more of these lipids, we will be able to better reconstruct the lifestyle of these animals. For example, it would be interesting to find out whether feathered dinosaurs, as the ancestors of birds, already possessed uropygial glands and preened their plumages," adds Jakob Vinther of the University of Bristol, one of the study's co-authors, in closing.

Friday, October 20, 2017

Bird Mummy

Like falling from the sky, a good bird story can sometimes come out of nowhere. Little did I know that this “nowhere”, would happen to fall right out of my mothers-in-law chimney, and straight into my hands. 

Sitting at the bottom of an old paper bag was the remarkably well-preserved and complete remains of a European Starling. Not what you would call your average bird carcass, this one appeared mummified, its structure maintained without the full decomposition.

Desiccated European Starling  
Photo Credit: Paul Cianfaglione
Desiccated European Starling
Photo Credit: Paul Cianfaglione

Another term used for this occurrence is called desiccation; the starling was preserved by a lack of air (dehydrated), so that its recovered body did not decay further when kept in the chimneys cool, dry conditions. 

As opposed to well-known Egyptian mummies, natural desiccation is a very unique and rare form of preservation. 

I have only come across a few birds preserved in this fashion including a Scarlet Tanager, which I accidentally preserved while holding it temporarily in a box.

Desiccated Scarlet Tanager 
Photo Credit: Paul Cianfaglione
One of the more important desiccated bird specimens is that of the moa, in particular, Megalapteryx didinus. Several remarkable examples of moa remains have been found which exhibit soft tissues (muscle, skin, feathers), that were preserved through desiccation when the bird died in a naturally dry site (for example, a cave with a constant dry breeze blowing through it). Most of these specimens have been found in the semi-arid Central Otago region, the driest part of New Zealand (Source:Wikipedia).

Desiccated Moa Foot
Image Credit: https://www.theepochtimes.com/assets/uploads/2014/11/30/Moa_foot.jpg
Desiccated Moa
Image Credit: https://www.researchgate.net/figure/232985591_fig4_Figure-5-Desiccated-type-specimen-of-upland-moa-Megalapteryx-didinus-Owen-1883
Lastly, on a recent trip up to the Beneski Museum of Natural History in Amherst Massachusetts, I recall photographing an unusual specimen that I have never seen put on a display before. Described on its placard as a bird in guano (looks like a duck to me), this Holocene aged specimen comes from Guanape Island, Peru. It goes on to mention that following death, this bird was buried in bird excrement or guano and was preserved.

Duck Preserved in Guano
Photo Credit: Paul Cianfaglione

Tuesday, October 17, 2017

Messelornis cristata; a terrestrial bird with only moderate flight capabilities?

Fossils from the Early to Middle Eocene of Europe and North America indicate that some 50 to 55 million years ago, the neornithine radiation had given rise to most major lineages of living birds (Mayr 2009). Just recently has this evidence been available to us, the general public, in the way of two new publications; Gerald Mayr’s Paleogene Fossil Birds (2009), and Avian Evolution; The Fossil Record of Birds and its Paleobiological Significance (2017). Both provide for the first time a detailed look at the Paleogene fossil record of birds, as well as an introduction to the world’s most important known fossil localities. 

These locations include the Paleocene of Mont de Berru France, the Middle Eocene deposits of the Green River Formation USA, the Upper Eocene and Lower Oligocene of Quercy, again of France, and the Messel oil shale of Germany.  

While many of the fossils covered in these accounts represent extinct taxa, which exhibit unusual morphology not found in modern birds, others are strikingly familiar. For example, the partial skeleton of the frogmouth Masillapodargus from the early Eocene of Messel in Germany and extant Podargus are shown side-by-side, both displaying the same characteristic bill shape and postcranial anatomy. 

Another startling fossil is that of the swift Scaniacypselus (Apodidae). This small-sized bird from the Eocene of Europe preserves feathers that shows that it was similar to modern swifts. However, Scaniacypselus is a stem group representative of the Apodidae and differs from extant swifts in plesiomorphic features of the humerus, as well as in a proportionally longer ulna. This indicates that it was less aerial than its living relatives, some of which visit firm ground only during the breeding period and even sleep in flight (Mayr 2015). 

Photo property of https://www.google.com/culturalinstitute/beta/exhibit/vQISvdIHAVTSIQ
One of the more intriguing birds from the German oil shales is Messelornis cristata, otherwise known as the “Messel Rail”. It is by far the most abundant bird found, represented by over five hundred skeletons. For the record, I am one of a few collectors out there who have in their possession a fully articulated specimen of Messelornis cristata. 

Messelornis cristata
Photo Credit: Paul Cianfaglione
That being said, I have never really sat down and actually studied the fossil myself, relying instead on information brought forth by prominent researchers. It is often described as a terrestrial bird (only moderate flight capabilities) with long legs and short wings (Mayr 2009; Bertelli 2011), approximately the size of a Common Moorhen (Gallinula chloropus). Noted also is its short, holorhinal beak and long tail feathers (Hesse 1990). 

Others who have actually examined the fossil will happily agree with this assessment, especially when it comes to the bird’s stilt-like legs. However, the portrayal of the rails shorter wings has always been a source of confusion for me, appearing (on specimens other than mine) in my opinion, to be long enough for better than average flight.  

Messelornis cristata wing
Photo Credit: Paul Cianfaglione
Remember the proportionally longer ulna of the fossil Scaniacypselus, an indication that it was less aerial than its living relatives. This had me considering the taking of my own Messel Rail measurements. How would the length of the bones measure up to other living species?

But before doing that, I would to share with you some of my fossils key features.  

The fossil has a nicely preserved skull measuring 46mm. Also preserved around the eye is the scerlotic ring, the opening measuring 7mm. Most of the sternum is present along with a shallow portion of the keel, this is roughly 26mm in length. Both coracoids are fully exposed (medial aspect?). Between the two coracoids lies a portion of the furcula called the scapus claviculae, which appears to be U-shaped and robust. The feet show that the phalanges decrease length distally, indicative of terrestrial adaptation. 

Messelornis cristata skull
Photo Credit: Paul Cianfaglione
Messelornis cristata sternum with partial keel
Photo Credit: Paul Cianfaglione
Messelornis cristata foot
Photo Credit: Paul Cianfaglione
The wing and hindlimb measurements provided below aim to create a size and structural comparison between the Messel Rail and three extant species. These species include the Common Moorhen (Gallinula chloropus), which has been used in scientific papers and books as a size reference. The King Rail (Rallus elegans), a water-bird whose structure is sometimes used by paleoartists to depict the Messel Rail.

Messelornis cristata paleoart
Image property of https://paleoaeolos.deviantart.com/art/Messelornis-cristata-48950746
The Upland Sandpiper (Bartramia longicauda), chosen specially for its overall similarity in bone length to Messelornis cristata. Bone measurements taken from Avian Osteology, by B. Miles Gilbert, Howard G. Savage, and Larry Martin (1981). 

                                         Humerus      Ulna         Radius       Cmt  

Messelornis cristata           37mm        33mm        32mm       21mm

Common Moorhen              55mm        45mm        42mm        34mm

King Rail                            59mm        50mm        45mm        33mm

Upland Sandpiper             47mm        50mm        48mm        28mm

                                           Femur        Tibiotarsus      Tmt       

Messelornis cristata           35mm           62mm          53mm             

Common Moorhen              52mm           91mm          56mm             

King Rail                            59mm           91mm          59mm             

Upland Sandpiper             35mm           63mm          55mm            

The numbers at first glance seem typical of what we would expect from these species, but they don't tell us the full story. The Upland Sandpipers humerus to ulna ratio confirms the bird’s known ability to migrate 10,000 km each year, from Alaska to South America. The Messel Rail, King Rail and Common Moorhen all exhibit humerus/ulna ratios that suggests less proficiency in the air. The moorhen in particular shows the greatest size discrepancy between the bones, however, despite having short rounded wings, moorhens are fully capable of migrating over 2,000 km from some of their northern breeding localities. 

Upland Sandpiper
Photo property of http://oregonconservationstrategy.org/strategy-species/upland-sandpiper/
Common Moorhen
Photo Credit: Paul Cianfaglione
Can these measurements and fossils tell us more about Messelornis cristata? For one, the overall size and structure of the bird was probably more likened to that of an Upland Sandpiper, rather than a moorhen. In spite of its proportionally longer ulna and shorter wings, there are some derived features that may point to stronger, more explosive flight capabilities. The list includes a large sternum and keel, furcula, elongated coracoids with procoracoid process (seen on other Messel Rail fossils) suggesting the presence of a triosseal canal, decent sized deltopectoral crest on humerus for attachment of flight muscles and large tail feathers which aid in the generation of both thrust and lift, thereby enabling flight.

In addition to this information, I also thought it was important to take into account what type of ecosystem the Messel Rail lived in. 

The Eocene was a warm period in Earth’s history, and the climate and habitat of what is now Messel would have somewhat resembled today’s tropical rain forests. The lake would have been surrounded by heavily forested areas, and animals were living in the lake, in the trees, and on the forest floor (Source: gemmabenevento).

Messel environment 47 million years ago
Photo property of gemmabenevento

This led me to wonder about the Messel Rails lifestyle; how it ate, what it fed on, did it move around much and how it interacted with other animals in the environment. 

The diversity in Messel’s fauna is staggering. There are thousands of delicate insect fossils, some of them even with their coloration preserved. Fish fossils are extremely abundant, and fossil reptiles include crocodiles and alligators, snakes and turtles. At the time of deposition of Messel’s fossil fauna, the “Age of Mammals” was in full swing and the first members of modern groups appear during this time.

Researchers have described a skeleton of Messelornis cristata which is preserved with the remains of a percoid fish Rhenanoperca minuta in the area of the esophagus. The gut contents of other specimens consist of seeds. This type of varied diet suggests that it may have shuttled back-and-forth to different feeding habitats. What habitats, other than shallow waters is still unclear to me, but with long legs, small feet and a rather short bill, the Messel Rail was most certainly a successful terrestrial bird. 

The success of this abundant bird could also be attributed to its ability to quickly flee, or nest away from potential predators. Species such as Buxolestes, a somewhat modern-day otter, could have incorporated rails eggs and chicks into its mainly piscivorous diet. Crocodiles and lakeside snakes may well have targeted feeding adults. Another small mammalian predator, Leptictidium, is also found in the Messel oil shale. Fossil remains of this animal have been found with stomach contents, revealing that they ate a varied diet of insects, lizards, and plants.

Some scientists also believe that they can determine when a species of bird hunted based on the size of their scleral ring opening and eye socket. According to my own fossil of Messelornis cristata, the 7mm opening of its scerlotic ring may prove that the rail had crepuscular or nocturnal foraging habits, which would have enabled the rail to feed in relative safety. 

Messelornis cristata scelotic ring
Photo Credit: Paul Cianfaglione

With over five-hundred specimens known to science, the Messel Rail is one of our best-known, and most celebrated fossil birds. Its knack for surviving and reproducing in such great numbers should cause those interested in the rail to stop, and reconsider the species overall flight capabilities.   

Monday, October 2, 2017

The Avian Alula; keeping birds in control for millions of years.

Theories based on the functional role of ancestral feathers have remained at the heart of the discussions about the origin of birds, and the origin of flight. The feathers themselves are anything but controversial, appearing modern as in today’s birds; tufted down, filament-like and fully vaned are all recognized.

However, what is controversial are the purpose of those feathers, on fossilized animals that look nothing like we would recognize today. Together, these feathered creatures present us with a laundry list of question marks. 

Archaeopteryx, our first and most celebrated bird, is known by a handful of largely two-dimensional fossils. With a feather arrangement like that of modern birds and similarly asymmetrical flight feathers on its wings and long tail, it appeared that Archaeopteryx was adapted for flight. But under its feathers, Archaeopteryx tells us a completely different story. 

Archaeopteryx lithographica
Berlin specimen
The architecture of the wing and pectoral girdle of Archaeopteryx differed from that of extant birds, causing skeletal constraints that prevented the wings from lifting as much as more advanced birds. Moreover, Archaeopteryx lacked a bony breastbone for the attachment of flight muscles, which suggests that the “Urvogel” was not a very strong flier. 

These anatomical limitations indicate that Archaeopteryx and similar animals such as Anchiornis and Jeholornis were not capable of sustained and powerful flapping flight with high wing-beat amplitude. Likewise, these taxa are unlikely to have been able to perform sophisticated aerial maneuvers, such as starting from and landing on the ground, as well as slow or long-distance flights (Wellnhofer 2009). 

More in line with today’s birds are the Enantiornithes, which occurred throughout the Cretaceous and achieved a global distribution by the end of the Mesozoic. 

Most Enatiornithines, at least in China, were the size of a typical songbird. Researchers agree that the advanced skeletal features of Enatiornithines (strong pygostyle for one), well developed wings and small size, signify that even the earliest of these birds, approximately 131 million years ago, had aerodynamic abilities approaching those seen in their extant counterparts (Chiappe, Glorified Dinosaurs 2007). 

But the aerodynamic abilities of Enantiornithines would never have been achieved, in my opinion, without the help and development of a small “winglet” called an alula.

Here again is paleornithologist Luis Chiappe in his book Glorified Dinosaurs, to describe the alula, and its importance. 

The alula plays a key role during slow flight as well as during landing and takeoff. This small winglet, attached to the fleshy movable thumb, is located at the midpoint of the leading edge of the wing. It is usually held flush against the wings edge but when moved forward it creates a gap that separates it from the main wing, an equivalent of a planes slot. As this air flows through this gap and over the wing, it generates aerodynamic conditions that enable birds to achieve additional lift. In turn, this increased lift allows flying birds to angle their wings into a position that reduces their speed without stalling, a critical maneuver for touching down. The alula thus plays a critical function when birds need additional lift, particularly as they slow down for safe landing. It also helps birds achieve the necessary lift taking off from the ground. 

Enatiornithine Alular Digit
Photo Credit: Paul Cianfaglione
Proof of an actual alula from the Cretaceous Period comes from the 115 million- year-old fossil Eoalulavis hoyasi from Spain, and a more recently described pair of Enatiornithines, whose mummified precocial bird wings were found embedded in mid-Cretaceous Burmese amber.

Eoalulavis hoyasi fossil
Birds of Stone Luis Chiappe 2016
Text photo credit/http://avianmusing.blogspot.com/



Image property of Ryan McKellar

As birdwatchers, we are able to see firsthand the role of the alula in bird’s flight. 

Landing styles depend largely on a combination of body mass and wing size and shape. For most birds, these factors are a compromise between what is ideal for their lifestyle (that is, how they get food) and efficient flight (Eldon Greij). 

For instance, the Yellow-rumped Warbler (Setophaga coronate) is a small bird with large, broad (relatively speaking) wings. It’s an efficient feeder, flitting from branch-to-branch, searching for insects. Success in this type of environment relies solely on its ability to change the angle of its alula feathers, allowing it to land softly and precisely where prey may be.

Yellow-rumped Warbler (Setophaga coronate) 
Image Credit: https://powdermillarc.org
The Double-crested Cormorant (Phalacrocorax auritus) on the other hand is not an efficient flyer. Its bulky body and narrow wings makes landing anything but graceful. It flies fast with rapid wingbeats, lowers its trajectory, then hits the water fast from a low angle.

Double-crested Cormorant
Photo Credit: Paul Cianfaglione
It then hauls itself out of the water, with help from the alula, to dry its wings on a dock or jetty. To get back in the air, the cormorant uses an extensive taxiing takeoff, while at the same time employing the alula to help gain lift.

Double-crested Cormorant
Photo Credit: Paul Cianfaglione