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 feather attachment
Photo Credit: Paul Cianfaglione
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

Tuesday, September 26, 2017

Fly away home? Ice age may have clipped bird migration Study challenges traditional presumptions of migratory behavior

An interesting study worth highlighting;

The onset of the last ice age may have forced some bird species to abandon their northerly migrations for thousands of years, says new research led by a University of Nebraska-Lincoln ornithologist.

Published Sept. 20 in the journal Science Advances, the study challenges a long-held presumption that birds merely shortened their migratory flights when glaciers advanced south to cover much of North America and northern Europe about 21,000 years ago.

The study concluded that the emergence of glaciers in those regions instead acted as an "adaptive switch" that turned off migratory behavior, transforming the tropics from a cold-weather resort into a long-term residence for certain bird species.

The University of Nebraska-Lincoln's Robert Zink
Credit: Craig Chandler, University of Nebraska-Lincoln

Of the 29 long-distance migrant species examined in the study, 20 likely saw their northern breeding grounds become uninhabitable, according to models developed by the researchers. When the climate again warmed and glaciers retreated back to the Arctic, those species presumably resumed their seasonal migrations.

Lead author Robert Zink said the conclusions could alter how scientists reconstruct the history of bird migration. "It fundamentally changes the way we study the evolution of migration and think about the migratory behavior of birds," said Zink, professor of natural resources and biological sciences at Nebraska.

Researchers generally agree that, millions of years ago, many birds did not migrate from the tropics. But as the global climate began to warm, some species ventured beyond their native habitats to capitalize on better breeding and feeding opportunities afforded by the longer days and insect-rich environments of northern latitudes.

Those species eventually ventured farther and farther from their habitats, finally stopping when they reached environments that could not sustain them during the autumn and winter. They continued to migrate south when seasonal temperatures dropped and food sources waned.

In that context, Zink said his hypothesis suggests that the origin story of bird migration simply underwent multiple reboots, with the "migratory machinery" of birds halting for each of the 20 or so ice ages that have glazed Earth during the past 2.5 million years.

"Migrations are costly and risky," said Zink, curator of zoology at the University of Nebraska State Museum. "They're costly in terms of safety, energy -- anything you can think of."

Rather than paying those costs to reach breeding grounds that the encroaching glaciers had shrunk to tiny fractions of their former size, he said, birds instead resorted to their ancestral state: tropical homebodies.

"Some of them were forced so far south that it was no longer a fitness advantage to migrate, because the extra young they could produce south of the glacier wasn't enough to compensate for the cost of migration," Zink said, "and then coming back to the tropics and re-establishing their territory.

"To some people, that's so completely off the wall that they may have trouble wrapping their heads around it -- except that it's the way they would explain to their classes the evolution of migration in the first place. So, in a sense, what I'm proposing is nothing novel. What's novel about it is that (the advent of migration) probably occurred many times."

Zink and his co-author, the University of Minnesota's Aubrey Gardner, conducted their study using a computer model that linked the modern-day distribution of bird species with climate variables -- temperature, precipitation, seasonality -- that characterize their habitats. By comparing those climates with conditions that existed during the last ice age, the model mapped the regions that likely could have supported each of those species from about 21,000 to 12,000 years ago.

In many cases, Zink said, the model either found no habitable regions beyond the tropics or located habitats so miniscule that they would have struggled to support sizable populations of the species.

"Some species were probably just forced (slightly) south of the glaciers, and their habitats were extensive enough that they would maybe maintain some migratory ability," he said. "But for others, I think there was so little predicted habitat that they just ceased migration all together.

"This evolution of migration is a very (variable) thing. Normally, when we think of evolution, we think of singular, unique events in evolutionary history. But in this case, the ability to migrate is entrenched in birds. They have the ability to navigate using the sun, the stars, the (Earth's) magnetic field. They have the ability to put on large amounts of fat and sustain trans-gulf migrations. Birds are (adaptive) enough in their behavior and physiology that this wasn't a reinvention of some incredible phenomenon."

And if some species did transition back and forth from sedentary to migratory states, researchers should consider pruning certain evolutionary trees accordingly, Zink said. Many evolutionary trees currently treat migration as an irreversible trait rather than a variable behavior, he said, and that assumption could be misinforming discussions of when and where it evolved.

"I wanted to point out that this was a real danger and fallacy that's being committed: mapping something onto an evolutionary tree where the feature -- migration or sedentariness -- changes faster than new species evolved," he said. "You would have constructed the history of migration totally differently."

Story Source:

Materials provided by University of Nebraska-Lincoln. Original written by Scott Schrage. Note: Content may be edited for style and length

Journal Reference:

Robert M. Zink, Aubrey S. Gardner. Glaciation as a migratory switch. Science Advances, 2017; DOI: 10.1126/sciadv.1603133

Saturday, September 23, 2017

Halcyornithids; Early Paleogene parrot-like birds.

It’s always been a wonder to me how paleornithologists identify fossils birds on the basis of one isolated bone. Nothing, in my opinion, showcases this more than the online research paper titled; Mass extinction of birds at the Cretaceous-Paleogene (K-Pg) boundary. The papers findings provide definitive evidence for the persistence of a range of archaic birds to within 300,000 years of the K–Pg boundary. See paper attachment below.  


Here, researchers reexamine the birds from the Late Maastrichtian of western North America to assess the relationships of these fossils and the diversity of the assemblage. They focused on the most commonly preserved element, the coracoid, to avoid counting the same taxon several times on the basis of nonoverlapping material. Bird coracoids show minimal variation within species or even genera; thus, different morphotypes can confidently be identified as different species. Rather than naming new species, scientists identify morphotypes on the basis of unique combinations of apomorphies and plesiomorphies, differences in shape, and overall size. 

Inspired by this and other studies on fragmentary remains, I decided to have a look at some of my own seemingly unidentifiable bird fossils.

The fossil that I believed showed the most promise for possible identification hailed from the Fossil Butte Member of the Green River Formation (dated to approximately 51.66 +/- 0.09 Ma in age). Nicely preserved on the plate were avian wing bones; coracoid, humerus, ulna, radius, radiale, ulnare, partial scapula and carpometacarpus. 

Possible Cyrilavis colburnorum fossil
Fossil Butte Member of the Green River Formation
Photo Credit: Paul Cianfaglione
In a long shot attempt to try to identify this fossil myself, I turned to an avian osteology (Gilbert-Martin-Savage) book for some comparative bone samples. In my assessment of the fossil (albeit weak) I determined that the structural characters of both the coracoid and humerus corresponded well with a small duck species such as a teal, while at the same time noticing that the metacarpal process on the fossil carpometacarpus appeared blunt, also reminiscent of extant Anatinae. Could this be a species of waterfowl? Were there enough distinctive features on the coracoid and humerus to support each other in an identification?

Blue-winged Teal Coracoid
Avian Osteology
Photo Credit: Paul Cianfaglione

However, one of the key reservations I had with my interpretation was the difference in size among the bones. For instance, the length of the fossil bird’s coracoid measured 19mm, as opposed to the teal which measures 36mm. The same size discrepancy arose with the humerus, 34mm with the fossil, 61mm with a teal.  

Frustrated, I turned to an expert in the field of paleornithology for some much-needed advice. The researcher was gracious enough to respond to my inquiry, recommending that rather than waterfowl, I should instead be taking a closer look at a group of parrot-like birds called Halcyornithidae. Attached with the researcher’s response was a recent pdf study on these birds, which permitted me to see whether the size of my specimen corresponds with the described fossils.

STEM PARROTS (AVES, HALCYORNITHIDAE) FROM THE GREEN RIVER FORMATION AND A COMBINED PHYLOGENY OF PAN-PSITTACIFORME (Ksepka, Clark, Grande; 2011), provided an incredible look at a new species of stem parrot from the early Eocene Fossil Butte Member of the Green River Formation. Well-preserved specimens including a complete skeleton and referred partial postcranial skeleton reveal new osteological details of the clade Halcyornithidae and expand the known diversity of the Green River avifauna. Cyrilavis colburnorum n. sp. shares key morphologies with the smaller Green River halcyornithid Cyrilavis olsoni. 

In addition to the comprehensive study, the paper also offered wonderful photos and line drawings illustrating details of Cyrilavis colburnorum (FMNH PA 754). 

Cyrilavis colburnorum
Image is property of author Ksepka

Quality images of the pectoral girdle and distal wing allowed for a thorough examination of the bones, bones which bore strong similarities to my own fossil. 

Cyrilavis colburnorum
Image is property of author Ksepka
Halcyornithids are small birds (see measurements below), distinguished from extant parrots in many skeletal features (Mayr 2014). Unlike in other early Eocene skeletons of Psittacopasseres, the clade including parrots and passerines, the coracoid of Halcyornithids exhibit a foramen for the supracoracoideus nerve. This was evident on my fossil coracoid, as was the deep, subcircular and cup-like cotyla scapularis mentioned in the article.

Probable Cyrilavis colburnorum fossil
Photo Credit: Paul Cianfaglione
Another interesting feature of the coracoid was the well-developed processus lateralis. On my fossil, the tip of the processus lateralis is missing, however, when viewed under the microscope, it’s outline in the matrix is quite evident. By failing to notice this during my initial assessment, I was unwittingly led down a wrong path toward a duck identification. 
Probable Cyrilavis colburnorum fossil
Photo Credit: Paul Cianfaglione
The humerus of halcyornithids also have some distinctive features, according to scientists, are elongated and slender resembling those of owls. The head of the humerus is rather low, wide, and lozenge-shaped (similar to my fossil), lacking the proximally projected and domed shape present in extant parrots. The proximal end of the humerus is more similar to that in Falconidae than any extant parrot in terms of the shape and projection of the crista bicipitalis and crista deltopectoralis (Description from study). 

The blunt shaped metacarpal process I eluded to earlier in this article, is once again verified in the paper as being a conspicuously weaker projection than in extant parrots.

Probable Cyrilavis colburnorum fossil
Photo Credit: Paul Cianfaglione
The ulna is also noted to be significantly longer than the humerus on halcyornithids, while the radius has a shallow sulcus tendinosus. Measurements of my fossils ulna and humerus confirm these claims.

Probable Cyrilavis colburnorum fossil
Photo Credit: Paul Cianfaglione
Measurements of the four fossil bones reads as follows; 

Fossil in question 

Coracoid   -   19 mm

Humerus   -   33 mm

Ulna          -   38 mm

Radius      -   35 mm

Cyrilavis colburnorum

Coracoid   -   19.5 mm

Humerus   -   32 mm

Ulna          -   37 mm

Radius      -   34 mm 

Cyrilavis olsoni (Type species) 

Coracoid   -   16 mm

Humerus   -   29 mm

Ulna          -   32 mm

Radius      -   30 mm

Based on the information at hand; fossil date, structure of bones and measurements, I believe with good confidence that this fossil bird wing most likely belongs to Cyrilavis colburnorum. 

A big bit (I mean big bit!) of thanks goes out to the paleornithologist who generously took the time to respond to my inquiry. Without this person’s help, I would have never considered this fossil to be a recently described species of stem parrot. 

For those of you who may, on the outside chance, have fragmentary remains of Paleogene birds hanging around the closet, I would recommend three books of enlightenment; 

The first is Dr. Gerald Mayr’s book; Avian Evolution; The Fossil Record of Birds and its Paleobiological Significance (2017). Fantastic Book! 

Avian Evolution, The Fossil Record of Birds and its Paleobiological Significance 
Author Gerald Mayr
Photo Credit: Paul Cianfaglione

The second is also Dr. Gerald Mayr’s book; Paleogene Fossil Birds (2009). Incredible Book!

The third is Avian Osteology (1996) by B. Miles Gilbert, Larry Martin and Howard G. Savage. If you love bird bones, a must-have book!

Wednesday, September 20, 2017

Dinosaur trio roosted together like modern birds

I didn’t see much hype or press about this incredible fossil discovery, so here is the article. 

Nature 548, 510 (31 August 2017) doi:10.1038/nature.2017.22508

Written by Traci Watson

Photo Credit: Gregory F. Funston

The fossilized remains of three young dinosaurs who seem to have been snuggled together in sleep have been found in a stone block that poachers hacked out of the Mongolian desert.

Researchers say the 70-million-year-old specimens are the first known example of dinosaurs sleeping in a group, a behaviour called communal roosting. Many modern species, including crows and bats, engage in the practice, which helps animals to regulate their body temperature and avoid predators.

The three dozy dinosaurs were probably relatives and possibly siblings, says vertebrate palaeontologist Greg Funston of the University of Alberta in Canada, who led the team that analysed the fossils. The trio “clearly had a quite close bond”, Funston says. “They were living together at the time of death.” He is scheduled to describe the fossils on 25 August at the annual meeting of the Society of Vertebrate Paleontology in Calgary, Canada.

Mongolian customs agents seized the stone specimen at an airport in 2006, before it could be smuggled out of the country. A geochemical analysis by Federico Fanti, a vertebrate palaeontologist at the University of Bologna in Italy, and his colleagues suggests that the dinosaurs probably come from the Bugiin Tsav fossil site in the Gobi desert. Fanti presented the geochemical data on 24 August, at the same palaeontology meeting

Funston’s team identified the fossils as a new species of oviraptorid — a group of dinosaurs with short faces, long necks and toothless beaks that lived during the Cretaceous period, 145 million to 65 million years ago. The species, which has not yet been formally named, has a domed crest on its head, like that of a modern-day cassowary, and walked on two legs.

Unlike most dinosaur fossils, two of the animals in the block are crouched belly down. These two, which are more complete than the third, have their necks curled back towards their bodies, while their arms cradle their heads. The pose “is quite similar to what ostriches and emus do when they get into deep sleep,” Funston says.

A handful of previously discovered fossils capture napping dinosaurs, but all show a lone animal. The new fossil suggests that communal roosting developed in animals with rich social lives, Funston says. Oviraptorids fit the bill: they browsed for food in groups and probably flashed their crests at rivals or potential mates. By contrast, another group of bird-like dinosaurs called troodontids lacked such sophisticated behaviours and did not roost communally.

From the width of the thighbones of the two more extensive skeletons in the block, the researchers estimate that each weighed roughly 45 kilograms, a little more than a German shepherd dog. The third skeleton is too fragmented for the researchers to estimate its weight. But it is roughly the same size as its companions, suggesting the three were close in age.

A female oviraptorid could lay dozens of eggs, always in multiples of two. So the animals might well have been siblings, Funston says, or perhaps cousins.

Two additional Mongolian fossils of the same species help to bracket the age of the sleeping trio. A previously discovered adult from a different bone bed weighed 75 kilograms. Another specimen recovered from poachers in 2006 was 33 kilograms and, judging by its bone development, was probably less than one-year old. That led the team to estimate the block animals’ age at 2 to 5 years — making them the equivalent of “teenagers hanging out in the parking lot”, jokes David Varricchio, a vertebrate palaeontologist at Montana State University in Bozeman.

Having specimens of varied ages will bring insights on how this class of animals grew and evolved, says Michael Pittman, a palaeontologist at the University of Hong Kong.

The configuration of the three animals implies they were touching each other, and the researchers think the youngsters were probably huddling for warmth. That suggests that the animals had tried to maintain a constant body temperature, Funston says, even though most animals that huddle for warmth are small. Funston speculates that frigid weather or a sand storm drove the three dinosaurs to nestle together.

Other researchers have reservations about that idea. The animals may have huddled together to hide or merely because the spot was “a great place to sleep”, says John Grady, a biologist at Bryn Mawr College in Pennsylvania who has studied the metabolic rates of dinosaurs. And Varricchio wonders whether the young reptiles were resting or taking shelter from harsh conditions rather than sleeping.

But Funston argues that modern animals that roost together don’t usually make direct contact except for warmth. Animals that died in events such as floods are preserved in very different stances from that of the oviraptorid trio, he says, making it unlikely that the young dinosaurs were awake.

Whatever the three fossilized dinosaurs were doing, researchers say that their remains suggest that young oviraptorids were social animals. There is fossil evidence of adult oviraptorids sitting on nests, and it makes sense that the young “should be palling around” rather than getting in the adults’ way, Varricchio says. The life-like pose of the fossils in the block, he adds, shows “they were alive together and they perished together”.

Monday, September 11, 2017

Birds of Stone; A pictorial book review

Birds have a rich and ancient past, their origins date back to the Jurassic Period, more than 150 million years ago. In that time, birds have evolved a stunning array of appearances, behaviors and adaptations. We know this thanks to the thousands of exquisite fossils that have been dug up from northeastern China, providing us with the clearest window into the earliest stages of the evolution of birds.

Thankfully, bird enthusiasts can now enjoy and learn about these fossils in a recently published book titled Birds of Stone; Chinese Avian Fossils from the Age of Dinosaurs, by prominent paleo-ornithologist Luis M. Chiappe.

Birds of Stone
Book Photo Credit: Paul Cianfaglione

Hardcover, 304 pages, 184 color photos, 5 b&w photos, 11-line drawings, 9 x 1 x 11 inches, Publisher: Johns Hopkins University Press (August 23, 2016). 

Similar in design to his previous book Glorified Dinosaurs (2007), Chiappe once again delivers a comprehensive summary of past and current fossil discoveries.

A little different this time is Chiappes decision to forego chapters, electing instead to divide the volume into two major parts. The first part, The Avian Fossils of Jehol, introduces readers to some of the finest fossils ever brought to print. High-resolution photographs (with descriptive accompanying text) of Sapeornis, Longipteryx, Jeholornis, Confuciusornis and Yanornis light-up every page, offering images rarely ever seen before.

Zhouornis hani
Birds of Stone
Book Photo Credit: Paul Cianfaglione

In addition to presenting complete and well-preserved specimens, Birds of Stone also includes a collection of fossilized feather types, skinfolds, ingested grit, fish remains and of course, teeth.

Archaeorhynchus spathula w/ingested stones
Birds of Stone
Book Photo Credit: Paul Cianfaglione
Enatiornithine indeterminate
Birds of Stone
Book Photo Credit: Paul Cianfaglione
Longipteryx chaoyangornis & Pengornis houi w/teeth
Birds of Stone
Book Photo Credit: Paul Cianfaglione

The second part, The Early Evolution of Birds, aims to revisit, and discuss the fact that all living birds are the descendants of ancestors that first evolved more than 150 million years ago. Sections on evolutionary relationships, feathered dinosaurs, flying dinosaurs, the origin of feathers, flight refinement and becoming airborne are all covered in Birds of Stone. 

Although much has been discovered and learned about bird evolution since the publication of Glorified Dinosaurs, much has also remained the same. For instance, despite numerous Microraptor discoveries, it is still unclear whether this four-winged animal was a glider that launched itself from an elevated perch, or was an animal capable of flapping its wings and taking off from the ground. 

Microraptor zhaoianus
Birds of Stone
Book Photo Credit: Paul Cianfaglione

The same can be said about Confuciusornis sanctus, the most celebrated fossil from the Jehol Biota and definitely the most abundant bird. Hundreds of fossils of this species, many with complete skeletons still surrounded by plumage, have been unearthed from Jehol rocks, yet its primitive design; heavily clawed hands, stout wing bones and foot grasping ability (could it perch?), have still made researchers wonder about the aerodynamic abilities of these animals.

Confuciusornis sanctus
Birds of Stone
Book Photo Credit: Paul Cianfaglione

One has to question why so much research is being done today on fossil feather coloration and bone tissue, when some of the most basic avian questions are still left unanswered? 

Which brings me back to this book. Birds of Stone not only offers fossils in incredible detail, it is written in a style that appeals to the general public, clear, concise and without the technical jargon. This is important because what is being presented and talked about on the web, and throughout this book, are in many ways still debatable subjects. 

This to me is the real reason why these detailed fossil images are so vital to the public. Who knows, with this type of available information, maybe you will find the answers to some of life’s unanswered questions?

Enantiornithine indeterminate
Birds of Stone
Book Photo Credit: Paul Cianfaglione
Luis Chiappe does a wonderful job of presenting the facts, while at the same time leaving the window open just enough for an alternative interpretation. Don’t get me wrong, Chiappe has a strong scientific opinion, but he also reminds us that researchers are dealing with flattened, 130 million-year-old fossils.    

It’s not every day that a world-class book on bird evolution is published. Remarkably, Luis Chiappe has done it twice, first with Glorified Dinosaurs, and now with Birds of Stone!  I highly recommend this book.