Friday, September 28, 2018

These Moths Drink the Tears of Sleeping Birds

An incredible article and photos that I just had to pass along...…….

PUBLISHED September 27, 2018

By Sandrine Ceurstemont

These Moths Drink the Tears of Sleeping Birds

These Moths Drink the Tears of Sleeping Birds.
Image Property of Leandro Moraes
A moth was spotted drinking a sleeping bird’s tears in the Amazon jungle in Brazil, the first time this behavior was reported in the country and only the third known case worldwide.

Moths and butterflies have often been observed feeding on the tears of crocodiles, turtles, and mammals. It’s thought to be a way of obtaining salt, an essential nutrient that isn’t present in nectar and can be hard to find elsewhere.

Birds’ tears may be targeted for the same reason. However, the area where the latest case was witnessed is flooded annually by a nearby river and the water soaks up lots of salt from the soil. Since salt is readily available, Leandro Moraes, who made the recent discovery published last week in the journal Ecology, is puzzled.

“The intriguing thing here is why these moths are complementing their saline diet by drinking tears from birds in such an environment,” says Moraes, a biologist at the National Institute of Amazonian Research in Manaus, Brazil.

A Rare Sight

Moraes was looking for amphibians and reptiles at night when he spotted the strange behavior. In the forest alongside the Solimões River, he saw a Gorgone macareamoth sitting on the neck of a black-chinned antbird. Even stumbling upon a sleeping bird is unusual, he says.

“The biggest surprise, however, came when I noticed what was happening, realizing that the moth was inserting its proboscis into the eye of the bird.”

The moth’s proboscis, a long tubular mouthpart, is used to suck up liquid like a straw. Another bird-tear-imbibing moth spotted in Madagascarhas hooks on its proboscis that may help anchor it during feeding, but whether the Amazonian moth’s proboscis has hooks too has yet to be investigated. However, it is long enough to allow the moth to remain quite far from its host’s eye and avoid waking it up.

Moths don’t typically use their “straw” to feed on animals though. In the part of the rainforest where the new tear-drinking moth was spotted, butterflies and moths congregate near flooded soil and slurp up the salty liquid with their proboscises, a behavior called mud-puddling. (Related: The surprising dark side of butterflies.)

However, as flood waters disperse, the salty fluid may be transferred elsewhere leaving the insects at a loss. “Scarcity of resources in a particular region in a specific month may explain why moths are seeking additional sources of nutrients in the tears of birds,” says Moraes.

Moths may also be seeking out another type of nourishment altogether: protein. Although they typically source the substance from plant nectar, tears—which contain albumin and globulin, two types of protein—can act as a supplement. A protein boost can help them fly longer and enhances their reproductive success and lifespan.

These Moths Drink the Tears of Sleeping Birds
Image Property of; Leandro Moraes
“Vertebrate fluids are the main alternative source for obtaining proteins,” says Moraes. Vampire moths, for example, feed on the blood of animals—or humans. (Related: Meet the vampire moths of Siberia.)

No Harm, No Fowl?

Regardless of what the moths are getting out of drinking tears, whether tear-feeding affects the bird hosts still needs to be solved. Moths target the animals while they are asleep, and it’s thought that the birds are indifferent to the tear extraction since they don’t show signs of discomfort.

“Sleeping birds usually wake up quickly and escape when they perceive a danger,” says Moraes.

It’s possible that the behavior could pose risks to birds. Tear-drinking moths are suspected of transmitting eye diseases to livestock, such as cattle and water buffalo, when they poke their eyes.

Moths aren’t the only insects to feed on tears, either. According to Michael Engel from the University of Kansas, who reported the first case of a tear-drinking stingless bee in Sri Lanka last year, new cases of different insects sucking up tears are growing. (Related: Tear-drinking flies spread parasitic worms to a woman’s eye.)

The behavior, however, has rarely been reported in the Amazon jungle, the biggest tropical rainforest in the world and home to an incredible diversity of animals, including about 1,300 bird species and an estimated 2.5 million types of insects.

A few years ago, an erebid moth was seen feeding on the tears of a roosting ringed kingfisher in the Colombian Amazon, the first case involving birds in this region. Solitary bees were also documented drinking the tears of river turtles in the Ecuadorian Amazon for the first time in 2012.

But most observations of the behavior have been in tropical parts of Africa, Asia, and Madagascar. “The new discovery helps expand an interesting biogeographic region where tear-feeding should be diverse and yet is scarcely known,” says Engel.

As Moraes continues his fieldwork in the Amazon, he will be carefully observing his surroundings. This report is “only a single case involving two Amazonian species, which leads me to imagine what other thousands of unknown ecological relationships exist,” he says.

See original article here;

Dinosaurs, How They Lived and Evolved. A Pictorial Book Review.

It is often said that dinosaur books are a dime-a-dozen. That is not far from the truth. In actuality, one can purchase a bundle of dinosaur books online for what it would cost to buy a single Starbucks latte. Granted most of the books are children’s encyclopedias, field guides and albums, but there are few that would certainly pass for serious adult reading.

One of the most interesting features of dinosaur books are their covers. Without even knowing the year it was first published, dinosaur enthusiasts can pretty much tell by the jacket art which decade a book was written in.

Comparing todays books with a book from the 1980’s is almost embarrassing. Remember, it wasn’t that long ago that Tyrannosaurus Rex was still depicted as dragging its tail and that sauropods were always found submerged up to their necks in water. Fortunately, recent scientific discoveries have all but changed our view of how dinosaurs lived and evolved. 
Big Animals of Long Ago. The Dinosaurs
Image Property of: 
We can also thank a couple of progressive thinking paleontologists for this change of ideas, the late John Ostrom and Robert T. Bakker. Bakker, along with his mentor John Ostrom, are responsible for initiating the ongoing "dinosaur renaissance" in paleontological studies, beginning with Bakker's article "Dinosaur Renaissance" in the April 1975 issue of Scientific American (source; Wikipedia). 

The Dinosaur Heresies by Robert T. Bakker Ph.D.
Photo Credit: Paul Cianfaglione
Incredibly, I believe we are once again in the midst of another "Dinosaur Renaissance", this time in print.

In todays age of online data, one could easily envision new dinosaur publications becoming a thing of the past. But as you will see in a moment, not only are dinosaur books still being published, they are getting better at providing ‘to the point’ information, neater layouts and incredible visuals. 

One of these recently published books is called Dinosaurs; How They Lived and Evolved (Smithsonian Books), by Darren Naish and Paul Barrett.
Dinosaurs. How They Lived and Evolved
Darren Naish & Paul Barrett
Photo Credit: Paul Cianfaglione
Published in 2016, Dinosaurs; How They Lived and Evolved is a hardcover book comprising of over 200 pages. The contents are separated into six chapters which include History, Origins and Their World, The Dinosaur Family Tree, Anatomy, Biology, Ecology and Behavior, The Origin of Birds and The Great Extinction and Beyond.

My first impression of this book was that of sheer clarity and simplicity. Each page is laid out in a bright, well- planned fashion with accompanying images.
Dinosaurs. How They Lived And Evolved.
Darren Naish & Paul Barrett
Photo Credit: Paul Cianfaglione
From the beginning, the reader will find page after page of sound, up-to-date facts. But don’t let the prospect of overly used scientific jargon dissuade you from buying this book. The authors smartly deliver a free-flowing, easy to understand text directed exclusively to the general audience.

As someone who has a special interested in the dinosaur to bird connection, it was encouraging to see this topic addressed right off the bat on page six. Here, Naish and Barrett write;

[Given how important birds are in terms of number of species, geographical distribution and anatomical innovation, it’s important that the dinosaurian nature of birds is introduced early on in any discussion of dinosaur history and diversity. It also has to be said that the inclusion of birds within dinosaurs makes it difficult to generalize about dinosaurs as a whole. When talking about predatory dinosaurs, for example, are we discussing owls, hawks and falcons as well as Allosaurus and Tyrannosaurus? And when discussing dinosaur extinction, are we referring to the demise of dodos and passenger pigeons?]

They continue;

[Paleontologists get around this problem in several ways. A solution used in some books is to state up front that the term ‘dinosaur’ is being used as a synonym for ‘non-bird dinosaur’. This might be convenient, but it’s inaccurate – the fact that birds really are dinosaurs is so important that we should deliberately think of them, not ignore them, whenever we hear the word ‘dinosaur’. Many scientists now use a number of technical terms that mean ‘all dinosaurs excepting birds’, most notably ‘non-avian dinosaur’ and ‘non-avialan dinosaur’. In this book we use the term ‘non-bird dinosaur’ when needing to refer specifically to those dinosaurs that aren’t birds, but also use ‘non-bird dinosaurs and archaic birds’ when talking of dinosaurs that do not include those birds that survived beyond the end of the Cretaceous. In general, our use of the term ‘dinosaur’ is intended to be synonymous with the group name Dinosauria: that is, birds and all.]

However, there were many other parts of the book that I really enjoyed, that didn’t necessarily have to deal directly with birds, such as the discussion on early sauropodomorphs like Plateosaurus which finds evidence that strengthens the view that they were bipeds and not quadrupeds, [with forearms that were fixed in a palms-inwards posture, meaning that the arms and wrists could not be rotated to allow the palms to face downwards] (source; Naish and Barrett. 2016). 

Plateosaurus Skeleton
Image Property: Wikipedia
I was also surprised to learn about the dinosaur Brachytrachelopan, a sauropod from Argentina that did not conform to the long-tailed, long-necked shape typical of the group. Highly unusual!

Another bit of sauropod information that I found fascinating was the fact that sauropods could evolve such lightweight neck skeletons, helping explain why they were so good at evolving incredibly long necks. A cross-section image of an Apatosaurus neck vertebrate in the anatomy chapter shows bones that are largely filled with air.

The anatomy section also touched upon dinosaur life appearances, in particular a hypothesis that now positions the dinosaur fleshy nostril openings far forward close to the mouth. Tyrannosaurus Rex is nicely illustrated here. 

Dinosaurs. How They Lived And Evolved.
Darren Naish & Paul Barrett
Photo credit: Paul Cianfaglione
The final chapter of the book deals with The Origin of Birds. Concise, but not for a lack of detail, Naish and Barrett do a nice job covering most of the evolutionary transitions that occurred within birds and their close relatives, including the origin of avian features, feather origins and how flight arose.

Dinosaurs. How They Lived And Evolved.
Darren Naish & Paul Barrett
Photo Credit: Paul Cianfaglione
If a picture is worth a thousand words, then this phrase is especially true when talking about the illustrations in Dinosaurs; How They Lived and Evolved.

Accompanying the text are numerous photos of real fossils, clear line drawings, and some outstanding paleoart, my favorites being the nighttime rendition of Scleromochlus, an incredibly detailed painting of Baryonyx, and nesting Maiasauras. 

Dinosaurs. How They Lived And Evolved. 
Darren Naish & Paul Barrett
Photo Credit: Paul Cianfaglione
Useful in every way, Dinosaurs; How They Lived and Evolved, is a must have book for any dinosaur fan both young and old. This is a very good book!

Saturday, September 15, 2018

Avian Skull Frontal Humps; a proposed purpose for certain cranial protrusions

When the movie Jurassic Park was first released in 1993, it was pretty cutting-edge for its time. It not only pushed the limits of film technology, it also depicted the dinosaurs as accurately as they could base upon known scientific theories of the day. 

From the notion that birds were a derived group of theropod dinosaurs to analysis into DNA extraction from amber, the movie’s creators appeared to be acknowledging the publics need for more scientific input.

Since then, the movie’s premises and topics have fallen flat, while at the same time ignoring such obvious dinosaurian traits as feather integument.

However, the lack of feathers is not the only evidence being overlooked in today’s films. Social behavior also seems to be taken a hit, especially in the latest installment of Jurassic World Fallen Kingdom, where movie hero Stygimoloch is seen headbutting everyone, and everything in its path.

At first glance, Stygimoloch takes on the role of Cretaceous Bighorn Sheep rather well. The morphology of their domed heads appears ideal as a battering ram for settling social conflicts among themselves, and against potential predators.

Stygimoloch Fossil Skull
Image Property of: Wikimedia Commons
But does this type of social behavior transfer over to other animals such as birds, which also posses a wide array of casques and bony cranial protuberances. Are these casques and bony cranial protuberances of birds also used for settling social conflicts?

Currently, there is some evidence to refute this long-held belief that Stygimoloch was a self-battering ram. In their 2016 book, Dinosaurs, A Concise Natural History, David E. Fastovsky and David B. Weishampel suggest an alternative use for their domed heads;

[The thickened skull cap of one North American pachycephalosaur- “Stygimoloch” – has been shown to contain abundant microscopic openings for blood vessels. With so much vascularization, the skulls of pachycephalosaurs may not have done well with either front or side impacts; this leaves the domes in this genus, and probably others, principally as display structures rather than WMDs.]

Advanced studies like this has forced some researchers to rethink social behaviors of dinosaurs, as well as birds like the Cassowary (Casuarius casuarius). Cassowaries, like Stygimoloch, are also portrayed as using their “casqued-heads while running full tilt through the vegetation, brushing saplings aside and occasionally careening into small trees. The casque would help protect the skull from such collisions". There was even speculation by one researcher that the wedge-shaped casque may protect the head by deflecting falling fruit!

Cassowary Skull Casque
Image Credit:
[Contrary to earlier findings, the hollow inside of the Cassowary casque is spanned with fine fibers which are now believed to have an acoustic function, amplifying deep sounds, which may aid in communication in dense rainforest (source; Wikipedia).]

But is any of this information regarding domes, casques, frontal bumps and other bony cranial protuberances sound science, or are these theories just mere speculation?

Frustrated, I decided to search the internet for additional resources and ideas that may help me better understand casque usage and their evolution.

One of the most exciting findings I made while researching on this topic was the discovery of a new scientific paper (May 2018) just published by Dr. Gerald Mayr titled; A survey of casques, frontal humps, and other extravagant bony cranial protuberances in birds.

It is in this online paper where one will find not only a thorough discussion on the structural diversity of avian protuberances, but also a virtual field guide to all the known bird skulls exhibiting these peculiar appendages. In my opinion, a much needed and timely examination. The abstract reads as follows;  

[The occurrence of casques, frontal humps, and other bony cranial protuberances in birds is reviewed. Several previously overlooked examples are reported and casques of some rare taxa are for the first time figured. Bony cranial protuberances are most widespread among galloanserine birds, which is particularly true for helmet-like casques on top of the skull. In the species-rich clade Neoaves, by contrast, bony protuberances rarely occur on top of the skull and are mainly restricted to the beak. Similar structures have a different ontogenetic origin, with the casque of cassowaries being mainly formed by the mesethmoid and that of the Helmeted Guineafowl (Numida meleagris) deriving from the frontal bones. The pneumatic frontal humps of anseriform birds are formed through inflation of diverticula of the antorbital and/or fronto-ethmoidal sinus, and air sac diverticula are likely to be involved in the formation of other casques. In some Galloanseres, bony cranial protuberances are associated with integumentary structures that have a signaling function, but such correlations do not exist for other taxa, for which a physiological, acoustic or sensory function of the protuberances has to be considered. Casques also occur in pterosaurs and non-avian dinosaurs, but most comparisons between these extinct animals and birds were confined to the casques of cassowaries. The full spectrum of bony cranial outgrowths in birds has not yet been considered and the present survey may serve as a basis for future comparisons. Prominent casques on top of the skull are more likely to evolve in terrestrial or aquatic birds, in which the head is particularly exposed and plays a role in intraspecific signaling, but their absence in most neoavian taxa is noteworthy and requires future studies to address possible ontogenetic, ecological, or functional constraints on their formation.]

The section of the research paper that I found particularly noteworthy was the discussion involving the casques and frontal humps of both Galliformes and Anseriformes. Not only was I familiar with all of the species in the study, the material also helped me recall a similar bulbous appendage located on one of my own personally held specimens. 

Southern Screamer (Chauna torquata) Skull with paired frontal humps
Photo Credit: Paul Cianfaglione
The Southern Screamer (Chauna torquata) is truly a bizarre bird. Besides lacking the characteristic uncinate processes on their ribs, screamers also possess large bony spurs on its wings which are used for protection against rival screamers and other enemies. They share another peculiarity solely with mousebirds, penguins, and ostriches—their feathers grow over the body without any bare spaces (called apteria) in between (source;]

Southern Screamer (Chauna torquata) bony spurs on wing
Photo Credit: Paul Cianfaglione
Even though the Southern Screamer was not recognized during the Mayr study, there were other waterfowl species surveyed with nearly identically paired appendages. 

Skulls of species of Anas (Anseriformes, Anatidae)
Image Property of Gerald Mayr (2018)
A survey of casques, frontal humps, and other extravagant bony cranial protuberances in birds

The Sunda Teal (Anas gibberifrons) for instance, also have matching frontal bumps (Fig. 4a-c), which develop from the processus rostrales of the nasal bones and are due to inflation of diverticula of the antorbital or fronto-ethmoidal sinus. Paired frontal humps are also very distinct in male and female individuals of A. capensis (Fig. 4f) and A. georgica (Fig. 4d), for which they are here reported for the first time (Mayr. G. 2018).

So, why do birds possess such an array of casques, frontal humps, and other extravagant bony cranial protuberances? Are they for defense? Display? Sexual selection? Acoustics? Do they act as a sensory mechanism?

Dr. Mayr does a very nice job explaining some of the possibilities for this type of cranial evolution, especially as it relates to the Southern Screamers unusually shaped head;

[It is reasonable to assume that some of the bony cranial protuberances in galloanserine birds exhibit an evolutionary relationship to integumentary structures found in these birds, that is, that bony and integumentary appendages evolved in an integrated way, although the exact nature of interdependence, which may differ from taxon to taxon, has yet to be determined. Outside Galloanseres, crowned cranes and turacos have large feather crests on their skulls, and the species of Fratercula feature unusually colorful beaks, with other auks, such as Cerorhinca or Aethia, having conspicuous integumentary structures at the base of the upper beak. Bony cranial casques, humps, and shields with a conspicuous shape or coloration are suggestive of an intraspecific signaling function and to have evolved due to sexual selection, but again, generalizations are not possible and each occurrence has to be analyzed individually. In particular, an ornamental or display function is unlikely for the frontal humps in some species of Anas. Even though the marked frontal humps of A. gibberifrons enhance the head profile, as do those of Bucephala and Oxyura, those of other Anas species are much smaller and the fact that they are hardly visible in the skull of the living animal conflicts with an origin as display traits due to sexual selection. In these and other species of ducks, the pneumatized frontal humps may have a physiological, sensory, or acoustic function, but detailed studies of the soft tissue anatomy are required for confident conclusions (Mayr. G. 2018).]

Speculation with regards to the purpose of frontal humps in living birds is no easy task. Conversely, a better option is having the skull in hand, examining and comparing features mentioned in this recently published study.

What I found by placing the skull under a stereo microscope is that the paired frontal humps of the Southern Screamer are covered with what appears to be sensory pits. 

Southern Screamer (Chauna torquata) paired frontal humps with possible sensory pits
Photo Credit: Paul Cianfaglione
[Also known as Herbst Corpuscles, they are the most widely distributed receptors in birds, and are found in the dermis layer of the skin, the beak, & the legs. Herbst corpuscles are also closely associated with rictal and facial bristles in many species of birds (source; Avian Brain and Senses).] 

Southern Screamer (Chauna torquata) frontal humps with possible sensory pits
Photo Credit: Paul Cianfaglione
Southern Screamer (Chauna torquata) frontal humps with possible sensory pits
Photo Credit: Paul Cianfaglione
Are the feathered pneumatized frontal humps on some Anseriformes there solely for sensory purposes? 

Southern Screamer (Chauna torquata)
Image Property:
The distribution of sensory pits on the paired frontal humps may support the notion that the Southern Screamer is a hyper-sensitive species.

Their behavior and ecology places them primarily on the ground, feeding in tall grasslands and cultivated fields. Receptors embedded deep in the screamers skull may be able to send information about a bird’s surroundings through sensitive muscular and nervous systems, giving it a heightened sense of feeling. 

Southern Screamer (Chauna torquata)
Image Property:

Saturday, September 1, 2018

Pelagornithid tooth growth and function

Sometimes a story is not totally a surprise, other times it comes out of the blue. An example of this is in today’s posting, which was pretty much unforeseen up until a few days ago.

It all began last week, when I came across an article by paleontologist Mark Witton cheerfully titled; ‘Those Terrific Pelagornithids’. Pelagornithids were the dominant seabirds over most oceans throughout the Cenozoic, and were among the largest flying birds ever to live with wingspans estimated at over 4-meters.

In addition to its enormous size, Pelagornithids were also known for their bony-toothed facial expression, outgrowths of the premaxillary and mandibular bones.

Mark Witton’s outstanding article provides a concise natural history of what is currently know about Pelagornithids, including anatomy, taxonomy and histological studies. He even includes some of his own paleoart, an amazing rendition of an adult and two chicks on a cliffside nest. See Mark Witton’s website and store here;

Pelagornithid adult and young
Image Property of Mark Witton
But there was one other part of the article that really grabbed my attention. This was found in the last paragraph where Witton notes a recent study (Louchart et al. 2013) that shows that pseudoteeth erupted from the jaw relatively late in pelagornithid growth, meaning juvenile Pelagornis would have looked like regular, cute baby birds before developing their toothy smiles as adults. This has several interesting implications for pelagornithid growth and ecology. The first is that the cornified beak tissue covering their jaws must not have hardened until after the teeth had fully developed (recall from a previous post that cornified sheaths, on account of being inert, dead tissue, can’t be easily modified once deposited). This characteristic is not common among birds, but occurs in a number of Anseriformes. This observation is not a deal clincher for the pelagornithid-anseriform phylogenetic hypothesis, but it's an interesting connection nonetheless.

Secondly, studies show that the emerging pseudoteeth were relatively delicate and potentially unable to withstand stresses imparted by thrashing fish or squid until late in development. This being the case, Louchart et al. (2013) proposed that pelagornithids might have been altricial, feeding regurgitated food to their offspring until they were fully grown and able to forage for themselves; or else that the juveniles were foraging on different foodstuffs. Altriciality would be unusual behaviour for a stem-neoavian as most bird species of this grade have precocial offspring that feed themselves straight after hatching. Insight into these hypotheses would be provided by fossils of juvenile pelagornithids but these remain extremely rare. I wonder if these animals were like living pelagic birds and nested atop cliffs in isolated offshore settings? If so, I wouldn’t hold your breath waiting for fossils of their hatchlings (Witton, Mark. 2018. Those Terrific Pelagornithids).

These ideas were certainly inspiring, enough so that I needed to take a closer look at my own collection of Pelagornithid material. I thought, could any of these fossils shed new light on what is presently known about juvenile growth and ecology? Chances are very small. Besides, how would I even know what a juvenile fossil looks like?

Displayed carefully on my desk were a number of fragile Pelagornithid fossils, in all shapes and sizes. With the juvenile growth and ecology concept still fresh in my mind, I was immediately drawn to a tiny mandible, still embedded in matrix. Why was this fossil so small?

Possible Juvenile Pelagornithid Fossil
Photo Credit: Paul Cianfaglione
Appearing weathered and unassuming, the fossil lay for years virtually overlooked in a protective case. But I do remember the day that I acquired the fossil, questioning its identification and diminutive size. Not a bone you would expect to find on one of the largest flying birds ever to exist!

All of my Pelagornithid fossil material hail from the Oulad Abdoun Basin (also known as the Khouribga Basin), which is a phosphate sedimentary basin located in Morocco, near the city of Khouribga. It is the largest in Morocco, comprising 44% of Morocco's phosphate reserves, and at least 26.8 billion tons of phosphate. It is also known as an important site for vertebrate fossils, with deposits ranging from the Late Cretaceous (Cenomanian-Turonian) to the Eocene epoch (Ypresian), a period of about 25 million years (source; Wikipedia).

Bird fossils are common in the Basin, which includes the oldest birds in Africa. At least three orders and several families of sea birds are represented, including Procellariiformes (albatrosses and petrels, fossils assignable to Diomedeidae and Procellariidae), Pelecaniformes (pelicans and allies, fossils assignable to Phaethontidae, Prophaethontidae, Fregatidae and Pelagornithidae), and Anseriformes (waterfowl, including fossil Presbyornithidae).

According to the book Avian Evolution; The Fossil Record of Birds and its Paleobiological Significance, by Gerald Mayr (2017), the fossils of Pelagornithid species from the late Paleocene/early Eocene deposits of Morocco are recognized as the species Dasornis emuinus. 

Avian Evolution by Gerald Mayr
Interestingly, the wing skeleton of Dasornis was less specialized for sustained soaring than that of later pelagornithids, with some characteristics of the foot skeleton suggesting that the taxon was also more aquatic.

Dr.Gerald Mayr goes on to note that Pelagornithids exhibit some highly peculiar characteristics that are unparalleled by other birds, of which the pseudoteeth are the most outstanding. These projections of the cutting edges of the upper and lower beak are hollow outgrowths of the jaws. Differences exist in the formation and orientation of the pseudoteeth of pelagornithids, but they are fairly regularly arranged in all species and very large pseudoteeth are separated by smaller second and third-order ones. Vasular furrows on their surface indicate that these projections were covered by the rhamphotheca, and a basal plate separates their hollow lumen from that of the jaws. It was therefore hypothesized that either pseudoteeth formation or hardening of the rhamphotheca occurred comparatively late in ontogeny, after growth of the jaw bones was complete (Louchart et al. 2013). Pseudoteeth are readily distinguished from true avian teeth in that they are not covered with enamel, do not rest in alveoles, and their histology is typical of bone (Louchart et al. 2013). Louchart paper can be found here;

Below are the comparative images of two Pelagornithid fossils unearthed in the country of Morocco.

The larger fossil, an embedded skull and maxilla (upper mandible), is one of my most cherished collection pieces. It has a skull length of 90mm, a section of bill from the base that measures 80mm, and a separate 85mm long outer end. The width of the bill (not including the teeth), at its widest point, measures 20mm. The tooth size, from largest to smallest, measures 10mm-8mm-4mm respectively. 

Possible adult and juvenile Pelagornithid fossils
Photo Credit: Paul Cianfaglione
The smaller of the Pelagornithid fossils (tiny mandible embedded in matrix) measures 70mm long and has a maximum width of 10mm. The dentary features nine partial teeth, the longest being 5mm long. The fossil also reveals what appears to be a neurovascular sulcus.

So, what does this side-by-side comparison and measurements tell us about these two Pelagornithid fossils? Why is there such a large discrepancy in actual size? Is the smaller mandible a juvenile bird? If so, what does that now tell us about previous hypotheses?

If this smaller sized fossil is indeed a juvenile Pelagornithid, it may be necessary to envision a completely different growth and ecology scenario, a scenario in which early tooth development itself sets off a chain of thoughts more in line with precocial behavior.  

Possible juvenile Pelagornithid fossil mandible
Photo Credit: Paul Cianfaglione
We can now visualize in our minds a fast-growing, fully toothed (adept) juvenile Pelagornithid surface feeding just offshore in the company of other juveniles and adults. Surface feeding is supported by fossil evidence showing characteristics of the foot skeleton suggesting that the taxon (Dasornis) was also more aquatic (Mayr. G. 2017).

The so-called delicate teeth are now thought of as strong formidable tools, enabling the juveniles to feed themselves, securing plankton, squid or even smaller sized fish, similar to modern day gulls.

Bonaparte's Gull (Chroicocephalus Philadelphia) feeding on slipper shell flesh
Image Property of
This new theory may be supported by close-up, inner images of the alleged juvenile fossil, showing possible signs of dense mandibular bone mass.

Possible juvenile Pelagornithid fossil mandible
Photo Credit: Paul Cianfaglione
Possible juvenile Pelagornithid fossil mandible
Photo Credit: Paul Cianfaglione
To protect the important, growing jaw and teeth of a Pelagornithid chick, the rhamphotheca would remain wholly soft (reformed) until reaching adult size, comparable to what is seen in today’s Southern Giant Petrel (Macronectes giganteus).

Southern Giant Petrel (Macronectes giganteus) with chick
Image Credit: Wikipedia