Friday, April 30, 2010
Pterosaur and bird wing structures are very interesting and obviously related.
We can see that in the development from pterosaur to modern bird that the pterosaur fifth finger (which is often incorrectly labeled as the fourth finger) was shortened and some fingers (digits) were fused.
This is a large topic which I will discuss in the next few posts.
For now, just notice the pterosaur thumb metacarpal sticking out. It is not numbered in the picture and is a little hard to see but it is shown. In standard evolution terminology this is called the "pteroid bone".
Thursday, April 29, 2010
"From this, the scientists were able to deduce that pterosaur brains were very bird-like, with reduced olfactory lobes and large optic lobes — suggesting that, like modern birds, they were more interested in what they could see than what they could smell
However, a surprising finding was that the pterosaur brains had two very pronounced balance-related regions called 'floccular lobes'. It is thought that these may have gathered information from the wing membranes, which functioned as sense organs, to enable the reptile to build up a detailed map of the forces experienced by its wings."
"The new findings confirm earlier studies4, 5 showing that pterosaurs had a remarkably bird-like brain — for example, it had reduced olfactory lobes and large, laterally displaced optic lobes."
"A study of pterosaur brain cavities using X-rays revealed that the animals (Rhamphorhynchus muensteri and Anhanguera santanae) had massive flocculi. The flocculus is a brain region that integrates signals from joints, muscles, skin and balance organs.
The pterosaurs' flocculi occupied 7.5% of the animals' total brain mass, more than in any other vertebrate. Birds have unusually large flocculi compared with other animals, but these only occupy between 1 and 2% of total brain mass.
The flocculus sends out neural signals that produce small, automatic movements in the eye muscles. These keep the image on an animal's retina steady. Pterosaurs may have had such a large flocculus because of their large wing size, which would mean that there was a great deal more sensory information to process."
Here are a few videos of birds landing.
In SLOW MOTION it is something to behold.
And here is info about pterosaurs:
"A set of Pterosaur footprints unearthed in France is the first to show one of the winged reptiles coming into land - and suggests they did so in much the same way as most modern birds.
An exceptional set of footprints preserved in 150-million-year-old rock near Crayssac in south-west France holds some answers to pterosaur behaviour. They record the moment a small pterosaur came into land, says Kevin Padian at the University of California, Berkeley.
Padian's team says the prints are similar to those produced by a landing bird. Although most pterosaur tracks show the animals walking on all fours, the first prints in the newly discovered tracks are of the rear limbs only.
That's because the pterosaur used its wings to "stall" as birds do, says the team, so that the animal's body swung up from a horizontal flight position to near vertical, enabling it to land gently on its hind feet.
"The smaller ones, like the smallest birds, are all good flappers, so they [could] 'flap-stall' to land," says Padian. Larger pterosaurs might have stalled by simply holding their wings against the airflow. Either way, the pterosaurs would have needed sophisticated neural control on a par with modern birds, the researchers say.
After the flap stall, the tracks show the animal stabilised itself with its arms, as it hopped a little way forward before it began to walk away on all four limbs.
David Martill, a pterosaur specialist at the University of Portsmouth, UK, says that although the tracks record a "small moment, perhaps no more than three seconds, in the life of a pterosaur", they offer a real insight into the lives of the ancient animals.
But Michael Habib at Chatham University in Pittsburgh, Pennsylvania, points out that the real mystery of pterosaur flight remains unsolved.
"Any flying animal larger than a large insect will need to use some kind of controlled stall or hover mechanism to land," he says, but the new track "does not give us any new information about launch".
Earlier this year Habib suggested that the largest pterosaurs took flight by using all four limbs to leap into the air – a technique similar to that used by some bats but quite unlike the take-off behaviour of modern birds.
Padian says Habib's theory may have been possible. "On the other hand, pterosaurs seem perfectly capable of standing on their back legs, so a two-legged [bird-style] take-off, whether from a standing pose or running, seems equally plausible – depending on the pterosaur."
"Birds have one of the most complex respiratory systems of all animal groups. Upon inhalation, 75% of the fresh air bypasses the lungs and flows directly into a posterior air sac which extends from the lungs and connects with air spaces in the bones and fills them with air. The other 25% of the air goes directly into the lungs. When the bird exhales, the used air flows out of the lung and the stored fresh air from the posterior air sac is simultaneously forced into the lungs. Thus, a bird's lungs receive a constant supply of fresh air during both inhalation and exhalation."
By utilizing a unidirectional flow of air, avian lungs are able to extract a greater concentration of oxygen from inhaled air. Birds are thus equipped to fly at altitudes at which mammals would succumb to hypoxia. This also allows them to sustain a higher metabolic rate than an equivalent weight mammal.
For those who wish to know more about it, please check here.
Here are references to pterosaur breathing:
"A 2009 study showed that pterosaurs had a lung-air sac system and a precisely controlled skeletal breathing pump, which supports a flow-through pulmonary ventilation model in pterosaurs, analogous to that of birds. The presence of a subcutaneous air sac system in at least some pterodactyloids would have further reduced the density of the living animal."In current evolution theory thinking, birds evolved from dinosaurs. That means that according to the current "dino to bird" evolution thinking, birds and pterosaurs both evolved this unique and complex breathing system completely INDEPENDENTLY.
In evolution theory, this idea is called "convergent evolution". The similar characteristics are called "analogous".
In the position I am presenting in this blog, we do not need to rely on a (miraculous) convergent evolution. Modern birds developed from pterosaurs so the development was not independent.
Postcranial skeletal pneumaticity and air-sacs in the earliest pterosaurs
Richard J. Butler1,*,
Paul M. Barrett1 and
David J. Gower2
Pterosaurs breathed in bird-like fashion and had inflatable air sacs in their wings
Posted by Darren Naish on February 18, 2009
"Pterosaurs were flying reptiles of the clade [group] or order Pterosauria. They existed from the late Triassic to the end of the Cretaceous Period (220 to 65.5 million years ago).
Pterosaurs are the earliest vertebrates known to have evolved [developed] powered flight. Their wings were formed by a membrane of skin, muscle, and other tissues stretching from the legs to a dramatically lengthened fourth [actually fifth] finger. Early species Rhamphorhynchoidea had long, fully-toothed jaws and long tails, while later forms Pterodactyloidea had a highly reduced tail, and some lacked teeth. Many sported furry coats made up of hair-like [feather-like] filaments known as pycnofibres, which covered their bodies and parts of their wings. Pterosaurs spanned a wide range of adult sizes, from the very small Nemicolopterus to the largest known flying creatures of all time, including Quetzalcoatlus and Hatzegopteryx.
Pterosaurs are sometimes referred to in the popular media as dinosaurs, but this is incorrect. The term "dinosaur" is properly restricted to a certain group of terrestrial reptiles with a unique upright stance (superorder Dinosauria), and therefore excludes the pterosaurs, as well as the various groups of extinct aquatic reptiles, such as ichthyosaurs, plesiosaurs, and mosasaurs.
Traditionally, they are organized into two suborders:
- Rhamphorhynchoidea: A group of early, basal ("primitive") pterosaurs, many of which had long tails and short metacarpal bones in the wing. They were small, and their fingers were still adapted to climbing. They appeared in the Late Triassic period, and lasted until the late Jurassic.
- Pterodactyloidea: The more derived ("advanced") pterosaurs, with short tails and long wing metacarpals. They appeared in the middle Jurassic period, and lasted until the Cretaceous-Tertiary extinction event [when they developed into modern birds].
"Ramphorhynchoids were the first pterosaurs to have appeared, in the late Triassic Period. Unlike their descendants the pterodactyloids, most rhamphorhynchoids had teeth and long tails, and most species lacked a bony crest, though several are known to have crests formed from soft tissue like keratin. They were generally small, and disappeared at the end of the Jurassic Period."
"They appeared during the middle Jurassic Period, and differ from the basal rhamphorhynchoidea by their short tails and long wing metacarpals (hand bones). The most advanced forms also lack teeth. Many species had well developed crests on the skull,"
"Other distinguishing characteristics that set Pteranodon apart from other pterosaurs include narrow neural spines on the vertebrae, plate-like bony ligaments strengthening the vertebrae above the hip, and a short tail in which the last few vertebrae are fused into a rod."
" A new compilation of data for the Lower Cretaceous hints at a broad differentiation between pterosaurs that lived in continental habitats (anurognathids, ctenochasmatoids, dsungaripteroids) and those that frequented marine environments (ornithocheiroids). Moreover, there is evidence of further differentiation within continental habitats, between pterosaurs living in lowland and coastal regions (anurognathids. ctenochasmatoids) and those living in more inland environments (dsungaripteroids). "
Wednesday, April 28, 2010
Here is a preliminary summary of some of the similarities between pterosaurs and modern birds. I will analyze these and many more in later posts.
Here is a preliminary summary of some of the similarities between pterosaurs and modern birds. I will analyze these and many more in later posts.
"Pterosaur bones were hollow and air filled, like the bones of birds. They had a keeled breastbone that was developed for the attachment of flight muscles and an enlarged brain that shows specialised features associated with flight. In some later pterosaurs, the backbone over the shoulders fused into a structure known as a notarium, which served to stiffen the torso during flight, and provide a stable support for the scapula (shoulder blade).
As evidenced by hollow cavities in the wing bones of larger species and soft tissue preserved in at least one specimen, some pterosaurs extended their system of respiratory air sacs into the wing membrane itself.
Unlike most archosaurs, which have several openings in the skull in front of the eyes, in pterodactyloid pterosaurs the antorbital opening and the nasal opening was merged into a single large opening, called the nasoantorbial fenestra. This likely evolved as a weight-saving feature to lighten the skull for flight
Pterosaurs are well known for their often elaborate crests.
The presence of pycnofibres (and the demands of flight) imply that pterosaurs were endothermic (warm-blooded).
The mechanics of pterosaur flight are not completely understood or modeled at this time, but it is almost certain that this group of animals was capable of powered flight in at least as wide a range of conditions as modern birds.
The wings were probably flapped in a manner grossly similar to that seen in birds (a group which displays many different flapping strategies among and within different species and different situations).
A 2009 study showed that pterosaurs had a lung-air sac system and a precisely controlled skeletal breathing pump, which supports a flow-through pulmonary ventilation model in pterosaurs, "analogous" to that of birds. The presence of a subcutaneous air sac system in at least some pterodactyloids would have further reduced the density of the living animal
The pterosaurs' flocculi occupied 7.5% of the animals' total brain mass, more than in any other vertebrate. Birds have unusually large flocculi compared with other animals, but these only occupy between 1 and 2% of total brain mass
Pterosaur's hip sockets are oriented facing slightly upwards, and the head of the femur (thigh bone) is only moderately inward facing, suggesting that pterosaurs had a semi-erect stance.
Pteranodon had slightly larger feet (47% the length of the tibia), while filter-feeding pterosaurs like the ctenochasmatoids had very large feet (69% of tibial length in Pterodactylus, 84% in Pterodaustro), adapted to walking in soft muddy soil, similar to modern wading birds
It is not known whether pterosaurs practiced any form of parental care, but their ability to fly as soon as they emerged from the egg and the numerous flaplings found in environments far from nests and alongside adults has led most researchers, including Christopher Bennett and David Unwin, to conclude that the young were only dependent on their parents for a very short period of time, while the wings grew long enough to fly, and left the nest to fend for themselves within days of hatching."
Note that the word "analogous" is a technical evolution theory word which relates to the idea of (what is called in evolution theory) "convergent evolution". I will talk about this later.
This series of creatures lacks credibility. The alternative that birds developed from pterosaurs is exceptionally more credible, as this blog will lay out over the course of a number of posts.
Here is a good summary of the dino-to-bird idea:
And see the chart in the Relationships section on this site:
Also here is some history:
"In 1969, this dinosaur was described and named Deinonychus by John Ostrom of Yale University. The next year, Ostrom redescribed a specimen of Pterodactylus in the Dutch Teyler Museum as another skeleton of Archaeopteryx. The specimen consisted mainly of a single wing and its description made Ostrom aware of the similarities between the wrists of Archaeopteryx and Deinonychus.
In 1972, British paleontologist Alick Walker hypothesized that birds arose not from 'thecodonts' but from crocodile ancestors like Sphenosuchus. Ostrom's work with both theropods and early birds led him to respond with a series of publications in the mid-1970s in which he laid out the many similarities between birds and theropod dinosaurs, resurrecting the ideas first put forth by Huxley over a century before. Ostrom's recognition of the dinosaurian ancestry of birds, along with other new ideas about dinosaur metabolism, activity levels, and parental care, began what is known as the Dinosaur renaissance, which began in the 1970s and continues to this day.
Ostrom's revelations also coincided with the increasing adoption of phylogenetic systematics (cladistics), which began in the 1960s with the work of Willi Hennig. Cladistics is a method of arranging species based strictly on their evolutionary relationships, using a statistical analysis of their anatomical characteristics. In the 1980s, cladistic methodology was applied to dinosaur phylogeny for the first time by Jacques Gauthier and others, showing unequivocally that birds were a derived group of theropod dinosaurs. Early analyses suggested that dromaeosaurid theropods like Deinonychus were particularly closely related to birds, a result which has been corroborated many times since."
Avialae vs. Aves"Gauthier (page 34) identified four conflicting ways of defining the term "Aves", which is a problem because the same biological name is being used four different ways. Gauthier proposed a solution, number 4 below, which is to reserve the term Aves only for the last common ancestor of all living birds and all of its descendants. He assigned other names to the other groups.
- Aves can mean those advanced archosaurs with feathers (alternately Avifilopluma)
- Aves can mean those that fly (alternately Avialae)
- Aves can mean all reptiles closer to birds than to crocodiles [ie. dinosaurs and pterosaurs] (alternately Panaves)
- Aves can mean the last common ancestor of all the currently living birds and all of its descendants (a "crown group"). (alternately Neornithes)
Tuesday, April 27, 2010
Two of the taxa (groups) within Pterodactyloidea are Ornithocheiroidea and Azhdarchoidea.
Within Ornithocheiroidea are Pteranodontids which are similar to the modern day albatross.
"The wing shape of Pteranodon suggests that it would have flown rather like a modern-day albatross. This is a suggestion based on the fact that the Pteranodon had a high aspect ratio (wingspan to chord length) similar to that of the albatross — 9:1 for Pteranodon, compared to 8:1 for an albatross. Albatrosses spend long stretches of time at sea fishing, and utilize a flight pattern called "dynamic soaring" which exploits the vertical gradient of wind speed near the ocean surface to travel long distances without flapping, and without the aid of thermals (which do not occur over the open ocean the same way they do over land)."
Within Azhdarchoidea are azhdarchids which are considered by researchers to be "stork- or ground hornbill-like generalists".
"However, azhdarchid footprints show that their feet were relatively small, padded and slender, and thus not well suited for wading. We argue that azhdarchids were stork- or ground hornbill-like generalists, foraging in diverse environments for small animals and carrion".
"According to scientists and paleontologists, the Rhamphorhynchus hunted in a manner similar to the modern-day pelican wherein it would dive into water and use its long beak to scoop out fish, insects and frogs from water and then toss them down its throat pouch.
The fossils of Rhamphorhynchus that have been found have been well-preserved. One can see not just the skeleton but also the outline of the internal organs. Some fossils have been found with the throat pouch intact. Many Rhamphorhynchus fossils have been found in southern
"Throat pouches (like those of a pelican) can be seen in Pterodactylus and can be inferred in Ludodactylus."
"Rhamphorhynchus probably ate fish and it is believed that one of the ways it hunted was by dragging its beak in the water, catching fish and tossing them into its throat pouch, a structure similar to that of pelicans, which has been preserved in some fossils. This method of catching fish is found today in skimmers."
"Unlike many of the other Pterosaurs Quetzalcoatlus lived inland and probably had a vulture-like existence. It's long neck would have helped it to "probe" dinosaur carcasses for meat.
Others think they may have been carrion feeders, like modern vultures, and fed upon the carcasses of dinosaurs. Their long beaks and necks made them capable of probing deeply for food, on sea or land."
Reconstructed wing planform of Quetzalcoatlus compared to the Wandering Albatross and the Andean Condor
"Based on Mark Witton's research (he's the most decent pterosaur paleobiologist I've seen so far), here's a brief comparation between pterosaur and bird niches (note: niches occupied as adults; since pterosaurs were precocial, they occupied several niches throw their lifestyle, and I have no idea what can be said about them):
-Azhdarchoids: storks, teratorns, ground hornbills, bustards, secretary bird/seriema, herons, galliformes
-Dsungaripteroids: oyester catchers, open bills storks
-Ctenochasmatoids: shorebirds, flamingoes, seagulls
-Ornitocheiroids: albatrosses, frigate birds, pseudodontorns, vultures
-Advanced "basal" pterosaurs (Rhamphorhynchus & kin): same as above (only to a smaller scale), except for the vulture niche; they probably produced falcon like things though.
-Dimorphodontids: hawks, owls"