Saturday, February 25, 2012

Pterosaur and Bird Similarities (Redux)

In a very early post I quoted a passage of basic info about pterosaurs which indicates that there is a great deal of similarity between pterosaurs and birds. Here I review them again.

"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.[4] 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.
Most pterosaur skulls had elongated, beak-like jaws. Some advanced forms were toothless (such as the pteranodonts and azhdarchids, though most sported a full complement of needle-like teeth
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[22][23], 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% inPterodaustro), 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."

Summary of Similarities:

Here is a summary of the posts on this site that refer to particular similarities between pterosaurs and birds:








Glenoid fossa:
"As in birds, the glenoid fossa in most pterosaurs is elevated by a dorsolaterally directed elongation of the coracoid and lies almost level with the vertebral column"

Fused pelvic bones:


Gizzard Stones (Gastrolith)

Uncinate Processes:



Keeled Breastbone:

Warm Blooded (Endothermic):



Powered flight:


Horizontal thigh bone:


Small genomes:




Carpus (wrist):




High metabolic rate:

Pubic bones:



Aspiration Pump:

Sternal Ribs:

Fingers and Wrists:


  1. More info:
    "The pterosaur wrist consists of two inner (proximal) and four outer (distal) carpals (wrist bones), excluding the pteroid bone, which may itself be a modified distal carpal. The proximal carpals are fused together into a "syncarpal" in mature specimens, while three [actually four] of the distal carpals fuse to form a distal syncarpal. The remaining distal carpal, [actually the thumb metacarpal] referred to here as the medial carpal, but which has also been termed the distal lateral, or pre-axial carpal, articulates on a vertically elongate biconvex facet on the anterior surface of the distal syncarpal. The medial carpal [actually thumb metacarpal] bears a deep concave fovea that opens anteriorly, ventrally and somewhat medially, within which the pteroid articulates.[16]"

    My modifications are in square brackets [ ].

    1. What references do you have to support those "modifications"?

  2. I cover that in detail on the site.
    Please read it.
    And if you wish to post again please include a made-up name.

  3. For reference:

    "Over the course of Cenozoic diversification,
    other birds did assume modes of life similar to those
    vacated by pterosaurs: skimmers may roughly correspond to
    Tropeognathus with its keeled jaws, swallows and swifts to
    Pterodactylus with its similar size and wing proportions, flamingos
    to Pterodaustro with its bristling array of fringe-like teeth, and
    perhaps even condors to the enormous Quetzlcoatlus".

  4. Posts concerning the pterosaur wrist:

  5. I saw absolutely no support to justify those modifications. It seems that, at this point, you are simply asserting the distal carpal is the thumb metacarpal. Some evidence in support of that position would be useful.


  6. You also provide this picture:

    That image is nothing like a metacarpal.

  7. Anonymous, could you please elaborate? And when you do please include a made-up name.

  8. Hello John. What is your preferred alternative.

  9. I have no preferred alternative. I was asking you for some support for your position. "What is your preferred alternative" is not support for your position.


  10. Hi John. When you can give an alternative we can discuss. Please see the site for the support of my position.

  11. I did. I checked the links you provided. In all of them, you simply assert that the carpal is the "thumb metacarpal". No support.

    And why do you want a specific alternative to discuss your theory? A theory, any theory, stands or falls on its own. Science is not some postmodernist endeavor, in which we examine which version is more 'cool'. It is a scientist's obligation to provide support for his own theory, not demand from others to provide something to refute their unsupported assumptions.


  12. Please post your concern on the post where I discuss this and you claim I have not supported my proposal.
    Also I ask for your preferred alternative because all the people to date who have raised objections to these ideas were wasting my time. Some intentionally. I no longer waste my time. Here is how I do it now. I ask you for your preferred alternative. When you tell me then I ask you about it. If you are serious you can make that small effort.
    You may disagree with my approach. That is your right of course. But that is the ground rule I have set up to avoid my time being wasted.