Wednesday, April 28, 2010

Pterosaur / Bird Similarities

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.[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% 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.


  1. Bats and insects are also full of weight-saving features. Did one evolve into the other as well?

    Convergent evolution is NOT anagenesis.

  2. You have said:
    "Bats and insects are also full of weight-saving features. Did one evolve into the other as well?"
    We would have to look at the specific case. Are bats and insects an interest of yours? Although bats and insects are very interesting I am not focusing on them.

    Also, I agree that convergent evolution is not anagenesis. Did you think I was saying that?