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:

Thursday, February 23, 2012


It is possible to be more precise about the point where pterosaurs developed into primitive birds. I have been saying (for simplicity) that that point is the appearance of maniraptors. But not all taxa that are labeled "maniraptor" are birds. (For example, members of Ornitholestes are not birds).
At least the "maniraptors" from the paraves/oviraptors to the present, are birds. They are called Aviremigia.
Also called Chuniaoae.

Here is Naish:

The fact that long remiges have now been documented in oviraptorosaurs, dromaeosaurids and other maniraptorans shows that feathered arms essentially the same as those present in basal birds evolved somewhere round about the base of the oviraptorosaur + paravian clade, and there is no evidence that wing-like arms were present in more basal coelurosaurs, nor in other theropods, or other dinosaurs, or other archosaurs.

Overview of basic ideas

Note that I am just focussing now on the idea that basal pterosaurs evolved into basal Paraves and not on the following: 

The pterosaur to bird theory contains two basic ideas, that differ from current mainstream thinking.
The first idea is that pterosaurs developed into a set of primitive bird lines.
The second is that EACH ONE of those primitive bird lines then developed into a set of corresponding modern birds, in what might be called a set of "parallel lines".

For example:
Seabirds (Ichthyornithes line)
  • Pterosaur (Ornithocheiroidea) eg. Pteranodon --> 
  • An Ichthyornithes subgroup --> 
  • Gulls, Skimmers (Charadriiformes/Lari)
Here we see one of the parallel lines of primitive birds (Ichthyornithes), developing into the set of corresponding modern birds.

If any of this is not clear, I invite questions and comments.

Note: Most of the posts on this site present evidence supporting the pterosaur to bird theory. Some of the posts show the flaws in the current, mainstream dinosaur to bird theory. I have put an asterisk (*) at the beginning of the post titles that are on the flaws of the dinosaur to bird theory.

Categories (Updated)

See the updated version posted on Jan 15, 2013.

For ease of reference, here is the list of links to the updated categories I have analyzed to this point. This is a work in progress.


See the updated version posted on Jan 15, 2013.

For reference:
As a result, the possibly fish-eating Ctenochasma and Rhamphorhynchus may have had similar activity patterns to modern nocturnal seabirds, and the filter-feeding Pterodaustro may have had similar activity patterns to modern anseriform birds that feed at night. 
Some [pterosaur] advanced beaked forms were toothless, such as the pteranodonts and azhdarchids, and had larger, more extensive, and more bird-like beaks.[25]
210–124.5 Ma

Cladogram showing the most recent classification of Neoaves, based on several phylogenetic studies.

Not yet categorized:
  • Pelican
  • Vulture
  • Condor

Thursday, February 16, 2012

Pterosaur brachiopatagium to bird postpatagium

Lets look at the brachiopatagium of the pterosaur and see how it changed in the development to bird.
"Several sheets of tough, tendinous tissue form significant parts of the wing structure: the patagium and the patagialis longus muscle and tendon actually form much of the leading edge of the wing"
Note page 128 of this reference:
n. In ornithology, the triangular fold of skin, just back of the shoulder-joint, which runs from the side of the body to the upper posterior face of the upper arm.

It may well be the case that the development from the pterosaur  brachiopatagium  to the primitive bird wing skin took place in one step through a mechanism such as "facilitated variation".

See the following references for more info on the fascinating topic of facilitated variation:

Friday, February 10, 2012

* No antecedent structures in dino to bird theory
Feathers, however, are hierarchically
complex assemblages of numerous
evolutionary novelties—the feather follicle,
tubular feather germ, feather branched structure,
interacting differentiated barbules—that
have no homolog in any antecedent [dinosaur] structures

(Brush 1993, 1996, 2000; Prum 1999). Genuine
evolutionary novelties are distinct from
simple microevolutionary changes in that they
are qualitatively or categorically different from
any antecedent or homonomous structure.
"In conclusion, the morphological and
molecular developmental details shared by
avian feather and scales support homology
between these structures at the level of the
placode. The morphology and development
of all subsequent structures within the feather
are evolutionary novelties that have no homologs
in avian or reptilian scales.
 "Many features of feathers and feather development meet this definition and qualify as evolutionary novelties. The follicle, the differentiated sheath and feather germ, differentiated barb ridges, barb rami, barbules, differentiated pennulae of the proximal and distal bar bules, and the rachis are all evolutionary novelties, as are the derived mechanisms by which these novel structures develop. At a molecular level, the derived 10 kilodalton -keratins of feathers are also novel"

In regards to the feather, the dino to bird theory (according to Prum and Brush) depends on a series of miracles (aka "numerous evolutionary novelties that have no homolog in any antecedent structures").
The pterosaur to bird theory is not based on miracles.

Saturday, February 4, 2012

* Dinosaurs did not have wing-like arms

I could hardly have put it better than the following:
The fact that long remiges have now been documented in oviraptorosaurs, dromaeosaurids and other maniraptorans shows that feathered arms essentially the same as those present in basal birds evolved somewhere round about the base of the oviraptorosaur + paravian clade, and there is no evidence that wing-like arms were present in more basal coelurosaurs, nor in other theropods, or other dinosaurs, or other archosaurs.
The dino to bird folks do not specify their imagined lineage. But they have some belief that coelurosaur dinosaurs evolved into Paraves and those Paraves evolved into modern birds. But it leaves open when in that lineage "wing-like arms" appeared.
Naish asserts that "feathered arms essentially the same as those present in basal birds evolved somewhere round about the base of the oviraptorosaur + paravian clade".
He then says that "there is no evidence that wing-like arms were present in more basal coelurosaurs, nor in other theropods, or other dinosaurs, or other archosaurs."
In other words, concerning wing arms, there is no connection whatsoever between dinos and paraves/oviraptors.
Page 9/10
The relative length and diameter of the humerus in several theropod taxa. We use
the ratios of humeral length to femoral length, and humeral diameter to femoral diameter, as
indicators of forelimb length and robustness. Relative to the femur, the humerus is
significantly longer and thicker in basal paravians than in non-paravian theropods, derived
dromaeosaurids and troodontids (the relatively short and slender forelimbs in the last two
groups are secondarily evolved according to the current phylogenetic analysis).
Page 28/29
The discovery of Xiaotingia further demonstrates that many features
previously regarded as distinctively avialan actually characterize the
more inclusive Paraves. For example, proportionally long and robust
forelimbs are optimized in our analysis as a primitive character state
for the Paraves (see Supplementary Information). The significant
lengthening and thickening of the forelimbs indicates a dramatic shift
in forelimb function at the base of the Paraves, which might be related
to the appearance of a degree of aerodynamic capability. This hypothesis
is consistent with the presence of flight feathers with asymmetrical
vanes in both basal avialans and basal deinonychosaurs6,23

* Hypothetical Creatures

But, ultimately, BCF is entirely unsatisfactory: we're supposed to construct scientific hypotheses based on the evidence we have, rather than on the evidence we think there should be, and BCF is just way too speculative. It proposes the existence of a whole lineage of hypothetical creatures that are absent from the fossil record.
Naish makes it sound like there is a problem if you propose the existence of a whole lineage of hypothetical creatures that are absent from the fossil record.

But of course that is EXACTLY what the dino to bird theory does!
As I have pointed out again and again.

Thursday, February 2, 2012

* Paraves to modern bird;jsessionid=D85984F3042F8E00C550060394176368.d03t02?systemMessage=Wiley+Online+Library+will+be+disrupted+4+Feb+from+10-12+GMT+for+monthly+maintenance
"Shared behavioural, morphological and physiological characteristics are indicative of the evolution of extant birds from nonavian maniraptoran dinosaurs. One such shared character is the presence of uncinate processes and respiratory structures in extant birds. Recent research has suggested a respiratory role for these processes found in oviraptorid and dromaeosaurid dinosaurs. By measuring the geometry of fossil rib cage morphology, we demonstrate that the mechanical advantage, conferred by uncinate processes, for movements of the ribs in the oviraptorid theropod dinosaur, Citipati osmolskae, basal avialan species Zhongjianornis yangi, Confuciusornis sanctus and the more derived ornithurine Yixianornis grabaui, is of the same magnitude as found in extant birds. These skeletal characteristics provide further evidence of a flow-through respiratory system in nonavian theropod [maniraptors] dinosaurs and basal avialans, and indicate that uncinate processes are a key adaptation facilitating the ventilation of a lung air sac system that diverged earlier than extant birds."

Great evidence that birds developed from Paraves. No evidence that Paraves developed from dinosaurs.

See this earlier post concerning pterosaurs and uncinate processes:

Citipati osmolskae, Zhongjianornis yangi, Confuciusornis sanctus and Yixianornis grabaui are all members of Aviremigia. They are not dinosaurs.