Friday, January 9, 2015

Dino to bird - off on the wrong foot

The revival of the dino to bird idea began with the work of John Ostrom in the 1970's. But the problem is that Ostrom made the mistake of taking the secondarily flightless Deinonychus to be a land-based transitional between dinosaur and Paraves.
It is now clear that Deinonychus is a secondarily flightless member of Paraves. It is considered a dromaeosaur which is included in Paraves.
The current dino to bird opinion dates back to Ostrom's mistake in the 1970's.
The problem is still that there is no connection between real dinosaurs and Paraves.

Relevant links:

Tuesday, January 6, 2015

Dinosaur to bird - implausible rates of change

For the dino to bird theory to be correct, the evolutionary rates must have been up to four times faster. But that would mean that for the dino to bird theory to be correct, it would require rates of evolution comparable to those in the Cambrian Explosion.
Huge meat-eating, land-living dinosaurs evolved into birds by constantly shrinking for over 50 million years, scientists have revealed.
Theropods shrunk 12 times from 163kg to 0.8kg before becoming modern birds.
The researchers found theropods were the only dinosaurs to get continuously smaller.
Their skeletons also changed four times faster than other dinosaurs, helping them to survive.
They found that the dinosaur group directly related to birds shrank rapidly from about 200 million years ago.
It showed a decrease in body mass of 162.2kg (25st 7lb) from the largest average body size to Archaeopteryx, the earliest known bird.
These bird ancestors also evolved new adaptations, including feathers, wishbones and wings, four times faster than other dinosaurs.
Shrinking and new bird-like traits jointly influenced the transition of dinosaurs to birds, researchers say.
The researchers concluded that the evolution of the branch of dinosaurs leading to birds was more innovative than other dinosaur lineages.
There is a better explanation for the improbable rates of change:
Birds did not evolve from dinosaurs.

Because our results allow us to map the appearance dates of lineages onto the phylogeny, we can see that evolutionary rates across part of the lineage leading to birds occurred much faster than expected compared to the rest of the tree – up to four times faster, in fact (Lee et al. 2014a). This seemingly explains why several groups of tetanuran theropods – allosauroids, tyrannosauroids, compsognathids and others – appear near-simultaneously in the fossil record: it seems that the time intervals between their originations really were very short. Why evolution was occurring so rapidly in these animals remains, of course, an unknown.
According to the dino to bird theory, Paraves appeared "near-simultaneously" with its purported coelurosaur dinosaur ancestor . This is no longer evolution theory. This is creationism.

The study itself:


Full study:

The study Supplementary Material:

Notice the red line connecting the compsognathid branch and the ornithomimosaur branch.
This is an indication that they are not similar:

The near-simultaneous appearance of most modern animal body plans (phyla) ~530 million years ago during the Cambrian explosion is strong evidence for a brief interval of rapid phenotypic and genetic innovation, yet the exact speed and nature of this grand adaptive radiation remain debated [1–12]. Crucially, rates of morphological evolution in the past (i.e., in ancestral lineages) can be inferred from phenotypic differences among living organisms—just as molecular evolutionary rates in ancestral lineages can be inferred from genetic divergences [13]. We here employed Bayesian [14] and maximum likelihood [15] phylogenetic clock methods on an extensive anatomical[16]and genomic[17] data set for arthropods, the most diverse phylum in the Cambrian and today. Assuming an Ediacaran origin for arthropods, phenotypic evolution was ~4 times faster, and molecular evolution ~5.5 times faster, during the Cambrian explosion compared to all subsequent parts of the Phanerozoic. These rapid evolutionary rates are robust to assumptions about the precise age of arthropods. Surprisingly,these fast early rates do not change substantially even if the radiation of arthropods is compressed entirely into the Cambrian (~542 mega-annum [Ma]) or telescoped into the Cryogenian (~650 Ma). The fastest inferred rates are still consistent with evolution by natural selection and with data from living organisms, potentially resolving ‘‘Darwin’s dilemma.’’ However, evolution during the Cambrian explosion was unusual (compared to the subsequent Phanerozoic) in that fast rates were present across many lineages.
This means that the dino to bird theory is right up there with the Cambrian Explosion in terms of it being unusual.
The near-simultaneity and the much faster rates of evolution required by the dino to bird theory are VERY UNUSUAL. As unusual as the Cambrian Explosion.


Friday, January 2, 2015


The dino to bird folks are slowly coming to the idea that birds originated in the trees, "trees down". They are acknowledging that it is not plausible that birds evolved "ground up".
But that creates a problem for the dino to bird theory.
Since Archaeopteryx did not evolve in an arboreal environment, it now contradicts the dino to bird theory
The excellent preservation of Archaeopteryx fossils and other terrestrial fossils found at Solnhofen indicates that they did not travel far before becoming preserved.[48] The Archaeopteryx specimens found are likely therefore, to have lived on the low islands surrounding the Solnhofen lagoon rather than to have been corpses that drifted in from farther away. Archaeopteryx skeletons are considerably less numerous in the deposits of Solnhofen than those of pterosaurs, of which seven genera have been found.[49] The pterosaurs included species such as Rhamphorhynchus belonging to the Rhamphorhynchidae, the group which dominated the niche currently occupied by seabirds, and which became extinct at the end of the Jurassic. The pterosaurs, which also included Pterodactylus, were common enough that it is unlikely that the specimens found are vagrants from the larger islands 50 km (31 mi) to the north.[50]
The islands that surrounded the Solnhofen lagoon were low lying, semi-arid, and sub-tropical with a long dry season and little rain.[51] The closest modern analogue for the Solnhofen conditions is said to be Orca Basin in the northern Gulf of Mexico, although that is much deeper than the Solnhofen lagoons.[49] The flora of these islands was adapted to these dry conditions and consisted mostly of low (3 m [10 ft]) shrubs.[50] Contrary to reconstructions of Archaeopteryx climbing large trees, these seem to have been mostly absent from the islands; few trunks have been found in the sediments and fossilized tree pollen also is absent.

See page 88 here for an inconsistent rationalization of mainstream thinking:

Thursday, January 1, 2015

How did birds come into being?

How did birds come into being?
First we must distinguish between modern birds on the one hand, and their feathered ancestors called "basal paraves" on the other.
Basal paraves were feathered, long-bony-tailed, flying creatures (eg. scansoriopteryx). No modern birds have long-bony-tails.

So the question becomes, how did basal paraves come into being?
The dinosaur to bird theory suggests that basal paraves evolved from coelurosaur dinosaurs (eg. tyrannosaurs).
The pterosaur to bird theory suggests that basal paraves evolved from pterosaurs (eg. rhamphorhynchids). 
The topic immediately becomes complicated, because there is a set of feathered, long-bony-tailed creatures that did not fly (eg. oviraptors, alvarezsaurids).
The dinosaur to bird theory views these creatures as transitional between ground-based coelurosaur dinosaurs and flying basal paraves. They call them "non-paraves maniraptors".
The pterosaur to bird theory views these creatures as secondarily flightless* members of basal paraves.

It is important to realize that according to the known fossil record, all these flightless, feathered creatures came after (closer to today than) the flying members of basal paraves.
This is straightforwardly consistent with them being secondarily flightless. On the other hand, for them to be transitional between dinosaurs and flying basal paraves, requires purported lengthy ghost lineages (up to tens of millions of years in length) and purported exaptations.

* An ostrich is an example of a "secondarily flightless" modern bird.

Wednesday, December 17, 2014

Pubis evolution
Pterosaur pubis (in green) and prepubis (in yellow). The drawing of MPUM 6009 is the most relevant.

The pterosaur pubis is homologous with the basal paraves superior pubic ramus and pubic body.
The pterosaur prepubis is homologous with the basal paraves inferior pubic ramus.
pterosaurs also have a fourth pelvic bone in the form of the pre-pubis. This pair of bones (one for each side) lie, and no points for guessing this, in front of, and articulate with, the pubes.
The prepubis of pterosaurs is a pelvic bone not found in the vast majority of tetrapods. It is not homologous with the prepubis of monotremes and marsupials. Nor is it homologous with the so-called “prepubic” bones of crocodilians, which are homologous with the pubic bones of other amniotes (Seeley 1901). The prepubis of ornithischian dinosaurs is a process of the pubis and not a separate ossification.
For example:
The pubis/prepubis parts of MPUM 6009 above, correspond to the 3 parts of the paraves pubis, as seen in the oviraptor pubis in drawing "C" below.

Working hypothesis:
Pterosaurs could not walk upright because the acetabulum was completely closed. They splayed their legs. In the transition to basal paraves, the acetabulum no longer closed completely. A hole in the bottom of the acetabulum appeared. This allowed an upright stance as well as continuing the ability to splay the legs. This made flying with hindlimb feathers possible using splayed legs, while also gaining the ability to walk upright.

Sunday, December 14, 2014


Pterosaur feet are like basal paraves feet. Dinosaur feet are not like basal paraves feet.
The foot of Epidendrosaurus [a Scansoriopterygidae] is unique among nonavian
theropods. Although it does not preserve a reversed
hallux, metatarsal I is articulated with metatarsal II at
such a low position that the trochleae of metatarsals I–IV
are almost on the same level (see Figs. 1, 2d), which
is similar to
those of perching birds including the Early
Cretaceous flying birds Sinornis (Sereno 1992) and
Longipteryx (Zhang and Zhou 2001), as well as many arboreal
It [Scansoriopteryx] also had an unusually large first toe, or hallux, which was low on the foot and may have been reversed, allowing some grasping ability.[1]
The Scansoriopterygidae are among the most basal members of Paraves.
Other features of digits I-IV of the D. weintraubi foot indicate a capacity for grasping that is consistent with an ability to climb but is unexpected in an obligate cursor. The claws are moderately curved (nearly as strongly as the claws of the manus); all phalanges except the most proximal have well developed flexor tubercles for the insertion of digital flexors (Fig. 2); and all of the IP joints allow for extensive flexion of the digits (as exhibited by digit IV; Fig. 2). Furthermore, the phalangeal proportions of the digits of Dimorphodon and other basal pterosaurs are similar to those of birds with grasping feet (that is, perching, climbing, and raptorial species) and unlike those of primarily ground-living birds, bipedal dinosaurs and the primitive dinosauromorphs Lagerpeton and Marasuchus.

Friday, December 12, 2014

The [Epidendrosaurus] material described in this paper was collected from a new locality, Daohugou, in east Nei Mongol, northeast China, which is west of Liaoning Province. Many salamanders(Wang 2000), plants and insects (Zhang 2002)have recently been discovered from this new locality. It is notable that an anurognathid rhamphorhynchoid pterosaur with beautiful hair [pycnofibers] covering the whole body has also been reported from this locality (Wang et al. 2002). The estimated age of the deposit at this locality is very controversial and ranges from the Middle Jurassic or the Early Cretaceous according to various authors (Wang etal. 2000; Zhang 2002); however, most workers currently regard it as being Late Jurassic.
Epidendrosaurus is a Scansoriopterygidae and one of the most basal members of Paraves.

Monday, December 8, 2014


It needs to be kept in mind that the vocabulary that is routinely used in discussing the origin of birds is based on the dino to bird theory. The vocabulary is not neutral. It assumes the dino to bird theory*.
This makes it tricky to even describe the pterosaur to bird theory. You have to use very qualified expressions, which even then, imply a dino to bird theory.
For example, I often use the phrase "basal paraves". This is intended to mean the long-bony-tailed feathered flying and secondarily flightless creatures. For example, Scansoriopterygidae.
But the category "paraves" is defined WITHIN the dino to bird theory. It assumes the dino to bird theory. So I obviously do not mean to include the baggage that the term "paraves" carries within the dino to bird theory.
For example, I do not mean that basal paraves evolved from dinosaurs and I do not mean to exclude oviraptors from the group.

* for example consider this:
Paraves is a branch-based clade defined to include all dinosaurs which are more closely related to birds than to oviraptorosaurs.

Sunday, November 30, 2014

Intramandibular joint

Basal paraves and pterosaurs do not have an intramandibular joint. Dinosaurs do have an intramandibular joint.

The unusual intra-mandibular joint described above is found only in herrerasaurids and theropods among dinosaurs. Dinosaurian outgroups (pterosaurs, crurotarsal archosaurs) also lack an intra-mandibular joint.


Page 21:
[Archaeopteryx] does not appear to have had an intramandibular joint
.....intramandibular articulation something that is actually absent in Archaeopteryx, but found in many of its theropod relatives.[2]


It would not tax the imagination to engender a long list of obstacles for the now dominant model of a theropod origin of birds, including....the sliding lower jaw joint [intramandibular joint] of theropods (absent in birds)
The traits uniting Theropoda seem to include:
An intramandibular joint between the dentary and post-dentary bones: this may have served as a shock absorber while feeding on live prey. (Herrerasaurs have a slightly different configuration of the intramandibular joint, and thus may be convergent.)
the analysis of Benton (2004) demonstrated that the only unequivocal synapomorphy diagnosing Theropoda is the presence of an intramandibular joint.


Friday, November 21, 2014


Here is a comparison of basal pterosaur, basal paraves and coelurosaur dinosaur.
As we can see, basal paraves are like pterosaurs. Basal paraves are not like dinosaurs.
This is a work in progress.
If anyone would like to contribute to this analysis, please feel free.

Basal Pterosaur: Rhamphorhynchidae
Basal Paraves: Scansoriopterygidae
Coelurosaur Dinosaur: Proceratosauridae
(or Compsognathoidea)

Basal Basal
Pterosaur Paraves Dinosaur

Back 1 Notarium: absent (0) present (1) ? ? 0
2  Hyposphene-hypantrum: absent (0) present (1) ? 0 1
Breathing 1 Respiratory air sacs: absent (0) present (1) 1 1 x 0
2 Aspiration pump: absent (0) present (1) 1 1 x 0
3 Rib lever processes: absent (0) present (1) 1 1 x 0
Chest 1 Keeled breastbone: absent (0) present (1)  1 ?
2 Furcula (wishbone): absent (0) present (1) 0 0 ?
Leg 1 Thigh bone: horizontal (0) not horizontal (1) 1 1 1
Foot 1 Hyperextended second toe: absent (0) present (1) 0 x 1 x 0
2 Hinge-like ankle joint: absent (0) present (1) 1 1 1
Pelvis 1 Pubic bone: pointing to back (0) to front (1) downward (2) 1 1 1
2 Pubic bones: not fused together (0) fused together (1) 0 ? ?
3 Acetabulum: closed (0) partial open (1) fully open (2) 0 x 1 x 2
4 Pelvic bones: not fused (0) fused (1) * * ?
5 Pre-pubic bone: absent (0) present (1) 1 ** **
6 Supra-acetabular shelf: not present (0) present (1) 0 0 x 1
7 Antitrochanter: absent (0) present (1)  0 0 x 1
Tail 1 Caudal vertebrae: less than 15 (0) greater than 15 (1) 1 1 1
2 Caudal rods: absent (0) present (1) 1 1 x 0
3 Muscle mass of M. caudofemoralis longus: small (0) large (1) 0 0 x 1
Skull 1 Beak like jaw: absent (0) present (1) 1 1 x 0
2 Teeth: absent (0) present (1) 1 1 1
3 Crest: absent (0) present (1)  1 1 1
4 Neck attaches to skull; from rear (0) from below (1) 0 0 0
5 Serrated teeth: absent (0) present (1) 0 0 x 1
6 Semicircular canals:  expanded (0) not expanded (1) 0 ? ?
7 Intramandibular joint: absent (0) present (1) 0 0 x 1
8 Mandibular fenestra: absent (0) present (1) * * *
Shoulder 1 Strap-like scapula: absent (0) present (1) 1 1 x 0
2 Scapula orientation to backbone: subparallel  (0) parallel (1) 1 1 x 0
3 Glenoid fossa: elevated (0) not elevated (1) 0 0 x 1
Feather 1 Stage 2 feathers: absent (0) present (1) 1 1 x 0
2 Pennaceous feathers: absent (0) present (1) 0 x 1 x 0
Wing 1 Propatagium: absent (0) present (1) 1 1 x 0
2 Patagium: absent (0) present (1)  1 1 x 0
3 Wing membrane: absent (0) present (1) 1 x 0 0
4 Elongated 4th finger: absent (0) present (1) 1 1 x 0
5 Number of fingers: 2 fingers (2) 3 fingers (3) 4  fingers (4) 4 x 3 2/3
6 Pteroid bone: absent (0) present (1) 1 x 0 0
7 Capable of flapping flight: not capable (0) capable (1) 1 1 x 0
Wrist 1 Semilunate carpal: absent (0) present (1) 0 x 1 x 0
2 Proximal carpals: not fused (0) fused (1) 1 ? ?
3 Distal carpals: not fused (0) fused (1) 1 ? ?
4 Carpometacarpus: absent (0) present(1) 0 x 1 x 0
5 Angle of abduction:  less than 25% (0) greater than 25% (1) ? ? 0
General 1 Warm blooded: absent (0) present (1) 1 1 ?
2 Neural flight control system: absent (0) present (1) 1 ? 0
3 Pneumatic bones: absent (0) present (1) 1 1

                 * = varies within group
                 ** = see link
                 x = Difference

Sunday, November 9, 2014

Shoulder Joint


From the article on page 267 (by Frey et al.):
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
Among living tetrapods, birds are unique in having completely separated the locomotor functions of fore and hindlimbs. The propulsive excursions of the forelimbs, which primarily involve elevation and depression in a transverse plane, differ fundamentally from those of most other tetrapods (pterosaurs and bats excepted) in which the forelimbs protract and retract in anteroposterior planes.
Pterosaurs and birds present a number of striking parallelisms in the structure of their flight apparatus and the glenoid is yet another example of their independent derivation of similar features.
In both rhamphorhynchoid and pterodactyloid pterosaurs the glenoid is distinctly saddle shaped with laterally as well as dorsally facing regions of the articular surface.
The origin of the pterosaurian glenoid must have involved the same evolutionary migration of position and orientation that has been outlined here for the avian lineage.
In contrast to the bulbous humeral head of birds, however, the humerus of pterosaurs bears a saddle-shaped facet, thus constraining the wingbeat excursion. This difference is likely a reflection of the relative structural versatility of the two wing types: an outstretched, sail-like membrane supported principally by a single digit versus a flexible airfoil composed of individual feathers, each with its own structural and functional integrity.
The [pterodactyl pterosaur] coracoid is about 75 per cent of the length of the scapula. It is expanded at its contact with the scapula, but has a more gentle decrease in width over its length. A small, blunt coracoid process is present, but it is not possible to tell if a groove separates it from the glenoid fossa. The sternal articulation is concave, faces posteroventrally, and lacks a posterior expansion. A large glenoid fossa faces anterodorsally with a dorsoventrally concave and anteroposteriorly convex saddle shape.
Wing skeleton. Both [pterodactyl pterosaur] wings are present in NGMC 99-07-1 (Text-figs 2, 4; Table 2). The humeri are complete though the right deltopectoral crest has become detached and rotated from its anatomical position (Text-fig. 2). The humeral head has an anteroposteriorly concave and dorsoventrally convex, saddle-shaped articulation so that it mirrors the shape of the glenoid.
Whether or not Microraptor could achieve powered flight or only passive gliding has been controversial. While most researchers have agreed that Microraptor had most of the anatomical characteristics expected in a flying animal, some studies have suggested that the shoulder joint was too primitive to have allowed flapping. The ancestral anatomy of theropod dinosaurs has the shoulder socket facing downward and slightly backward, making it impossible for the animals to raise their arms vertically, a prerequisite for the flapping flight stroke in birds. Some studies of maniraptoran anatomy have suggested that the shoulder socket did not shift into the bird-like position of a high, upward orientation close to the vertebral column until relatively advanced avialans like the enantiornithes appeared.[12] However, other scientists have argued that the shoulder girdle in some paravian theropods, including Microraptor, is curved in such a way that the shoulder joint could only have been positioned high on the back, allowing for a nearly vertical upstroke of the wing. This possibly advanced shoulder anatomy, combined with the presence of a propatagium linking the wrist to the shoulder (which fills the space in front of the flexed wing and may support the wing against drag in modern birds) and an alula or "bastard wing" may indicate that Microraptor was capable of true, powered flight.[13] 

It is not an easy task to get all the needed information about the shoulder joint but this is how it appears:
Rhamphoryncidae had a saddle joint. Both the glenoid fossa and the humerus head were saddle-shaped.
Basal paraves had a half-saddle joint. The glenoid fossa was still saddle shaped but the humerus head was bulbous.

PTEROSAUR scapula, coracoid and glenoid
Some pterosaur bones are quite unusual. This scapulo-coracoid is photographed from both sides. The glenoid cavity of the shoulder joint can be seen, where the humerus articulates the wing to the body.
 A large [pterodactyl] glenoid fossa faces anterodorsally with a dorsoventrally concave and anteroposteriorly convex saddle shape.
The lower (right?) coracoid doesn't seem to be articulated with the scapula either, with its narrow proximal neck lower than and partially overlapping the base of the scapula. I would argue the coracoid would be bent so that the neck is in a different plane from the oval distal end, and this makes the C-shape we see in the Epidendrosaurus and Scansoriopteryx holotypes. The glenoid may be oriented ventrally or laterally- I cannot discern it.
On the other hand:
It is important to mention that scansoriopterygids retained a caudoventrally oriented glenoid,a subrectangular coracoid with reduced biceps tubercle, and a distally fan-shaped scapular blade, all representing plesiomorphic character states in respect to paravians.

DINOSAUR scapula, coracoid, glenoid and tiny arm.
Scapula orientation in theropod dinosaurs is quite interesting and it is worth looking, to begin with, at what orientation is displayed in primitive reptiles. The scapula is generally held at an angle of 90 degrees to the horizontal line held by the backbone – in other words it was held in a perpendicular fashion. At the other extreme, extant birds rotated the scapula so that it lies parallel to backbone – a position also evolved by the pterosaurs.

Theropods, and non-avian dinosaurs in general (but not bird-like theropods), evolved a condition that can be described as something in between – an intermediate position if you will. The scapula is held in an oblique position laterally to the ribcage but actually determining the exact position is somewhat problematic. There are not that many fully articulated specimens that can be referred to and there is always the spectre of both taxanomic and taphonomic variation to throw yet another spanner into the works.

Here is a very interesting video:
AgnolĂ­n and Novas. 2013. Avian ancestors
In this way, the scapulae of unenlagiids lie close to the vertebral column, dorsal to the ribcage, with the flat costal surface of the scapular blade facing ventrally, a condition seen in microraptorans (i.e. Microraptor), basal avialans (e.g. Archaeopteryx, Rahonavis), and ornithothoracine birds (Senter 2006), in which the shoulder socket sits high on the back, and the margins of the glenoid are smooth, thus this surface becomes shalower and consequently more continuous with the rest of the lateral surface of scapula
(Burnham 2008). In sum, the lateral orientation of the scapular glenoid in unenlagiids
(and probably also in other basal averaptorans), together with the absence
of acute ridges delimitating the glenoid cavity, suggest that the humerus in these
taxa was able to be elevated close to the vertical plane, 
as proposed by Novas and Puerta (1997) (Figs. 5.1, 5.2).
It is important to mention that scansoriopterygids retained a caudoventrally oriented glenoid, a subrectangular coracoid with reduced biceps tubercle, and a distally fan-shaped scapular blade, all representing plesiomorphic character states in respect to paravians.

Here is a good overview of the shoulder girdle of modern birds:

Friday, October 31, 2014

Dino to bird claims

What we see again and again is that there is no actual link between ground-based coelurosaur dinosaurs and arboreal paravians. They inhabit different niches (obviously) with no link between them. And even more importantly, they do not share characteristics. Almost all (if not all) the bird-like characteristics that are found in the paravians are not found in the ground-based coelurosaur dinosaurs. That is because they are not related.

So the question arises:
How in the world could there be so many claims for years and years that birds evolved from dinosaurs? 
In addition to the points noted above:

First, is the misleading convention of calling paraves "dinosaurs". So any bird-like character found in paraves is said to confirm the dino to bird theory. But paraves are not dinosaurs, they did not evolve from dinosaurs. People focus on the wrong place. The Achilles Heel of the dino to bird theory is that there is no connection between actual dinosaurs and paraves.

Next is to misinterpret the characters of actual dinosaurs as if they were bird-like or "proto" bird-like characters. Thus for example, we get the claim of "protofeathers" on ground-based coelurosaur dinosaurs, which does not stand up. 

Also we get secondarily flightless paravians being called "non-paraves maniraptors". As if they were transitional between actual dinosaurs and arboreal paravians. That does not stand up. They are secondarily flightless members of paraves.

And also the cladistic analyses that have been done, generally include only dinosaurs and use an inappropriate outgroup. The very significant exception to this is the James and Pourtless study, which not co-incidentally found other explanations as credible as the dino to bird theory. 

Thursday, October 30, 2014


In the dino to bird theory, there is a good deal of claimed exaptation.
Feathers, enlarged brain and abducted wrists are claimed to have evolved before they were used for flight. These are simply stories. These stories are made up in response to evidence that contradicts the dino to bird theory.
Exaptation and the related term co-option describe a shift in the function of a trait during evolution. For example, a trait can evolve because it served one particular function, but subsequently it may come to serve another.

Carpal asymmetry [abducted wrists] would have permitted avian-like folding of the forelimb in order to protect the plumage, an early advantage of the flexible, asymmetric wrist inherited by birds.
However, it is likely that mobility of the wrist was initially associated with other functions, such as predation (Padian 2001).
It had originally been proposed that this flexibility could be attributed to hunting, but the same changes are seen in maniraptorans that were herbivores and omnivores so it is unlikely that hunting provides the answer. Instead, the authors of the new study propose, the ability to fold the hands backwards would have protected the feathers of the arms. This would have prevented the feathers from getting damaged or from being in the way as the dinosaurs moved about, although the authors recognize that this hypothesis requires further evidence.
Perhaps more significant, however, is how this wing-folding mechanism may have allowed birds to take to the air. Birds do flex their wrists while flapping their wings to fly, and so it appears that the wrist flexibility that first evolved in dinosaurs was later co-opted for flight in birds. This is what is known as "exaptation," or when a previous adaptation takes on a new function. Indeed, as more is discovered about the evolution of birds, the more traits paleontologists find that evolved for one function but have been co-opted for another at a later point (feathers themselves being the most prominent
example). There is relatively little separating birds from their feathered dinosaur ancestors.

As Darwin elaborated in the last edition of The Origin of Species,[14] many complex traits evolved from earlier traits that had served different functions. By trapping air, primitive wings would have enabled birds to efficiently regulate their temperature, in part, by lifting up their feathers when too warm. Individual animals with more of this functionality would more successfully survive and reproduce, resulting in the proliferation and intensification of the trait.
Eventually, feathers became sufficiently large to enable some individuals to glide. These individuals would in turn more successfully survive and reproduce, resulting in the spread of this trait because it served a second and still more beneficial function: that of locomotion. Hence, the evolution of bird wings can be explained by a shifting in function from the regulation of temperature to flight.
Exaptation is a term used in evolutionary biology to describe a trait that has been co-opted for a use other than the one for which natural selection has built it.
It is a relatively new term,proposed by Stephen Jay Gould and Elisabeth Vrba in 1982 to make the point that a trait’s current use does not necessarily explain its historical origin. They proposed exaptation as a counterpart to the concept of adaptation.
For example, the earliest feathers belonged to dinosaurs not capable of flight. So, they must have first evolved for something else. Researchers have speculated early feathers may have been used for attracting mates or keeping warm. But later on, feathers became essential for modern birds’ flight.

Several ancient dinosaurs evolved the brainpower needed for flight long before they could take to the skies, scientists say.
Bird brains tend to be more enlarged compared to their body size than reptiles, vital for providing the vision and coordination needed for flight.
Scientists using high-resolution CT scans have now found that these "hyper-inflated" brains were present in many ancient dinosaurs, and had the neurological hardwiring needed to take to the skies. This included several bird-like oviraptorosaurs and the troodontids Zanabazar junior, which had larger brains relative to body size than that of Archaeopteryx.

See page 261 of "Riddle of the Feathered Dragons"

Did preadaptations for flight precede the origin of birds (Aves)? The origin of flight in birds is one of the great evolutionary transitions and has received considerable attention in recent years (Padian and Chiappe 1998; Clarke and Middleton 2008; Dececchi and Larrson 2009; Benson and Choiniere 2013; Dececchi and Larrson 2013). The evolution of birds is often considered coincident with the origins of flight, but many traits associated with flight evolved before the origin of Aves (Padian and Chiappe 1998).