Tuesday, March 25, 2014

Body size and forelimb length

Bird-like characteristics are found in basal Paraves. They are not found in dinosaurs.
That is because basal paraves are not descended from dinosaurs. They are descended from pterosaurs.

Let's look at body size and forelimb length.
Notice that the changes appear for the first time at the origin of Paraves (not earlier).

Mark Puttick and colleagues investigated the rates of evolution of the two key characteristics that preceded flight: body size and forelimb length.  In order to fly, hulking meat-eating dinosaurs had to shrink in size and grow much longer arms to support their feathered wings. 
"We were really surprised to discover that the key size shifts happened at the same time, at the origin of Paraves," said Mr Puttick of Bristol's School of Earth Sciences.  "This was at least 20 million years before the first bird, the famous Archaeopteryx, and it shows that flight in birds arose through several evolutionary steps." 
Being small and light is important for a flyer, and it now seems a whole group of dozens of little dinosaurs were lightweight and had wings of one sort or another. Most were gliders or parachutists, spreading their feathered wings, but not flapping them.                                               
'High rates of evolution preceded the origin of birds' by Puttick, M.N., Thomas, G.H., and Benton, M.J. in Evolution: DOI: 10.1111/evo.12363
The origin of birds (Aves) is one of the great evolutionary transitions. Fossils show that many unique morphological features of modern birds, such as feathers, reduction in body size, and the semilunate carpal, long preceded the origin of clade Aves, but some may be unique to Aves, such as relative elongation of the forelimb. We study the evolution of body size and forelimb length across the phylogeny of coelurosaurian theropods and Mesozoic Aves. Using recently developed phylogenetic comparative methods, we find an increase in rates of body size and body size dependent forelimb evolution leading to small body size relative to forelimb length in Paraves, the wider clade comprising Aves and Deinonychosauria. The high evolutionary rates arose primarily from a reduction in body size, as there were no increased rates of forelimb evolution. In line with a recent study, we find evidence that Aves appear to have a unique relationship between body size and forelimb dimensions. Traits associated with Aves evolved before their origin, at high rates, and support the notion that numerous lineages of paravians were experimenting with different modes of flight through the Late Jurassic and Early Cretaceous.

Note that in the following two references the researchers are working within the dino to bird paradigm. To make the evidence fit the theory they are also forced to claim improbable rates of evolution.

Mike Lee et al

Sustained miniaturization and anatomical innovation in the dinosaurian ancestors of birds

Recent discoveries have highlighted the dramatic evolutionary transformation of massive, ground-dwelling theropod dinosaurs into light, volant birds. Here, we apply Bayesian approaches (originally developed for inferring geographic spread and rates of molecular evolution in viruses) in a different context: to infer size changes and rates of anatomical innovation (across up to 1549 skeletal characters) in fossils. These approaches identify two drivers underlying the dinosaur-bird transition. The theropod lineage directly ancestral to birds undergoes sustained miniaturization across 50 million years and at least 12 consecutive branches (internodes) and evolves skeletal adaptations four times faster than other dinosaurs. The distinct, prolonged phase of miniaturization along the bird stem would have facilitated the evolution of many novelties associated with small body size, such as reorientation of body mass, increased aerial ability, and paedomorphic skulls with reduced snouts but enlarged eyes and brains.



Stephen Brusatte et al
Gradual Assembly of Avian Body Plan Culminated in Rapid Rates of Evolution across the Dinosaur-Bird Transition
The evolution of birds from theropod dinosaurs was one of the great evolutionary transitions in the history of life [ 1–22 ]. The macroevolutionary tempo and mode of this transition is poorly studied, which is surprising because it may offer key insight into major questions in evolutionary biology, particularly whether the origins of evolutionary novelties or new ecological opportunities are associated with unusually elevated “bursts” of evolution [ 23, 24 ]. We present a comprehensive phylogeny placing birds within the context of theropod evolution and quantify rates of morphological evolution and changes in overall morphological disparity across the dinosaur-bird transition. Birds evolved significantly faster than other theropods, but they are indistinguishable from their closest relatives in morphospace. Our results demonstrate that the rise of birds was a complex process: birds are a continuum of millions of years of theropod evolution, and there was no great jump between nonbirds and birds in morphospace, but once the avian body plan was gradually assembled, birds experienced an early burst of rapid anatomical evolution. This suggests that high rates of morphological evolution after the development of a novel body plan may be a common feature of macroevolution, as first hypothesized by G.G. Simpson more than 60 years ago [ 25 ]. 


  1. There are basal coelurosaur dinosaur fossils and there are basal feathered flying Paraves fossils.
    The basal coelurosaur fossils show all the characteristics of basal coelurosaur dinosaurs.
    The basal Paraves fossils show all the characteristics of basal feathered flying Paraves.
    And nothing in between.

  2. bullshit. total and utter bullshit. your an idiot. No references, no copy and paste. just you, pissing in the wind, wasting your time and energy. What a way to waste a life.

  3. Unfortunately this is typical of the comments that I receive. (I just do not post them).The folks who disagree with what I am proposing are not particularly articulate or thoughtful.

  4. http://www.sciencemag.org/content/284/5423/2137.abstract
    The ascendancy of dinosaurs on land near the close of the Triassic now appears to have been as accidental and opportunistic as their demise and replacement by therian mammals at the end of the Cretaceous. The dinosaurian radiation, launched by 1-meter-long bipeds, was slower in tempo and more restricted in adaptive scope than that of therian mammals. A notable exception was the evolution of birds from small-bodied predatory dinosaurs, which involved a dramatic decrease in body size. Recurring phylogenetic trends among dinosaurs include, to the contrary, increase in body size. There is no evidence for co-evolution between predators and prey or between herbivores and flowering plants. As the major land masses drifted apart, dinosaurian biogeography was molded more by regional extinction and intercontinental dispersal than by the breakup sequence of Pangaea.

  5. Hello Dr Pterosaur,

    I am uncertain about one aspect of your hypothesis: namely, how could the quadropedal Pterosaur gait evolve into the bipedal Avian gait?

    I'm sure you know all this, but for the benefit of readers...

    Pterosaur's walked on all fours, planting their weight on their wings in a manner somewhere between a gorilla and a lizard, with their wing finger folded up alongside themselves. They were quadrupeds. This gait was very unique and distinctive, and made sprinting a difficult-to-impossible prospect.

    (Rhamphorhynchidae, the example you use of long-bony-tailed basal pterosaurs)

    Avians and theropods, on the other hand, balance their weight over their pelvis similar to a theropod dinosaur, with their wings folded against their back. They're bipedal, but not in the same sense that humans are: their center of mass is situated directly over their pelvis, where most other tetropods (including pterosaurs) have it situated higher up the back.

    (A chook)


    For comparison purposes, Compsognathus, a primitive Coelurosaur (considered by the mainstream community to be much closer than pterosaurs)


  6. Check this reference: