Here's my latest pondering the Universe question and answer seeling, for what it's worth.
It's become clear birds evolved from dinos. So, were there multiple ancestral lines or was there a single 'adam and eve' flock of dinos that went on to be the bird branch of the tree of life?
So, I looked into it and found
"only the neornithine birds persevered to continue the massive diversification that began in the Cretaceous period".
So, the next question I had was similar. How many lines of neornithine birds were there?
Current thought was that there were 3 lines of dinos with bird features.
From the Tree of Life web project
Ornithischia - Bird-hipped plant-eating dinosaurs
Sauropodomorpha - Long-necked plant-eating dinosaurs
Both those lines died out.
The Theropoda - (Bipedal predatory dinosaurs) evolved into birds.
From Theropoda came Coelurosauria (tyrannosaurs, Oviraptor, Velociraptor, birds, and relatives) and the other branches became extinct.
next came the following branches
* Ornitholestes
* Compsognathidae
* Alvarezsauridae
* Ornithomimidae (ostrich-like dinosaurs)
* Therizinosauridae
* Tyrannosauroidea
* Maniraptora
o Oviraptorosauria
o Dromaeosauridae (Velociraptor and relatives)
o Troodontidae
o Aves (birds)
Aves then became
* Archaeopteryx
* Confuciusornithidae
* Enantiornithes
* Euornithes (true birds)
o Patagopteryx
o Hesperornithiformes
o Ichthyornithiformes
o Neornithes (modern birds)
And the neornithes branched into 3 lines of birds we have today.
Then I found my way to EvoWiki and
The Neornithine 'Big Bang' page.
In light of the evaluation offered within this essay, the author submits a revised scenario to that previously advanced in Avian Phylogeny and Origins.
Originating sometime in the latest Cretaceous, within the Campanian/Maastrichtian interval, the basal neornithines, perhaps derived from forms similar to Apatornis celer and represented by the graculavids and other “transitional shorebirds,” experienced a very modest adaptive radiation within a severely restricted niche, namely, the near-shore environment. The decline of the Hesperornithiformes and Ichthyornithiformes during the later Cretaceous may have facilitated this modest diversification of the “transitional shorebird” lineage, or alternatively, may have been caused by it.
With the events at the KT Boundary (whatever those were), the dominant aviary of the Mesozoic, represented by the spectacularly diverse Enantiornithes and the scattered lineages of archaic ornithurines, were extinguished, leaving the incipient neornithine dynasty to undergo an explosive primary adaptive radiation. Within a period of some ten million years, the base of the neornithine lineage diversified so extensively that almost all extant orders were present by the Lower Eocene, as witnessed by the avifauna of such deposits as the London Clays and Green River Formation of Wyoming. With such a rapid branching of clades from their respective nodes, the ordinal relationships of Neornithes are largely unknowable, and thus we have a m�lange of taxa of uncertain affinity.
The base of Neornithes is something of a hub and spokes, with unresolved branching patterns for multiple orders in what is a thoroughly unpleasant poltyomy.
So I guess we don't yet know how many variations of these Neornithes survived the KT Boundary event. But I think this sounds like there was probably one line of descent that had already began branching into new species at the time of the KT event which survived the devastation. Sort of like having most domestic dogs surviving something that wiped out all the wild canine species and subsequently evolving.
And at least now I have a better idea where Archaeopteryx fits into the dino picture.
And it made it easier to understand what they were talking about on the NOVA program which is
summarized on this page explaining the controversies about which bird features evolved when.
Journey through time, from birds to dinosaurs
The evolution of the characters that make flight possible - feathers, lightweight bones and joints that could articulate a flapping motion and provide control during flight, probably all came about for different reasons. Once the ability to fly had evolved however, refinements in the efficiency of flight could be further evolved.
BTW, the Microraptor either has a different scientific name or it isn't listed in the Tree of Life Project yet.
