[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: Campbell's even crazier than a MANIAC? (archeopteryx climbing)

> Perhaps theropods were flapping even before parachuting

Unlikely, or we'd find more hypertrophied sterna, and scapula-coracoid 
arrangements that would not have prevented simultaneous dorsal movement of the 
arms as much as they apparently did in about everything non-ornithothoracine.

What we can be *sure* of is that a) Archie was not a percher*, and b) that its 
ability to take off from level ground in the absence of favorable circumstances 
was very limited, maybe nonexistent. And what we can strongly suspect, for 
reasons of geography alone, is that the mode of flight of Archie is about as 
informative for anything *except* Archie as would be undeniable proof of an 
arboricolous _Microraptor_ for the evolution of flight in _Sapeornis_ - at 
least as long as no Kimmeridgian avialan from E Asia is known. 

Perhaps Archie is relevant to the evolution of flight in theropods these days, 
perhaps it isn't. It certainly occurred very far away from where the main 
action took place. And by now, there is enough evidence to show that a) sooner 
or later it was as inevitable that *some* maniraptoran became volant as things 
are "inevitable" in evolution and b) that it did not only happen but in all 
likelihood happened at least 2 times (Eurasia and Madagascar), probably 4 times 
(twice in Asia, once each in Europe and Madagascar) or more.


A less related thing: as it seems, the terrestrial/arboreal bias of 
Enantiornithes vs lacustrine/coastal Neornithes is not an artefact. Anyone who 
studies why the former didn't make it across the boundary while a few of the 
latter did might want to look into this.

Of course there were non-arboreal enantis, but as far as anyone can tell the 
diversity of these was smaller at least in relative terms and, given the 
concentration of basal Neornithes lineages in Gondwana where there is a less 
complete fossil record, probably in absolute terms also. A combination of being 
geographically lucky and having been outcompeted by enantis from habitat that 
was prime choice for avians *except* for a few 100.000 years at the start of 
the Cenozoic (when it totally sucked to be adapted to it - what does a 
tree-living bird do during fern spike conditions?) is an intriguing 
possibility. But maybe the real question to answer is: why did some 
proto-procellariiform and some proto-larid survive, and _Ichthyornis_ did not 
(if the latter did occur at the Turgay Sea - if it was limited to North 
America, the answer might simply lie in the trajectory of the Chichxulub 

* Not that this would be crucially important, but what is the general opinion 
of the angle between toes I and IV in Archie? Am I correct in assuming that the 
evidence is better explained by it having been in the 90-110° region or so, and 
not >180°?



Do You Yahoo!?
Sie sind Spam leid? Yahoo! Mail verfügt über einen herausragenden Schutz gegen