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

Re: Way cool kagu

Kagu are indeed very good birds.  Two quick notes on your letter:

- Kagu do have asymmetric primaries, but looking at the photos online (not 
ideal, I know) they don't look
to be strongly asymmetric.  In other words, they are probably anatomical 
asymmetric but not functionally
asymmetric.  This is common among flightless birds, and is one reason that 
using "asymmetry" as a binary
character (as has been the case in much of the literature) is ill advised (not 
that you said anything of the kind
in your note, I just thought it was a good moment to make the point).

- The bending strength of the femur in Archaeopteryx is considerably greater 
than that for the humerus, at
least in cantilever bending.  So I would not say the humerus is more robust 
than the femur, nor that the 
forelimb must have been the more heavily muscled system.  Your other 
osteological points regarding 
Archaeopteryx still stand, of course.


On Jul 19, 2013, at 9:52 AM, GSP1954@aol.com wrote:

> Until it was mentioned recently on the list I did not even know about the 
> kagu (so did not discuss in DA). Since it is the only living nearly 
> flightless bird with big wings it is very important, and I wanted to see the 
> skeleton. Was afraid would have to go all the way down to the Smithsonian and 
> arrange to get into birds and so on and so forth. But right there on Google 
> is an 
> old figure of the skeleton via Parker 1868 bless em, the paper is on the web 
> (it starts with rather a bit of a tiff with Professor Huxley over the 
> proper identity of the great maxilla before it gets down to describing the 
> kagu - 
> ah those were the days:-). Also on Google is an excellent photo of a kagu 
> with its wings held up in display, showing the entire left ventral surface 
> flat on to the camera. So did a skeletal restoration with the wing profile 
> (was able to get the correct wing size on the skeleton by using the lengthes 
> of 
> the arm, head and metatarsus which all produced similar results). 
> The kagu is a set of really long legs anchored on a very big pelvis 
> attached to a remarkably short,  deep body, and a very large head with big 
> eyes.  
> The area of the wing is typical for a flying bird at its mass and similar 
> to Archaeopteryx and Microraptor. Yet there are remarkably few primary (they 
> are asymmetrical) and inner feathers, just 16 along the whole span of the 
> wing. The sternum lacks a keel and is very narrow. Sternal ribs look normal, 
> uncinates rather small. Really notable is that the furcula is very thin, and 
> the coracoid is quite narrow. Scapula blade rather reduced. The humerus 
> shaft is slender, especially at mid shaft, being much weaker than the femur. 
> The 
> pectoral crest is hardly there. The very thin furcula and teeny pectoral 
> crest suggest extreme reduction of flight muscles. The leg muscles onthe 
> oversized pelvis and long long limbs must be a far larger percent of total 
> mass. 
> Toe claws are flat of course, short, tips seem to be worn a bit. Kagus are 
> adapted for running and not flying. They show what a full winged but nearly 
> flightless ground dwelling theropod looks like. 
> Archaeopteryx does not have an ossified sternum. But the furcula is much 
> more robust, the pectoral crest is many, many times larger, and the coracoid 
> is broader. The humerus is more robust than the femur. The pelvis is dinky 
> and the legs are not all that long, toes claws are large, shapr and more 
> curved. The arm muscles should have been stronger than those of the legs, 
> indicating that the arms were the main locomotary organs via some level of 
> powered 
> flight (probably better than kagu) and quad climbing. This is what a 
> scansorial winged theropod looks like. 
> Microraptor also has very large pectoral crest, stout furcula and coracoid, 
> plus a sternal plate that is broader than that of a kagu, and a flattened 
> central finger to support the outer primaries not present in Archaeopteryx. 
> The legs are very long, but that is because they too are supporting big 
> wings. Pelvis is rather small. Toe claws big, strongly arced and very sharp. 
> Must 
> have been a better powered flier and climber than Archaeopteryx. This is 
> what a highly arboreal winger theropod looks like.  
> What we really need is a lot more data on the kagu. So one of you get a 
> grant to go to New Caledonia (very nice place, McCale and his PT 73 crew went 
> on leave there, is big tourist beach destination for the French). Find out 
> exactly what their flight abilities are and are not. Really badly needed is 
> the weight of the combined flight muscles as a percent of body mass (also of 
> leg muscles). So kill a kagu or two - never mind that they are endangered and 
> it is very illegal - and get that data. How's that for a project? 
> Of course we will probably never know the exact size and nature of kagu 
> flight muscles. Sigh. 
> GSPaul</HTML>