Freethought & Rationalism Archive

Valentine Pontifex · 01-23-2003, 09:35 PM

Got another link. This is by Tom Holtz who a scientist in this field.

Holtz Post on the Dinosaur mailing list.

This one is well worth looking at.

Doubting Didymus · 01-23-2003, 09:40 PM

From Holtz:

Quote:

Now, for the big interpretation. Xu et al. consider the elongated leg wing feathers as gliding supports, and have a restoration of _Microraptor_ with its leg splayed out to the side. I find this very questionable, given that there is no particular evidence that _Microraptor_ to move into this position (which in your typical dinosaur would require popping the femoral head out of the socket).

No, I don't have any good alternative explanation for the elongated leg feathers. Rudder? Aid in prey capture? Display? Genetic link by serial homology with the arm feathers? Nevertheless, given the constraints of the pelvic anatomy, I do not see how the leg feathers could be used as a laterally-oriented flight surface.

Very convincing, and very interesting. Would they still aid in the 'running up things' theory? (forgets impressive sounding formal name of said theory)

Nic Tamzek · 01-24-2003, 02:23 AM

Since the paper is up for free I will put the pics in here:

Quote:

Figure 1 Microraptor gui. a, Skeleton of Microraptor gui (IVPP V13352). Scale bar, 5 cm. b, A computerized tomography (CT) image of the major part of the IVPP V13352. Scale bar, 13 cm. Scanning was performed using a CT machine (LightSpeed Qx/i) at an energy level of 140 kV and 250 mA. The images were collected at a size of 800 600 pixels. On the basis of comparison of adjacent fracture-face geometries, density of adjacent pieces, and continuity across fractures of bones (see ref. 45), we find a few pieces are unverified or assembled in the wrong position (marked by asterisks). For example, one small piece containing the anterior end of the skull and a medium-sized piece near the right forelimb preserving some arm feathers are dubious. The latter is actually from the counter slab. However, the CT information suggests that most pieces lie together in their natural relationships, including pieces containing the forelimb, hindlimb and associated feather impressions. This is concordant with microscopic observations. c, A reconstruction of M. gui showing the morphology and distribution of the pennaceous feathers. Scale bar, 6 cm.

And check out 2g for the definitely non-trivial (although the exact function may be up for grabs) hind leg feathers:

Quote:

Figure 2 Feathers of IVPP V13352 and TNP00996. Feathers attached to the skull (a), the tail (d), the forelimb (f), the manual digit I (i), and the hindlimb (g) of IVPP V13352, and to the skull (b) and the tail (e) of TNP00996; close-up of the skull feathers of TNP 00996 (c), and of secondaries (h) and large pennaceous feathers on distal metatarsus (j) of IVPP V13352. Note the pennaceous feathers attached to the digit (i) that might be a precursor to the alula. This is concordant with the fact that M. gui has a short manual digit I, because the alula is often associated with a reduced alular digit except in Protopteryx24. Scale bar, 5 cm.

At the end they say:

Quote:

We carefully examined the specimens under the microscope and with high-resolution X-ray computerized tomography (CT) to test the authenticity of one of the studied specimens45 (IVPP V13352) and can guarantee the accuracy of the information that we provide in this study.

...in case this wasn't clear, ref 45 is to the Archaeoraptor forgery, meaning that one of the pieces of the Archaeoraptor was a chunk of M. gui.

Truth was stranger than fiction in this case...

Nic Tamzek · 01-24-2003, 02:30 AM

Boy, taking a 2nd look at the pics I'm even more impressed. Imagine being back in time 150 years and seeing that thing woosh by like some dinosaurian flying squirrel.

This kind of thing must give the antievos nightmares. And the BANDits also.

Good summary from the News & Views article:

http://www.nature.com/cgi-taf/DynaPa...21323a_fs.html

Quote:

Birds are traditionally considered to be animals with a difference: that is, to be a distinct vertebrate class despite their origins within the reptiles. But advances in palaeontology, phylogenetics and evolutionary biology have erased the anatomical gap between birds and their dinosaur ancestors10. Now that dromaeosaurs have taken to the air, in the form of Microraptor, there remain no major traits that are unique to birds � with the possible exception of powered flight. Although some may be irked at this lost distinction, the benefits will be a fuller, more integrated understanding of avian biology. This new evidence of an arboreal, gliding stage in the evolution of bird flight complements the evidence of terrestrial evolution in the theropod dinosaurs. Terrestrial theropod dinosaurs had evolved for millions of years before the ancestors of Microraptor and the birds took to the trees or to the air. Moving beyond the arboreal versus cursorial debate over the origins of bird flight4, the task ahead is to understand which components of the avian flight apparatus evolved in a terrestrial and which in an arboreal context.

(bold added)

cricket · 01-24-2003, 12:42 PM

Quote:

Imagine being back in time 150 years and seeing that thing woosh by like some dinosaurian flying squirrel.

Yes it would be weird to see, especially 150 years ago.

Nic Tamzek · 01-24-2003, 07:40 PM

Quote:

Originally posted by cricket
Yes it would be weird to see, especially 150 years ago.

:banghead:

err, 150 million years.

Gotta stop posting while watching TV in the middle of the night I guess...

cricket · 01-24-2003, 09:09 PM

We all knew whatcha meant.

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01-23-2003, 09:35 PM	#21
Valentine Pontifex Veteran Member Join Date: Jul 2001 Location: Orion Arm of the Milky Way Galaxy Posts: 3,092	Got another link. This is by Tom Holtz who a scientist in this field. Holtz Post on the Dinosaur mailing list. This one is well worth looking at.

01-24-2003, 09:09 PM	#27
cricket Veteran Member Join Date: Aug 2001 Location: St Louis MO USA Posts: 1,188	We all knew whatcha meant.

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