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

Campbell's even crazier than a MANIAC?



I finished reading Campbell's actual paper to make sure my critique of his 
abstract (http://dml.cmnh.org/2008Aug/msg00168.html) wasn't off base.  If 
anything, Campbell's even crazier than I thought.

Scott will be happy to learn "There is one point, however, upon which all 
students of archaeopterygians seem to be in agreement: archaeopterygians could 
fly."  Stop pretending to be a student of archaeopterygians by being a coauthor 
of papers describing them, Scott! ;)  

The possibility of fusion between metacarpals I and II in Archaeopteryx which 
is stated in the abstract is misleading.  The actual text states "Furthermore, 
the tight, inter­locking relationship between Metacarpal II [=I] and Metacarpal 
III [=II] is indicative of a solid trend toward fusion of the meta­carpals that 
appears to have been well underway (contra El­zanowski, 2002)."  So the uh... 
trend toward fusion was underway.  Not the fusion itself.

I previously noted Gisklick (2001, 2002) found flattening Deinonychus hands 
palm downward resulted in a distally displaced metacarpal III, as in some 
Archaeopteryx specimens.  Gishlick uses the example of the left Munich manus as 
one which did not flatten this way and has metacarpals II and III with 
approximately equal proximal extension.  Campbell (figure 4) reinterprets this 
manus as having a distally placed metacarpal III, but you can see where his 
dotted outline veers away from the dark lateral margin of the bone (right above 
the label 'IV').  Furthermore, his proximal outline of metacarpal II in that 
figure is far too convex and proximally extending, whereas a roughly straight 
line between a light metacarpal and dark sediment can be seen right at the 
upper level of his metacarpal "IV" (=III) outline.  Similarly, metacarpal I 
(his II) has a less angled proximal outline which can be seen going 
horizontally from its proximal contact with metacarpal II (his III).  Campbell 
begs the
 question in his reasoning against Gishlick- "The statement by Gishlick (2001) 
that Metacarpal IV would have contacted the semilunate carpal in the Munich 
speci­men if the wrist had not been pulled apart is incorrect be­cause the 
metacarpals of that specimen were not dislocated and Metacarpal IV is in its 
natural position."  So it's not dislocated because it's not dislocated and 
furthermore is in natural position.  Hmm.... Note that in the right Eichstatt 
hand and in both hands of the Thermopolis specimen, mcIII's are distally 
placed, but even Campbell would agree they are disarticulated, as their 
proximal ends lie dorsal to metacarpal II.   Campbell furthermore states "That 
Metacarpal IV did not contact the semilunate carpal is also demonstrated by the 
absence of any articular surface that might have con­nected the two bones. 
Indeed, the semilunate carpal did not extend posteriad beyond the posterior 
border of Metacarpal III, so there was no part of it in a position to articulate
 with Metacarpal IV."  Gishlick finds a ventral!
 tubercle
s into a slight lateral depression in the semilunate in Deinonychus.  Most 
Archaeopteryx hands are in dorsal view, with the exceptions of the left 
Eichstatt hand and the left Munich hand (the left Solnhofen hand doesn't 
preserve metacarpal bases).  Figure 8 of Wellnhofer (1974) clearly shows a 
ventral tubercle, which might be visible in the Munich hand as well (figure 5 
of Campbell), though the latter is fragmented.  As for the claim that there's 
no room on the semilunate for it to articulate, figures 1 and 3 clearly show 
the semilunate extends a bit lateral to metacarpal II and has a lateral surface 
that could be articulated with.

As for the fusion of metacarpals II and III, the situation is even worse than 
that for I and II.  "Indeed, once removed from the wrist joint, in the absence 
of fusion, there would be little to hold Meta­carpal IV [=III] in position. 
This would be particularly disadvanta­geous if, as in modern birds, Metacarpal 
IV [=III] provided support for primary feathers attaching to Metacarpal III 
[=II]. Thus, the fusion of Metacarpal III [=II] and Metacarpal IV [=III] 
proximally can be interpreted as a functional requirement to provide rigidity 
and strength to the precursor of the modern carpometacarpus once Metacarpal IV 
[=III] became disengaged from the wrist joint."  So because III is distal to II 
(which it wasn't in life) and because Archaeopteryx flew (which it may not 
have), metacarpals II and III MUST be fused.  Sutures be damned.

Another avian character is supposed to be the bowed third metacarpal.  "As seen 
in the Munich and Solnhofen specimens, the midshaft of Metacarpal IV bows away 
from that of Meta­carpal III (Fig. 5), just as in most modern birds. This 
bowing is not as apparent in the Berlin and Eichstätt specimens, but some 
bowing, or at least separation, also can be seen in those specimens. The bowing 
is interpreted as providing support for the primary feathers that attach to 
Metacarpal III. Indeed, even in its broken and fragmentary state, the left 
manus of the Solnhofen specimen is immediately recognizable as hav­ing an 
avian-style carpometacarpus [compare Fig. 5B with Figs. 2 and 6(left)]."  It's 
also present in all microraptorians, Deinonychus, Sinornithoides, 
Jinfengopteryx and Protarchaeopteryx of course.  And yes, Archaeopteryx 
certainly has an "avian-style carpometacarpus", even though it lacks the fusion 
that defines the word carpometacarpus.  *rolls eyes*

As for the phalangeal orientation of the digits, Campbell argues the anteriorly 
facing manual unguals in Archaeopteryx indicate it flexed its fingers more 
anteriorly than ventrally.  An angled articulation is widespread in 
saurischians for digit I, so that's no surprise.  For digit II, Campbell notes 
a "slight rotation" based on the position of the ligament pit, but provides no 
rationale for digit III flexing anteroventrally.  Gishlick (2001- figure 3) 
shows the plane which digit II flexes in Deinonychus is also slightly 
anteriorly angled.  Manual unguals point anteriorly in the flattened hands of 
Beipiaosaurus, Protarchaeopteryx, Caudipteryx and Sinornithosaurus too, and 
vary between hands in Scipionyx, Huaxiagnathus and NGMC 91. It is likely all 
maniraptorans had somewhat angled digits.  

Campbell states "The dorsoventral expansion of the distal end of the 
metacarpals in archaeopterygians is in contrast to the func­tional ginglymoid 
joints observed at these positions in thero­pods. This contrast in mobility 
should not be minimized as it is indicative of stark functional differences of 
the manus in these two vertebrate groups."  The expansion on metacarpal I is 
the normal medial dorsal condylar ridge, which is also present in Deinonychus 
(Gishlick, 2001- figure 3B) and other theropods.  The same is true of 
metacarpal II, as is apparent in figure 4.3 of Paul (2002).  The convexity is 
visible in Deinonychus as well, as the uppermost point in figure 3B of 
Gishlick.  Whether Archaeopteryx had the slight concavity lateral to this that 
Deinonychus has, or a straight edge, seems like a minor detail.  Metacarpal III 
is not ginglymoid in most tetanurines, so is generally convex dorsally at its 
distal end.

When it comes to the direction the interphalangeal joints flexed, Campbell may 
be correct that the convex posterior edge of phalanx II-1 is due to that 
actually being the bone's normal convex dorsal edge.  Yet the left hand 
illustrated by Paul (2002) clearly shows the distal articular surface of a 
dorsoventrally flexing joint, with phalanx II-2 disarticulated.  In digit III, 
Campbell admits the preserved articular surfaces "would almost have to have 
been in the dorsal-ventral plane", which agrees with Paul showing that phalanx 
III-3 (and therefore ungual III) is only anteriorly projected because it is 
disarticulated (this can also be seen in the Eichstatt specimen).  Yet "This 
would seem to preclude an angle of flexion/exten­sion that would take the 
ungual of Digit IV [=III] under Digit III [=II]", and "in order for Digit IV 
[=III] to serve any imaginable function, it had to extend forward under Digit 
III [=II]".  Why couldn't it have a grasping function?  Because "With the 
rotation
 of the digits and other modifications to the manus, the use of the unguals for 
grasping in the traditional sense was lost. That is, the use of the unguals to 
grasp prey, or vegetation for climbing in the normal manner, does not work 
because the unguals now point anteriad, ..."  Yet no evidence for making digit 
III flex anteriorly is ever given, and he even admits contrary evidence exists. 
 But because Campbell can't imagine another function for digit III besides 
ventrally crossing underneath digit II to "provide structural support to Digit 
III to prevent bending along its long axis during flight", it MUST have flexed 
forward instead of down.  "Resolution of the question as to why and how Digit 
IV [=III] could have crossed under Digit III [=II] in life requires further 
detailed study of the joint structure in the original specimens." What about 
the question of IF digit III crossed under digit II?!  

In "Avian Status of Archaeopteryx", Campbell argues the anteriorly rotated 
digits would have prevented grasping, yet almost all saurischians show a 
rotated first digit, the distal articulation of phalanx II-1 faces ventrally 
and still allows grasping even when the proximal articulation is rotated a bit 
(as in Deinonychus), and the third digit is merely assumed to be rotated via 
circular logic.  And we get the huge hyperbole non sequitur "Thus, when all of 
the osteological features of the archaeopterygian manus are taken into 
consideration, it is clear that the manus of these vertebrates was well on the 
way toward achieving the avian condition and that it bore no rela­tionship, 
structural or functional, to that of theropods."

In "Implications for Avian Accestry", he uses Atreipus to prove "that there 
were presumed primitive, pre-dinosaurian archosaurs in the Triassic in which 
there was “a clear shift of emphasis to manual digits II, III, and IV rather 
than I, II, and III.” Yet Atreipus is generally regarded as being an 
ornithischian, not a pre-dinosaurian archosaur (maybe it's actually a 
shuvosaur, given the theropod-like pes tracks?).  Not that it matters because 
"This is not to suggest that Atreipus was related to the ancestry of birds, 
particularly in light of the lack of skeletal material ref­erable to this 
ichnotaxon, but only to point out that there was precedence in some 
archosaurian lineages in the Triassic for retention of digits II, III, and IV 
over I, II, and III."  Well, if it's not related to bird ancestry, its manual 
formula is really irrelevant, isn't it? 

Campbell seems even crazier than Martin and Feduccia in claiming Microraptor, 
Caudipteryx and Protarchaeopteryx are birds, yet oviraptorids and 
dromaeosaurids including Sinornithosaurus(!) are theropods.  "Indeed, of the 
several “feathered dinosaurs” from the Cretaceous of China discussed by Norell 
and Xu (2005), the three genera with modern appearing feathers (i.e., 
Pro­tarchaeopteryx, Caudipteryx, and Microraptor Xu, Zhou, Wang, 2000) have 
rotated digits. On the other hand, those genera possessing a filamentous 
covering, or what is com­monly referred to as “dino-fuzz,” (i.e., 
Sinosauropteryx Ji and Ji, 1996; Beipiaosaurus Xu, Tang, and Wang, 1999; 
Si­nornithosuarus Xu, Wang, and Wu, 1999; and Dilong Xu, Norell, Kuang, Wang, 
Zhao, and Jia, 2004) either have a typical theropod manus or a manus 
reconstructed as that of a theropod."  Wow.  Just wow.  Sinornithosaurus and 
Microraptor must be the most amazing cases of convergence ever.  Of course, 
Beipiaosaurus and Sinornithosaurus are
 actually preserved with anteriorly facing digits, as noted above, and the 
position of Dilong's hands hasn't been published.

"To posit Caudip­teryx as a basal oviraptorosaur requires the loss in the more 
“advanced” oviraptorosaurs of the avian manus (and a re­version to a normal 
theropod manus) and a loss of feathers. Neither of these possibilities is 
considered likely."  Ah yes, a loss of feathers in which oviraptorosaurs 
exactly?  

"Although there has been a recent tendency to con­sider the possibility that 
some dinosaurs are actually flight­less birds [see Paul (2002) and discussion 
in Feduccia et al. (2005)], I think this is probably more a result of forms 
like Caudipteryx and Microraptor being confused with dinosaurs because of a 
lack of understanding as to what structures comprise synapomorphies for birds, 
and why, than because of any actual phylogenetic relationship between birds and 
theropod dinosaurs. I would suggest that all of the known “feathered dinosaurs” 
that bear true feathers and have rotated manual digits represent distinct, 
disparate lineages of early birds unrelated to theropod dinosaurs."  So 
Campbell IS even crazier than Feduccia.  He's not truly a MANIAC (Maniraptorans 
Are Not In Actuality Coelurosaurs), but is an even more extreme form of BAND.  
We need a new acronym! ;)

Mickey Mortimer






[http://gfx1.hotmail.com/mail/w3/pr01/ltr/i_charity.gif] EMAILING FOR THE 
GREATER GOOD
Join me