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RE: Oryctos Is Back



>From Campbell's abstract-

"A close examination of the wrist and manus of five archaeopterygians confirms 
the presence of numerous previously recognized, as well as unrecognized, 
derived avian characters. These include, but are not limited to, Metacarpal II 
very short, slightly wrapping around and probably fused to Metacarpal III for 
much of its length; Metacarpal II with small Processus extensorius for 
attachment of M. extensor carpi radialis; Metacarpal IV with proximal end lying 
well distal to proximal ends of metacarpals II and III, wrapping under and 
fused to ventral surface of Metacarpal III; joint between Metacarpal II and 
Phalanx 1 of Digit II ginglymoid near plane of wing, allowing Digit II to 
function as a primitive alula; joints between metacarpals III and IV and their 
respective phalanges relatively immobile; and “palmar” surfaces of distal 
phalanges facing anteroventrad or anteriad when wing is extended. The above 
features are not found in theropods, but their more highly derived counterparts 
are
 found in all modern birds with wings, whether volant or not. The avian, rather 
than theropodian, structure of the wrist and manus of archaeopterygians 
indicates significant functional differences between the forelimbs of 
archaeopterygians and theropods, which is not surprising if different digits 
are involved. Some prominent “feathered dinosaurs” are recognized as having a 
more advanced avian manus than that found in archaeopterygians, indicating 
their avian, rather than dinosaurian, ancestry."

It'd be great if these MANIACs who deny a theropod ancestry for maniraptorans 
actually knew theropod anatomy.  Of the supposedly avian characters he lists in 
archaeopterygid hands which are supposedly not found in theropods...

- Paravians primitively have a short metacarpal I (remember in his abstract the 
metacarpals are numbered II-III-IV, not I-II-III), as do Scipionyx, Juravenator 
and Compsognathus, though some taxa like Deinonychus and confuciusornithids 
lengthened theirs.  Most therizinosaurs, oviraptorosaurs and basal coelurosaurs 
have slightly longer metacarpal I's, showing a gradation into the neornithine 
state.

- A metacarpal I which overlaps metacarpal II dorsally and ventrally is found 
as basally as therizinosaurs (Falcarius, Alxasaurus).

- Metacarpal I of Archaeopteryx isn't fused to the rest of the metacarpus, 
which can also be said of all non-ornithothoracine birds (Shenzhouraptor, 
Sapeornis, confuciusornithids).

- Metacarpal I has an extensor flange in Compsognathus, Alxasaurus, 
oviraptorosaurs and paravians (Gishlick, 2002).  It gets large in Apsaravis, 
Yixianornis and similarly derived taxa.

- A distally placed metacarpal III is a dislocation caused by the hand being 
flattened palm down (Gishlick, 2002), and is seen in some other taxa with 
reduced hyperextension in digit III as well (e.g. Protarchaeopteryx, some 
oviraptorids).

- Metacarpal III with a proximal end wrapping under metacarpal II is present as 
basally as Allosaurus (Chure, 2001), ornithomimosaurs (Harpymimus, Gallimimus), 
therizinosaurs (Falcarius, Alxasaurus).

- Metacarpals II and III aren't fused in Archaeopteryx, or in any 
deinonychosaurs.

- Metacarpal I was distally ginglymoid in basally all theropods (exceptions 
include derived ornithomimosaurs and birds).

- The asymmetrical condyles on metacarpal I and twisted phalanx I-1 meant that 
most theropods moved digit I in a somewhat transverse plane.  This includes 
Tanycolagreus, Ornitholestes and Allosaurus (Senter, 2006; Carpenter, 2002).

- Deinonychus has reduced hyperextension in digits II and III, but plenty of 
flexion (Gishlick, 2002).  Archaeopteryx seems to as well, especially in digit 
III and between II-1 and II-2 (Paul, 2002).  Paul further notes 
confuciusornithids retain flexible digit III, though digit II is less flexible 
in them and microraptorians.  Reduced hyperextension was probably present in 
therizinosaurs (Falcarius lacks extensor pits, for instance) and 
ornithomimosaurs (Gallimimus- Osmolska et al., 1972) as well.

- Determining the orientation of phalanges in an extended wing would require a 
three-dimensional model to work with, which doesn't exist for the flattened 
Archaeopteryx specimens.

So once more the supposed "significant differences" between theropods and birds 
can be shown to form a continuum, and certainly don't provide evidence for 
Archaeopteryx having different digits than theropods.

Saurischia
- metacarpal I ginglymoid with asymmetrical condyles
- twisted phalanx I-1

Avetheropoda
- proximal end of metacarpal III ventral to metacarpal II

Coelurosauria
- metacarpal I reduced to ~45% of metacarpal II length

Maniraptoriformes
- digits II and III with reduced hyperextension

Maniraptora
- metacarpal I wraps around metacarpal II
- extensor flange on metacarpal I

Paraves
- metacarpal I reduced to ~30% of metacarpal II length

Ornithurae sensu Gauthier
- metacarpals II and III fused to carpometacarpus
- digit II with reduced hyperflexion

Ornithothoraces
- metacarpal I fused to carpometacarpus

Ornithurae sensu Gauthier and de Queiroz, 2001
- extensor flange enlarges into process


Mickey Mortimer




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> Date: Wed, 27 Aug 2008 10:10:13 -0600
> From: jharris@dixie.edu
> Subject: Oryctos Is Back
> To: dinosaur@usc.edu
>
> Hi All -
>
> Just found the new web site for _Oryctos_
> (http://www.dinosauria.org/oryctos.php), and it looks like the most recent
> ish, vol. 7, is chock full o' birdly goodness. I don't have any of the
> papers yet, though... If anyone gets any of them, please forward!
>
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> Jerry D. Harris
> Director of Paleontology
> Dixie State College
> Science Building
> 225 South 700 East
> St. George, UT 84770 USA
> Phone: (435) 652-7758
> Fax: (435) 656-4022
> E-mail: jharris@dixie.edu
> and dinogami@gmail.com
> http://cactus.dixie.edu/jharris/
>
> "Football is like chess, only without
> the dice."
> --- German soccer player Lukas
> Podolski
>
> "I don't fail. I find new ways to not
> succeed."
> --- Christopher Titus
>
>