New phylogenetic theory (was Re: I will be ostracized because of this)

["Jaime Headden" <jaemei@hotmail.com>]

No criticism offered.

<Dinosauria
 |--_Eoraptor_
 |--+--Herrerasauridae (or "herrerasaurids")
 |  +--Phytodinosauria
 |     |=="primitive segnosaurs" (?)
 |     |--_Therizinosaurus_
 |     |--Sauropodomorpha
 |     |--Therizinosauridae (_Segnosaurus_, _Nanshiungosaurus_, etc.)
 |     +--Ornithischia
 +--Theropoda>

This is very interesting, and a while back, I came up with something 
similar (not on the list, though). I will not bore everyone with it, 
yet. What it generally says is that, using the most primitive forms of 
the main dinosaur groups (i.e. those forms showing the least derivation 
of character from the basic morphology, while other forms specialize 
like crazy as if they were Darwin's finches), there is a tree that 
supports your composition. These genera are: *Thecodontosaurus* for the 
Sauropodomorpha [later horizon than "advanced" melanorosaurs like 
*Euskelosaurus* does an advanced dinosaur not make], *Pisanosaurus* and 
*Technosaurus* and *Fabrosaurus/Lesothosaurus* of Ornithschian grade, 
and *Eoraptor*, *Staurikosaurus*, and *Herrerasaurus* along with 
coelophysoids and all their descendants for the Theropoda, 
"Paleotheropoda" as described by Paul (1988).

<Note that several authors have cited the short ilium, pes with 
metatarsal I reaching the tarsus, and vestigal remnant of metatarsal V 
as basis for making Theropoda exclusive of herrerasaurids. Theropods 
have a relatively long ilium characterized by a long preacetabular 
process (Paul, 1988; Glut, 1997). Currie (1997) characterizes theropods 
as having a strap-like scapula. This is seen in advanced herrerasaurids, 
but not in _Eoraptor_ (as reconstructed by Paul in Benton, 1997). 
Indeed, the scapula of _Eoraptor_, as reconstructed, does not differ 
significantly from that of primitive archosauriforms like _Euparkeria_ 
(as reconstructed by Paul in Parrish, 1997). It seems possible, then, 
that advanced  herrerasaurids might have developed the strap-like 
scapula independently of theropods.>

Oviraptorids have short ilia, as does *Microvenator* and caenagnathids, 
even primitive ornithomimosaurs, that aren't all the different from some 
therizinosaur ilia.

<Morphology of the foot and pelvis of therizinosaurids might place them 
as descendants of a line that gave rise to sauropodomorphs and then 
later ornithischians. The therizinosaurid line would represent a state 
more derived than than those "segnosaurs" which gave rise to 
sauropodomorphs and primitive to the "segnosaurs" which were the direct 
ancestors of ornithischians.>

If only we could find the most primitive oviraptors, ornithomimids, 
tyrannosaurs, dromaeosaurs, and segnosaurs. <Sigh>

The humerus of *Erlikosaurus* is quite like that of prosauropods, but 
also some primitive theropods (ceratosaurs).

<The basal "segnosaurs" might have been more derived than _Eoraptor_, 
but primitive to _Staurikosaurus_ based on comparisons of the pelvis and 
skull in these two forms as compared with the relatively derived 
_Segnosaurus_ and "prosauropods".>

Leaf-shaped teeth like those which *Segnosaurus* and *Erlikosaurus* bear 
are found in only troodontids, earlier prosauropods (plateosaurids) and 
*Mononykus*.

<Morphology of the coracoid of _Therizinosaurus_ seems to be similar to 
that of _Herrerasaurus_ itself (based on several photographs and 
reconstructions).>

Also to prosauropods and sauropods in general. Good character, but some 
few dinosaurs have retained this throughout advanced stages of dino 
evolution with more "primitive" genera having specialized (derived) 
coracoids, reminding us that reversing characters are still possible and 
do occur.


<As for _Alxasaurus_:

Coelurosauria
|=="primitive forms"
+--Maniraptoriformes
   |--Coeluridae
   |--Arctometatarsalia
   |--Compsognathidae
   +--Maniraptora
      |--Ornitholestidae
      +--+--+--_Alxasaurus_****
         |  +--+--_Microvenator_
         |     +--Oviraptosauria
         +--Paraves>

I like this one for some reasons, but not for others. Again, I will not 
bore the list with my conclusions, yet.

<As described in Glut (1997) and Maryan'ska (1997), there is no way to 
be certain that _Alxasaurus_ is a therizinosaurid. Skull material is 
lacking and the portion of the dentary might well be pre-oviraptosaur. 
The anterior edge of the ilium is unknown as is the pubis. The ischium 
(again, as restored) is reminiscient of an oviraptorsaur. The neural 
spines on the cervical vertebrae appear to be more reduced than in 
supposedly more primitive therizinosaurids. This animal is damaging to 
my case for a "segnosaur" origin of phytodinosaurs, but mostly because 
my information about the pes is limited and I must rely solely on a 
single reconstruction reproduced twice.>

Retained mt V is a limited relic reserved for Sauropodomorpha, 
Herrerasaurids and *Eoraptor*, and Ornithschia. And, of course, 
therizinosaurs and segnosaurs.

<I'm sure that this post will never be read by most of you, you probably 
see the "absurd" clagogram at the top and dismiss me as an idiot.>

You dismiss the list too easily. A scientific community we are, and as 
thus all ideas are shared and compared. Yours is sound in many ways, but 
requires somes one with a magnifying glass to sit down with all the 
relevant bones (whichever those ones are) and compare. No one's done 
that yet, unfortunately.

Until that new Chinese dino that no one's talking everything about,

Jaime A. Headden

"Chocolate? What chocolate?" he says while wiping his mouth of a 
conspicuous brown stain.

______________________________________________________
Get Your Private, Free Email at http://www.hotmail.com