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Therizinosaurs and the Maniraptora



Before I start my rant I would like to say one thing about my mistake on 
hawk pellets. I was totally wrong. While in my brief absence from the 
list I was with a ornithologist and I told him about the mistake and he 
gave me hell about it. But I did learn  something valuable: never, ever 
make another mistake on this list or you will be ripped to shreds 
emotionally, physically and intellectually. But enough with my errors 
and on with another person's errors  : - )



Dinogeorge wrote: About dermal armor.
>         Plesiomorphic for dinosauria? I do not recall evidence for 
off-axial
> dermal armor in any primitive dinosaur (and there is evidence for 
axial
> dermal armor in all three groups). I believe "_Lagosuchus_" has 
scutes. Is
> there any evidence tat early "phyotdinosaurs" had a greater degree of 
dermal
> armor?>>
>
>You might be right about this. Of course, it depends on what counts as 
dermal
>armor. Dermal armor is found in a number of phytodinosaurian groups but
>not--unless you count the small dorsal ossicles of _Ceratosaurus_--in
>Theropoda, as a rule.
In Lagosuchus ( Marasuchus, whatever ) there is no evidence to my 
recollection of dermal armor but it is possible. And don't forget what 
GPaul said in PDW that it may be possble that Herrerasaurus had armor 
and also the Ceratosaurus armor was a reevolution or reoccurance of this 
lost trait since all dinosaurian relatives have armor.

><< >a functional fifth pedal digit
>>         Plesiomorphic for Ornithosuchia, and possibly more inclusive 
clades.
> I realize you (George) cannot accept reversals in the locomotor 
apparatus,
> but such an objection cannot be supported in the presence of clear
> phylogenetic analyses to the contrary. I do not recall there being any 
basal
> Ornithiscian with a functional fifth digit...>>
Dinogeorge:
>The analyses are hardly "clear." I have yet to see any cladistic 
analysis
>that demonstrates beyond reasonable doubt that any terrestrial 
vertebrate has
>>regained< a functional digit that was previously lost. Digital loss is 
a
>one-way street: down. Indeed, the occasional cladistic analyses that 
purport
>to demonstrate this phenomenon should be regarded with great 
skepticism. If
>this >has< happened, it would be a "remarkable occurrence, requiring
>remarkable proof." Not just some cladogram.
 Oh it is not such a remarkable or unbelieveable occurance. a genetis 
quirk can reevolve a certain body part. If what you say is true then the 
occasional horse with 3 toes and the whale with large and presumeably 
functional hindlimbs is impossible. Evolution is not a one way street it 
is a many way street with many options. While looking at the 
therizinosaur foot it just looks rebroadened and metatarsal 1 is 
lenghthned slightly.
><< >leaf-shaped herbivorous dentition.
>         As noted by Gauthier (1986), this morphology is a common 
adaption of
> reptilian tooth pattern, as it occurs in lacertillians as well as 
several
> archosaur groups.  While it is a potential synapomorphy, the 
diagnostic
> utility of this feature is doubtful.>>
Dinogeorge:
>At the level of Phytodinosauria, it's very close to being a 
synapomorphy.
>It's certainly a derived state (primitive would be some kind of 
insectivorous
>dentition). I know of no archosaurs with leaf-shaped dentition that are
>anywhere close to Dinosauria. Aetosaurs are the only others, and they 
seem to
>have acquired this as an apomorphy.
 Well I cannot argue with you there you are completely right.
><< >(3) Heterodontosaurids are not ornithopods [...]
> >and there is [not] an obturator process on the ischium. 
>         It is possible that many of common conceptions concerning the
> diagnostic utility of this element are in error.  I would argue that 
the
> *absence* of the obturator process is by no means significant, excep 
tint he
> context of one being present ancestrally, as it appears to have 
dissappeared
> several times over dinosaurian history, and may have even been 
redeveloped
> in some lineages.
>         See Britt 1992 and Novas 1997.>>
Dinogeorge:
>In Ornithischia, the obturator process developed well along in the 
group's
>evolution. Along with having a prepubic process that extends farther 
forward
>than the anterior process of the ilium, it is a synapomorphy of 
Ornithopoda.
 Hard to argue there too.
><< >(4) Segnosaurs (= therizinosaurs) are not theropods.
>         Therizinosaurs (= segnosaurs).
> 
> >theropods, the semilunate carpal evidently formed by fusion of the 
proximal
> >carpals (radiale and intermedium), whereas in segnosaurs it formed by 
the
>         Hasn't this particular homology been questioned?  I believe 
that
> Hinchcliffe's (?) work on avian ontogeny has some things to say about
>this.>>
Dinogeorge:
>I'm going by Ostrom's description of the semilunate carpal in 
_Deinonychus_.

><< >carpal structure differs greatly from that of theropods and cannot 
be
>derived
>         "Always with you what cannot be done...">>
Dinogeorge:
>Like I said before, a remarkable occurrence requiring remarkable proof.
> 
><< >from theirs. The forelimb and manus of segnosaurs are highly 
specialized,
>so
> >the fact that it the manus is tridactyl should not be used as a 
character
> >uniting segnosaurs with theropods.
>         This is patently ludicrous! Ornithomimids has a far more 
specialized
> manus, and no one argue the homology of their manus! Again you 
eliminate
> homology a priori of a phylogenetic analyses.>>
Dinogeorge:
>Sorry, the ornithomimid manus is nothing like as specialized as a 
segnosaur
>manus. "Far more specialized" is going off the deep end.
 Come on Dinogeorge the therizinosaur manus is not as specialized as you 
claim and obviously in early forms the manus is same as the typical 
maniraptoran manus.
><< >The ascending process on the astragalus differs in detail from that 
found
> in >theropods and probably developed independently.
>         So your argument then becomes "any feature which is 
significantly
> derived from the ancestral condition may no longer be considered
> homologous"?  Let's let the data speak for themselves: therizinosaurs 
and
> other theropods have large astragalar as.p.s.>>
Dinogeorge:
>They certainly do, and in my phylogeny they developed them 
independently. I
>never said, "Any feature significantly derived from the ancestral 
condition
>may no longer be considered homologous." That's nonsense.
Agree.
><<>The feet
>         The feet show clear signs of being secondarily quadradactyl 
(Russell
> and Dong 1993).>>
Dinogeorge:
>Nonsense. The signs, if any, are not clear at all.
 Geez the signs are very very clear. The typical therizinosaur pes is 
not at all like prosauropods and does show signs of rebroadening as 
described above.
><< >jaws
>         The lower jaw of _Erlicosaurus_ is similar to that of 
_Harpymimus_,
> as P. Buckholz [sic? sorry Pete] has pointed out.>>
>
>It's much more similar to the lower jaws of >any< prosauropod, as well 
as
>many sauropods and even stegosaurs.
 Wrong. How can you say that? Even just by looking at the general shape 
it is similiar to the Harpymimus mandible. 
><< >teeth
>         These teeth are possibly just as similar to those of 
_Mononykus_ and
> _Pelecanomimus_ as they are to your "phytodinosauria".>>
 Dinogeorge:
>They are nearly identical (no pun intended) in conformation, relative 
size,
>to the teeth of most prosauropods. Including the interdental plates.
 Interdental plates are not good taxonomic charactors since they are 
just the same from species to species. And the teeth are similiar to 
BOTH groups. 
><< >pelvis
>         Retroverted pubes are present in some maniraptors, and anyway 
are,
> in this case, possibly related to herbivorous habits and are thus not 
to be
> excluded from the possibility of convergence.>>
 Dinogeorge:
>So are segnosaurs dromaeosaurids or birds? Those are the only theropods 
that
>display retroverted pubes. >Of course< retroverted pubes in segnosaurs 
are
>convergent with theropod retroverted pubes; but they could well be 
homologous
>with retroverted pubes in Ornithischia.
 Homolougus to Ornithiscian pubes?! No way. They resemble dromaeosaurid 
pubes to a T with the degree of retroversion, structure of the pubic 
foot, the small ventral ilia process, the musclatore ( short and compact 
not like ornithiscians but like dromaeosaurids), and the laterally 
compression of the pubis. 
><<         CHARACTERS WHICH INDICATE THAT THERIZINOSAURS ARE 
CEOLUROSAURS:
>         (Abridged)
>         1.  Manus tridactyl>>
 Dinogeorge:
>Convergent.
 How? The structure is the same, the carpals ( in early forms ) are the 
same , and no other archosaurs have evovled this tridactyl manus. And 
convergence as expressed by Darwin is usually the result of similiar 
lifestyles and how did therizinosaurs converge on lifestyle with 
theropods?
><<         2.  Manual proportions similar to other ceolurosaurian 
groups>>
Dinogeorge:
>Convergent. Too vague to be a real character.
 Vague? It makes perfect sense. No other animals have lenghtened the 
manus to the extent of maniraptorans.
><<         3.  Lip on manual ungual II (Archaey, Oviraptorsauria)>>
Dinogeorge:
>So does this make segnosaurs archaeopterygids or oviraptorosaurs? 
Convergent.
 Well I agree with you on that. 
><<         4.  Enlarged preacetabular portion of Ilium (Neotheropoda)>>
 Dinogeorge:
>Also noted in all Ornithischia; probably a synapomorphy of segnosaurs 
and
>ornithischians, convergent with theropods.
 No. The enlargened preacetabular blade ( ventral ilia process ) is more 
like that of theropods espicially Harpymimus( and maybe dromaeosaurids) 
in that it bears a distinct sloping triangle shape and the ornithiscian 
preacetabular blade is more like a block.
><<         5.  Elongate ascending process of astragalus>>
>
>Just been through this one. Convergent.
 Agree.
><<         6.  Leaf-shaped teeth (Ornithomimidae, Mononykus)>>
>
>So--are segnosaur ornithomimimds or mononykosaurs? Also noted in
>ornithischians and sauropodomorphs.
 Well if you take the mandible and pelvis characteristics into account 
it is possible that therizinosaurs are ornithomimid relatives as 
expressed by Sereno.
><<         7.  Preacetabular blade of ilium dorsovetrally elongate 
(ovir,
>microv)>>
Dinogeorge:
>Segnosaur apomorphy.
 Wrong. Read above. All maniraptorans have a preacetabular blade region 
like this.
><<         8.      "       "       "       with hooked anterior margin
>(ornith, ov)>>
Dinogeorge:
>Again, does this make them ornithomimosaurs or oviraptorosaurs? 
Convergent.
 One thing I find interesting is that among the maniraptora the 
therizinosaurs, oviraptors, and ornithomimidae are all considered NEAR 
to herbivorous and all have the same preacetabular region. 
><<         9.  Antero-dorsal expansion of lip of acetabulum (ov, 
microv)>>
 Dinogeorge:
>Ditto.
 Ditto. See above.
><<         10. Obturator process triangular (ceolurosauria)>>
>
>Segnosaur apomorphy. The obturator process of segnosaurs is in a 
different
>location on the ischium. Ornithopods have an obturator process; does 
this
>make coelurosaurs ornithopods or vice versa?
>
><<         11. Pubic boot enlarged.>>
 Dinogeorge:
>Too vague. Enlarged which way? Anteriorly, posteriorly, both?
 Yes too vague but you should take this into account. Maniraptorans and 
therizinosaurs have similiar pubic feet. 
><<         12. ?Ventral migration of obturator process (questionable)>>
Dinogeorge:
>I'll say. See above.
 Yes questionable, but interesting.
><<         13. Strap-shaped scapula (Theropoda)>>
 Dinogeorge:
>Too vague. Depending on what you consider "strap-shaped," sauropods,
>prosauropods, and ornithischians also have strap-shaped scapulae.
 Not true at all. The basic form of the therizinosaur scapula and 
theropod scapulae are the same.
><<         14. Tridactyl pes (reversed in Therizinosauroidea)>>
 Dinogeorge:
>Bah.
 It is possible to "reevolve" characteristics. But the way I look at it, 
it is not a reevolution just an adaptation to support the greater weight 
of therizinosaurs. 
><<         15. Semilunate carpal with transverse trochlea backs dig I 
and II
>         etc etc etc...>>
 Dinogeorge:
>Convergent; see above. The carpus of _Alxasaurus_ is much different 
from the
>derived carpus of maniraptorans. Or manuraptors, as Charig & Milner 
have it.
 Bull. It is just the same and I find it if the carpus was just found 
alone in the sediments some people would find it like a maniraptoran 
carpus. 


Dinogeorge:
>What you have here is a list of characters found randomly among 
theropods and
>other dinosaurs that could easily have been acquired by convergence 
during
>the long interval of segnosaur evolution for which there is as yet no 
fossil
>record. There's >nothing< like a robust character suite here--just a 
few
>lumps and bumps
 Not at all. The features fit a coherent picture that shows that 
therizinosaurs fit snugly in the maniraptora.
><< >and limbs of segnosaurs all derive much more readily from
>prosauropod-like
> >sauropodomorphs than from theropods
>         And snakes derive more readily from eels, but that doesn't 
make it
> right.>>
 Dinogeorge:
>Aw come on. Take almost any part of the segnosaur skeleton, from skull 
to
>tail, and compare it with the corresponding region in prosauropods. The
>similarities are too many to be lightly dismissed.
 The similiarities are due to a similiar lifestyle and the basic 
features of the therizinosaurs fit nicely into the maniraptora.
><< >(5) _Mononykus_ is not a bird, nor is it an alvarezsaurid. It's a
>perfectly
>         In the absence of a phylogenetic hypothesis to the contrary, 
we are
> left with this conclusion. Care to clade a better one?>>
 Dinogeorge:
>Since I don't accept cladistic analysis as anything more than simply 
one more
>way of constructing phylogenies, I don't see what good this would do.
 I do not agree that Mononykus is not a bird. It share so many flight 
characteristics with birds it is hard to dismiss the likely-hood that it 
is not a bird. 
><< >good arctometatarsalian or avimimiform theropod with a highly 
derived,

Dinogeorge:

       Avimimiform?  Do you have access to material on this taxon that 
the
> rest of us do not?  I am interested to know what autopomorphies 
_Avimimus_
> and _Mononykus_ might share, which the latter taxon does not share 
with
> birds or arctomets. >>
 They do not share any they are unrelated. 
 Dinogeorge:
>Very slender, distally tapering fibula, closely appressed to the tibia, 
for
>one. _Mononykus_ can't be a bird because, like _Avimimus_, it doesn't 
have an
>avian metatarsus; it has an arctometatarsalian metatarsus. And a well
>developed tail with elongate chevrons. So the slender fibula becomes a
>potential synapomorphy of _Mononykus_ and _Avimimus_. There may be 
others,
>particularly among the femoral trochanters, but I haven't finished 
looking at
>the literature.
 No, no and no. The two species are totally different and Avimimus may 
well be a chimera like Protoavis. 
 
 Well here is my rant. Though nothing is for certain in paleontology it 
can be said that we have certainty on the therizinosaur issue. They are 
simply maniraptorans. Phylogenies can be sticky but that's the way its 
always been.
 
 WMattTroutman

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