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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
> dermal armor in any primitive dinosaur (and there is evidence for
> dermal armor in all three groups). I believe "_Lagosuchus_" has
> there any evidence tat early "phyotdinosaurs" had a greater degree of
>You might be right about this. Of course, it depends on what counts as
>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
> I realize you (George) cannot accept reversals in the locomotor
> but such an objection cannot be supported in the presence of clear
> phylogenetic analyses to the contrary. I do not recall there being any
> Ornithiscian with a functional fifth digit...>>
>The analyses are hardly "clear." I have yet to see any cladistic
>that demonstrates beyond reasonable doubt that any terrestrial
>>regained< a functional digit that was previously lost. Digital loss is
>one-way street: down. Indeed, the occasional cladistic analyses that
>to demonstrate this phenomenon should be regarded with great
>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
><< >leaf-shaped herbivorous dentition.
> As noted by Gauthier (1986), this morphology is a common
> reptilian tooth pattern, as it occurs in lacertillians as well as
> archosaur groups. While it is a potential synapomorphy, the
> utility of this feature is doubtful.>>
>At the level of Phytodinosauria, it's very close to being a
>It's certainly a derived state (primitive would be some kind of
>dentition). I know of no archosaurs with leaf-shaped dentition that are
>anywhere close to Dinosauria. Aetosaurs are the only others, and they
>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
> *absence* of the obturator process is by no means significant, excep
> context of one being present ancestrally, as it appears to have
> several times over dinosaurian history, and may have even been
> in some lineages.
> See Britt 1992 and Novas 1997.>>
>In Ornithischia, the obturator process developed well along in the
>evolution. Along with having a prepubic process that extends farther
>than the anterior process of the ilium, it is a synapomorphy of
Hard to argue there too.
><< >(4) Segnosaurs (= therizinosaurs) are not theropods.
> Therizinosaurs (= segnosaurs).
> >theropods, the semilunate carpal evidently formed by fusion of the
> >carpals (radiale and intermedium), whereas in segnosaurs it formed by
> Hasn't this particular homology been questioned? I believe
> Hinchcliffe's (?) work on avian ontogeny has some things to say about
>I'm going by Ostrom's description of the semilunate carpal in
><< >carpal structure differs greatly from that of theropods and cannot
> "Always with you what cannot be done...">>
>Like I said before, a remarkable occurrence requiring remarkable proof.
><< >from theirs. The forelimb and manus of segnosaurs are highly
> >the fact that it the manus is tridactyl should not be used as a
> >uniting segnosaurs with theropods.
> This is patently ludicrous! Ornithomimids has a far more
> manus, and no one argue the homology of their manus! Again you
> homology a priori of a phylogenetic analyses.>>
>Sorry, the ornithomimid manus is nothing like as specialized as a
>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
><< >The ascending process on the astragalus differs in detail from that
> in >theropods and probably developed independently.
> So your argument then becomes "any feature which is
> derived from the ancestral condition may no longer be considered
> homologous"? Let's let the data speak for themselves: therizinosaurs
> other theropods have large astragalar as.p.s.>>
>They certainly do, and in my phylogeny they developed them
>never said, "Any feature significantly derived from the ancestral
>may no longer be considered homologous." That's nonsense.
> The feet show clear signs of being secondarily quadradactyl
> and Dong 1993).>>
>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
> The lower jaw of _Erlicosaurus_ is similar to that of
> as P. Buckholz [sic? sorry Pete] has pointed out.>>
>It's much more similar to the lower jaws of >any< prosauropod, as well
>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.
> These teeth are possibly just as similar to those of
> _Pelecanomimus_ as they are to your "phytodinosauria".>>
>They are nearly identical (no pun intended) in conformation, relative
>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
> Retroverted pubes are present in some maniraptors, and anyway
> in this case, possibly related to herbivorous habits and are thus not
> excluded from the possibility of convergence.>>
>So are segnosaurs dromaeosaurids or birds? Those are the only theropods
>display retroverted pubes. >Of course< retroverted pubes in segnosaurs
>convergent with theropod retroverted pubes; but they could well be
>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
> 1. Manus tridactyl>>
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
><< 2. Manual proportions similar to other ceolurosaurian
>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)>>
>So does this make segnosaurs archaeopterygids or oviraptorosaurs?
Well I agree with you on that.
><< 4. Enlarged preacetabular portion of Ilium (Neotheropoda)>>
>Also noted in all Ornithischia; probably a synapomorphy of segnosaurs
>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.
><< 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
Wrong. Read above. All maniraptorans have a preacetabular blade region
><< 8. " " " with hooked anterior margin
>Again, does this make them ornithomimosaurs or oviraptorosaurs?
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,
Ditto. See above.
><< 10. Obturator process triangular (ceolurosauria)>>
>Segnosaur apomorphy. The obturator process of segnosaurs is in a
>location on the ischium. Ornithopods have an obturator process; does
>make coelurosaurs ornithopods or vice versa?
><< 11. Pubic boot enlarged.>>
>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)>>
>I'll say. See above.
Yes questionable, but interesting.
><< 13. Strap-shaped scapula (Theropoda)>>
>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)>>
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
><< 15. Semilunate carpal with transverse trochlea backs dig I
> etc etc etc...>>
>Convergent; see above. The carpus of _Alxasaurus_ is much different
>derived carpus of maniraptorans. Or manuraptors, as Charig & Milner
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
>What you have here is a list of characters found randomly among
>other dinosaurs that could easily have been acquired by convergence
>the long interval of segnosaur evolution for which there is as yet no
>record. There's >nothing< like a robust character suite here--just a
>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
> >sauropodomorphs than from theropods
> And snakes derive more readily from eels, but that doesn't
>Aw come on. Take almost any part of the segnosaur skeleton, from skull
>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
> In the absence of a phylogenetic hypothesis to the contrary,
> left with this conclusion. Care to clade a better one?>>
>Since I don't accept cladistic analysis as anything more than simply
>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
Avimimiform? Do you have access to material on this taxon that
> rest of us do not? I am interested to know what autopomorphies
> and _Mononykus_ might share, which the latter taxon does not share
> birds or arctomets. >>
They do not share any they are unrelated.
>Very slender, distally tapering fibula, closely appressed to the tibia,
>one. _Mononykus_ can't be a bird because, like _Avimimus_, it doesn't
>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
>particularly among the femoral trochanters, but I haven't finished
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
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