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Re: My take on Allosaur Phylogeny



Peter Buchholz wrote:

>Ok, since everyone else has tried at this, I guess it's my turn now.

        Shoot!

>Family Piatnytzkisauridae
>-Piatnytzkisaurus
>-Monolophosaurus
>-Afrovenator

        Forgive me, but this seems just a touch too polyphyletic for
words...

>Metriacanthosauridae (=Sinraptoridae) [see below]
>-Marshosaurus

        This taxon needs study...

>Torvosauridae
>-Gasosaurus

        Disagree.  I think it's likely a basal allosauroid or
sinraptorid

>Megalosauridae
>-Megalosaurus
>-Chilantaisaurus

[P.B. I reformated your cladogram to work in courier (hope this
works): ]

>Mg Ab To  Al Me Ca Pi Co
> \ /   \   \ /   \ / /
>  2     \   6     7 /
>   \     \   \   / /
>    \     \   \ / /
>     \     \   5 /
>      \     \  \/
>       \     \ 4
>        \     \/
>         \    3
>          \  /
>           \/
>            1

>Mg = Megalosauridae; Ab = Abelosauria (Abelosauridae + Noasauridae);
>To = Torvosauridae; Al = Allosauridae; Me = Metriacanthosauridae
>(=Sinraptoridae); Ca = Carcharodontosauridae; Pi =
>Piatnytzkisauridae; Co = Coelurosauria.  NNode 1 = Tetanurae; Node 2
>= Megalosauroidea; Node 3 =Neotetanurae; Node 4 = Avetheropoda; Node
>5 = Allosauria; Node 6 = Allosauroidea; Node 7 is unnnamed.

>I created the family Piatnytzkisauridae for P., Monolophosaurus, and
>Afrovenator because they all posses relatively large nares, very
>similar maxilla and, in M. and A. at least, Lacrimals that have a
>"wiggle" or bend in

        If you want to base taxa on lacrimal structure, there is a
strong twist which all allosaurs have, which is otherwise known only
in Ornitholestes and Tyrannosaurs, and then only barely.  This
structure looks, from the side, as if the back edge of the lacrimal
bar has been folded around to touch the front at the middle of the
lacrimal, and produces also a wing-shaped rostral jugal process of the
lacrimal.  This structure is consistantly known in most recognized
allosauroid genera, including Allosaurus, Acrocanthosaurus,
Cryolophosaurus, Carcharodontosaurus ( Tom Holtz :) ), and, oddly
enough, Afrovenator.  I have never seen it figured for
Piatnitzkysaurus.  I have yet to see a solid cladistic analysis which
places Piatnitzkysaurus within the Carnosauria.

>them. I chose P. to name the family because it was named more than a
>decade before the other two. I think that perhaps Afrovenatoridae
>might have been a wiser coice though.

        I am no expert on this, but I believe that it is customary to
name a family for oldest genus known or the type genus.  Considering
that your interpretation of the position of Afrovenator differs from
all others (which I have seen, at least), it seems that your choice
was prudent, and will support the future stability of your taxonomy.

>I believe that it is the sister group to
>Carcharodontosauridae. Other than that, I think my cladogram is
>pretty normal.

        Do you have any synapomorphies to support this?

>The name Sinraptoridae has to be supressed if Metriacanthosaurus is
>included in it because Metriacanthosaurinae (Paul 1988) has priority
>since it was named before S. was even discovered.

        No one seems prepared to come forward with a well argued case
for Metriacanthosaurus being a close relative of Yangchuanosaurus
except for Paul.  If this is done, then Sinraptoridae would be
synonymous.
        You have good point that needs to be looked at.  You have the
following situations:
        STRUCTURE 1:    (Sinraptor,Yangchuan, Metria, Szechuan)
[quadrochotomy], the clade is
                                Metriacanthosauridae (Paul, 1988)
        STRUCTURE 2:    (Szech, (Sinraptor,(Yangchuan, Metria)))
                                Metriacanthosauridae (Paul, 1988)
        STRUCTURE 3:    (Sinraptor, (Yanchaun, Metria, Szech)), the clade is
                                Sinraptoridae, with the included node as
Metriacanthosaruinae
        Bascially, Sinraptoridae is Yangchuanosaurus+Sinraptor, and
Metriacanthosauridae/inae is Met+Szech+Yangchuan.  Resolve based on
your phylogeny, and apply.

>Also, if Eustreptospondylus is in the Torvosauridae as I beleive it
>might, I think that the name Eustreptospondylidae (Paul 1988) has
>priority, but I'm not sure though...

        I have checked on this.  The only way Paul's taxon has priority is
if Jensen didn't name a new family for Torvosaurus.  Sereno has probably
looked into this.

>Why are there SO SO many Theropod names with SOOOO many letters??
>Enough of Carcharodontosaurus, Piatnytzkisaurus, Giganotosaurus,
>Metriacanthosaurus, Yangchuanosaurus, Eustreptospondylus! The list
>could go on forever. Stop making such big names!

        I aggree (and I'm sick of "place-osaurus"s), but it is every
scientists right...

Wagner

Between egg predation and theropod phyolgeny, it's a wonder any of you
lurkers stick around... :)