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Re: Megalancosaurus, Longisquama & other oddballs



On Sun, 18 Mar 2001 Dinogeorge@aol.com wrote:

> In a message dated 3/18/01 2:22:27 PM EST, tmk@dinosauricon.com writes:
>
> << It might be a good idea to revise the definition of _Dinosauromorpha_
>  (currently Clade(_Dinosauria_ <-- _Pterosauria_)), too, since it would
>  also greatly expand if _Pterosauria_ were not included in _Archosauria_.
>  Clade(_Iguanodon bernissartensis_ <-- _Pterodactylus antiquus_,
>  _Crocodylus niloticus_) might be better. _Pterosauromorpha_ (currently
>  Clade(_Pterosauria_ <-- _Dinosauria)) may need revision, too, or it might
>  become a synonym of _Prolacertiformes_ (has this ever been defined?)
>  (which already might be a synonym of _Protorosauria_). >>
>
> This is a nice dose of the problems inherent in being too inflexible with the
> definitions of higher taxa.

I see it more as a problem inherent in basing definitions on the
assumption that your phylogeny is the correct one, and not heeding
alternative hypotheses.

Definitely a wide sample of phylogenies should be considered in the making
of the companion volume to PhyloCode. Firm definitions are supposed to be
a main benefit of PhyloCode -- the clades exist free of our arbitrary
notions of membership. But it is true that in order to make the system as
backwards-compatible as possible, great care should be taken in
formulating definitions. PhyloCode has many recommendations for this.

While I'm at it, can anyone think of any objections to these definitions?:

_Prolacertiformes_ == Clade(_Prolacerta_ <-- _Passer_, _Trilophosaurus_, 
_Rhynchosaurus_)

_Protorosauria_ == Clade(_Protorosaurus_ <-- _Passer_, _Trilophosaurus_, 
_Rhynchosaurus_)

_Archosauria_ == Clade(_Passer_ + _Crocodylus_)

_Pseudosuchia_ == Clade(_Crocodylus_ <-- _Passer_, _Iguanodon_, _Megalosaurus_)

_Avemetatarsalia_ == Clade(_Passer_ + _Iguanodon_ <-- _Crocodylus_)

_Ornithodira_ == Clade(_Pterodactylus_ + _Passer_) within _Archosauria_

_Pterosauromorpha_ == Clade(_Pterodactylus_ <-- _Iguanodon_)

_Dinosauromorpha_ == Clade(_Iguanodon_ <-- _Pterodactylus_, _Crocodylus_)

_Dinosauriformes_ == Clade(_Marasuchus_ + _Iguanodon_ + _Megalosaurus_)

_Dinosauria_ == Clade(_Iguanodon_ + _Megalosaurus_)

(generic names stand for the type species of those genera; taxa listed in
order of precedence)

Application under various phylogenies:

"the standard":

|--_Rhynchosaurus_
|--_Trilophosaurus_
|--_Prolacertiformes_ (=_Protorosauria_)
|  |--_Protorosaurus_
|  `--_Prolacerta_
`--+--_Pseudosuchia_
   |  `--_Crocodylus_
   `--_Avemetatarsalia_
      `--_Ornithodira_
         |--_Pterosauromorpha_
         |  `--_Pterodactylus_
         `--_Dinosauromorpha_
            `--_Dinosauriformes
               |--_Marasuchus_
               `--_Dinosauria_
                  |--_Iguanodon_
                  `--+--_Megalosaurus_
                     `--_Passer_

Dilkes:

|--_Protorosauria_
|  `--_Protorosaurus_
`--+--_Rhynchosaurus_
   `--+--_Prolacertiformes_
      |  `--_Prolacerta_
      `--_Archosauria_

Peters:

|--_Rhynchosaurus_
`--+--_Prolacertiformes_ (=_Protorosauria_, _Pterosauromorpha_)
   |  |--_Pterodactylus_
   |  `--+--_Prolacerta_
   |     `--_Protorosaurus_
   `--_Archosauria_

Feduccia et al. (well, they've never produced a cladogram, but if they
did, it might look like this -- I have no idea what they think of
_Pterosauria_, BTW):

_Archosauria_
|--_Rhynchosaurus_
|--_Trilophosaurus_
|--+--_Prolacertiformes_
|  |  `--_Prolacerta_
|  |--_Protorosauria_
|  |  `--_Protorosaurus_
|  `--_Passer_
`--+--_Pseudosuchia_
   |  `--_Crocodylus_
   `--_Dinosauromorpha_
      `--_Dinosauriformes_
         |--_Marasuchus_
         `--_Dinosauria_
            |--_Megalosaurus_
            `--_Iguanodon_

Just trying my hand....

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