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Re: Megalancosaurus, Longisquama & other oddballs

I agree you can cladistically define Avemetatarsalia precisely, but you may forever condemn teachers to having to explain that this name is based on a homoplastic character which arose independently in pterodactyls.
This is why I find phylogenetic classifications inherently unstable, confusing, and impractical. They are too finely split, and trying to pack way too much phylogenetic information into "formal" taxon names which all too often are based on homoplasies.
Way too many names, conflicting cladograms, homoplastic complexities, and you have the perfect recipe for endless bickering even among the dinosaur people. I shudder to think what PhyloCode has in store for arthropods----- that will be a perpetual nightmare that will make our dinosaur nomenclature problems look like a picnic. I'm even starting to scare myself, so will shut up now.
HAPPY EQUINOX tomorrow (Spring up here; Autumn down there).
From: "T. Mike Keesey" <tmk@dinosauricon.com>
Reply-To: tmk@dinosauricon.com
To: Ken Kinman <kinman@hotmail.com>
CC: <dinosaur@usc.edu>
Subject: Re: Megalancosaurus, Longisquama & other oddballs
Date: Mon, 19 Mar 2001 01:01:32 -0500 (EST)

On Mon, 19 Mar 2001, Ken Kinman wrote:

> Mike,
> I would agree that something like Crocodylotarsi would be preferable to
> Pseudosuchia. However, Avemetatarsalia is probably at best the paraphyletic
> mother group that gave rise to Crocodylotarsi (not sister groups), and
> Avemetatarsalia may well turn out to be actually polyphyletic.

Not if phylogenetically defined as Clade(_Passer_, _Iguanodon_ <--
_Crocodylus_). It would be either monophyletic, or invalid in the unlikely
event that _Crocodylus_ falls inside Clade(_Passer_ + _Iguanodon_). If
_Pterosauria_ turn out not to belong, so be it.

>       And I also agree that Ornithischia is preferable to Predentata,
> although I'm not particularly crazy about either one of them.

_Predentata_ is, in all fairness, a great name, since it sums up the one
trait completely unique to the group. But, yes, you really can't supplant
such a well-restablished name as _Ornithischia_, IMHO.

> I'm just crossing my fingers and hoping Phytodinosaura might be a good
> clade.  Time will tell.

Even if it is, _Ornithischia_ should be a subclade of it. The definition
really should be changed to Clade(_Iguanodon_ <-- _Megalosaurus_,
_Saltasaurus_), or something similar. _Phytodinosauria_ could be
Clade(_Iguanodon_, _Saltasaurus_ <-- _Megalosaurus_) (invalid under most

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