Re: Dinosaur Classification

I have come up with a new Dinosauria cladogram. The is classification is based on the new findings of Isanosaurus, a sauropod that lived in the Triassic and had its legs set at a slight "semi-sprawl."

I can't find this in the description

Éric Buffetaut, Varavudh Suteethorn, Gilles Cuny, Haiyan Tong, Jean Le Loeuff, Sasidhorn Khansubha & Sutee Jongautchariyakul: The earliest known sauropod dinosaur, Nature 407, 72 -- 74 (7 September 2000).

Any sort of semi-sprawl would be highly illogic in such a large animal. Besides, Isanosaurus has straight femora.

Dinosauria

|

|---Saurischia

|     |---Sauropoda ·

|   |---Prosauropoda º

  |     |?---Lagosachus & Marasuchus*
|      `---Theropoda

`---Ornithischia

* The placement of Lagosuchus and Marasuchus is uncertain, it could be before Theropoda, Prosaurpoda, or it may not belong to the clade dinosauria.

It is very certain that they don't belong to Dinosauria. HP Mickey Mortimer posted a few synapomorphies of Dinosauria exclusive of Lago- & Marasuchus recently IIRC.

Is this what causes the unresolved, er, tetrachotomy (if I'm correctly interpreting your cladogram)?

º Some prosauropds were omnivorous based on a find in Nova Scotia this is just one reason that prosauropods may not belong with the sauropods in a clade known as sauropod[o]morpha.

· Isanosaurus shows features [...] that prove that sauropods did not evolve from prosauropods and that they were close to the "Proto-Dinosaur."

Isanosaurus is "markedly different from prosauropods", but this is not enough evidence to dissolve Sauropodomorpha (while it may be enough to make Prosauropoda holophyletic). No phylogenetic analysis was done in that paper. Omnivorous prosauropods (if real -- I have to wait for the paper) simply conserve the plesiomorphy and don't automatically destroy Sauropodomorpha either.