Re: [dinosaur] phylogeny tyrannosauroid dinosaurs

["David Marjanovic" <david.marjanovic@gmx.at>]

> I don't know what ventral and anterior margins are and what angle is
> being measured.
>
> [...]
>
> 13) Premaxilla, orientation and shape of anterior margin: smoothly
> curved and projection posterodorsally, angle between ventral margin of
> premaxilla and anterior margin is less than 90 degrees (0); smoothly
> curved and projecting vertically or slightly anterodorsally, angle
> between ventral margin of premaxilla and anterior margin is equal to or
> greater than 90 degrees (1); projecting vertically or slightly
> anterodorsally, with a discrete inflection point between a more vertical
> ventral portion and a more horizontal dorsal portion (2). ORDERED
> (Brusatte et al. 2010:13).

"Anterior" is simply "front". "Ventral" is "down" in this and most other cases: 
venter = belly. So, the ventral margin of the pmx is the one with the teeth. 
You hold a ruler to the front side, another along the toothrow, and measure the 
angle between them.

The character could also be worded as "pmx pointed (0); blunt, rounded (1); 
rectangular or slightly overhanging (2)", but that wouldn't be precise enough 
to deal with borderline cases. (In my work I've encountered lots of characters 
that were worded in such imprecise ways, and lots of borderline cases that were 
hard to score for such characters.)