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[dinosaur] phylogeny tyrannosauroid dinosaurs

I'm pouring over this paper on phylogeny tyrannosauroid dinosaurs.  I'm
not understanding what is being measure in the premaxilla bone, which is
a measured characteristic 13.  Does anyone have an example of a diagram
of what is being measured?

(Premaxilla orientationa and shape of anterior margin)

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).

This character is slightly modified following Brusatte et al.
(2014:485). We have transformed the original character of Brusatte et
al. (2010:13) into an ordered multistate by adding a new intermediate
state referring to an approximately vertical (or slightly anterodorsally
inclined) anterior margin of the ventral portion of the premaxilla.
State 2 now refers to a special condition of this state, in which the
anterior margin is vertical (or anterodorsally inclined) and there is
also a discrete inflection point between the more vertical ventral
portion of the anterior margin and the more horizontal dorsal portion of
the margin. Taxa with this condition, therefore, do not possess a
smoothly curved anterior margin of the premaxilla. Tyrannosauroids are
characterized by either state 1 or state 2, with state 2 referring to a
subset of basal tyrannosauroids (Dilong, Guanlong, Kileskus,
Proceratosaurus, Sinotyrannus).