Re: Tetanurae

[Jamie Stearns <stearns5@cox.net>]

It seems a lot of ways to define Tetanurae are problematic, and with no easy 
way to resolve. The usual three options all have problems:

Stem-based: This, as stated earlier, could create problems when abelisaurs 
are taken into account.

Node-based: Normally, this would be a good solution. However, this is also 
problematic with things like Piatnitzkysaurus, Cryolophosaurus, etc. 
floating around out there (laughs at ridiculous thought of 25-foot theropods 
floating around in inner tubes)

Apomorphy-based: This may be more viable then the other two, as a popular 
"rule of thumb" (no pun intended) places Tetanurae as "theropods with three 
or fewer digits on hand." Unfortunately, as many of the big theropods have 
dinky little arms that are rarely found, this comes with its own set of 
problems. Nevertheless, a refined version of an apomorphy-based definition 
that includes a few more characteristics may be the way to go.