Re: An even dumber question

[Tetanurae@aol.com]

Peter Markman wrote:
<<What is it about crocodilians that makes them NOT dinosaurs? Ditto 
Komodo Dragons, other monitors, etc...>>

Dinosaurs, share a number of unique characters that show that they are not 
"close" to crocodilians.  You should pick up:

Novas, F E.  1996.  Dinosaur Monophyly.  Journal of Vertebrate Paleontology 
16(4): 723-741.

Sereno, P C and A B Arcucci.  Dinosaurian precursors from the Middle Triassic 
of Argentina: _Marasuchus lilloensis_, gen. nov.  Journal of Vertebrate 
Paleontology 14(1): 53-73.

Dzik, J.  2003.  A beaked herbivorous archosaur with dinosaur affinities from 
the early Late Triassic of Poland.  Journal of Vertebrate Paleontology 23(3): 
556-574.

To make a long story short, besides an upright stance, the following features 
(as well as tons more) define dinosaurs and some of them link dinosaurs with 
things like pterosaurs, _Scleromochlus_, _Marasuchus_ and _Silesaurus_.

-Advanced mesotarsal ankle
-Distal articular surface on calcaneum with transverse width 35% or less that 
of astragulus
-Articular facet on distal tarsal 4 for metatarsal V reduced
-Mid-shaft diameters of metatarsals I and V less than those of metatarsals 
II-IV
-Centrum shape in presacrals 6-9 (or 10): parallelogram shaped
-Anterior trochanter on femur present (I think this is generally referred to 
as the lesser trochanter in dino literature)
-Cnemial crest present on proximal tibia
-Acetabulum partially or fully perforate
-Ascending process of the astragulus pyramid shaped, with posterior 
subvertical facet and presence of an eliptical depression behind it
-Postfrontal absent
-Quadrate head laterally exposed
-Temporal musculature extended anteriorly onto skull roof
-Deltopectoral crest proximodistally elongate, more than 34% the length of 
the humerus

Crocodilians and Crurotarsian archosaurs (like aetosaurs, rauisuchians, 
phytosaurs etc) have a very different ankle joint which is pretty distinct from 
what's seen in dinosaurs.

As for Komodo Dragons....  They're lizards for one thing, and not archosaurs, 
so they lack an antorbital fenestra, and like all lizards, lack the lower 
border of their lateral temporal fenestrae.

A composite cladogram would look something like this:

--+--Lepidosauria (incl Komodo Dragons)
  `--+--Crurotarsi (incl Crocodiles)
     `--+--Pterosauria
        |--Scleromochlus
        `--+--Lagerpeton
           `--+--Marasuchus
              `--+--Silesaurus
                 `--+--Saurischia
                    `--Ornithischia

Pete Buchholz