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new reference and some taxonomy



Dear all,

A quite recent interesting paper which has not been mentioned yet:

David Dilkes 1998: The Early Triassic rhynchosaur Mesosuchus browni 
and the interrelationships of basal archosauromorph reptiles. 
Philosophical Transactions of the Royal Society series B 353, 
501-541.

The author restudies some well preserved remains of the primitive 
rhynchosaur Mesosuchus and confirms it to be the most plesiomorphic 
member of Rhynchosauria. A historical review of rhynchosaur taxonomy 
is given with some additional comments on doubtful rhynchosaur taxa.
The most interesting part of the paper is a new phylogenetic 
analysis, including six well-known rhynchosaur taxa, as well as some 
early diapsids, prolacertiforms, choristoderes and archosauromorphs. 
The technical aspects of this analysis I gladly leave to the more 
educated on this list: here are some remarkable conclusions:

The rhynchosaurs form a strongly supported clade (Rhynchosauria is 
properly defined as node-based taxon) which forms the sister group of 
a clade consisting of Prolacerta and Archosauriformes (represented by 
Euparkeria and Proterosuchus in the cladogram). Indeed, 
Prolacertiformes is paraphyletic, as Prolacerta shares a more recent 
common ancestor with Archosauriformes than with the other taxa that 
traditionally have been included in Prolacertiformes (Protorosaurus, 
Macrocnemus, Langobardisaurus, Tanystropheus, Megalancosaurus and 
Drepanosaurus): these remaining taxa still form a clade that branches 
off at the base of Archosauromorpha.
Choristoderes (represented by Champsosaurus, Cteniogenys and 
Lazarussuchus) still form a clade (Choristodera is properly defined 
as node-based taxon), but not within Archosauromorpha; the clade even 
falls outside Sauria (most recent common ancestor of Lepidosauria and 
Archosauria plus all descendants).

Pieter Depuydt