Mekosuchus

[MKIRKALDY@aol.com]

(Posted for Chris Brochu - mk)
_____

<Yes, *Mekosuchus*, which had relatives in Australia during the 
Neogene(*Quinkana* and others), but the mekosuchines (what "family" do they 
belong to?) hadn't yet evolved, AFAIK, before the K-T extinction. Neither had 
Euramerican Paleogene pristichampsine crocodylids (which apparently died out in 
the Eocene-Oligocene event), but at least some of the South American groups 
were, and I was talking about crocodiles that probably didn't need wetlands but 
survived the K-T event.>

< Is HP Christopher Brochu onlist again? >

No, I'm not, but I check the archives from time to time.

Mekosuchus (the New Caledonian croc alluded to earlier) was initially thought 
to represent some sort of basal croc unrelated to modern croc lineages.  This 
may be why someone linked it with things like Baurusuchus
(though an actual relationship was never suggested).  Newer material worked on 
primarily by Paul Willis demonstrates that Mekosuchus was a crocodylid (or at 
least a crocodyloid - closer to living true crocs than to alligators); Paul's 
tree and mine on this subject differ by exactly one node, so there's little 
real conflict there.  Mekosuchines (you're still using "families?") are present 
in Australia from at least the early Eocene.

I had a chance to see Mekosuchus a couple of years ago.  Definitely 
crocodyloid, but I can see why Balouet and Buffetaut thought it was more 
"primitive" - there are some really weird features in the lower jaw that
are sorta kinda primitive-like, though they are almost certainly reversals.

Pristichampsus and its relatives (e.g. Planocrania) are crown-group crocs, and 
are closer to alligators and crocodiles than they are to Gavialis, but are 
neither alligatoroid nor crocodyloid.  Quinkana (the Australian
ziphodont) is a mekosuchine, not a pristichampsine.  You are correct in that 
pristichampsines have a first fossil appearance in the Tertiary (Upper 
Paleocene, to be exact), but on phylogenetic grounds, the lineage must have 
been present by at least the Campanian.

The South American ziphodonts are not crown-group crocs.

chris

------------------------
Christopher A. Brochu
Assistant Professor
Department of Geoscience
University of Iowa
Iowa City, IA 52242

christopher-brochu@uiowa.edu
319-353-1808 phone
319-335-1821 fax