RE: Sauropod-eating snakes

["John Scanlon" <riversleigh@outbackatisa.com.au>]

There's no particular anatomical signature for constriction, but I can't see 
any reason to assume madtsoiids or other basal snakes couldnât do it. But there 
are lots of different components to 'macrostomatan' adaptations for swallowing 
large prey, and some of them are actually primitive for snakes, so 'wide' vs. 
'narrow' gape is a false dichotomy: scolecophidians and 'anilioids' absolutely 
do not represent ancestral stages or adequate models for large Cretaceous 
snakes, which is indeed one of the main conclusions drawn by Wilson et al. 
Also, their phylogeny (Jason Head's work, which I think is his first published 
phylogenetic analysis) is just one of several recent morphology-based versions, 
and they all need testing against the very significant molecular data sets now 
available for extant groups... in fact somebody is working on it already ;)

If 3.5 m Sanajeh (95 mm skull length with very short supratemporals) could 
swallow 50 cm sauropods, what does that tell us about 6 m madtsoiids with 150 
mm skulls and long supratemporals (but still short quadrates) like Yurlunggur? 
Presumably, few Miocene mammals would be safe. Then you've got your 9 m 
Madtsoia bai (the one in the fantasy painting) or Gigantophis from the Fayum. 
They'd have been serious predators even without the palatal kinesis of modern 
snakes, and maybe just had to work a bit harder to eat the same-sized prey.

-----------------------------------------------
Dr John D. Scanlon, FCD
Riversleigh Fossil Centre, Outback at Isa
riversleigh@outbackatisa.com.au
http://www.outbackatisa.com.au/Fossil-Education/Palaeontologist.aspx
 
"Get this $%#@* python off me!", said Tom laocoonically.

-----Original Message-----
From: Tim Williams [mailto:tijawi@yahoo.com] 
Sent: 03 March, 2010 4:44 PM
To: dinosaur@usc.edu
Cc: bchoo@museum.vic.gov.au; tijawi@yahoo.com
Subject: RE: Sauropod-eating snakes


Brian Choo <bchoo@museum.vic.gov.au> wrote:

 
> Wasn't too disappointed as the accompanying William Service
> narration describes the engagement as an unsuccesful attack
> that seems plausible:  the serpent instinctively
> strikes the young sauropod and coils around it.  It
> constricts but fails to suffocate the prey item, then
> finally relinquishes its grip and retreats.


But would any Cretaceous snake coil itself around live prey to suffocate it, 
prior to swallowing?  Madtsoiids like _Sanajeh_ were narrow-gaped snakes.  The 
authors of the _Sanajeh_ paper suggest that titanosaur eggs had to be crushed 
by constriction before swallowing.  I assume that small prey items (like 
titanosaur hatchlings!) were eaten alive.  AFAIK, there are no known wide-gaped 
(macrostomatous) snakes in the Cretaceous.  So no Cretaceous snakes were 
capable of swallowing very large prey, in the manner of a boa constrictor (for 
example). 
 

The phylogeny in the _Sanajeh_ paper recovers the pachyophiids as sister taxon 
to the macrostomatous snakes.  This would drag the origin of the wide-gaped 
snakes back to the mid-Cretaceous, suggesting that macrostomatous snakes were 
around in the later Cretaceous.  But the phylogenetic relationships of 
pachyophiids are controversial.  Pachyophiids like _Pachyrhachis_ retain fairly 
well-developed hindlimbs, and some phylogenetic analyses place them outside the 
crown-group, as very primitive snakes.


I wish I still had my Service/Stout book.  :-(  


Cheers

Tim