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RE: Yet more fun with squamate phylogeny



Thanks for the plug, David!

Seems like a fair summary; as for coexistence with pythons, that probably
only happened for a relatively 'short' time from the late Oligocene when (I
think) pythons invaded the Lost World (aka Australia): 
*Yurlunggur* and *Morelia* are found together in many Riversleigh LFs and a
few similar-aged sites in the Northern Territory, but probably differed in
being terrestrial vs. arboreal as well as size.  
>From the Pliocene the pythons are more diverse (*Liasis* and *Antaresia*
turn up) and NEVER yet found in the same faunas with *Yurlunggur* or
*Wonambi* (e.g. madtsoiids at Chinchilla, Lake Kanunka, Naracoorte,
Wellington, Wyandotte; pythons at Bluff Downs, Mt Etna & Marmor).  Also,
*Yurlunggur* and *Wonambi* have non-overlapping ranges except for the small
*W. barriei* in the early Mio, so it seems big madtsoiids weren't very good
at sharing. *Morelia* now lives around Wellington, Naracoorte and in
southern WA, but only *Wonambi* has been found in the cave deposits there. 
The record's pretty sparse (this is Australia we're talking about), but to
me it sure looks like competitive exclusion.
Cheers,
John
 
-----------------------------------------------
Dr John D. Scanlon
Palaeontologist, 
Riversleigh Fossil Centre, Outback at Isa
19 Marian Street / PO Box 1094
Mount Isa  QLD  4825
AUSTRALIA
Ph:   07 4749 1555
Fax: 07 4743 6296
Email: riversleigh@outbackatisa.com.au
http://www.outbackatisa.com.au/default.asp?d=55719&p=55589

> -----Original Message-----
> From: David Marjanovic [mailto:david.marjanovic@gmx.at]
> Sent: Thursday, February 16, 2006 8:40 AM
> To: DML
> Subject: Yet more fun with squamate phylogeny
> 
> John D. Scanlon: Skull of the large non-macrostomatan snake *Yurlunggur*
> from the Australian Oligo-Miocene, Nature 439, 839 -- 842 (16 February
> 2006)
> 
> Abstract (refs removed):
> "Understanding the origin and early evolution of snakes from lizards
> depends
> on accurate morphological knowledge of the skull in basal lineages, but
> fossil specimens of archaic snakes have been rare, and either fragmentary
> or
> difficult to study as a result of compression by enclosing sediments. A
> number of Cenozoic fossil snakes from Australia have vertebral morphology
> diagnostic of an extinct group, Madtsoiidae, that was widespread in
> Gondwana
> from mid-Cretaceous (Cenomanian) to Eocene times, and also reached Europe
> in
> the late Cretaceous period. Despite this long history, only about half the
> skull is known from the best-known species *Wonambi naracoortensis*, and
> the
> few known cranial elements of other species have added little further
> evidence for phylogenetic relationships. Conflicting hypotheses have been
> proposed for their relationships and evolutionary significance, either as
> basal ophidians with many ancestral (varanoid- or mosasaur-like) features,
> or advanced (macrostomatan) alethinophidians of little relevance to snake
> origins. Here I report two partial skeletons referred to *Yurlunggur*,
> from
> the late Oligocene and early Miocene of northern Australia, which together
> represent almost the complete skull and mandible. The exceptionally
> preserved skulls provide new evidence linking *Yurlunggur* with *Wonambi*
> and other madtsoiids, falsifying predictions of the macrostomatan
> hypothesis, and supporting the exclusion of Madtsoiidae from the clade
> including all extant snakes."
> 
> In total practically the complete skull is now known -- and full of
> plesiomorphies, many of them relating to limited (but not absent) kinesis.
> The teeth look like a boa's. Riversleigh fossils are preserved in 3D,
> usually undistorted, and can be acid-prepared, as the specimens mentioned
> here were.
> 
> *Yurlunggur* and *Wonambi* each have a few different convergences on
> Macrostomata!
> 
> Madtsoiidae is mentioned to be "presumed to be constrictors ecologically
> analogous to living pythons and boas", followed by a long string of
> references. Don't ask me why they co-occurred with pythons, then...
> 
> Bremer decay index left, bootstrap support right:
> 
> --+--composite "varanoid" outgroup
>   `--+--*Pachyrhachis*
>      `--3,86--*Haasiophis*
>            `--3,67--4,82--*Yurlunggur*
>                  |       `--*Wonambi*
>                  `--5,72--*Dinilysia*
>                       `--11,98--34,100,Scolecophidia (3 OTUs)
>                             `--3,62--3,48,Anilioidea (4 OTUs)
>                                  `--14,99,Macrostomata (10 OTUs)
> 
> The last three lines are the ophidian crown-group (Serpentes), the last
> two
> are called Alethinophidia. The character matrix comes from Lee & Scanlon
> 2002 (abstract:
> http://www.journals.cambridge.org/action/displayAbstract?fromPage=online&a
> id=120939).