Re: "Study shows more to a lizard bite than a nasty nip"

[David Marjanovic <david.marjanovic@gmx.at>]

----- Original Message -----
From: "Allan Edels" <edels@msn.com>
Sent: Wednesday, November 16, 2005 9:30 PM
Subject: "Study shows more to a lizard bite than a nasty nip"

> The study effectively doubles the number of potentially
> venomous reptile species to 4,600 from 2,300.

(And mentions in passing that there are 7,900 squamate species. Wow! Last 
time I looked there were only 6,000 or so.)

The trick is that the paper comes with a molecular phylogeny of 
Lepidosauria, which follows:

--+--*Sphenodon*
 `--Squamata
      |--Dibamidae
      |--Gekkonidae
      `--+--Scincoidea
         |    |--Scincidae
         |    |--Cordylidae
         |    `--Xantusiidae
         `--+--+--Teiioidea
            |  |    |--Gymnophthalmidae
            |  |    `--Teiidae
            |  `--+--Amphisbaenia
            |     `--Lacertidae
            `--1--Serpentes
               `--+--Iguania
                  `--2--Varanidae
                     `--+--Anguidae
                        `--Helodermatidae

1: Venom starts here. Very strongly supported clade. Only called "venom 
clade".
Serpentes (well, probably far inside that clade): Venom is elaborated, venom 
glands in the upper jaw fuse.
2: Venom is elaborated, venom glands in the upper jaw disappear, those in 
the lower jaw fuse.

I wonder if Serpentes and Iguania should switch places. The optimization of 
the venom and venom gland characters wouldn't change, and based on 
morphology the position of the snakes looks like long-branch attraction... 
but then, no less than five genes were used, as well as both maximum 
likelihood and Bayesian methods. I'm just wonder about the branch length of 
*Sphenodon*, and about the confusing fact that the Methods section says 
Scincoidea was used as the outgroup. Hm. Someone with more time than I 
should download the supplementary information -- a pdf file of no less than 
1.2 MB.

Oh, the ref:

Bryan G. Fry, Nicolas Vidal, Janette A. Norman, Freek J. Vonk, Holger 
Scheib, S. F. Ryan Ramjan, Sanjaya Kuruppu, Kim Fung, S. Blair Hedges, 
Michael K. Richardson, Wayne. C. Hodgson, Vera Ignjatovic, Robyn Summerhayes 
and Elazar Kochva: Early evolution of the venom system in lizards and 
snakes, Nature advance online publication, published online 16 November 2005
http://www.nature.com/nature/journal/vaop/ncurrent/full/nature04328.html

There's an impressive list of grants in the acknowledgments.