Current taxonomy of Boas and Pythons

Squamata (~ 9,556 species) was traditionally divided for lizards, worm lizards (Aphisbaenia) and snakes. New research founding however disagree with this taxonomy and establish that old divisions are paraphyletic (not all descendants are within right taxa). (To check snakes phylogeny follow names with green lines.) Currently we recognize five subordo Dibamidae, Gekkota, Scincimorfa, Lacertata and Toxicofera. Our beloved animals (snakes) are in Toxicofera subordo what you can see in graphic below. This group of animals are known for using venom (YES! Iguania and Anguimorpha distant relatives used venom in the past). Within Toxicofera we distinguish anguimorpha, iguanas and snakes. This taxa started to use venom approx 200 my ago in Triassic period. It's hard now to say what of this taxa are sister lineage to snakes (closest relatives). 

At present we recognize ~ 3,458 species of snakes which makes them one of the biggest taxa in all reptiles and even between other classes. And what is the most exciting thing there? - the species number in snakes still growths! Inside snakes we have simple division on two. First are basal Scoleocophidia (popular blind snakes) and the second one is Alethinophidia (true snakes). Because pythons and boas are Alethinophidians I will follow more deeply in this direction. As you can see below Alethinophidia are divide on another two taxa: Henophidia and Caenophidia (where Henophidia are more basal one). 

P. Puszkiewicz "Cranial morphology analysis in Pythonidae and Boidae in philogenetical and ecological context" 2014.

Now can be little bit harder.  We know now that pythons and boas are within Henophidia taxa but there is another artificial division for Macrostomata. Snakes in this taxa have ability to open they jaw widely or more simple snakes with large gapes. Inside Macrostomata we have also Caenophidia where we classified snakes such as cobras and vipers. Caenophidia are commonly known as advanced snakes and in this taxa we found most of the most venomous snakes. However they are don't interest us now we are curious about core Macrostomatan taxa - pythons and boas. They both contains 101 species which is quite nice number. As you can see pythons are don't longer within boas taxa. There are clear that this two groups are philogenetcially more distant than we thought (they are not close relatives). The similarities between boas and pythons are mostly results of similar ecology. We call this convergent evolution. These both groups are mirrors each other but there are some clear differences which about I write more in near future. We don't know everything about their origins but we can suspect that they are originated on earlier cretaceous Gondwanaland, and they divided from each other 40-30 my later.

To sum up this post  they are within Toxicofera taxa where are all reptiles with venom glands. Boas and pythons are also Alethinophidians and Henophidians. They also have possibility to largely open their gape (Macrostomata) in contrast to Uropeltidae for example. In the past pythons was classified as subfamilly of Boidae. Pythons are not boas! they form different taxa they are don't even sister taxa. Why I need to scream about that - because there are still places where they are grouped together.

Next time I will write more closely about pythons and boas because there are even more taxonomical changes!

Do you think that this changes are good or you prefer old classification?

Comment below and let me know what do you think.

Useful research papers

1.      Fry, B.G., Vidal, N., Norman, J.A., Vonk, F.J., Scheib, H., Ramjan, S.F.R., Kuruppu, S., Fung, K., Blair Hedges, S., Richardson, M.K., Hodgson, W.C., Ignjatovic, V., Summerhayes, R., Kochva, E., 2006. Early evolution of the venom system in lizards and snakes. Nature 439, 584–588. doi:10.1038/nature04328

2.      Fry, B.G., Vidal, N., van der Weerd, L., Kochva, E., Renjifo, C., 2009. Evolution and diversification of the Toxicofera reptile venom system. Journal of Proteomics 72, 127–136. doi:10.1016/j.jprot.2009.01.009

3.      Greene, H.W., Burghardt, G.M., 1978. Behavior and phylogeny: constriction in ancient and modern snakes. Science 200, 74–77. doi:10.1126/science.635575

4.      Kluge, A.G., 1991. Boine snake phylogeny and research cycles. Miscellaneous Publications of Michigan Museum of Zoology.

5.      Noonan, B.P., Chippindale, P.T., 2006. Dispersal and vicariance: the complex evolutionary history of boid snakes. Molecular Phylogenetic Evolution 40, 347–58. doi:10.1016/j.ympev.2006.03.010

6.      O’Shea, M., 2011. Boas & Pythons of the World. New Holland Publishers Ltd, London.

7.      Pyron, R.A., Burbrink, F.T., Wiens, J.J., 2013. A phylogeny and revised classification of Squamata, including 4161 species of lizards and snakes. BMC Evolutionary Biology 13, 93. doi:10.1186/1471-2148-13-93

8.      Reynolds, R.G., Niemiller, M.L., Revell, L.J., 2014. Toward a Tree-of-Life for the boas and pythons: Multilocus species-level phylogeny with unprecedented taxon sampling. Molecular Phylogenetic Evolution 71, 201–213. doi:10.1016/j.ympev.2013.11.011

9.      Schleip, W., O’Shea, M., 2010. Annotated checklist of the recent and extinct pythons (Serpentes, Pythonidae), with notes on nomenclature, taxonomy, and distribution. ZooKeys 66. doi:10.3897/zookeys.66.683

10.      Vidal, N., Delmas, A.-S., Hedges, S.B., 2007. The higher-level relationships of alethinophidian snakes inferred from seven nuclear and mitochondrial genes. Biology of Boas and Pythons 27–33.

11.      Vidal, N., Hedges, S.B., 2009. The molecular evolutionary tree of lizards, snakes, and amphisbaenians. Comptes Rendus Biologies. 332, 129–139. doi:10.1016/j.crvi.2008.07.010

12.      Wiens, J.J., Hutter, C.R., Mulcahy, D.G., Noonan, B.P., Townsend, T.M., Sites, J.W., Reeder, T.W., 2012. Resolving the phylogeny of lizards and snakes (Squamata) with extensive sampling of genes and species. Biology Letters 8, 1043–1046. doi:10.1098/rsbl.2012.0703