Reptile & Amphibian Forums

Hi folks,

Back in 1990 Underwood & Stimson assumed the python species to form a natural group and divided the python generas into two tribes. One called "Pythonini", containing only the genus Python, for the african and asian pythons, and a second named "Morelini", including the generas Morelia and Aspidites for all the australasian pythons species.
Because of their results of the phylogenetic analysis for the Australiasian pythons that were "...not yet robust, cautionusly, follow Storr et al. (1986) and assign all of these species to Morelia" (Underwood & Stimson, 1990:594). Earlier Schwander & Dessauer (1986) tested McDowell's (1975) taxonomic proposals by Immunodiffusion analysis and found the australasian species indistinguishable from each other, but clearly distinguishable from P. regius. This might have supported Underwood & Stimsons assumption, placing them all into the genus Morelia, even though earlier workers (i.e. Worrell 1960, McDowell, 1975) found out a lot of morphological differences between e.g Liasis and Morelia.

So, even though, obviously different morphological characters separate the species and the generas, U & S lumped together everything. Perhaps it was a common thing to do these days?

Any suggestions?

Cheers,
Wulf

Reference:
Underwood & Stimson, 1990, A classification of pythons (Serpentesythonidae), J. Zoo. Lond. 221, 556-603
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Hi Wulf,

One might say, a bit of both. First, they were unable to satisfactorily resolve relationships among Australasian pythons, apart from the strong distinction of Aspidites. Then they decided to adopt a classification that did not (according to the weakly resolved phylogeny) imply much more knowledge than they actually had.

Various reasons might be suggested for the low-resolution result, including inadequate sampling of taxa and characters, inadequate outgroup (Loxocemus, or was it Xenopeltis? - just one species, anyway), and an analysis method (rarely ever used) that throws away any characters that aren't perfectly consistent with the rest. The low amount of character evidence retained, and 'bad' outgroup, could result in the low resolution; the outgroup (again) and number of missing taxa could also result in the root being misplaced.

Given this result, it was quite proper (ideologically) to keep as genera only those groups that were supported as monophyletic by the analysis; and, conveniently, Storr & Smith's highly-lumped classification had been published only a few years before (my impression was that Storr & Smith had already been filled in on Underwood & Stimson's unpublished results).

Kluge (1993) worked with many more specimens and characters, multiple outgroups, and used maximum parsimony, so it's not surprising that he found a lot more phylogenetic structure. Of course, that doesn't guarantee getting the true tree!

Recent and current work at the South Australian Museum and other places is generating a lot of mitochondrial and nuclear sequence data, microsatellite characters etc., so we should know soon whether Kluge (as I suspect) rooted his cladogram in the wrong place despite his methodological rigour. It would seem hard to explain that all Oligocene and Miocene python fossils are either Python or Morelia (Scanlon 2001), if they are the last clades to have originated (as in Kluge 1993).

Cheers, John

Ref:
Scanlon, J.D. 2001. Montypythonoides: the Miocene snake Morelia riversleighensis (Smith and Plane, 1985) and the question of the geographic origin of pythons. Memoirs of the Association of Australasian Palaeontologists 25: 1-35.
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John D. Scanlon
Riversleigh Fossil Centre
Outback at Isa
Mount Isa, Queensland, Australia
riversleigh@outbackatisa.com.au