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Squamate phylogeny

New paper on phylogeny of squamates:

Lee, M. S. Y. 2005. Squamate phylogeny, taxon sampling, and data congruence.
Organisms Diversity and Evolution 5 (1): 25-45.

"To investigate the affinities of snakes, amphisbaenians and dibamids, the
phylogenetic relationships among the major lineages (families) of extinct
and extant squamates are assessed through a combined analysis of 248
osteological, 133 soft anatomical, and 18 ecological traits. The
osteological data set represents a revision of previous data, taking into
account recent criticism; the ecological data set is new. In addition,
potentially critical fossil taxa (polyglyphanodontids and macrocephalosaurs)
are included for the first time. The osteological and soft anatomical data
sets each place snakes within anguimorphs, with dibamids and amphisbaenians
near gekkotans. The putative primitive fossil amphisbaenian Sineoamphisbaena
groups with macrocephalosaurs and polyglyphanodontids, together the sister
group to scleroglossans. All three data sets are congruent, and these
results are reinforced by combined analyses. In these, as in the
osteological analyses, snakes are nested within marine lizards. However,
exclusion of fossil taxa from the osteological data set results in a
?limbless clade¹ consisting of snakes, amphisbaenians and dibamids, and
introduces significant conflict between osteology and soft anatomy. Also,
deletion tests and character weighting reveal that the signal in the reduced
osteological data set is internally contradictory. These results increase
confidence in the arrangement supported by the all-taxon osteological, the
soft anatomical, and the combined data, and suggest that exclusion of
fossils confounds the signal in the osteological data set. Finally, the
morphological data support the nesting of snakes within marine lizards, and
thus a marine origin of snakes. This result still holds when relationships
between living forms are constrained to the topology suggested by molecular
sequences: if marine lizards are allowed to ?float¹ within this molecular
framework, they form the stem group to snakes, and do not group with
varanids as previously suggested."


        Christopher Taylor