RE: Genealogy of Scaly Reptiles Rewritten by New Research

["Jaime A. Headden" <qilongia@yahoo.com>]

Mickey Mortimer (mickey_mortimer111@msn.com) wrote:

<Iguania and Anguimorpha were weakly combined to the exclusion of Serpentes
with a BPP of 58 and a ML bootstrap of 53. I agree Bifurcata, Unidentata,
Episquamata, Toxicofera and Lacertibaenia are useful. But Scincoidea already
exists for Scinciformata, and Lacertiformes for Laterata. Teiformata and
Lacertiformata seem superfluous. I think the philosophy for most was to
conserve equal 'ranks' of suffices. But Laterata was specifically advocated
because Lacertiformes didn't originally include amphisbaenians and doesn't
describe their shape accurately, neither of which I feel is a good reason to
rename a clade. Lee's (1998) definition of the clade doesn't explicitly exclude
amphisbaenians. It's the Eueulipotyphla philosophy so common in mammal
taxonomy.>

  Well, Vidal and Hedges seem to have chosen to to really define the clades,
but name the clades for retention of a specific apomorphy, and including some
clades, but do not explain their reasoning beyond this. The use of molecular
(nuclear) genes, including HOXA-13, is remarkably synched with several
morphological features:

  Bifurcata is named for the retention of a forked tongue, and excludes
Dibamidae. Gekkotans are included in this clade, though tongue bifurcation is
not consistent among taxa, and some lack a forked tongue. Dibamidae is split
off into the Dibamia as the opposing "same rank" group from bifurcatans.
Dibimidae and Dibamia are thus equivalent in content and likely equivalent in
use, and if they were explicitly defined, it's possible we would have no need
of Dibamia, but some people like clade names in profusion.

  Unidentata is used to include all other "standard" scleroglossans (in which
case paraphyletic due to retention of *Iguana*, which it excludes to the
retention of *Anguis*) which have a single egg tooth, and the name means "one
toothed" for this feature (Uniovidentata may be too long or two-vowely for the
authors).

  Episquamata includes the remaining lacertilians, excluding skinks, which have
been named Scinciformata (the "shape of skinks") instead of Scincomorpha which
I guess is treated as the paraphyletic combination of anguids + scincoids. As
Mickey noted, Scincoidea is available for definition (literally, "the shape of
skinks"), but this would actually defeat the purpose of these names, and be
redundant to have both names in the same tree; the authors considered
Scincoidea to only include Scincidae and Cordylidae. Episquamata includes the
iguanians plus the remaining anguimorphs, including snakes and amphisbaenids.
However, differing from other topologies, including Fry et al.s
online-published study of the toxin evolution and application to phylogeny of
lacertilians, snakes are the most basal member of Episquamata, the "top
squamates". The name alone suggests a bias towards the top predatory reptiles.

  Episquamata is diphyletic, split between the "venom-bearers" Toxicofera
(which includes iguanians plus Anguimorpha, and snakes), and Laterata, named
for the "lateral" tile-shaped scales in amphisbaenians, teioids, and lacertoid
lizards (some of which have also been shown to be venom-bearers by Fry).

  As Mickey noted, Teiioidea and Teiiformata are effectively the same taxon, as
Teiioidea includes Teiidae and Gymnophthalmidae (some of my favorite lizards,
actually, along with skinks), which is what Teiiformata was coined to
contained. But aside from Lacertibaenia, named in mammalogist-fashion to
include Lacertidae and Amphisbaenia, most names are coined based on
morphological features, and are used in support of features.

  Thus I argue here that given differential phylogenies, the names are
apomorphy-based clade names for the most part, and content-based stem-defined
nodes on the other. Given one's phylogeny, these names will apply to redically
different groups than Vidal and Hedges support, as a result.

  Lacertiformata -- "Lacertiformata (new name) includes Lacertidae." (pg. 1004)
This name has no effective definition, and the default would be to make it a
stem-based clade with multiple external specifiers, where each other clade used
in the analysis is included for purposes of the analysis. This would be
excessive, perhaps.

  Lacertibaenia -- "Lacertibaenia (new name) includes Lacertiformata and
Amphisbaenia, and is a name that includes elements of both words." (pg.
1004-1005) This might best be explained as the node-based clade "Lacertiformata
+ Amphisbaenia" or their type species specifiers.

  Teiformata -- "Teiformata (new name) includes Teiidae and Gymnophthalmidae."
(pg. 1005) This would be a node-based clade, "Teiidae + Gymnophthalmidae",
which would be effectively the same clade as Teiioidea.

  Laterata -- "Laterata (new name) includes Lacertibaenia and Teiformata,
referring to the presence of tile-like (squarish or quadrangular, and sometimes
raised) scales that form the rings in Amphisbaenia, and are also present
ventrally in Lacertiformata and Teiformata (while recognizing that squarish
scales occur in other taxa, such as xantusiids and some anguimorphs)." (pg.
1005) I find a lot of difficulty with this one, and it makes me think the
choice of apomorphy inclusions was not explicitly requested. However, this may
be described as either the stem-defined node "Lacertiformata + Amphisbaenia +
Teiiformata not Xantusiidae not Anguimorpha" or, the more applicable and longer
apomorphy-based stem-defined node (very possibly more obviously paraphyletic
than the previous definition), "tile-like (squarish or quadrangular, and
sometimes raised) scales in Amphisbaenia + Lacertiformata + Teiiformata". I
hate this definition.

  Toxicofera -- "Toxicofera (new name) includes Iguania, Anguimorpha, and
Serpentes, referring to the presence of venom." (pg. 1005) I am tempted to
suggest "venom in Iguania + Anguimorpha + Serpentes".

  Episquamata -- "Episquamata (new name) includes Toxicofera and Laterata,
referring to its derived position in the tree of squamates (?top squamates?)."
(pg. 1005) This name again suggests that the authors are once again not
actually defining names correctly, and that arguing by content is the only way
to use the names, thus a node-based clade, "Toxicofera + Laterata" and their
subgroups.

  Scinciformata -- "Scinciformata (new name) includes Scincidae, Xantusiidae,
and Cordylidae." (pg. 1005) This name is, again, identical to Scincomorpha in
general content, and aside from Xantusiidae, almost identical in content to
Scincoidea. However, a node-based definition is likely, "Scincidae +
Xantusiidae + Cordylidae".

  Unidentata -- "Unidentata, includes Episquamata and Scinciformata and refers
to the presence of one egg tooth." (pg. 1005) Based also on an apomorphy, I
suggest using the apomorphy-based node-based definition, "single egg tooth in
Episquamata + Scinciformata".

  Bifurcata -- "Bifurcata (new name) includes Unidentata and Gekkota, referring
to the presence of a bifurcated tongue." (pg. 1005) Another apomorphy-based
node, "bifurcated tongue in Episquamata + Scinciformata + Gekkota".

  All I am surprised here is that the authors didn't propose new names to
include Gekkota, Amphisbaenia, et al.

  Cheers,

Jaime A. Headden

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)


                
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