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Date: Sat, 14 Apr 2001 12:49:33 +0200
From: David Marjanovic <david.marjanovic@gmx.at>
To: PhyloCode mailing list <phylocode@ouvaxa.cats.ohiou.edu>
Subject: Re: Nomina Conversa
> > > Maybe I did see _Eureptilia_ before... anyway, seems like a preferable
> > > name to me.
> >
> > I wouldn't want to have -reptilia again...
>
> Got a better name? (Preferably something in the literature already.)
No... At present it has the same content as Sauropsida, so no name is
necessary for the (Anapsida + Romeriida) node at the moment.
> > > > Sauria (another yucky name -- it is neither meant to have its
> > > > traditional paraphyletic meaning "lizards"
> > >
> > > Wasn't "Lacertilia" used for that group?
> >
> > Yes, as a synonym, seemingly based on personal preferences.
>
> Oh, I never saw Sauria used for that. (But it makes sense.)
It was used some decades ago and was even claimed to become more widely used
than Lacertilia.
> So how did it
> come to be appropriated for _Archosauromorpha_ + _Lepidosauromorpha_??
Absolutely no idea.
> > > I would much prefer _Sauria_ to _Reptilia_. Birds are already
> > > coelurosaurians, dinosaurians, and archosaurians; why not saurians as
> > > well?
> >
> > True. This would, however, increase the confusion among German speakers,
who
> > often use "Saurier" as an abbreviation for "Dinosaurier" as well as as
an
> > artificial group that includes most or everything that contains -saur-,
and
> > it would have little to do with the original meaning of the word (Greek
> > sauros = lizard).
>
> I'm no native speaker like you, but it seems to me German speakers use it
> just to mean "reptile", e.g., "Flugsaurier" (pterosaurs). "Saurian" is an
> (infrequent) English vernacular term, too, meaning, basically,
> "reptilian".
It is never used to mean "reptile", because turtles, tuataras, lizards and
snakes are never considered "Saurier", and crocs (as well as the Komodo
monitor) only by those who %*) think these are dinosaurs or very close
relatives of dinosaurs.
> Name relevance isn't a crucial issue -- after all, _Basilosaurus_ is a
> whale!
Sure!
> Coherence with older literature should be important, though.
Depends on what "old" is, and, after all, old literature isn't too coherent
either...
> > > ??? What's the definition of _Teleostomi_?
> >
> > According to the Dinosauricon :-] , it includes Acanthodii and
Osteichthyes
> > as sister taxa...
>
> I don't list a *definition*. Is it stem- or node-based?
No idea, I can't recall to have seen it elsewhere...
> > > It seems to me it would make
> > > sense as a stem-based clade, perhaps sister to _Chondrichthyes_. I'm a
> > > little ignorant about that part of the tree, though.
> >
> > So is everyone else. The Nature issue that contains the paper about the
> > feathers of *Sinornithosaurus* has one about a basal sarcopterygian and
> > mentions the general confusion about basal gnathostome phylogeny.
>
> Surely extant chondrichthyans clade outside of bony gnathostomes?
Not surely. Gnathostomata is an unresolved tetrachotomy [is this correct
from Greek?]; Placodermi have been thought to be the sister group of
Chondrichthyes or (Acanthodii + Osteichthyes) or Osteichthyes alone or as
basalmost gnathostomes, Acanthodii is usually considered the sister group of
Osteichthyes...
All primary literature I know on this is
Min Zhu, Xiaobo Yu & Per E. Ahlberg: A primitive sarcopterygian fish with an
eyestalk, Nature 410, 81 -- 84 (1 March 2001, not 1 April!!!)
Abstract: "The discovery of two Early Devonian osteichthyan (bony fish)
fossils has challenged established ideas about the origin of osteichthyans
and their divergence into actinopterygians (teleosts and their relatives)
and sarcopterygians (tetrapods, coelacanths, lungfishes and related groups).
*Psarolepis* from China and an unnamed braincase from Australia combine
derived sarcopterygian and actinopterygian characters with primitive
features previously restricted to non-osteichthyans, suggesting that early
osteichthyan evolution may have involved substantial parallelism between
sarcopterygians and actinopterygians. But interpretation of these fossils
has been hampered by poor phylogenetic resolution. Here we describe a basal
sarcopterygian fish, *Achoania [jarvikii]* gen, [typo] et sp. nov., that
fills the morphological gap between *Psarolepis* and higher [sic]
sarcopterygians. We also report the presence of eyestalk attachments in both
*Achoania* and *Psarolepis*, showing that this supposedly non-osteichthyan
feature occurs in basal sarcopterygians as well as the actinopterygian-like
Australian braincase."
Earliest Devonian, Yunnan/China.
"A phylogenetic analysis, based on a new data matrix of 158 [...]
[the Methods section says 157] characters [...] (Fig. 3a). Clade decay
values [...] are relatively high, indicating that their position is well
supported. [...]
The new phylogeny has major evolutionary and biogeographical
implications. Past analyses of osteichthyans have generated inferred
ancestral character complements for the clade based on known 'primitive'
genera such as *Mimia* and *Porolepis*, but these differ substantially from
the character suite revealed by *Achoania*, *Psarolepis* and AMF101607 [the
ominous Australian braincase]. Our well-supported resulution of *Achoania*
and *Psarolepis* as stem-group sarcopterygians shows that their seemingly
non-osteichthyan characters, such as an eyestalk, a placoderm-like shoulder
girdle with a separate spinal plate [whatever that is], and paired and
median fin spines, are present in the base of the osteichthyan crown group;
in all likelihood these characters are primitive for the Osteichthyes as a
whole. This implies that many apparent synapomorphies between previously
known actinopterygians and sarcopterygians (undivided cleithrum, lack of
eyestalk, lack of fin spines) are convergent between the two lineages. We
can no longer assume that direct comparisons between derived sarcopterygians
and actinopterygians will be informative about primitive conditions for the
Osteichthyes as a whole. Instead, attention should focus on basal taxa [...]
We must also reassess some supposed autapomorphies of different osteichthyan
groups, such as the 'extracleithrum' of coelacanths which, in the primitive
genus *Miguashaia*, closely resembles a spinal plate.
The character distributions observed in *Achoania*, *Psarolepis* and
AMF101607 make basal Osteichthyes appear more placoderm-like than recognized
previously. Many workers place the placoderms as the most primitive jawed
gnathostomes [sic] and explicitely deny any homology between the placoderm
and osteichthyan bone patterns, thus virtually guaranteeing wide
phylogenetic separation. [Placoderm skull bones have unique names such as
marginale, postmarginale, nuchale, mediolaterale...] However, evidence is
mounting for homology between the dermal shoulder girdles of osteichthyans
and placoderms. Our analysis places the placoderm *Dicksonosteus* as the
sister group of Osteichthyes, although the branching pattern within the
Osteichthyes is unaffected by the removal of *Dicksonosteus* (or any other
taxon) from the outgroup. Deep gnathostome phylogeny needs to be reviewed in
the light of these findings."
Fig. 3a (shortened here):
Gnathostomata
|--*Acanthodes* (Acanthodii)
|--*Ctenacanthus* (Chondrichthyes)
`--+--*Dicksonosteus* (Placodermi)
`--Osteichthyes
|--Acanthopterygii
| |--AMF 101607
| `--+--*Cheirolepis* + (*Mimia* + *Moythonasia*)
`--Sarcopterygii
|--*Psarolepis*
`--+--*Achoania*
`--crown-group Sarcopterygii
|--*Onychodus* + (*Diplocercides* +
*Miguashaia*) (Coelacanthi)
`--Choanata
|--Dipnomorpha
| |--*Porolepis* + *Glyptolepis*
(Porolepiformes)
| `--*Powichthys* + (*Youngolepis*
+ (*Diabolepis* + Dipnoi))
`--Tetrapodomorpha
|--*Kenichthys*
`--*Osteolepis* +
(*Eusthenopteron* + (*Panderichthys* + *Ichthyostega*))
Basic lesson of the article: Always include the basalmost taxa in a
cladistic analysis.
> > [...] mammals have AFAIK not been
> > considered therapsids for so long. I don't know most of the cladistic
> > literature on this, though.
>
> In the cladistic literature they are considered therapsids.
Good, so we can leave this issue to the mammalogists :-) Are there any
onlist?