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Re: Regarding Phytodinosauria...



In a message dated 95-08-13 00:16:53 EDT, you write:

<<   To get back to our discussion of a couple of days ago.  You said tha=
t
prosauropods were more advanced than brontosaurs and therefore closer to
ornithischians.  Why is it that you believe this? >>

All sauropod feet had five well-developed pedal digits, with digit V havi=
ng
two phalanges in the most primitive forms. In prosauropod feet, digit V w=
as
nearly vestigial, with at most one phalanx. This change is evolutionarily=

irreversible; you won't re-evolve a new phalanx or a new digit once it's
lost. Sauropods were also primitive in retaining a jaw architecture with =
the
articulation point with the skull at the same level as the dentary tooth =
row.
In the more advanced prosauropods, the jaw articulation point was markedl=
y
below the dentary tooth row. So those "advanced" prosauropods at least
diverged from sauropods before acquiring the lowered articulation point. =
One
or two sauropod genera (maybe families) later developed a lowered
articulation point (and a well-developed coronoid eminence, as in
_Giraffatitan_, which you know better as _Brachiosaurus brancai_), but th=
ey
acquired this character independently, and it was developed not nearly to=
 the
extent seen in prosauropods.

<<  Also, how is it that you define the ornithischia cladistically?  I wo=
uld
say Segnosauria (Therizanosauroidea) + Predentata. >>

An interesting thought, to add the segnosaurs to the base of Ornithischia=
=2E
But I think they were still too prosauropod-like to be considered
ornithischians; not enough "ornithischian" derived characters. Segnosaurs=

shared only one key derived character with ornithischians, namely, the
opisthopubic pelvis. Otherwise, the segnosaur pelvis was very different f=
rom
those of the other phytodinosaurs, the result of a lengthy and entirely
undocumented Jurassic history as a distinct evolutionary lineage (which
justifies retaining Segnosauria as a separate order within Phytodinosauri=
a).
Ornithischians were highly derived phytodinosaurs, separated from the oth=
er
members of the clade by a suite of familiar characters (predentary bone,
reduced antorbital fenestra and fossa, ilium with well-developed
preacetabular process, pedal digit V vestigial or absent, etc.). I would =
keep
Ornithischia =3D Predentata.

<< Also, what about that name priority for the segnosaurs?  Should it rea=
lly
be therizanosauroids?  I really hope it doesn't turn out to be
therizanosauroids; I dislike extremely scientific words that have more th=
an
five sylables and are extremely difficult to pronounce (phytodinosauria i=
s
easy to say).>>

ICZN rules do not govern names above family level. I retain Segnosauria a=
s
the name of the order, subdivided into three families: Alxasauridae,
Segnosauridae, Therizinosauridae (in cladistic order from least to most
derived). It is quite possible that further discoveries will show
Segnosauridae =3D Therizinosauridae, in which case the name with priority=
 is
Therizinosauridae (sorry). But Segnosauria can (and should) always be use=
d as
the name of the more inclusive clade. Alxasauridae may be paraphyletic, f=
or
it would contain the common ancestor of the known Segnosauria; that would=
n't
bother me, but it would bother cladists, so they should simply use the ge=
nus
_Alxasaurus_ as the monophyletic outgroup to the other segnosaurs.

<<  Anyway... it's too bad that smushed letters (yes I know, ligatures)
aren't allowed in scientific names anymore.  I could understand why they =
were
banned in the sixties because of the difficulty in printing them, but now=
,
with computers that can print ligatures easily, wouldn't it be better to
accept them as the correct spelling?  What about umlatzes?  _Tro=F6don_ s=
eems
almost always to be spelled with an umlatz, is that still correct? >>

Not umlatz: umlaut. Diacritical marks of any kind are dropped from zoolog=
ical
names, so the correct spelling is _Troodon_. Incidentally, your diacritic=
ally
marked letters and ligatures print fine on my computer, but when I try to=

transmit such characters through the dinosaur list, they come out with cr=
azy
formations and equals signs. Somewhere along the line, there is an
evolutionary bottleneck that irreversibly changes the characters...

<< And, do you know how to say Teresa Maryanska's last name?  There is a
diacritical mark on the "n".>>

I'm not sure (and I should be, since I once knew a little Polish), but th=
e
"accented n" is pretty close to the Spanish "tilde n" -- like the "ny" so=
und
in "Nyah, nyah."

<<Hoping that I can write _C=9Clophysis_ and _Opistic=9Clocaudia_ and be =
correct
some time in the future.>>

Hoping against hope, eh?

G.O.