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Congratulations on getting your paper
published! The aquatic hypothesis is very interesting....
David Marjanovic wrote-
> Archaeopterygidae is to mean A.
and Unenlagia ?= Megaraptor ?= Unquillosaurus (possible
> synonymies after the Dinosauricon); analyses
by HP Mickey Mortimer put U., at least, in the >
Dromaeosaurinae.
Unquillosaurus is not synonymous with
Unenlagia. Although they both have vertical pubes with similarily angled
feet, there are several important differences. Unenlagia lacks a pubic
notch, has a straighter anterior edge and thinner distal shaft, and has no
anterior component to its pubic foot. The differences are even
more obvious in anterior view. Unquillosaurus' is much more concave
laterally and has an apomorphic proximomedial sulcus. Its pubes expand
mediolaterally distally into a bulbous foot, whereas Unenlagia has the narrow
distal pubes typical of dromaeosaurids. Also keep in mind Unquillosaurus
is from the Los Blanquitos Formation, while Unenlagia is from the Rio Neuquen
Formation. Megaraptor cannot be compared to either Unenlagia or
Unquillosaurus, although it was larger than both and is from the same formation
as Unenlagia. As for putting Unenlagia in the same family as
Archaeopteryx, I'd like to know what characters they share that other
deinonychosaurs lack.
> Sometime it is mentioned that the latter three
taxa (troodontids and tyrannosaurs: Currie,
> 1995, oviraptorosaurs: Sues, 1997 contra
Norell et al. 2000) have a separate exit for the
> cranial nerve V1,
which normally exits the braincase through a large foramen together with V2 >
and V3. Dromaeosaurus (Currie, 1995) and Archaeopteryx
(Elzanowski & Wellnhofer, 1996)
> exhibit the primitive condition.
The derived state is also present in Allosaurus and
Carpenter and Currie (2000) code oviraptorids as having the primitive
condition. This shows the character distribution is more complex than
presented.
> Arctometatarsalians and oviraptorosaurs also
share pneumatised quadrates and articulars not >
occuring in Archaeopteryx (Elzanowski & Wellnhofer, 1996) and
Dromaeosaurus (Currie,
> 1995).
Caudipteryx lacks a pneumatic quadrate, as
do Shuvuuia and Confuciusornis. This character would thus be more
parsimoniously interpreted at convergently evolving in arctometatarsalians,
oviraptorids and ornithurines. Pneumatic articulars are much rarer among
theropods. They are present in Tyrannosaurus, Erlikosaurus and
Bagaraatan. They are certainly absent in Chirostenotes, Deinonychus and
Gobipteryx, and probably in Archaeopteryx. I also see no evidence of a
foramen in Confuciusornis. I'm not sure where segnosaurs or Bagaraatan go
in your phylogeny, but as Chirostenotes and Gobipteryx lack this feature (and I
don't know the condition in Caudipteryx and oviraptorids), the assertion
oviraptorosaurs and pygostylians can be united with it is weakened.
> Andrzej Elzanowski is sometimes referred to as
having discovered that some features of the
> oviraptorosaur
palate are more birdlike than that of Archaeopteryx. <Has
been published in
> detail in the meantime, I still haven't found
the paper.>
See http://www.cmnh.org/fun/dinosaur-archive/2000Dec/msg00487.html for
my opinions on that papers conclusions.
> Osmólska & Maryanska (1997) note that
oviraptorid quadrates are double-headed, i. e. they
> have an additional contact to the braincase,
and they are much more pneumatised than in
> arctometatarsalians
(Osmólska & Maryanska, 1997).
Oviraptorids have double-headed quadrates, but the
basal oviraptorosaur Caudipteryx lacks this character. This makes it
equally parsimonious for oviraptorids to have convergently evolved the
character.
> Oviraptorosaurs (Sues, 1997) (including
Caudipteryx <and Protarchaeopteryx?>) also share
> with alvarezsaurids (Novas, 1997) rather short tails that are not stiffened distally, a condition
> seen in no other theropods. <...>
True. Caudipteryx has an especially short
tail, only slightly longer than that of Confuciusornis. Yandangornis
and segnosaurs also have relatively short tails.
> Pneumatic features also fit this picture:
Archaeopteryx is no more extensively pneumatised
> than dromaeosaurids, i. e. cervical and dorsal
vertebrae as well as their ribs are pneumatised > (Britt et al., 1998). In
oviraptorosaurs (Currie, 1995) and alvarezsaurids (Novas, 1997),
> pneumatic foramina (or
depressions) occur as far back as the middle of the tail! (In recent
> turkeys (Britt et al., 1998), the sacral and
free caudal vertebrae are pneumatised, in ostriches > (Britt et al., 1998)
the caudals are not.)
There is a difference between the lateral
depressions found in the dorsals (confuciusornithids, enantiornithines) and
caudals (Patagonykus, enantiornithines) of some maniraptorans and the
pleurocoels (pneumatic foramina) found in the sacrals and caudals of
caenagnathids and oviraptorids. Patagonykus is the only alvarezsaurid
known to have such depressions, they are absent in Alvarezsaurus and
Parvicursor. No alvarezsaurid has sacral or caudal pleurocoels. On
the other hand, the dromaeosaurid Achillobator has pleurocoel-like foramina on
its proximal caudals, while Variraptor and Ornithodesmus have pleurocoels in the
first two sacral vertebrae. Also, the basal oviraptorosaurs Caudipteryx
and Microvenator lack caudal pleurocoels. This again suggests parallel
development to any birds which have such excavations.
> With the description of Nomingia
(Keesey, 2000, /genera/nomingia.html), the pygostyle has
> joined the list of maniraptoran (see
cladogram) synapomorphies (no alvarezsaurid tail end is
> known, Caudipteryx and
Protarchaeopteryx could have pygostyles <just discussed>, judging
> from photographs (Ackerman, 1998), the
resolution of which is too coarse to be certain)."
While Nomingia does have a pygostyle, Caudipteryx
and oviraptorids do not. Another reference (Zhou et al., 2000) can be
added to the list of experts who have verified this fact (Zhou and Wang 2000, Ji
et al. 1998). Oviraptorosaurs are sort of like the basal
diapsids/archosauromorphs of the birds-aren't-dinosaurs group. Put them
together (short tail and reversed hallux of Caudipteryx; pygostyle of Nomingia;
elongate radius of Microvenator; caudal pneumaticity of caenagnathoids; fused
jaw elements and absent coronoid of caenagnathids; double-headed quadrate
and triradiate palatine of oviraptorids) and you get a perfect
pygostylian sister group, but look at them separately and the picture's not so
clear.
> A single bird synapomorphy, according to
Elzanowski & Wellnhofer (1996), has been left to
> Archaeopteryx: the triradiate palatines. I think that it is most parsimonious
to explain this
> feature by convergence <ô
surprise>, though I have no idea why this should have
occurred."
Well, even though my analysis currently supports
Archaeopteryx as a basal deinonychosaur, I'll play devil's advocate.
Besides the reversed hallux, Archaeopteryx shares the following characters with
pygostylians not seen in dromaeosaurids, oviraptorosaurs or
arctometatarsalians.
- reduced olfactory lobes
- less than nine caudal vertebrae with transverse
processes
- very short anterior chevrons, none taller than
anteroposteriorly long
- manual digit I doesn't extend past manual phalanx
II-1
- phalanges on third manual digit reduced (III-1
and III-2 sutured, not jointed; possibly ancestral to the pygostylian condition
of having two non-ungual phalanges on digit III)
- proximodorsal ischial process
- tibia subequal in width and length in proximal
view
As you can see, the evidence is not as weak as you
claim. While I still find it is most parsimonious to interpret these as
reversed in dromaeosaurids, there's still a very good case for non-avian
dromaeosaurids.
> Birds down to Alvarezsauridae have prokinesis
(Chiappe, Norell & Clark, 1998);
> confuciusornithids have akinetic skulls (Hou
et al., 1999), which is probably secondary
> because the jugals don’t have ascending
processes.
While the akinetic skulls of confuciusornithids
could very well be secondary, they do possess ascending processes on their
jugals (Chiappe et al., 1999).
> '[a]nd in spite of the fact that
dromaeosaurids are often proclaimed to be the most birdlike of
> the theropods <...>, they lack many of
the theropod-avian synapomorphies found in other
> theropod families, and have too many
specialisations to be plausible avian ancestors'
Unlike those conservative oviraptorosaurs
;-)
>
First, protofeathers evolved as a protein sink: Bird ancestors, early
tetanurans,
> theropods, dinosaurs or ornithodirans in
general are commonly thought to have been
> insectivorous. Insects, which radiated in the
early Mesozoic, contain much more fat and
> protein than vertebrates and thus are a good
reason for becoming and staying endothermic.
> (Let’s simplify the case and assume that all
ornithodirans were endothermic – Paul & Leahy
> [1994] have shown excellently that even the
largest ones were forced to be.) But insect
> protein contains more sulphur than small
endotherms can use or excrete. So these animals
> deposited the sulphur-rich amino acids in
their scales, which are made of keratin, a protein
> containing up to 3 % sulphur. The scales were
enlarged and split during growth, used for
> insulation and display, and sometimes they
were shed to get rid of the sulphur. This is a
> wonderful explanation for why birds moult
(Reichholf 1997 <and others, which may be cited in > the published
version>). Sinosauropteryx, Sinornithosaurus and, if you kindly forget
its diet,
> Beipiaosaurus can be considered
examples for such animals.
While I can easily picture non-dinosaurian
dinosauriformes (Marasuchus, Lagerpeton) and smaller maniraptorans
(Microraptor, mononykines, Archaeopteryx, enantiornithines) being at least
partially insectivorous, basal theropods, sauropodomorphs and ornithischians
were too large to have depended on insects as their main food source.
Also, new evidence suggests feathers may not have developed from scales, while
the structure of Sinosauropteryx's integumentary filaments suggest feathers
evolved by adding branching filaments, not splitting scales.
Your aquatic hypothesis is quite interesting.
Seems defendable, but on the other hand difficult to test.
>
"Arctometatarsalians did the same,
but they changed to long-distance pursuing, as
> indicated by their feet. They were
already present at the same time as dromaeosaurids –
> there are the troodontid
Koparion, some ornithomimid teeth <and that Kimmeridgian finger
> from Great Britain -- thanks to the list
I mention it in the published version>
Jurassic ornithomimid teeth? What might the
reference for this be?
> Still
true. :-( Is it likely that a mobile scapula-coracoid joint can evolve twice (or
be a
> misinterpretation)? In this case
Rahonavis could belong to Archaeopterygiformes... MORE
> FOSSILS!!!
The mobile scapulocoracoid joint of Rahonavis
is certainly present. What's odd however is the absence of this character
in confuciusornithids. This could easily support a convergence or
loss.
>
Neotheropoda or earlier: furcula?
(not ossified – like the sternum – in e. g.
> compsognathids, attached to the scapula
by ligaments and therefore frequently falling off
> before burial, which explains its rare
preservation [Makovicky & Currie, 1998]; the ventral ends > of the
clavicles of Sinornithoides and probably Carnotaurus are
broken – perhaps the middle
> part of a furcula has broken away
[Mortimer, 2000 <in the List archives, can't find it now; it is > properly
cited in the published version>])
I'm actually referenced in a bibliography?
Thanks. Adam Yates should get the real credit though, as I heard the idea
from him:
I never even mentioned the Carnotaurus
furcula. That came from Thomas Holtz: http://www.cmnh.org/fun/dinosaur-archive/2000Apr/msg00635.html .
Mickey
Mortimer
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