Kilka lat temu odpowiedziałbym na to pytanie bez problemu, ale teraz to takie proste nie jest
.
Np. wg nowej pracy za dinonychozaurowatością przemawia "Pennaceous feathers on tibia". Cechy tej nie ma w innych analizach, np. Sentera a jej dodanie na pewno nie zmieniłoby wyniku patrząc na decay index. "Pennaceous feathers on tibia" byłoby plezjomorfią. Poza deinonychozaurami i archeopteryksema ja też jakiś enatornit. Więc to zależy od optymalizacji konkretnej cechy w konkretnym kontekście, a są jeszcze inne problemy.
U Turnera i in. (2012; Review of Dromaeosaurid Systematics and Paravian
.
Turner i in., 2012, s. 139-140 pisze:Recently Xu et al. (2011) reported the
discovery of an interesting new paravian
dinosaur from Late Jurassic of China, which
according to their phylogenetic analysis
significantly alters our understanding of
avialan origins. Most significantly the authors
claim to demonstrate for the first time
that Archaeopteryx (and its sister taxon
Wellnhoferia) is not a member of the clade
Avialae and therefore not a basal bird.
Through their discovery of a new clade of
paravians comprised of Archaeopteryx, Xiaotingia,
and Anchiornis, more closely related to
the deinonychosaurs, these authors challenge
the orthodox view of Archaeopteryx as the
basalmost bird taxon. Using the data published
by Xu et al. (2010) we reanalyzed the
new dinosaur Xiaotingia within our larger
phylogenetic dataset that samples paravian
diversity more comprehensively and instead
find Xiaotingia a basal troodontid, sister to
the very similar Anchiornis, and Archaeopteryx
lithographica still residing at the base of
Avialae (fig. 58).
Review of the Xu et al. (2011) matrix
reveals some character scorings that we
dispute. Xu et al. (2011) atomize the presence
of an enlarged and hyperextensible second
pedal digit into several traits (chars. 201,
320–322). Character 322 describes the development
of the flexor attachment heel on
phalanx II-2 in deinonychosaurian taxa with
the incipient condition of having a laterally
displaced, small heel as state 2, while the
possession of the more derived, enlarged heel
is designated as state 1. Although Xu et al.
(2011) describe and figure a ventrolateral
flange or heel on pedal phalanx II-2 of
Xiaotingia, they score it as absent in their
matrix. Likewise, they code only the incipient
condition as present in two unenlagiine taxa,
whereas they consider a number of basal
troodontids, such as Mei and Sinovenator,
and basal dromaeosaurids, such as Microvenator,
as having the more derived, enlarged
heel below the proximal articulation. Based
on our own study of the relevant specimens,
we disagree with these scorings and instead
code Xiaotingia, Mei, Sinovenator, Microraptor,
Unenlagia, and Sinovenator as having
state 2. Even without treating this character
as an ordered transformation series, we
recover a slightly different topology with
Xiaotingia and Anchiornis as basal troodontids.
Although we still discover Archaeopteryx
as closer to deinonychosaurs than to Avialae,
this result draws into doubt Xu et al.’s (2011)
contention that their result was predicated
entirely on the inclusion of Xiaotingia.
Another trait, whose scoring we find
contentious, is their character 366 that
describes the relative position of the postorbital
process of the jugal along the length of
that bone. Xu et al. (2011) score the process
as close to the middle of the bone (state 0) in
Epidexipteryx, which we agree with, but they
go on to consider the basal avialans Jeholornis,
Sapeornis, and Confuciusornis as well
as the unenlagiine Buitreraptor as sharing this
condition. Our study of these specimens, as
well as their own figure 4, shows that the
position of the postorbital process of the
jugal is far closer to the caudal end of the
bone in these paravian taxa, as it is in
Archaeopteryx, Xiaotingia, and basal troodontids
and dromaeosaurids. A reanalysis of
the matrix combining changes in the scoring
of this trait along with those in character 322
culminates in a strict consensus tree in which
the position of Troodontidae, Avialae (without
Archaeopteryx), Dromaeosauridae, and
the Archaeopterygidae clade found by Xu et
al. (2011) are fluid. The paravian node shows
eight resolutions in the set of 231 MPTs (TL
5 1511), only one of which places Archaeopteryx
as closer to a clade other than Avialae.
A majority rule consensus reveals that 89%
of resolutions favor the traditional alignment
of Archaeopteryx as the most basal avialan,
with Epidexipteryx and Epidendrosaurus
grouping with oviraptorosaurs with an equal
frequency (fig. 81). A possible relationship
between these two enigmatic Middle Jurassic
taxa and oviraptorosaurs has been previously
proposed by Xu et al. (2009), although it was
not tested at the time. As discussed above, an
oviraptorosaur status for these two taxa is
only one step longer than the most parsimonious
trees from our matrix.
Lee and Worthy (2011) recently reanalyzed
the Xu et al. (2011) dataset using maximum
likelihood and Bayesian optimality criteria.
They recovered Archaeopteryx at the base of
Avialae, and attributed the support for this
position as coming from fewer, but less
homoplastic characters than those recovered
under maximum parsimony as supporting a
position closer to Deinonychosauria. Other
parts of their recovered topology conflict
significantly with the parsimony results,
however, a point Lee and Worthy (2011) did
not comment on. Major discrepancies include
paraphyly of Tyrannosauroidea and a more
derived, but stratigraphically less congruent,
position for Epidexipteryx and Epidendrosaurus
among Avialae. This leaves some
question as to whether the differences are
due to opposing resolutions of conflicting
characters resulting from different optimality
criteria or uneven evolutionary rates, which in
this case translate to uneven character
sampling across the tree. We explored this
question by analyzing the data with parsimony
using implied weighting (Goloboff, 1993),
which downweights characters with increasing
homoplasy. The results (9 best-fit trees for
weight k 5 3; fit score 164.72) placed Archaeopteryx
within Avialae as more derived than
Epidexipteryx and Epidendrosaurus, with
Xiaotingia and Anchiornis posited as basal
troodontids. Overall, the results conflict less
with those from the unweighted parsimony
analysis than those found by model-based
analysis, although a couple of taxa with
copious missing data (Hagryphus, Haplocheirus)
exhibited anomalous affinities.
Taken altogether, these results show that it
may be premature to declare Archaeopteryx a
nonavian theropod. Much hinges on the
exact position of the Middle Jurassic taxa
Epidendrosaurus and, in particular, Epidexipteryx.
These taxa share with oviraptorosaurs
and basal avians a foreshortened
rostrum, highly modified mandible, and
reduced, unserrated dentition. A number of
the relevant traits of the dentition and
mandible have recently been identified as
representing a homoplastic suite of characters
that correlate with herbivorous habits
(Zanno and Makovicky, 2011) and evolve
independently in multiple maniraptoran lineages
including oviraptorosaurs and avialans.
Thus, it is possible that the phylogenetic
result offered by Xu et al. (2011) is driven in
part by adaptive ecological traits, a fact
supported by the implied weights analysis
and, to a less certain degree, by the model
based analyses of Lee and Worthy (2011).
Zob. też np.
Co piszą Xu i in. (2011):
Implications for paravian phylogeny
Wehave added Xiaotingia into a comprehensive phylogenetic analysis,
which places Xiaotingia and Anchiornis within the Archaeopterygidae
(Fig. 4 and Supplementary Information). Salient synapomorphies of
the Archaeopterygidae include: manual phalanx III-1 more than twice
as long as IV-1 (character state 292.1 in Supplementary Information);
manual phalanx IV-3 markedly longer than IV-1 and IV-2 combined
(character state 302.2 in Supplementary Information); furcula lateral
end with L-shaped cross-section (character state 369.1 in Supplementary
Information); and ventral notch between distal portion of obturator
process and ischial shaft (character state 307.0 in Supplementary
Information).
The most important result of our analysis is the removal of the
Archaeopterygidae from the Avialae and its placement at the base
of the Deinonychosauria, which challenges the long-held opinion that
Archaeopteryx represents a pivotal taxon for understanding the
transition to birds by virtue of having a phylogenetic position near
the very base of the Avialae10,21,24–27. Derived features shared by
Archaeopteryx and other deinonychosaurs include a large promaxillary
fenestra (character state 363.1 in Supplementary Information), a
T-shaped lacrimal with a long anterior process (character state 372.1
in Supplementary Information), a groove that widens posteriorly on
the dentary (character state 72.1 in Supplementary Information), a
manual phalanx IV-2 that is significantly shortened relative to IV-1
(character state 294.1 in Supplementary Information), a short ischium
that bears a distally located obturator process as well as a posterodistal
process (character states 171.2 and 334.1 in Supplementary Information),
and a highly extensible pedal digit II (character state 323.1 in
Supplementary Information), among others. Previous studies noted
the striking similarities between Archaeopteryx and other deinonychosaurs16,28,
and a close relationship between Archaeopteryx and dromaeosaurids
has been proposed22, but to our knowledge we are the
first to present a numerical phylogenetic analysis supporting deinonychosaurian
affinities for the Archaeopterygidae.
It should be noted that our phylogenetic hypothesis is only weakly
supported by the available data. Bremer support and bootstrap values for
the recovered coelurosaurian subclades are, in general, low, and a bootstrap
value less than 50% and a Bremer support value of 2 are obtained
for a monophyletic Deinonychosauria including the Archaeopterygidae
(see Supplementary Information). This low support is partly caused by
various homoplasies, many of which are functionally significant, that
are widely distributed across coelurosaurian phylogeny29. Xiaotingia
possesses salient anatomical features also seen in different paravian
taxa, further highlighting the phenomenon of widespread homoplasy.
This phenomenon is also seen in some other major transitions, including
the origins ofmajormammalian groups30, and creates difficulties in
recovering robust phylogenies.
Morphology and systematics of Archaeopteryx
Although Archaeopteryx has been known for about 150 years, debate
continues regarding various aspects—including even some skeletal
morphological features—of this extremely important taxon16,31
(Fig. 3a). Recent findings, particularly the discovery of the tenth
specimen, have greatly improved our knowledge of the morphology
of Archaeopteryx16,28,31. In addition to the similarities between
Archaeopteryx, Xiaotingia and some other deinonychosaurs
described above, we provide further information to highlight the
similarities between Archaeopteryx, Anchiornis, Xiaotingia and other
deinonychosaurs on the one hand, and the differences between
Archaeopteryx and other widely accepted basal avialans on the other.
The skull of Archaeopteryx is, in general, similar to those of
Anchiornis, Xiaotingia and other deinonychosaurs in having a subtriangular
lateral profile produced by a shallow snout and expanded
postorbital region16 (Fig. 4). In most basal avialans, including
Epidexipteryx, Sapeornis and Jeholornis4,32, the skull is relatively tall
and short with a deep, short snout, more reminiscent of the oviraptorosaurian
condition (Fig. 4).As in Anchiornis, Xiaotingia and other basal
deinonychosaurs6,11,16, the orbit is proportionally large and the infratemporal
fenestra is extremely narrow anteroposteriorly and strongly
inclined posteriorly. For comparison, oviraptorosaurs and basal avialans
have a proportionally smaller orbit and a larger infratemporal fenestra
that is much wider anteroposteriorly and less posteriorly inclined4,15,32.
The external naris is ventrally located as in Anchiornis, Xiaotingia and
other basal deinonychosaurs, in contrast to the high naris of oviraptorosaurs
and basal avialans such as Epidexipteryx and Jeholornis4,32.
The premaxilla of Archaeopteryx is shallow in lateral view and
much smaller than the maxilla, as in many theropods including
deinonychosaurs11. In oviraptorosaurs and basal avialans such as
Epidexipteryx, Sapeornis and Jeholornis4,32, the premaxilla is deep,
and larger than themaxilla.The anteroposterior length of the antorbital
fossa considerably exceeds its dorsoventral height, as inmost theropods
including Anchiornis, Xiaotingia and deinonychosaurs6,13,18. In oviraptorosaurs
and basal avialans12,32, the opposite is true, and the antorbital
fenestra within the fossa is thus much higher than anteroposteriorly
long in lateral view. The promaxillary fenestra is large (Fig. 3b) as
in Anchiornis, Xiaotingia and basal deinonychosaurs6,11,16,33—the
promaxillary fenestra, if present, is very small in other non-avian
theropods. Manyother theropods, including oviraptorosaurs and basal
avialans such as Epidexipteryx, Sapeornis and Jeholornis4,12, lack a
promaxillary fenestra (Fig. 4). The lacrimal has a long anterior process,
close in length to the descending process and extending anteriorly to a
point close to the anterior border of the antorbital fenestra, a feature
also seen in deinonychosaurs11,13,18. In most other theropods and
particularly in oviraptorosaurs and other basal avialans, the anterior
process is proportionally much shorter. The lacrimal also has a
posterior process, albeit a small one, as in oviraptorosaurs,
Anchiornis, Xiaotingia, dromaeosaurids and troodontids, and the process
is directed almost straight posteriorly as in Anchiornis, Xiaotingia
and deinonychosaurs13,18. In oviraptorosaurs, the posterior process
points posterodorsally, which seems also to be the case in some basal
avialans15.
The mandible of Archaeopteryx is long and slender as in Anchiornis,
Xiaotingia and basal deinonychosaurs6,11. For comparison, basal avialans
all have oviraptorosaur-like mandibles: the mandible is relatively
robust, the external mandibular fenestra is large and anteriorly located,
and the dentary has a convex dorsal margin and a concave ventral one
(however, the external mandibular fenestra is poorly known in
Jeholornis and Sapeornis)4,32.
As in Anchiornis and basal deinonychosaurs11,34, the dorsal vertebrae
of Archaeopteryx bear no distinct pneumatic foramina and instead
have shallow, elongate depressions on the lateral surface of the centrum.
In oviraptorosaurs and basal avialans such as Jeholornis and
Sapeornis, the dorsal vertebrae bear distinct pneumatic foramina35.
Archaeopteryx has five sacral vertebra as in Anchiornis, Xiaotingia,
basal troodontids and basal dromaeosaurids11,33. By contrast, basal
avialans have a greater number of sacral vertebrae35.
The scapula is significantly shorter and more slender than the
humerus, a feature also seen in other paravians11,35. Similar to the
condition in other deinonychosaurs, the coracoid bears a distinct
subglenoid fossa. An ossified sternum and uncinate processes are
absent as in Anchiornis, Xiaotingia and troodontids. The humerus
has a proximodistally long internal tuberosity, as in Anchiornis,
Xiaotingia and other deinonychosaurs11. The length of manual
phalanx IV-3 is considerably greater than the combined lengths of
IV-1 and IV-2, a feature also seen in Anchiornis, Xiaotingia and other
deinonychosaurs.
As in Anchiornis, Xiaotingia and deinonychosaurs14,36,37, but unlike
in basal avialans17, the pre-acetabular process of the ilium is relatively
deep. The supraacetabular crest is distinct as in Xiaotingia, Anchiornis
and basal deinonychosaurs. In oviraptorosaurs and basal avialans the
supraacetabular crest is absent. In the Solnhofen specimen, a lateral
expansion is present on the mid-shaft of the pubis (Fig. 3f), a feature
also seen in basal dromaeosaurids and troodontids11. The very short
and wide ischium has a distally located obturator process (Fig. 3g), as
in Anchiornis and basal deinonychosaurs11,33,37. Inmostmaniraptorans
including oviraptorosaurs, the ischium is short, but not to the degree
seen in Archaeopteryx and deinonychosaurs, and in all basal avialans
the ischium has a different shape: relatively long and slender, posteriorly
curved, and without an obturator process. The ischium has a
distally located process on the posterior margin (Fig. 3g) as in basal
deinonychosaurs and Xiaotingia, although the posterior margin of the
ischium of Jeholornis admittedly seems to bear a large convexity. A
trait uniquely shared with Anchiornis (condition unknown in
Xiaotingia) is the constricted base of the distally located obturator
process.
The metatarsus of Archaeopteryx approaches the arctometatarsalian
condition28 in that the proximal end of the third metatarsal is laterally
compressed as in Anchiornis and basal deinonychosaurs. In basal
avialans, metatarsal III is not laterally compressed4,17.
As described above, Archaeopteryx is more similar to Anchiornis,
Xiaotingia and basal deinonychosaurs than to known basal avialans
and oviraptorosaurs in numerous features, some of which are uniquely
shared. On the other hand, basal avialans such as scansoriopterygids,
Sapeornis, Jeholornis and the confuciusornithids are more similar to
oviraptorosaurs than to Archaeopteryx, Anchiornis, Xiaotingia and
basal deinonychosaurs in many features, particularly cranial and vertebral
ones. This supports the hypothesis that Archaeopteryx,
Anchiornis and Xiaotingia are referable to the Deinonychosauria, a
hypothesis consistent with some previous work on Anchiornis6,38.
Although Archaeopteryx is placed within the Avialae by nearly all
numerical phylogenetic studies10,11,21,24–26,39,40, some recent studies
have demonstrated that some of the suggested synapomorphies purportedly
shared by Archaeopteryx and basal avialans are questionable.
For example, two salient avialan features—the absence of a jugal
process on the palatine and the presence of a reversed hallux—are
now considered to be absent in Archaeopteryx28,31 (Fig. 3h). Some
other suggested synapomorphies are present in recently described
basal deinonychosaurs, and are thus likely to represent paravian
rather than avialan synapomorphies23,37. These features include an
antorbital fossa that is dorsally bordered by the nasal and lacrimal,
a relatively small number of caudal vertebrae, a relatively large proximodorsal
process of the ischium, a relatively long pre-acetabular
process of the ilium, and fusion of the proximal part of the metatarsus11,37,41.
Consequently, there are few derived features shared by
Archaeopteryx and basal avialans but absent in basal deinonychosaurs,
thus documented morphological support for the avialan affinities of
Archaeopteryx is fairly weak. The alternative hypothesis that
Archaeopteryx, Anchiornis and Xiaotingia are all deinonychosaurs is
better supported by the available morphological data, and these taxa
share with some basal deinonychosaurs some unique features
unknown in any other theropod group (Figs 3 and 4; see also Supplementary
Information).
Within the Deinonychosauria, Archaeopteryx is more similar to
Anchiornis and Xiaotingia than to dromaeosaurids and troodontids in
many features, although few of these features are uniquely shared by the
three taxa. Of note, however, are some unique features related to the
pelvis. For example, the ischium appears to be proportionally even
shorter in Archaeopteryx and Anchiornis than in other deinonychosaurs,
and these two taxa also share a basally constricted obturator process
(condition unknown for both characters in Xiaotingia). On the other
hand, Archaeopteryx, Anchiornis and Xiaotingia lack many derived
similarities shared by troodontids and dromaeosaurids, such as lateral
exposure of the splenial, a muscle scar on the deltopectoral crest, and
an enlarged, raptorial ungual on pedal digit II. This suggests that
Archaeopteryx, Anchiornis and Xiaotingia are probably most closely
related to each other, whereas dromaeosaurids and troodontids form a
separate clade within the Deinonychosauria (see additional comparative
figures in Supplementary Information).
Implications for avialan origins
The discovery of Xiaotingia further demonstrates that many features
previously regarded as distinctively avialan actually characterize the
more inclusive Paraves. For example, proportionally long and robust
forelimbs are optimized in our analysis as a primitive character state
for the Paraves (see Supplementary Information). The significant
lengthening and thickening of the forelimbs indicates a dramatic shift
in forelimb function at the base of the Paraves, which might be related
to the appearance of a degree of aerodynamic capability. This hypothesis
is consistent with the presence of flight feathers with asymmetrical
vanes in both basal avialans and basal deinonychosaurs6,23.
All taxa recovered as basal avialans by our analysis, such as the
scansoriopterygids, Sapeornis and Jeholornis, resemble oviraptorosaurs
and to a lesser degree therizinosaurs4 but differ from deinonychosaurs
including archaeopterygids in having such cranial and
dental characteristics as a dorsoventrally high premaxilla that is significantly
larger than the maxilla, a dorsally positioned external naris,
a dorsoventrally tall antorbital fossa, a jugal with a relatively vertical
postorbital process and a long quadratojugal process, a quadrate with a
large pterygoid ramus, a relatively long parietal, an anteriorly downturned
and strongly dorsally convex mandible, a large external mandibular
fenestra, and enlarged anterior teeth. Some of these features are
optimized by our analysis as synapomorphies of a clade containing the
Oviraptorosauria, the Therizinosauroidea, the Avialae and the
Deinonychosauria, but are lost in the last group (see Supplementary
Information). Some previous phylogenetic analyses have placed the
Oviraptorosauria within the Avialae42, and a recent study suggests that
the Oviraptorosauria and Scansoriopterygidae are sister taxa, forming a
clade at the base of the Avialae38. However, our analysis indicates that
placing the Oviraptorosauria outside the Paraves is much more parsimonious
than placing it within the Avialae (see Supplementary
Information). In either case, many oviraptorosaur-like features are
plesiomorphic for the Avialae. These features contribute to forming a
relatively tall and robust cranium, in contrast to the shallower andmore
gracile craniumseen in the Deinonychosauria. These results invite a reevaluation
of the ancestral condition for birds from the perspective of
morphology, behaviour and ecology. Under the phylogenetic framework
shown in Fig. 4, a robust skull and a herbivorous diet (which has
been suggested to characterize the Maniraptoriformes43,44) probably
represent ancestral traits that are retained in basal birds, and the
Deinonychosauria is exceptional in having a more gracile skull and a
carnivorous diet.