In the vein of recent discussions involving
enigmosaurs and alvarezsaurids, I figured I'd present a similar case as an
example of how easy it is to make an alternative phylogeny. This phylogeny
is supported by good synapomorphies, but is less parsimonious than the currently
accepted one.
I suggest confuciusornithids are in fact volant
oviraptorids. This is supported by the following characters-
1. toothless premaxilla
This is actually more parsimoniously seen as a
confuciusornithid-oviraptorid character. Otherwise, two steps would be
required when oviraptorids and confuciusornithids each developed this
convergently (with ornithurines too).
2. toothless maxilla
The situation is similar to the above, but even
more so, as toothless maxillae didn't evolve until neornithines. Also in
the more basal Chirostenotes and Caudipteryx.
3. toothless dentary
Just like the toothless maxilla. Also in the
more basal Chirostenotes and Caudipteryx.
4. elongate external mandibular fenestra (>24%
of mandibular length)
Unique to confuciusornithids, oviraptorids,
Chirostenotes and Caudipteryx.
5. process of surangular process invades external
mandibular fenestra
Only found in confuciusornithids and oviraptorids
among theropods.
6. maxilla reduced compared to
premaxilla
May have developed as early as Caudipteryx.
Not seen in other non-ornithurine birds.
7. extensive dentary
symphysis
Known in Chirostenotes, oviraptorids and
confuciusornithids. This is absent in non-neornithine birds.
8. rod-like jugal
In oviraptorids and
confuciusornithids.
9. double-headed quadrate
In confuciusornithids, oviraptorids and probably
Chirostenotes. Would help explain why Sinornis, Patagopteryx and
hesperornithiformes have single-headed quadrates.
10. two elongate posterior dentary
processes
Only seen in oviraptorosaurs and
confuciusornithids.
11. nasals strongly reduced in size
Present in confuciusornithids and oviraptorids, but
not in basal birds like Eoenantiornis or Sinornis.
12. seven sacral vertebrae
Like Ingenia, a possible sister group to
confuciusornithids within the Oviraptoridae.
13. fused sternal plates
Again, known in Ingenia.
14. manual ungual II much smaller than
I
Another synapomorphy indicating Ingenia the
confuciusornithid sister group, not known in any other theropod.
Note that confuciusornithids' fused scapulocoracoid
fits better with this hypothesis, as the traditionally more basal Rahonavis has
an articulated scapulocoracoid. Similarily, Confuciusornis has a poorly
developed acromial process, unlike other basal birds and eumaniraptorans.
Also note the similar reduction in maxillary fenestrae, similarily shaped
dentary, boomerang-shaped furcula (not seen in Velociraptor, Caudipteryx, etc.).
Many supposedly avian characters are also developed
in at least some oviraptorosaurs (naris larger than antorbital fenestra,
pygostyle, less than thirteen dorsal vertebrae, less than twenty-five caudal
vertebrae, radius longer than 90% of humeral length, proximally fused
metatarsus, reversed hallux), showing these aren't reliable avian synapomorphies
of confuciusornithids. Most of the remaining synapomorphies are directly
related to flight, so were probably developed in parallel to true birds for that
reason.
I propose referring to Confuciusornis and
Changchengornis as members of the Confuciusornithinae, as they are within the
family Oviraptoridae. This makes the so far unnamed clade Enigmosauria +
Paraves the Pygostylia.
|--+--Segnosauria
| `--+--Caudipteryx | `--+--Chirostenotes | |--"other oviraptorids" | `--+--Ingenia | `--Confuciusornithinae `--+--Troodontidae |--Dromaeosauridae `--Ornithothoraces What's everyone think? ;-)
Mickey Mortimer
|