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Michael Mortimer wrote:
Depending on whether you are a ground-up believer or a tree-down believer,
the creature would have been either a good runner (cursorial-style legs)
or a good climber (well-developed manus claws and shorter legs).
Er... why? The taxa around the base of Avialae seem to be okay runners and
okay climbers (Archaeopteryx, Rahonavis, Microraptor, Jinfengopteryx, Mei).
I agree with Mickey. One of the encouraging trends in recent years is that,
when it comes to the origin of avian flight, we have steered away from the
traditional 'trees-down' versus 'ground-up' dichotomy. Rather, the first
birds (and their immediate forbears, and their sister taxa) may have divide
dtheir time between the ground and the trees (or other elevated substrates,
like boulders as suggested by the "Pouncing Proavis" hypothesis).
Furthermore, there is no reason why both terrestriality and arboreality may
not have both played a role in the evolution of powered flight. Certainly,
_Archaeopteryx_ and many near-avian maniraptorans show a suite of features
consistent with both climbing and running.
Another question is whether pre-_Archaeopteryx_ ancestors of birds passed
through a four-winged ("tetrapteryx") gliding stage on the way to evolving
flight. Some non-avian maniraptorans and primitive birds show long hindlimb
feathers, called "hindwings" or (more imaginatively) "butt-fans". In
_Microraptor_ and _Cryptovolans_ (which are probably the same) there are
long feathers on the tibia and even longer feathers on the metatarsus. Long
metatarsal feathers are also seen in the putative non-avian _Pedopenna_.
One enantiornithine specimen (IVPP V13939) exhibits long feathers on the
tibiotarsus. _Archaeopteryx_ shows short feathers on the tibiotarsus, but
we cannot know (yet) whether this character in _Archaeopteryx_ is incipient
or represents a secondary reversal from a four-winged ancestor that had
At any rate, this taxon probably lived sometime in the late Triassic or
This I have to disagree with. We don't even have tetanurines from that
I wonder... if the Ceratosauria is paraphyletic, and coelophysoids and
ceratosauroids (=ceratosaurids, abelisaurids, etc) are successive outgroups
to the Tetanurae, would this mean that tetanurines might not have evolved
until the Jurassic?
Falcarius killed the segnosaurian identity of Eshanosaurus.
Any takers on what _Eshanosaurus_ really is? I still suspect that it's
theropodan rather than a sauropodomorph.
I say Middle Jurassic, where we have taxa slightly less derived than
Archaeopteryx (Epidendrosaurus), and basal paravians (Pedopenna).
The age of _Epidendrosaurus_ and _Pedopenna_ depends upon the dating of the
Daohugou Beds, and a Middle Jurassic age is still controversial. It would
be nice though...