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RE: Hoatzin & Archaeopteryx
Amtoine Grant wrote:
Just thinking, has anybody compared the skeletons of Archaeopteryx.
Especially with the controversy regarding manual digits 1,2,3 & 4 in
theropods & extant birds, this could prove interesting.
The "controversy" is somewhat of a red herring. The DML archives should be
helpful in pining down the references.
I've been wondering if the Hoatzin could be a late-surviving
Archaeopteryid[to coin a phrase] -
If only that were true. Alas, not a chance. _Opisthocomus_ is a
card-carrying member of the Neornithes - although its closest affinities
(whether cuckoos, seriemas or something else) are still murky.
As a side note, not much has been said of Protoavis. I understand that the
remains are fragmentary. Can it be discerned from what information is
available whether Protoavis may have possibly been an ancestor of
One problem is that the total material assigned to _Protoavis texensis_ may
include parts of several different animals. For example, some bits look
like they come from a drepanosaur, other bits look more dinosaurian, and
others ... who knows? Chatterjee's reconstructions certainly make
_Protoavis_ appear very bird-like (and more advanced in form than
_Archaeopteryx_), but most researchers have grave doubts concerning the
accuracy of his reconstructions. Unlike _Archaeopteryx_ and the Liaoning
maniraptorans, the two specimens of _Protoavis_ (one larger than the other)
were found dissociated and strewn over a fairly wide geographical area.
There may be maniraptoran (and perhaps even avialan) material among the
bones referred to _Protoavis_. If there were Early Jurassic therizinosaurs,
why not Late Triassic birds? The material certainly requires further
revision. However, _Archaeopteryx_ still holds the honor as the oldest
or an example of convergent evolution, as in phytosaurs & crocodilians?
The heads of drepanosaurids (and _Longisquama_) are superficially very
bird-like - which is why Senter coined the name Avicephala for the clade
containing these critters. Drepanosaurids also show narrow neck vertebrae
that bear hypapophyses - also as in maniraptorans. Certain features may
prove to be convergent between birds and _Protoavis_, but first we have to
determine what _Protoavis_ actually is.