[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
Re: SCIAM fossil bird article
> Teaser from the article
I hope the wing is not of _Teviornis_
Because if so, the "widely held view of bird evolution" in question has been
refuted since 2002, and cannot be said to be "widely held" for half a decade
now... and given that there was a tendency to assign Hornerstown/Navesink/Lance
Creek material to Charadriidae, Phalacrocoracidae, Procellariidae and whatnot
(Hope reviews this nicely in her chapter in "Mesozoic Birds"), I wonder whether
"Tertiary origin of modern birds" was ever a widely accepted theory.
Also interesting: http://digitallibrary.amnh.org/dspace/handle/2246/2812
So, either this is something really sensational - a Cretaceous crown
hummingbird, perhaps... but after "Archaeoraptor", would such a major figure in
the field as Dyke publish something so novel and ground-breaking in NG? Or it's
just a few years late and has never been controversial, and more effort should
be spent on determining *where* the K-Pg boundary runs through Neornithean tree
than to setting straw men on fire.
For until now, I have not heard of anything beyond "higher waterbirds" from the
Mesozoic. But of the latter, there seems to be quite a lot - fragmented,
disarticulated material, mostly, and too plesiomorphic to recognize a "modern"
lineage (think "neither albatross nor cormorant"). And the latter fact in
itself is very illuminating. Crown Galloanseres can be safely inferred. For
crown Charadriiformes, the case is also good. But even for crown "higher
waterbirds", the case is weak.
Besides, some of the more outrageous "molecular-only" claims drag the origin of
"near passerines" (Piciformes, Coraciiformes, Psittaciformes, Trogoniformes and
Coliiformes) so deep into the Mesozoic that for the phylogeny to remain
consistent, BAD itself gets into trouble. And this is a very bad thing, because
the inferred molecular molehill should not overrule the factual fossil mountain
So, while the Maastrichtian avifauna deserves intense scrutinity, Popper should
not be thrown out of the window. Meaning: it should never be forgotten to
ascertain, as much as this is possible, for what neornithean lineages there is,
and remains, NO evidence from the Mesozoic.
It stands to note that the base of the "higher landbirds" is still molecularly
unresolvable. One paper has claimed that there is no trace of an explosive
radiation in that part of the (molecular) tree, but at least one other study
(Galapagos finches, err tanagers) has shown that the molecular signature of
explosive radiations is extremely hard to pin down: after a few Ma, the signal
of genetic drift gets obliterated, so that only murky polytomies remain - and
these can, by assaulting them with the right kind of math, be broken down into
dichotomies. Whether these dichotomies are in any way a correct representation
of the actual phylogeny is quite a different question...