Re: New Mesozoic bird papers (advance publication)

[Tim Williams <tijawi@gmail.com>]

> David A. Burnham; Alan Feduccia; Larry D. Martin; Amanda R. Falk (2010)
> Tree climbing -- a fundamental avian adaptation. Journal of Systematic 
> Palaeontology (advance online
> publication) http://www.informaworld.com/smpp/content~db=all~content=a9
> 31297342~frm=abslink


I really REALLY shouldn't comment on this paper, in light of the fact
that I haven't actually read it yet... BUT I think it's worth pointing
out that while it is quite likely that the first birds might have
climbed trees, they clearly weren't very good at it.  In fact, they
plain sucked.  So I really hope Burnham, Feduccia, Martin and Falk do
not trot out the usual line that birds evolved from small arboreal
archosaurs that were not dinosaurs, because dinosaurs were terrestrial
cursors and did not climb trees, et cetera, et cetera, blah blah blah.


Which brings me to this: "When birds developed an effective backstroke
permitting easy ascent from flat surfaces, the need for manual claws
disappeared, which would suggest that they were primarily used for
climbing tree trunks and had little function in prey capture."


I fail to see why manual claws couldn't be used for *both* climbing
and prey capture - especially among the first birds. After all, if
_Velociraptor_ had feathered forelimbs (based on the presence of quill
knobs), and used its forelimbs in prey capture - why couldn't some
early birds have done the same?  Although I'm not suggesting that
birds attacked large prey the way _Velociraptor_ did.


I'll stop there.  If anyone could forward me a copy (and the O'Connor
et al. _Boluochia_ paper) I'd be eternally grateful!


Cheers

Tim



On Thu, Dec 16, 2010 at 9:18 PM,  <bh480@scn.org> wrote:
> From: Ben Creisler
> bh480@scn.org
>
> In case these advance online-publication papers have not
> been mentioned yet:
>
>
> David A. Burnham; Alan Feduccia; Larry D. Martin; Amanda
> R. Falk (2010)
> Tree climbing -- a fundamental avian adaptation.
> Journal of Systematic Palaeontology (advance online
> publication)
> http://www.informaworld.com/smpp/content~db=all~content=a9
> 31297342~frm=abslink
>
>
> There have been a number of studies on the claws of
> Mesozoic birds, largely driven by interest in the habitat
> of Archaeopteryx. Many Mesozoic avians have large, well
> formed manual claws, largely absent in contemporary
> birds. Juvenile hoatzins are the only living birds with
> claws that are large enough to be generally functional,
> but not equivalent to those of Mesozoic birds. When birds
> developed an effective backstroke permitting easy ascent
> from flat surfaces, the need for manual claws
> disappeared, which would suggest that they were primarily
> used for climbing tree trunks and had little function in
> prey capture. This hypothesis has both phylogenetic and
> functional implications. The numerous claw studies to
> date are based primarily on measurements taken of the
> bony core, all that is usually preserved in fossils.
> Examination of contemporary birds shows that this is a
> poor estimator of the size and shape of the horny sheath
> that actually forms the functional claw. The discovery of
> vast numbers of exceptionally preserved fossil birds from
> the Late Jurassic and Early Cretaceous of China means
> that we now have an opportunity to compare actual horny
> claw data from the earliest birds with that of modern
> birds and test hypotheses on climbing, terrestrial
> activity, and predation.
>
> Jingmai K. O'Connor; Zhonghe Zhou; Fucheng Zhang (2010)
> A reappraisal of Boluochia zhengi (Aves: Enantiornithes)
> and a discussion of intraclade diversity in the Jehol
> avifauna, China.
> Journal of Systematic Palaeontology (advance online
> publication)
> http://www.informaworld.com/smpp/content~db=all~content=a9
> 31293250~frm=titlelink
>
> A careful reappraisal of the only known specimen of the
> poorly understood fossil enantiornithine bird Boluochia
> zhengi reveals numerous morphological similarities that
> suggest this taxon is closely related to the well-known
> Longipteryx chaoyangensis, and so is assignable to the
> most diverse recognized clade of Early Cretaceous
> enantiornithines, the Longipterygidae. This new study of
> the holotype of B. zhengi reveals new longipterygid
> synapomorphies and expands our knowledge of the temporal
> and geographical ranges and diversity of the clade. We
> suggest that the trophic specialization that
> characterizes longipterygids may have been a major factor
> contributing to the success of this clade.
>
> Zhonghe Zhou; Larry D. Martin (2010)
> Distribution of the predentary bone in Mesozoic
> ornithurine birds.
> Journal of Systematic Palaeontology (advance online
> publication)
> http://www.informaworld.com/smpp/content~db=all~content=a9
> 31286291~frm=abslink
>
> In this paper we review the distribution of the
> predentary bone in Mesozoic ornithurine birds. The
> predentary bone, well known in ornithischian dinosaurs,
> has now been reported not only in hesperornithids and
> ichthyornithids but also in a number of Early Cretaceous
> basal ornithurines, such as Yanornis, Yixianornis,
> Hongshanornis and Jianchangornis. In many Early
> Cretaceous ornithurines the predentary bone is not
> preserved, but the anterior end of the dentary has a
> blunt, often inclined margin and usually shows a
> distinctive pit. These are characteristic features of a
> predentary attachment. The predentary bone is absent in
> extant birds, and examination of known enantiornithines
> and more basal avians now represented by hundreds of
> specimens show that none of them preserved a predentary
> bone, confirming that this bone was independently derived
> in the Ornithurae, and lost in the Neornithes. The
> predentary bone is found to be associated with both
> toothed and edentulous dentaries in basal ornithurines.
> In toothed birds the edentulous predentary bone always
> corresponds to an edentulous anterior portion of the
> premaxilla. Although it is possible that the presence of
> the predentary bone is related to a piscivorous diet in
> some birds, this may not be true for all the basal
> ornithurines with a predentary bone. It is almost certain
> that it was functionally very different from the
> predentary bone in ornithischian dinosaurs.
>
>
>