[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

RE: 11th specimen of Archaeopteryx

/open mouth
/insert foot


  Jaime A. Headden
  The Bite Stuff (site v2)

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)

"Ever since man first left his cave and met a stranger with a
different language and a new way of looking at things, the human race
has had a dream: to kill him, so we don't have to learn his language or
his new way of looking at things." --- Zapp Brannigan (Beast With a Billion 

> Date: Thu, 27 Oct 2011 17:52:57 -0400
> From: jaseb@amnh.org
> To: MHabib@Chatham.edu
> CC: david.cerny1@gmail.com; dinosaur@usc.edu
> Subject: Re: 11th specimen of Archaeopteryx
> Dr. Habib, is this the presentation at SVP Bristol that you mentioned?
> Also, the literature says that some modern birds do not have humeral remiges, 
> using proximally directed secondaries to fill that role. Is it possible it 
> was the same for Archaeopteryx?
> Poster Session II, (Thursday)
> WEISHAMPEL, David, Johns Hopkins University, Baltimore, MD, USA; HABIB, 
> Michael,
> Johns Hopkins University, Baltimore, MD, USA
> Birds inherited a bipedal gait and feathered airfoils from their theropod 
> ancestry. These
> features produce specific tradeoffs with regards to launch, maximum size, 
> lift coefficient,
> and limb disparity. There are subtle effects related to the use of feathered 
> wings, such as
> the ability to utilize separated wingtip slots and extensive span reduction, 
> which have
> also influenced avian flight evolution. Combining information from structural 
> mechanics,
> aerodynamics, and phylogeny, we conclude that the basal state for avian 
> takeoff was a
> leaping launch, not a running launch. We find that several morphological 
> features of early
> birds, inherited from theropod ancestry, predisposed them to radiation in 
> inland habitats. We
> find that Archaeopteryx could sustain substantial loads on both its forelimbs 
> and hindlimbs,
> but structural ratios between the forelimb and hindlimb of Archaeopteryx are 
> indicative
> of limited volancy. Limb strength in Confuciusornis was modest, suggesting an 
> emphasis
> on cruising flight and limited launch power. We find little evidence to 
> support extensive
> competition between birds and pterosaurs in the Mesozoic. Prior literature 
> has suggested
> that pterosaurs competed with early birds for resources and may have helped 
> shape the early
> evolution of birds. There is some evidence of partitioning between pterosaurs 
> and birds in
> ecological space. Evidence from the Jehol fauna suggests that pterosaurs 
> dominated near
> coastlines during the Early Cretaceous, while birds were more important 
> inland. However,
> flight is a complex character. Flight mechanics vary considerably across 
> volant animals.
> Some flyers experience only limited competition for resources with other 
> flying species,
> and might compete most intensely with non-flying taxa. As a baseline for 
> understanding the
> interactions between Cretaceous birds and pterosaurs, the flight dynamics of 
> the two groups
> need to be compared in a quantifiable framework. Birds and pterosaurs 
> inherited different
> morphologies, and this impacted their flight regimes. Comparing the two 
> systems provides
> a basis for hypotheses related to competition in the Cretaceous, and the 
> influences on early
> avian evolution.
> On Oct 27, 2011, at 4:21 PM, Habib, Michael wrote:
> > Also, the possible (likely) lack of a complete inner wing and the 
> > relatively weak forelimbs (see Weishampel and Habib presentation at SVP 
> > Bristol for the latter; full paper still pending as we are adding to it).
> >
> > Cheers,
> >
> > --Mike H.
> >
> > Sent from my iPhone
> >
> > On Oct 27, 2011, at 3:55 PM, "David Černý" <david.cerny1@gmail.com> wrote:
> >
> >> David Marjanović <david.marjanovic@gmx.at> wrote:
> >>
> >>> What are these, other than the apparent inability to lift the wing above
> >>> horizontal?
> >>
> >> The (admittedly controversial) feather study of Nudds & Dyke (2010), 
> >> perhaps?
> >>
> >> Nudds RL, Dyke GJ 2010 Narrow primary feather rachises in
> >> _Confuciusornis_ and _Archaeopteryx_ suggest poor flight ability.
> >> Science 328(5988): 887-9
> >>
> >> --
> >> David Černý
> Jason Brougham
> Senior Principal Preparator
> American Museum of Natural History
> jaseb@amnh.org
> (212) 496 3544