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Re: dracrorex and National Geographic



Yeah, and I thought their quiz was a tad outdated, namely the question about
extinction. (They say there are indications of declining diversity before
the impact event, implying at least that dinos were on their way out...)
Scott Perry
High Mountain Writers' House
Irasburg, Vermont
----- Original Message ----- 
From: "Denver Fowler" <df9465@yahoo.co.uk>
To: <dinosaur@usc.edu>
Sent: Monday, November 26, 2007 5:03 PM
Subject: dracrorex and National Geographic


> I just saw this month's National Geographic magazine. Isn't it a tad
embarrassing to see "Dracorex hogswartsia" on the cover, and in the
article?: when "Dracorex" was recently outed (along with "Stygiomoloch") as
growth stages of Pachycephalosaurus (Horner et al, SVP2007): not even
mentioned in the article. I find it pretty surprising that National
Geographic would sit so behind the times like this.
>
> ----------------------------------
> Denver Fowler
> df9465@yahoo.co.uk
> Work:
> http://www.museumoftherockies.org
>
> Fieldwork  pictures NM 2002-4 & China 06:
> http://www.statemuseumpa.org/notes05.htm
>
http://www.wald.heim.at/urwald/540645/JH-Projekte/China_04-2006/chinaset.htm
>
> TV Work:
> http://www.impossiblepictures.co.uk
> http://www.bbc.co.uk/dna/h2g2/A664661
>
> Art:
> http://dino.lm.com/artists/display.php?name=df9465
> -----------------------------------
>
> ----- Original Message ----
> From: Sarah Werning <swerning@gmail.com>
> To: david.marjanovic@gmx.at; dinosaur@usc.edu
> Sent: Monday, 26 November, 2007 2:29:33 PM
> Subject: Re: Marsupial forelimbs... or rather hindlimbs
>
> Well, it'll be nice to see this paper when it comes out. Obviously, to
> speak about a heterochrony you need to compare ontogenies across
> phylogeny, and though there are studies that have looked at this
> question (and similar ones) for these groups, this is certainly the
> largest placental-marsupial developmental comparison to date.
>
> I don't know that this is especially novel in terms of thinking,
> though; there are papers that have suggested deceleration of hindlimbs
> is what is going on in marsupials (although the majority do suggest it
> is acceleration of forelimbs). It will be interesting to see their
> methods: do they hold timing of development of hindlimbs constant
> relative to a third event, such as brain development? Or constant to
> time/developmental stage? A lot of the current literature holds brain
> development constant and compares limb or facial development relative
> to that. I'm especially curious about which outgroups they used and
> what's going on in them.
>
> In terms of comparing forelimb to brain development, there is a large
> body of literature that suggests that marsupials are indeed developing
> their forelimbs earlier than placentals in both absolute and relative
> terms. In several cases (e.g., Monodelphis, Dasyurus) you get
> development and ossification of the facial and forelimb bones (and
> significant development of their associated muscles) while the brain
> is still undifferentiated neuroepithelium (and while big chunks of the
> rest of the body is undifferentiated mesenchyme). The
> forelimb-hindlimb timing is interesting, but think the story with the
> timing of brain/braincase and limbs is more interesting.
>
> For some really cool research by someone who completely gets
> heterochrony, and who works on limb and craniofacial development in
> marsupials and placentals, check out Kathleen K Smith's website:
>
> http://www.biology.duke.edu/kksmithlab/
>
> Most of her papers are available as free pdf's.
>
> Sarah
>
> -- 
> Sarah Werning
> reply to: swerning@berkeley.edu
> Museum of Paleontology and Department of Integrative Biology
> University of California, Berkeley
> 1101 Valley Life Sciences Building
> Berkeley, CA 94720-4780
>
>
>
>
>
> On 11/26/07, David Marjanovic <david.marjanovic@gmx.at> wrote:
> > Here's the promised SVP meeting abstract, _emphasis_ (italics) in the
>  original:
> >
> > ---------
> >
> > Vera Weisbecker, Anjali Goswami, Marcelo Sánchez-Villagra & Stephen
>  Wroe: Postcranial sequence heterochrony and the marsupial-placental
>  dichotomy, SVP meeting abstracts 2007, 164A
> >
> > It has long been recognized that there is a deep dichotomy between
>  marsupials and placentals in terms of taxonomic and ecological diversity.
>  Marsupial species known today comprise a small percentage of the
>  number of placental species, and have no extremely specialized (e.g.
aerial
>  or fully aquatic) representatives. The comparative lack of marsupial
>  diversity is particularly eident in the marsupial forelimb, which is much
>  less diverse compared to that of placentals. Marsupials are born in an
>  extremely altricial state, and i
> using its forelimbs. Current consensus holds that
>  the crawl to the pouch is related to heterochronic acceleration of the
>  marsupial forelimb. Howeve, this hypothesis has only experienced limited
>  formal testing. We analysed postcranial ontogeny in a new dataset of
>  ossification sequences of 13 placentals, 11 marsupials, and three
>  outgroup taxa, considering 25 events. Data were obtained from
clear-stainin!
> > g and/or
> >  micro-computed tomography of ontogenetic series, and in some cases
>  from the literature. The ossification sequence data were analyzed using
>  the event-pair[-]based Parsimov analysis. To examine their potential
>  phylogenetic signal, a parsimony analysis of the event-pair data was
>  conducted. This did not retrieve any of the recognized mammalian clades
>  except for monophyletic marsupials (except *Petaurus*) nested within
>  placentals. This suggestes that postcranial ossification sequences carry
>  some limited phylogenetic signal for marsupials, although [this is] not
>  sufficient to separate them from placentals. Event distributions within
>  species suggest that a larger amount of events occurs in younger animals
>  compared to older specimens, a pattern particularly obvious in
>  marsupials. We expect[ed?] that this is due to fast appearance of the
forelimb
>  long bones, shoulder girdle, cervical and thoracic elements in the
>  youngest marsupials. Parsimov analysis reports that ossification events!
> >  in the
> >  hindlimb of marsupials are _decelerated_ with respect to forelimb
>  long bone ossification events. This novel ypothesis challenges the
>  long-held tenet of an ontogenetic "bottleneck" on marsupial forelimb
>  diversity.
> >
> > ----------
> >
> > So, it's not the brain that the placentals develop while the
>  marsupials are developing their forelimbs. It's the hindlimbs.
> >
> > Marsupials don't develop the forelimbs earlier than placentals, they
>  develop the hindlimbs later than placentals.
> > --
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>
>
>
>
>
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