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Re: Epidendrosaurus, Systematic Observations pt. 1



Being very tired, the first thing that strikes me about this reconstruction
is how it looks like a terrestrial croc, with a bit of dinosaur thrown in.
Just my weary mind talking though, probably.
Peace,
Rob

Student of Geology
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Northern Arizona University
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----- Original Message -----
From: "Jaime A. Headden" <qilongia@yahoo.com>
To: <dinosaur@usc.edu>
Sent: Friday, August 30, 2002 7:59 PM
Subject: Epidendrosaurus, Systematic Observations pt. 1


> Okay,
>
>   The "Part 1" refers to this post being a preliminary observation. The
> part two will have me running the analysis in someone else's trees, but
> for now this is essentially just a first step: analyzing what's been
> published.
>
>   http://qilong.8m.com/Epidendro.html
>
>   includes the re-run analysis (Forster_Rahonavis Epidendrosaurus.nex,
> .tre, and epidendro.txt for the output results -- there may be problems
> with the .nex files on the page, I can email it to you) as published by
> Zhang et al., 2002, in _Naturwissenschaften_ (published online, and much
> thanks to Ben Creisler for getting this for me). Zhang et al. used Forster
> et al.'s *Rahonavis* analysis, and coded *Epidendrosaurus* for 34 of the
> 113 characters, 30% of the matrix. Problematically, I could verify only 12
> of these, whereas I noted almost the entirety of the rest of their codings
> were wrong, or based on questionable interpretations. Where is could
> _sorta_ see the condition, I recoded with variable, bipolar states (01),
> (1?) in order to provide the matrix with more data. After recoding, I had
> only 29 characters of 113, and this accounts for a low percentage (26%) of
> the matrix.
>
>   Nonethless, the analysis provides three MPT's of 239 steps each, and
> *Epidendrosaurus* is placed in three positions: the sister group to the
> ornithomimid clade, the sister group to the troodontid+bird clade
> (exclusive of dromaeosaurids), and the sister group to the
> Archaeopteryx+bird clade (exclusive of both troodontids and
> dromeosaurids). Synapomorphies for these are listed below, with position
> one as characters A, position two as B, and so on.
>
>   Characters:
>
> A:
>   2(2): teeth lack denticles.
>   7(1): frontals triangular from above and narrow rostrally.
>   9(1): frontals at least nearly as long as twice that of the parietals.
>
> B:
>   7(1): frontals triangular from above and narrow rostrally.
>   9(1): frontals at least nearly as long as twice that of the parietals.
>   59(1): radius thinner than ulna, diameter less than 0.7.
>   66(1): manus longer than ulna by 20%.
>
> C:
>   3(1): teeth slightly compressed and nearly conical.
>
>   The concensus tree collapses at Maniraptoriformes, but Aves remains
> resolved. Both bootstrap and jackknife analyses refuse to resolve the
> position, and no support is given to *Epidendrosaurus* other than
> Maniraptoriformes, despite the authors placing this taxon between
> Troodontidae and Aves, as in tree #2.
>
>   Hopefully, adding *Epidendrosaurus* to the Holtz and Xu et al./Hwang et
> al. matrices may resolve this slightly, but the data is hampered by poorly
> preserved vertebrae, no pelvic material, poorly preserved femora, the
> tibia exposed in posterolateral view, and probably an hourglass-shaped
> element on the left tibia that may be part of the astragalus, and not much
> of the skull. The authors coded several features of the tail and sacrum
> that are plainly just not there.
>
>   I have attempted a restoration of the skeleton that (hopefully) improves
> on that provided by the authors, and it is at:
>
>   http://qilong.8m.com/Epidendrosaurus_ningchengensis_skeleton.jpg.
>
>   And I guess with the latter, I suspect some on this list think of me as
> just an educated artist ... I wonder why....
>
>   Cheers,
>
> =====
> Jaime A. Headden
>
>   Little steps are often the hardest to take.  We are too used to making
leaps in the face of adversity, that a simple skip is so hard to do.  We
should all learn to walk soft, walk small, see the world around us rather
than zoom by it.
>
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