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Re: A Whole Bunch Of Questions



> Date: Mon, 31 Mar 2003 17:48:10 +0800
> From: "Dino Rampage" <dino_rampage@hotmail.com>
> 
> 1) What is the status of the Euhelopodidae? Is it considered basal
> to the Neosauropoda? And are Euhelopus, Omeisaurus & Mamenchisaurus
> still considered a monophyletic clade? Would Shunosaurus be
> considered closely related to, or part of Euhelopodidae?

Analyses differ, but the most recent and perhaps most carefully and
completely coded is Jeffrey Wilson's 2002 paper, _Sauropod dinosaur
phylogeny: critique and cladistic analysis_ (Zoological Journal of the
Linnean Society, 2002, 136, pp217­276.)  He concludes that the
"Euhelopodidae" is a paraphyletic assemblage with only _Omeisaurus_
and _Mamenchisaurus_ forming a clade, and _Euhelopus_ itself coming
out as a titanosauriform!

His topology is:

        +--_Vulcanodon_
        +--_Shunosaurus_
        +--_Baraposaurus_
        +--_Patagosaurus_
        +--+--_Omeisaurus_
        |  +--_Mamenchisaurus_
        +--_Jobaria_
        +--Diplodocoidea
        +--_Camarasaurus_
        +--_Brachiosaurus_
        +--_Euhelopus_
        +--Titanosauria

Here's the abstract:

        Sauropoda is among the most diverse and widespread
        dinosaur lineages, having attained a near-global
        distribution by the Middle Jurassic that was built on
        throughout the Cretaceous.  These gigantic herbivores
        are characterized by numerous skeletal specializations
        that accrued over a 140 million-year history.  This
        fascinating evolutionary history has fuelled interest
        for more than a century, yet aspects of sauropod
        interrelationships remain unresolved.  This paper
        presents a lower-level phylogenetic analysis of
        Sauropoda in two parts.  First, the two most
        comprehensive analyses of Sauropoda are critiqued to
        identify points of agreement and difference and to
        create a core of character data for subsequent
        analyses.  Second, a generic-level phylogenetic
        analysis of 234 characters in 27 sauropod taxa is
        presented that identifies well supported nodes as well
        as areas of poorer resolution.  The analysis resolves
        six sauropod outgroups to Neosauropoda, which
        comprises the large-nostrilled clade Macronaria and
        the peg-toothed clade Diplodocoidea.  Diplodocoidea
        includes Rebbachisauridae, Dicraeosauridae, and
        Diplodocidae, whose monophyly and interrelationships
        are supported largely by cranial and vertebral
        synapomorphies.  In contrast, the arrangement of
        macronarians, particularly those of titanosaurs, are
        based on a preponderance of appendicular
        synapomorphies.  The purported Chinese clade
        `Euhelopodidae' is shown to comprise a polyphyletic
        array of basal sauropods and neosauropods.  The
        synapomorphies supporting this topology allow more
        specific determination for the more than 50
        fragmentary sauropod taxa not included in this
        analysis.  Their distribution and phylogenetic
        affinities underscore the diversity of Titanosauria
        and the paucity of Late Triassic and Early Jurassic
        genera.  The diversification of Titanosauria during
        the Cretaceous and origin of the sauropod body plan
        during the Late Triassic remain frontiers for future
        studies.

Hope this helps.

 _/|_    _______________________________________________________________
/o ) \/  Mike Taylor  <mike@indexdata.com>  http://www.miketaylor.org.uk
)_v__/\  "We don't watch _Batman_ as a documentary on the LAPD" --
         Luis Chiappe's comment on the inaccuracies in the _Jurassic
         Park_ films.

--
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