Re: Utahdactylus is not a Pterosaur

["Rob Gay" <rob@dinodomain.com>]

This brings something to mind, reading about Utah and pterosaurs. There are
pterosaur (possibly large azhdarcid) from the Blackhawk Formation, Mesa
Verde Group, Manti-La Sal National Forest. These are described and
illustrated in one of Martin Lockley's many books on footprints, IIRC.
Peace,
Rob

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----- Original Message -----
From: "Jaime A. Headden" <qilongia@yahoo.com>
To: <dinosaur@usc.edu>
Sent: Friday, October 04, 2002 6:02 PM
Subject: Utahdactylus is not a Pterosaur


> Not sure what unambiguous conditions led the authors to conclude this, but
> reading Bennett's comments detailing his impressions, and getting scans of
> the figures from Mickey Mortimer, I am aghast that the authors did not see
> what was likely the most "obvious" interpretation: *Utahdactylus* appears
> to comprise vertebrae of a sauropod. Three vertebrae, CEUM 32588, are
> shown in sagittal section where the trabecullar structure of the centra
> and neural arches are exposed. The centra are somphospondylous, very
> complex in their camellae, and the neural arches are, by contrast,
> polycamarate (using the terminology of Wedel et al., 2001, _Acta Pal. Pol.
> 45(4)). This condition occurs in many neosauropodans, with a
> somphospondylous centrum in macronarians. The centra are short, about as
> long sagittally as twice their caudal height, and what have been
> identified as dorsals (figs. 4-5) may be short cervicals. Another slab
> refered to *Utahdactylus* (figs. 6-7), has a series of long slender bones
> that may be cervical ribs, and there is a positive cast of a long
> structure that may be the impression of a ventral cervical centrum. Other
> elements include a scapulocoracoid (figs. 10-11), and rather than
> contradicting this, it is easily corroborated as such, only the authors'
> id can be reversed: their coracoid is a scapular blade, and their proximal
> scapula is a partial coracoid, where the glenoid is clearly exposed and
> the dorsal margin of the articulated (not fused) elements are missing. A
> rib and dorsal vertebral centrum not in section are associated dorsal to
> the element. Finally, figs. 8-9 are the positive casts of a long element
> identified as a "humerus" with "scapulocoracoid" fragment, though how this
> conclusion was garnered I know not. They in fact appear to be pelvic in
> nature, and possibly pubic where one end bears a likely ambiens process;
> an ischiadic identity is also possibly, and the "process" may be the iliac
> peduncle.
>
>   This is, as Mickey Mortimer tells me as I write it, a "helluva misnomer"
> ... *Utahdactylus* is a sauropod? What is clear is it is not a pterosaur,
> and S. Chris Bennett et al. may have the "real" first pterosaurs from
> Utah.
>
>   Now, which taxa does it resemble as a sauropod? can it be referred to
> another taxon, or will *Utahdactylus* become one of the oddest sauropod
> names ever? First off, the most diagnoistic elements to this comparison
> are the vertebrae, which are fairly short, camellate in the centra, and
> camarate in the neural arches. This morphology is known in
> *Haplocanthosaurus* and some macronarians such as brachiosaurs, only the
> centra is far more camellate (somphospondylous) than in "brachiosaurids."
> Perhaps it is referrable to *Haplo.* or *Brachio. altithorax,* perhaps
> unique. Maybe Matt Wedel, if he's still monitoring this list, could help
> as this is relevant to his dissertation research.
>
>   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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