*Spinostropheus* Replaces "Elaphrosaurus," a Possible "Elaphrosaurid"

["Jaime A. Headden" <qilongia@yahoo.com>]

With publication of Sereno, Wilson, and Conrad, two new taxa are
described, one being a new genus for the previously applied
*"Elaphrosaurus" gauthieri,* described by de Lapparent in 1960 from a
variety of material that does not appear to be very strongly associated,
as noted by Mickey. A more complete refered skeleton _could_ be designated
a neotype if it weren't for the fact that the diagnosis of gauthieri is
supported on vertebral material found in the "type" series of elements,
and the new specimen from Niger supports referal of these elements to a
single taxon, with a little reidentification. Associated limb material
agrees with the abelisaurian identification, but does not permit referal
to the same taxon, and the new material does not possess limb material.

  *Spinostropheus gauthieri,* as Tim Williams noted, is a new genus name
for the former ?Elaphrosaurus gauthieri of de Lapparent (1960). Ample
material, associated with *Jobaria,* provides an extensive comparison to
be made in the vertebral column, complete from the caudal half of the
third cervical all the way to the neural arches of the posterior dorsals
and three sacrals, the sacrals of which show co-ossification as well as
ossified tendons lateral to the neural spines between all sacrals and the
last dorsal. Sereno, Wilson, and Conrad (2004) diagnose the taxon by the
presence of a divided anterior cervical pleurocoel, cervical epipophyses
being broad and flat rather than attenuated and rod-like, neural spines
expanded craniocaudally in the cervicals and dorsals and very low in the
former, and mid-cervicals, as shown in both the holotype and referred
material, that have inclined cranial articulations. The cervical ribs, as
in *Noasaurus* and *Majungatholus,* are pneumatically perforated, and the
ribs are particularly massive. The transverse processes are broad and
appear downswept in the posterior dorsals, without a distinct lamina
between the diapophysis and parapophysis which, by the mid-point of the
dorsal column, are fully integrated onto the neural arch. Cervical and
dorsal pleurocoels are present, though only in the anterior few dorsals,
and these latter are particulatly large. The dorsals become more elongated
by distinct degrees further caudally, then shorten again in the last four.
Neural spines in the dorsals increase in height from half the neural arch
height, or a third the vertebral height, they become twice to three times
the basal neural arch height, and comprise almost half the vertebral
height altogether; dorsal central become shallower caudally. The sacrals
are fused, and the ossified tendons are particularly unique for a
theropod.

  The holotype is MNHN 1961-28, and consists of vertebrae and partial limb
material, though it should be restricted to the vertebrae for the moment,
as a "lectotype" as the material was not fully associated according to de
Lapparent. The new specimen is MNN TIG6, a complete post-axial to
presacral column, including three sacrals in articulation, and some ribs.
The preserved series is approximately 1 meter in length, and the total
animal would likely be 2.2 meters, or about 7 feet, with addition of a
largish head.

  De Lapparent (1960) illustrated a "caudal" (Plate V, fig. 5) as a
portion of his diagnosis, but it is almost painfully obvious that this is
a dorsal vertebra as the transverse processes are horizontal and well
above the centrum both anteriorly and caudally, without any suggestion of
a parapophysis on the centrum, as in *Spinostropheus,* as well as any
pleurocoel as in the cervicals. Its length and shape agrees with the
dorsals of *Spinostropheus,* rather.

  In the holotypic material, a tibia, partial humerus, and distal pubis
are also known, as well as what has been described as a caudal (this is
short and non-pneumatic, with transverse process massive and exclusively
on the centrum, suggesting it belongs to a sauropod). The tibia exhibits
the "typical" ceratosaurian astragalar articulation, where a fold of the
tibia encompasses the medial edge of the ascending process, as in
*Elaphrosaurus* (though much more weakly). The humerus is not well
preserved, as a proximal end and a distal end that, unlike
*Elaphrosaurus,* do not exhibit distinct angular corners, but are rather
more curved, without a distinct separation between adductor crest (medial,
= ventral process), humeral caput, and extensor crest (lateral). The
distal pubis has been amply described before by Mickey
(http://www.cmnh.org/dinoarch/2002Jul/msg00370.html), and doesn't provide
anything distinct for the diagnosis, as this is largely only more robust
in profile and larger than in *E. bambergi,* with both anterior and
posterior processes.

  *Spinostropheus* shares some features with *Elaphrosaurus,* including
elongated, low neural spines of the cervicals and dorsals, and epipophyes
broader than deep and largely oriented horizontally. This could affirm
this taxon as the first true inclusive representative of a monophyletic,
multi-taxon "elaphrosaurid" basal abelisaurian clade. Another taxon,
suggested earlier by Mickey, is *Chuandongcoelurus,* known with more
*Elaphrosaurus*-like cervicals, which suggests a third taxon, and likely
closer to *E.* than *S.* is.

  More to come on *Rugops.*

  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.

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


        
                
__________________________________
Do you Yahoo!?
Win a $20,000 Career Makeover at Yahoo! HotJobs  
http://hotjobs.sweepstakes.yahoo.com/careermakeover