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Re: JVP 25(2): New Dinos, Birds, Discoveries
The other day, I posted on the following paper:
Yates, A. and C. C. Vasconcelos. 2005. Furcula-like clavicles in the
prosauropod dinosaur *Massospondylus*. _JVP_ 25(2):466-468.
I had written:
<Yates and Vasconcelos described the the clavicles of a specimen of
*Massospondylus* (BP/1/5241) from a farm in the Barkly East District of Eastern
Cape, South Africa (Farm Upper Drombo), deriving from the upper Elliot
Formation, Karoo Supergroup, and Hettangian or Sinemurian in age, Early
Jurassic. Two long paried bones lie above the acromia of the scapula and above
the dorsal margins of the coracoids and adjoin one another in a V-shape of
nearly perfectly 90 degrees. One end overlaps the other slightly, and the
shafts are slightly arched along their lengths; striae at the distal ends imply
soft-tissue interaction as tendons binding the distal ends of the rods.>
<This suggests that saurischians may have possessed articulated V-shaped
clavicles ancestrally, and it may also afford that reports of *Segisaurus* and
*Coelophysis* clavicles may not form fused furculae, but only articulate as V's
given the lack of preservation at the median.>
In fact, Tykoski et al. (2002) has indicated a fused pair of clavicles in the
holotype of *Coelophysis kayentakatae*, which while exhibiting a suture, are
apparently firmly locked together and the distal (conjoining) epipohyses are
expanded, more srongly ventrally, and exhibit the appearance of a hypocleidium.
In regards to *Segisaurus*, which is reported in a talk and poster from Phil
Senter and John Hutchinson (SVP 2001), Tykoski et al. (2002, pg. 731) state:
"An individual clavicle was described in the type and only known specimen of
the coelophysoid *Segisaurus halli* (Camp, 1936), the implication at the time
being that paired clavicles were present. However, new preparation of this
specimen also reveals that the element in question is a furcula (Senter and
Hutchinson, 2001). *Segisaurus* is known from slightly younger sediments than
*Syntarsus*, and its phylogenetic position within Coelophysoidea is uncertain
at this time. Paired, unfused clavicles were reported and figured in the Late
Triassic coelophysid taxon *Coelophysis bauri* (Padian, 1997:fig. 3g).
Conflicting with this description, elements that may prove to be furculae were
more recently reported in other specimens of *Coelophysis* (Downs, 2000:fig.
2E). If the latter is confirmed, it will constitute the earliest temporal
occurrence of the furcula.
"Whether the clavicles were paired, fused, or absent is uncertain for most
other basal theropods, ceratosaurs, and basal tetanurans. A right clavicle was
reported in the abelisaurid *Carnotaurus sastrei* (Bonaparte et al., 1990).
However, Bonaparte et al. (1990:24) considered this interpretation tentative,
adding "...some portion of it may be missing." "
References of relevance:
Senter, P., and J. R. Hutchinson. 2001. New information on the skeleton
of the theropod *Segisaurus halli*. _JVP_ 21(3, Suppl.):100A.
Tykoski, R. S., C. A. Forster, T. Rowe, S. D. Sampson and D. Munyikwa. 2002.
furcula in the coelophysid theropod *Syntarsus*. _JVP_ 22(3):728-733.
Jaime A. Headden
"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)
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