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*Aucasaurus garridoi* and Some Stuff on Halluces (Just in Time, Too!)



Thanks to a list member friend, I received this paper from the new JVP:

  Coria, R.A.; Chiappe, L.M.; & Dingus, L.. 2002. A new close relative of
*Carnotaurus sastrei* Bonaparte 1985 (Theropoda: Abelisauridae) from the
Late Cretaceous of Patagonia. _Journal of Vertebrate Paleontology_ 22(2):
460-465.

*Aucasaurus garridoi*

Etymology:
*Aucasaurus garridoi* :: *Aucasaurus* > Auca (Mapuche) > Auca Mahuevo
[site of recovery of the holotype] + -saurus (Lat.) > sauros (Grk.)
lizard, reptile; *garridoi* > Garrido (for Sr. Alberto Garrido, discoverer
of the holotype) + -i (Lat.) masculine genitive suffix. *Aucasaurus
garridoi* may be translated as "[Alberto] Garrido's Auca [Mahuevo]
lizard."

  The holotype is MCF PVPH 236 (Museo Municipal Carmen Funes,
Paleontología de Vertebrados, Plaza Huincul, Argentina) and comprises a
nearly complete skeleton lacking only the distal third of the tail and
gastralia. As indicated from Coria et al., the animal is distinguished by
a a longer skull than in *Carnotaurus*, a longer antorbital fossa, a
horizontal ventral margin of this fenestra, maxillary fenestra is exposed
laterally, paired frontal swellings rather than horns, and a sigmoidal
outline of the maxilla; they differentiate the postcrania from
*Carnotaurus* by having a less developed "coracoidal process" (by which I
think they mean  the ventral process). a relatively longer forelimb, and
forearm, humerus with slender and craniocaudally compressed shaft,
well-defined distal condyles, no hooks ulnar process on the redius, and
dorsally unbridged haemal arches; the last is considered the only
unambiguous autapomorphy for *Aucasaurus*, as this is lacking in other
carnotaurines like *Carnotaurus* and *Ilokelesia* (another taxon Coria
indicated was a basal form with unknown affinities --- but which were very
clearly apparent).

  *Aucasaurus* is made one inclusive anchor of a new taxon, Carnotaurini,
along with *Carnotaurus*, as being exclusively defined. Like
*Carnotaurus,* *Majungatholus*, and *Ilokelesia*, the caudal transverse
processes bear successively narrower bases further distally, centra that
do not decrease in length distally in the series, and transverse processes
with cranial "awl-shaped" processes that reach up to half the length of
the distal end of each process. Interestingly, in *Carnotaurus* and
*Majungatholus*, the first caudal as in other theropods is straddled by
the ilia, and lacks the cranial "awls"; in *Aucasaurus*, these processes
begin on the first caudal, not the second, and the first caudal is behind
the ilia, rather than between them; furthermore, there is a caudal
(posterior) notch in each caudal iliac blade which in *Aucasaurus* is
articulated with the "awl" of the first caudal, while this is apparently
connected to the second caudal's awl in other taxa. This may further be
considered an ambiguous synapomorphy of carnotaurines (pers. obs.). the
manus is wierd. It apparently lacked articulations for any phalanges on
metacarpals I and IV. Distal ends of metacarpals II and III are associated
with phalanges, the third digit known with two bones. This also suggests
the spur like bone of the hand of *Carnotaurus* may not be a metacarpal,
but could be a variable carpal element (pers. obs.). I have reconstructed
it as such here (http://qilong.8m.com/Carnotaurus_sastrei_manus.jpg) last
year. Tibiae and proximal tarsals are fused, as are neurocentral sutures,
and several cranial sutures are well defined and not loose, indicating an
adult age of the specimen. The tibiotarsus is, oddly enough, shorter than
the femur, and cnemial crest is positively huge with an hemispherically
expanded distal end, and is elevated as in other ablisaurid cnemia. The
crest is almost laminate on it's distal edge and has a fine termination
along the tibial cranial edge. The ascending process is low, not high,
similar to *Ceratosaurus*, and not like *Xenotarsosaurus*. The entire pes
including metatarsus (not forming a tarsometatarsus, and having a defined
fourth? distal tarsal) is longer than the tibiotarsus. There is a first
metatarsal that is (get this, avian freaks) J-shaped, with the distal end
projecting _laterally_ on a perpendicular. The hallux was at least
laterally oriented; metatarsal II is almost as long as IV, and not much
shorter than III; the proximal morphology of metatarsal III is avian in
that is expands mediolaterally behind IV and thus buttresses it
(typically, theropods broaden the IVth, not the IIIrd).

  A cladistic analysis of a remarkable 29 characters in the age of 300+
matrices (only seven taxa), results in a phylogeny of:

--+--Tetanurae
  `--+--Ceratosaurus
     `--+--Ilokelesia
        |--Abelisaurinae
        |--Majungatholus
        `--+--Carnotaurus
           `--Aucasaurus

Tetanurae               00000 00000 00000 0n000 00000 0000
Ceratosaurus    01000 00000 00000 0n000 00000 0000
Abelisaurinae   11111 ????1 1???1 0n?1? ????? ????
Majungatholus   11111 11111 11111 10100 ????0 ?101
Carnotaurus     10111 11111 11111 11111 11111 1111
Ilokelesia      ??1?? ????? ????? ??000 ????? 1111
Aucasaurus      1??1? ???11 111?? 11111 11111 1111

  I may have a few codings wrong, so forgive me if they are. I will post a
corrected matrix if I need to.

  No measurements are given in the text. The figures do not give the
measures for the body in general, but the body is said to be around 30%
smaller than *Carnotaurus*, so make it around 19ft or 6.5m. It was a very
small animal, as is obvious from Luis Rey's painting of the Auca Mahuevo
site; the sauropods there could squat and kill these critters, even when
they were full size.

  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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