More on *Pycnonemosaurus nevesi*, Kellner & Campos, 2002

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

  My thanks go out to Tim Williams for providing me with a copy of this
paper.

  There is not much I can add to Tim's report on this taxon, except
perhaps a minor phylogenentic perspective.  This perspective does not
intend itself to be expansive and authoritative.  The material was
discovered in the Brazilian state of Mato Grosso ("thick forest") which
lent its name, in Greek, to the taxon [from _pycnós_ and _nemos_]; the
discoverer was the great Llewellyn Price, found along with various
titanosaur remains.  This form was not particularly small, as
representative of a tibial length of 78 cm.  This would give the taxon,
with a femur aproximately the same length as the tibia and proximal tarsal
length, a hip height of 2m (6.8 ft), and a length of nearly 10m, which is
approximately the same size as *Carnotaurus.*

  *Pycnonemosaurus* possesses a prominent cnemial crest on the tibia,
whose length is nearly half the total tibial length.  It is expanded
distally dorsoventrally, as in *Majungatholus,* *Aucasaurus,*
*Genusaurus,* *Velocisaurus,* *Ceratosaurus,* *Quilmesaurus,* and
*Xenotarsosaurus;* it is no wonder that Kellner & Campos (2002) considered
this feature as possibly diagnostic to abelisaurs, however being absent in
*Masiakasaurus,* *Ligabueino,* and *Elaphrosaurus.*  Unlike
*Ceratosaurus,* it is not knobby, but flattened mediolaterally.  The
process length is otherwise approaced only in a tibia of an abelisaur,
probably belonging to the new Indian form, previously described by von
Huene and Matley, 1933, and may indicate a close affinity between forms
with a short tibia, as the side of the femoral emplacement and crest
appears to be largely consistent with other "ceratosaurs."  The lateral
edge of the distal end is much lower than the medial edge, as in
*Quilmesaurus,* bot not as in other "ceratosaurs" save *Ceratosaurus*
itself.

  The tibia is the most diagnostic material available. Apart from the
tibia, there is a distal fibula, distal right pubis lacking a distinct
medial lamina (as in *Carnotaurus,* *Masiakasaurus,* *Elaphrosaurus,* and
*Ligabueino*), and partial caudal vertebrae including four proximal caudal
centra, two mid- to distal vertebrae from the proximal third of the tail,
and a proximal caudal transverse process, which resembles the same in
*Carnotaurus* in having a sigmoid cranial and caudal margin, lacking the
distinct awl-like process as in *Aucasaurus.* The tibiofibular crest of
the tibia is not distinct, but there are preservational problems with the
tibia, as much of it has been plastered and glued prior to description.
Teeth are also considered based on proximity as part of the type, and only
one preserves enough enamel to examine the denticulation, though the
authers did not figure these nor did they describe them in great detail;
the denticles vary in constancy along the crown, so that the basal crown
has 2 per mm, and the distal ends has 1.8 /mm.

  While Kellner and Campos (2002) were not able to place *Pycnonemosaurus*
more claerly within Abelisauria than generally, or were reluctant to, it
is clear than there are several abelisaurid features in the brevity of the
tibia and the shape of the distal caudal transverse process.  Other
features, such as the dorsoventrally ovate caudal centra faces, are
autapomorphic; this is circular in *Carnotaurus*, and dorsoventrally
compressed and therefore mediolaterally ovate in *Elaphrosaurus,*
*Masiakasaurus.* The pubis has bears a large, rhomboid pubic boot that
does not contact its opposite by possessing a groove between the paired
boots; this boot is larger than that inferred for *Carnotaurus* by Kellner
and Campos, though to be honest, Bonaparte et al. (1990) showed that this
material is not well-preserved and the shape of the boot is unknown. The
distal fibular is semi-ciurcular in section, and the bredth of the distal
tibia suggests it lay, as in *Xenotarsosaurus,* on the cranial surface of
the proximal tarsus.

  Now, a little more on some other data. The holotype (DGM 859-R) come
from a conglomerate sandstone, at Paulo Creek on the ranch Fazenda
Roncador of Max de Barros Erhart; this conglomerate has been dated based
on correlated biostrat to the upper Bauru Group, and would correspond
anywhere from the Turonian to the Maastrichtian (in other words, the
Senonian). This level is known in the region to occur as the Adamantina
and Merilia Formations, but to which *Pycnonemosaurus* belongs to is
unknown. Material from the Adamantina includes a premaxilla and various
teeth, and these were associated by Bertini (1996) as belonging to the
same taxon as the Paulo Creek form.

  References:

  Bertini, R.J. 1996. Evidências de Abelisauridae (Carnosauria:
Saurischia)
    do Neocretáceo da Bacia do Paraná. _Boletim, 4o Simpósio sobre o
    Cretáceo do Brasíl_ 267-271.
  Kellner, A.W.A. & Campos, D. de A. 2002. On a theropod dinosaur
    (Abelisauria) from the continental Cretaceous of Brazil. _Arquivos do
    Museu Nacional (Rio de Janeiro)_ 60 (3): 163-170.

=====
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)

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