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Vert Teeth from the Balabansai of Fergana Valley



  Alexander Averianov, Thomas Martin, and Aizek Bakinov have recently
published an analysis of teeth collected from the Fergana Valley of
Kyrgyzstan, south-western Asia. 

  All material derives from the Balabansai Svita site of Sarykamyshai 1, a
few miles west of Tashkumyr, Kyrgyzstan, situated within the northern
Fergana Valley, dated to the Callovian, upper Middle Jurassic (= Dogger in
the European system). The Balabansai Svita is made of variegated
sandstones, siltstones, gravels, claystones, and marls, indicating a
fluviatile, marginal marine system, likely a large lakeshore or shallow
coastal environment, and dominated by a deltaic system (siltstones with
marly claystones). All deposits of the vertebrates were in the lower
Balabansai Svita, and occur in mudstone lenses that imply catastrophic
depositional events, as in floods. Collection of the microverebrate
remains occured as recently as 2001.

  Among the material collected includes teeth referred to a
rhamphorhynchid pterosaur (said to resemble *Rhamphocephalus*) which had
been originally referred to as similar to *Angustinaripterus* and which
may still be a close similarity; a general theropod of tetanurine form, a
neosauropod (which bore denticles along the slightly recurved crown,
including a prominent lingual keel with a distoapical curvature along its
length), and what has already been mentioned in passing and was aluded to
by Mickey in his discussion of the new Cerro Condor theropod,
*Condorraptor.* Of note among the tetanurine teeth is that they do not all
correspond to a single morphotype, but in fact there is some substantial
variation among them, from height:FABL ratios (height of the crown (above
the root) relative to the fore-aft basal length (now the mesiodistal basal
length, or MDBL) to degree of curvature (never quantified in a character
analysis though Josh Smith has attempted to use a computer to quantify
relative curvature in shape analysis. Some teeth are more straight than
others, some short and strongly recurved, and some in the middle; some
crowns show much larger denticles on the distal carina than the mesial
one, others have no mesial denticles, and still others show a set of
ridges on the apical portion of the crown, either lingual, or on one
crown, both labial and lingual, and bear a morphology consistent with
*Paronychodon* as recognized by Sankey and others.

  A new ornithischian dinosaur has been described, based solely upon
teeth, named *Ferganacephale adenticulatum,* or "non-denticulated Fergana
head," an allusion to the authors' referral of the taxa to the
Pachycephalosauria. Nessov had originally referred the type tooth to the
Stegosauria, as the museum label clearly showed. The tooth (and all other
referred teeth) were referred to the Pachycephalosauria because "[t]he
only dinosaurs that have teeth with weak vertical crown ridges and
marginal denticles easily eliminated by wear at least from one crown side
are the Pachycephalosauria (Maryanska 1990[...]; Baszio 1997[...]; Sereno
2000[...])[,]" as well as "[...]tooth crowns in pachycephalosaurs are
asymmetrical with a prominent basal cingulum, and monognathically
heterodont dentition with the crown asymmetry increasing posteriorly." No
reasons are given for its referral to the Pachycephalosauridae, despite
the authors attributing it as the oldest member of Pachycephalosauria and
Marginocephalia, implying if it were to be the oldest, the "nearest"
family to be attributed to it would have been Homalocephalidae, but the
authors chose otherwise.

  The holotype is ZIN PH 34/42, an unworn, "adult" tooth. Referred teeth
include ZIN PH 5/42, a possible juvenile tooth; ZIN PH 4, 30-33/42, four
isolated adult teeth, all from sublocality FTA-30; ZIN PH 35/42, an
isolated heavily worn adult tooth, from sublocality FTA-31; and ZIN PH
36/42, an isolated adult posterior tooth, from sub locality FBX-23. The
teeth range from 6.75mm above the root (holotype) to worn, smaller
"juvenile" teeth at 2.65mm or so. The inferrence of mesiodistal increasing
asymmetry permits the authors to determine a marginal series.

  Averianov et al. diagnose *Ferganacephale* by the following suite of
characters:

  "(1) Teeth with both lingual and labial crown sides covered by enamel
(-)*; (2) tooth
   crowns asymmetrical in side view, with one crown side (mesial?) being
more convex than
   the opposite side (+)*; (3) main crown ridge poorly differentiated or
not distinguishable
   (+)**; (4) vertical crown ridges leading to the marginal denticles very
weak or absent
   (+)**; (5) marginal crown denticles absent or so small that they are
eliminated by the
   slightest wear (+)**; (6) basal crown cingulum present (+)*; (7) basal
cingulum more
   prominent on one crown side compared with the opposite side (on the
lingual side in the
   maxillary teeth and on the labial side in the mandibular teeth) (+)*;
(8) basal crown
   cingulum interrupted at the centre of the labial side in the maxillary
teeth and of the
   lingual side in the mandibular teeth (+)**; (9) vertical wrinkled
ornamentation could be
   present on the less concave crown side, adjacent to the basal cingulum
interruption, at
   least in some teeth (+)**; (10) dentition monognathically heterodont,
with the posterior
   teeth having lower and more asymmetrical crowns than the anterior teeth
(+)* (?-?
   primitive character, ?+? derived character, * character typical for
Pachycephalosauria,
   ** autapomorphy)."

  Of the autapomorphies listed for the taxon (3, 4, 5, 8 and 9), 9
represents a unique feature present in virtually no other ornithischian;
feature 3 is present in several taxa, including stegosaurs, some
ankylosaurs, and several basal marginocephalian, most of which were
ceratopsian; feature 4 may be related to 9 in the sense of a loss of
vertical ridge may correspond to development of wrinkles, otherwise that
the wrinkles are more or less the degraded vertical ridges without
denticles to "set" their placement, allowing them to undergo more mutation
without the selective control of the denticles; feature 5 is highly
unique, but the authors caution in the possibility of wear, I think this
is largely overridden by the high number of non-denticulate crowns whereas
other isolated teeth show persistence of denticles even when the crowns
exhibit marginal wear, with the exception of iguanodontian ornithopods.
Feature 9 is also considered less "distinct" since it is present in only a
few crowns recovered, so its distribution is not so distinct. This leaves
an autapomorphic diagnosis to features 4 and 9, which may be interrelated.
Feature 8, above, is present in a few other taxa, and marginocephalians
show a relative loss and lack of distinct expression of cingula, implying
this is part of a serial reduction towards non-cingulate ceratopsians. On
the meanwhile, pachycephalosaurs possess a distinct cingulum, and this may
suggest that the teeth do NOT belong to a pachycephalosaurid, as implied,
but perhaps a basal ceratopsian.

  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)


                
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