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Re: Age of Gobi formations



Tim Donovon (sirius531@yahoo.com) wrote:

<A map on page 574 of The Age of Dinosaurs in Russia and Mongolia clearly
indicates that Ukhaa Tolgod lies northeast of Khulsan.>

  The fact is, they lack contact, so deciding one overlay the other is a bit
far-reaching. Yes, I got the direction wrong. But the heart is still there :).

<"Chuuut Uul" is part of the Barungoyotskayasvita, which includes the Djadokhta
and Barun Goyot.>

  This is largely irrelevant, since the cited age for the Nemegt was at a
different cite. This stated that the middle Barungoyotian (a non-stratigraphic
term) was dated to 80-75 ma; The Barungoyotskaya svita does not correpsond to
the Barun Goyot _and_ the Djadokhta formations, just to the former, as the
latter comprises the Djadokhtinskaya svita. This was evidenced since the 1920s
and 1970s, when the formations were distinguished and named. Prior to 2001, the
Russian use of the "svita" seies had largely been abandoned except in Mongolian
and Russian texts, as in Russian the "svita" is equivalent to the use of
"formation" in western geo lit. The Barungoyotian and Nemegtian correspond to
bio "ages." This is why I distinguish use of Djadokhta and Barun Goyot
Formations, rather than a general Barungoyotian.

<IIRC someone-Horner?-suggested the knob-like termini are an old age feature.>

  In regards to the club-shaped spines of *Barsboldia*, however the angulation
of the spines might be related, this varies widely among taxa, and may not be
very indicative of much, but yes, it is something. However, the club-shaped
spine terminus does not compare to any other taxon, but is found in
iguanodontids to some degree; the spine length and sacrum features indicate
hadrosaurian, as in Osmólska and Maryanska's work. *Barsboldia* is too
incomplete to compare well, and at least some would synonymize *Hypacrosaurus*
with *Lambeosaurus* (Wagner, MS thesis) or with *Corythosaurus* (Paul, 1988),
this renders some comparability relatively limited in case of some theories.

  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)