Re: I'm back/ Ricardoestia or Richardestia? / Ma vs. M.y. vs. Mya

[Phillip Bigelow <bh162@scn.org>]

Well, I'm back on the list for a *short* while (other large-volume lists
are clogging my box), but wow, I hopped back in just at the right time
to toot a horn.

K. Wicks  <paleo_mont@excite.com> asked of the group:

>I have been told that there is a small meat-eating dinosaur called
>Richardestia

Wrong spelling, but not your fault (as DinoGeorge has already pointed
out).

>that was found in the Hell Creek Formation, but I have found no
>information on it.   However I have found info on Ricardoestia gilmorei
from
>the Judith River Formation, Currie, Rigby, and Sloan 1990.

It's in their paper.  Only a short mention of it on page 117.


>Are these two
>seperate animals

Most probably.  The Hell Creek specimen is an undescribed species of
that genus.


>or was my source incorrect on the time period and
>spelling?

Sources?  Did someone say sources?  <blowing my own horn>

http://www.dinosauria.com/jdp/misc/hellcreek.html

BTW: There's a cosmetic upgrade coming your way, Jeff.

Re: The conversation on Ma vs. M.y., Michael has got it pretty much
correct.  Ma was based on radioisotope ages (Uranium-lead;
rubidium-strontium, etc.) and in truth, it was never originally intended
to be 1:1 correlative with cosmologic (sidereal) years.  It is useful
mainly within the realm of geochronology. (archaeologists have known the
same thing regarding carbon 14 ages for years).

Now the good news:  Because of improvements in the science of
geochronology, sidereal years and radioisotope-based years are
converging.  Soon, it will be possible to achieve sidereal year accuracy
(+/- 10 years) back into the Early Pliocene (perhaps even earlier).
A good discussion of the joys and pitfalls of geochronology can be found
in the opening (Cenozoic?) chapter of:

Berggren, W. A., D.V. Kent, C.C., Swisher, M. Aubry, and J. Hardenbol
(eds), Geochronology, Time Scales and Global Stratigraphic Correlation.
SEPM Special Publication No. 54.

                                     <pb>