Re: Statistics and the fossil record

["Jerry D. Harris" <102354.2222@compuserve.com>]

Message text written by INTERNET:jjackson@interalpha.co.uk
>They have found small
olshevskyian bones in the Tendaguru, so some small arborial-type stuff was
found there, but no larger "cursorial" maniraptorans.  The ground there and
in the Morrison has been scoured.  Do you know how many turtles/crocs/small
herbivores have been found in just those two formations?<

        I think most of us have a good idea...but also think of how many
new taxa of relatively small animals in the Morrison have been discovered
just in the last couple of decades:  two new pterosaurs (_Mesadactylus_ and
_Kepodactylus_) as well as the nameless maniraptoran material from the Dry
Mesa Quarry, and several mammals, lizards, sphenodontians, etc., etc.  (And
let's not forget the hitherto unknown egg shell and eggs!)  Reasons why
these weren't found before are probably complementary and numerous,
including examining previously unexamined facies, better collecting
techniques including enough care to seek tiny elements.  Most of these tiny
taxa (such as the _Mesadactylus_ and unnamed maniraptoran material from the
Dry Mesa Quarry and _Kepodactylus_ and much small mammal material from the
Small _Stegosaurus_ Quarry) are found due to fortuitous taphonomic
circumstance:  they were all found amidst the sedimentologic log-jam of
giant dinosaur bones -- they'd be unlikely to survive fluvial transport
without such a stoppage, thus probably hindering their preservation.  Plus,
during much of the original Morrison excavations of the last century,
trophy-hunting of big, show-stopping animals took precedence over careful,
detail work, so lots of tiny things were probably simply overlooked (for
example, the site in Garden Park from which tthousands of shards of
eggshell and several more or less intact _Prismatoolithus_ eggs were found
is only a few hundred yards away from the Felch/Marsh Quarry and even
closer to the Cleveland Quarry [site of _Haplocanthosaurus delfsi_] -- it's
inconceivable to me that the site wasn't walked over by at least _one_
person over the course of excavations at either quarry...but they simply
didn't recognize the tiny black bits as eggshell!)  The Fruita microsites
that have produced relatively abundant squamate, sphenodontian, pterosaur,
and mammal material (see various papers by George Callison) seem to _favor_
the tiny things at the expense of big things...I don't recall the
interpreted paleoenvironment of the sites at the moment (anyone?), but
these too are in an area where numerous quarries for larger taxa and
hundreds (if not more) of prospectors have tromped over the years.

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                     Jerry D. Harris
                 Fossil Preparation Lab
          New Mexico Museum of Natural History
                   1801 Mountain Rd NW
               Albuquerque  NM  87104-1375
                 Phone:  (505) 899-2809
                  Fax: ; (505) 841-2866
               102354.2222@compuserve.com