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The fossils imaged here came an isolated outcrop of the
Middle Triassic Prida Formation in Nevada on Public Lands (at
least at the last time of collecting the site resided on Bureau
of Land Management-administered Public Lands). It's a world-famous
locality, well known to many amateur ammonoid enthusiasts and
professional paleontologists alike--a specific place that yields
41 species of ammonoids, plus five kinds of pelecypods (a remarkable
halobiid clam known as Daonella) and four varieties of belemnites;
all told, the Prida Formation bears 68 species of ammonoids that
span the entire middle Triassic age, or roughly 241 to 227 million
years ago. As a matter of fact, the specific Prida Formation
site referred to here yields one of the most complete middle
Triassic ammonoid successions in the world; and many cephalopod
specialists and paleontologists, in general, consider it the
single best Middle Triassic, late Anisian Stage (roughly 235
million years old) ammonoid locality in existence. Literally
tons of ammonoid-bearing limestones have been removed from the
site since its discovery by silver miners in the latter half
of the 1800s; that well-preserved, identifiable fossils still
occur there, after such concerted searching by hordes of avid
ammonoid enthusiasts over many decades, is somewhat of a miracle.
In the late 1980s, for example, many law-abiding, conscientious
amateur collectors, plus swarms of irresponsible, lawbreaking
commercial ammonoid hunters (it is illegal to either sell or
barter--in other words, trade--fossils collected on Public Lands)
"simultaneously rediscovered" the great fossil locality,
creating over the past couple of decades an often frenzied frequency
of overcollecting.
The geologic age of the specific, classic ammonoid site is transitional
latest Anisian/earliest Ladinian Stage of the Triassic Period,
which places the fossils found there directly in the middle of
the Mid Triassic, or roughly 235 million years old. At that distant
geologic date, what is now the classic Prida fossil locality
in the arid Great Basin Desert of Nevada rested at the bottom
of a shallow, tropical, warmwater Triassic seaway near the equator.
Please Note: I have heard that the Bureau of Land Management
carefully monitors fossil collecting activities at the incomparable
MiddleTriassic Prida ammonoid outcrops: the upshot, accordingly,
is that commercial fossil collectors caught raiding the Prida
strata will most certainly be prosecuted to the fullest extent
of the law. There has also been talk that, because commercial
collectors have so horribly desecrated the area, the Bureau of
Land Management will eventually place the world-class Prida ammonoid
locality into a special land-use category called an "Area
Of Critical Environmental Concern," a designation that would
permanently close the site to all but trained scientists with
a degree from an accredited university.
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