Location: La Mission, Baja California, Mexico
Geologic Period Range: Late Cretaceous
Traditionally estimated 100 to 60 million years BCE1
Age of Extinct Specimen: Generally estimated about 65 million years
Description: This "Small Ammonite" is
described on the Youngblood Energy Library website as a "prize example".2
This species, Pachydiscus Catarinae ("Thick Disc of Catreina"), is
traditionally believed to have become extinct about 65,000,000 years ago
Although no fossils have been discovered of this actual marine animal, nor
of a specimen with an intact fragile outer shell chamber where it lived, it
is believed that they may have been similar in function and appearance to
today's chambered nautilus found in tropical seas. (The worldwide search by
paleontologists for a complete and perfect specimen of this species
Fossils of this species, including this
specimen, are found in the Rosario Formation near La Mission in the State of
Baja California, Mexico. They are found in boulders (ranging approximately
from 4 to 10 foot diameters) made up of concretionary accumulations
of marine matrix originating as giant mud balls that were rolled up, which
then adhered to a central rock or fossil, much as a giant snowball rolls up
lawn grass and twigs, suggesting great force was applied to create these
boulders, probably catastrophic in nature. The Youngblood Library website
only 10% of these boulders contain ammonites and a fraction of these contain
specimens approaching the quality of this specimen."
It is also probable that very few approach
the beauty of this "prize" specimen.
Estimated by traditional Uniformitarian concepts (gradual, uniform changes
over great periods of time, similar to rates of change observed today).
For access to the Youngblood Library website it
is easiest to copy and paste to your browser: www.libraries.ou.edu/locations/?id=19
(Do not just click on link since it then leads back to the slow-loading and
difficult to navigate main O. U. Library Systems home page).
NEXT: Fossiliferous Limestone
on Page 12