|WHAT IS A FOSSIL FISH?
Fish are the oldest known vertebrates. All fish have a dorsal nerve cord with a
supporting rod (notocord), later replaced by a column of vertebrae (backbone).
All fish also have or had gill slits. Most fossil fish are very similar to modern
fish, however, early fossil fish were often much different. Some were simple,
jawless animals, others developed jaws and a bony outer "skin" for protection.
Eventually, these fish evolved into the general body plans that we see today.
Fish now inhabit every one of the world's oceans and rivers, and commercial
fishing has become one of the world's largest industries.
Fish are, and have always been, very diverse aquatic animals. They are divided
into four classes - agnatha (jawless fish), placoderms (armored fish),
chondricthyes (sharks and rays), and osteichthyes (bony fishes).
Agnatha are the most primitive of all vertebrates. This class of fish lacked
paired fins and true jaws. They date back hundreds of millions of years and still
have representatives living today (lamprey).
Placoderms are an extinct class of fishes with primitive jaws and paired fins.
Most placoderms had bony, armor-plated headshields or thick scales and spines.
This type also dates back hundreds of millions of years.
Chondricthyes (sharks and rays) have skeletons of cartilage and open gill slits.
Most are marine predators with well-developed teeth. Their fossilized body parts
(usually teeth) are extremely widespread in the fossil record.
Osteichthyes are the most abundant, diverse, and complex group of fishes. These
bony fishes have a bony skeleton, scale-covered body, well-developed fins, and
sleek tail. This group includes almost all of the types of fish in today's rivers
|GREEN RIVER FORMATION
The Green River Formation is, quite simply, the richest deposit of fish fossils
in the world. It is so named because the fossils were first discovered on the
banks of the Green River in Wyoming. The Green River Formation stretches for
hundreds of miles across Wyoming, Colorado, and Utah, and is over a mile thick!
The abundance of fossil fish and the wide diversity of species makes this area
very important in the ongoing study of ancient fish. Some of the types of
fossil fish found in the Green River Formation are:
Knightia - an extinct fossil herring, generally small (3 to 8 inches), and
possibly the most abundant fish found.
Diplomystus - an extinct predatory fish, could grow large (over 20 inches long),
a common, but beautiful, Green River fish.
Mioplosus - an extinct predatory fish with a double dorsal fin, medium to very
large (well over 20 inches long), not extremely uncommon.
Priscacara - an extinct perch-like fish, medium-sized (under 15 inches),
relatively rare and very displayable.
Phareodus - a voracious predator with present-day relatives, grew to be very
large (over 30 inches!), one of the most beautiful of the Green River fishes.
Amphiplaga - a small, bony fish (trout perch), rare in most layers, it is an
unusual little fish.
Heliobatis (Stingray) - an extinct stingray with stinger spines on the tail,
grew to 30 inches in length, a very displayable and collectible fish - one of
the most sought-after fossils from the Green River Formation.
Very Rare Types - Eohiodon (Mooneye), Amia (Dogfish), Notogoneus (Sucker or
Sand Fish), Lepisosteus (Gar), Crossopholis (Paddlefish).
Fossil fish have been found on every continent on Earth. Some important fossil
fish finds have been made in Brazil, Lebanon, Germany, Canada and China. Fish
were the first vertebrates and still flourish today - bony fishes represent more
species than all other vertebrates combined! Fossil fish are some of the most
beautiful and displayable of all vertebrate fossils. They are sought-after by
collectors and investors worldwide for their scientific value and aesthetic