The Green River Formation - Fossil Ecosystems of North America: A Guide to the Sites and their Extraordinary Biotas - page 181

herrings belonging to the family Clupeidae
and represented by two genera, Knightia
( 191 ) and the smaller Gosiutichthys .
Knightia (up to 25 cm [10 in] in length) is
the most common of all the Green River
fish and in 1978 alone, for example, more
than 20,000 were excavated in Wyoming. It
is a schooling fish and often occurs in mass-
mortality layers of up to 2,000 fish per
square metre (180 per square ft). Almost as
common (up to 30% of all fish found) is an
extinct, herring-like group represented by
Diplomystus (up to 65 cm [26 in] in length;
( 192 ), with their peculiar upturned
mouths characteristic of surface feeders.
They fed on smaller fish, including

Knightia , which are often found fossilized
in their mouths.
An unmistakable component of the
fish fauna is the freshwater stingray,
Heliobatis ( 193 ), a bottom-dwelling
species found mainly in the Fossil Lake
deposits. It is characterized by three
barbed spines ('stingers') on its tail and
reached 90 cm (3 ft) in length. Males can
be recognized from females by possessing
claspers behind the pelvic fins, used in
mating. By far the largest fish known
from Green River, however, are the gars,
Lepisosteus and Atractosteus ( 194 ), up to
2.14 m (7 ft) long, with their cylindrical
bodies covered in thick ganoid scales.

191

191 The freshwater
herring KnightiaPC.
Length 9 cm 3.5 in.

192

192 The herring-like fish
DiplomystusPC. Length
30 cm 1 ft.