The spiny-fin, or perciform, Mioplosus has been found,
although relatively rarely, in the exceptionally well-preserved
Green River Formation rocks of Wyoming, USA. Its two
dorsal (back) fins, and the comparable size of the 'second
(rearmost) of these to the anal fin, which is directly beneath,
are identifying features. The body is quite variable in
proportions, but its length and strong build give it an overall
perch-like appearance. Specimens of Mioplosus often seem
to have died while trying to swallow, and .
choking on, fish up to half
their own size. This
suggests Mioplosus
was a voraci06s
predator, while the
isolated nature of
the finds indicate
that it was solitary'
rather than shoaling.