Geoscience Reference
In-Depth Information
genera are known from Hell Creek
including
Pachycephalosaurus
itself, but
they are never common.
hesperornithiforms; large (1 m [3.3 ft]
tall) flightless diving birds first described
from the Upper Cretaceous Niobrara
Chalk Formation of Kansas.
Other reptiles and amphibians
These include frogs and salamanders,
lizards, a variety of turtles (including
baenids and trionychids as at Green
River; Chapter 11;
181
), crocodiles (
182
),
alligators, and the earliest boa snake. It is
interesting to record that the last known
pterosaurs occur in Hell Creek along with
some early birds belonging to the
Mammals
The mammal fauna, mostly known from
jaw fragments and teeth, falls, not
surprisingly, somewhere between that of
the Upper Jurassic Morrison Formation
(Chapter 9) and the Eocene Messel
deposits of Germany (discussed in
Chapter 11). Primitive multituberculates
181
181 The soft-shelled turtle
TrionyxBHIGR. Length
15 cm 6 in.
182
182 Crocodile scutes BHIGR.
Length 5 cm 2 in each.
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